Effect of the Functional Groups of Racemic Rodlike Schiff Base Mesogens on the Stabilization of Blue Phase in Binary Mixture Systems

Transcription

1 Article pubs.acs.org/jpcb Effect of the Functional Groups of Racemic Rodlike Schiff Base Mesogens on the Stabilization of Blue Phase in Binary Mixture Systems Chiung-Cheng Huang,*, Zong-Ye Wu, Bing-Han Sie, We-Hao Chou, Yu-Chang Huang, Mei-Ching Yu, Bo-Hao Chen, I-Jui Hsu,*, Lai-Chin Wu, and Jey-Jau Lee Department of Chemical Engineering, Tatung University, Taipei 104, Taiwan Department of Molecular Science and Engineering, National Taipei University of Technology, Taipei 106, Taiwan National Synchrotron Radiation Research Center, Hsinchu 300, Taiwan *S Supporting Information ABSTRACT: Four series of rodlike racemic Schiff base mesogens possessing different alkyl chains and two types of linkages, ester and alkynyl linkages, were synthesized and applied to induce cubic blue phases (BPs) in simple binary mixture systems. The mesophases of these Schiff base mesogens were confirmed by variable-temperature X-ray diffraction and the characteristic texture from polarized optical microscopy (POM). In general, when chiral additive S-(+)-2- octyl 4-(4-hexyloxybenzoyloxy)benzoate (S811; wt %) is added into the rodlike racemic salicylaldimine-based mesogens, the cubic BPs could be observed and its temperature range is larger than 20 K. The widest temperature range of the cubic BP (35 K) can be observed in the blending mixture composed of rodlike racemic salicylaldimine-based mesogen OH-TI n possessing alkynyl linkage and wt % S811. However, Schiff base mesogens possessing alkynyl linkage show a direct isotropic to chiral nematic transition when equal amount of chiral dopant is added. Notably, the termination temperature of BPs is very close to room temperature (ca. 35 C) after 40.0 wt % S811 is added into the salicylaldimine-based mesogens possessing terminal alkyl chains and ester linkage. Interestingly, wide BPs (>30 K) can also be induced by adding chiral additive 1,4:3,6-dianhydro-2,5-bis[4-(n-hexyl-1-oxy)benzoic acid]sorbitol (ISO(6OBA) 2 ) with a high helical twisting power into the racemic Schiff base mesogen possessing ester linkage. Cubic BPI and BPII can be confirmed by reflectance spectra and POM. The results of reflectance spectra indicate that the binary mixture composed of salicylaldimine-based mesogens and S811 easily exhibits a supercooling effect and induces BPI. However, only BPII can be observed in all binary mixtures containing Schiff base mesogens. On the basis of our experimental results and molecular modeling, we suppose that the values of biaxiality, polarizability, and the dipole moment of molecular geometry are the main factors that affect BP stabilization. 1. INTRODUCTION Thermodynamically stable blue phases (BPs) show well-known mesomorphic behaviors in frustrated liquid crystals (LCs). On cooling, three types of BPs, BPIII, BPII, and BPI, emerge from the isotropic phase to the chiral nematic phase. 1 Amorphous BPIII is believed to have a local cubic lattice structure in the director field and an isotropic phase with arbitrary orientation. However, as a result of having a fluid three-dimensional periodic structure in the director field, BPII and BPI possess higher-order simple cubic and body-centered cubic packing structures, respectively. As the lattice periods of cubic BPs (BPII and BPI) are of the order of the wavelength of visible light, cubic BPs exhibit no birefringence but Bragg reflections of circularly polarized light. Consequently, they are potentially useful for many applications such as fast light modulators, tunable photonic crystals, larger-screen flat panel display, and three-dimensional lasers. 2 5 However, the defect in their lattice structure (disclination) causes the narrow temperature range to limit their practical applications. 6 Therefore, modern research works are developing several methodologies to broaden and stabilize the temperature range of BPs. For synthetic chemists, novel single molecules can be designed and synthesized by incorporating optically pure groups, various linkages, and lateral substituents into liquid crystalline structures. 7 9 Thus, several bent-core molecules and banana-shaped, T-shaped, and U- shaped molecules have been designed and prepared. 4 In addition, polymer stabilization, 10 hydrogen bond induction, nanoparticle doping, light induction, and blending mixture techniques with chiral dopants have also been reported. 4,21 According to the literature mentioned above and Received: September 28, 2016 Revised: November 11, 2016 Published: November 12, American Chemical Society DOI: /acs.jpcb.6b09823 J. Phys. Chem. B 2016, 120,

2 The Journal of Physical Chemistry B Figure 1. Chemical structures of chiral dopants ISO(6OBA) 2 and S811. reviews, chirality, elasticity, flexoelectricity, fluoro-substituent, and molecular biaxiality are the important factors responsible for BP stabilization. Schiff base (azomethine) has been widely utilized as a linking group in the synthesis of many types of LC molecules. 22 Its derivative, salicylaldimine[n-(2-hydroxy-4-alkoxybenzylidene) aniline], possesses a quasi-six-membered ring resulting from intramolecular hydrogen (H)-bonding between the H-atom of the hydroxy group and the nitrogen (N)-atom of the imine linkage and thus exhibits more stability to moisture and heat than that of Schiff base analogues. With their synthetic versatility and ability to coordinate metals, they have also been applied in metallomesogens. Generally, nematic and/or Article smectic mesophases are present in achiral rodlike Schiff base mesogens. New phase sequences and frustrated mesophases could be discovered by introducing asymmetric carbon centers in the form of chiral alkyl tails or presenting within Schiff base molecular structures. For example, the first chiral metallomesogen, a monosubstituted ferrocene-based Schiff base derivative tethering (S)-2-methylbutoxy tail, 23 exhibited two frustrated phases, BP and TGBA* phases. Moreover, enantiotropic BPIII with a broad temperature range (22 K) could be presented in an unsymmetrical Schiff base, linking dimers featuring an achiral bent core tethered to a cholesteryl ester segment through a flexible odd-parity spacer. 24 Yelamagged et al. also reported that the symmetric Schiff base dimer with (R)-2-octyloxy tail exhibited a cubic BP range with approximately 9 K. 25 In addition, they also prepared chiral ferroelectric Schiff base mesogens possessing BPs with less than 1K. 26,27 Recently, Takezoe et al. also prepared an asymmetric dimer with a wide BP range using a flexible spacer with nine carbons to link a rodlike Schiff base mesogen and a cholesterol mesogenic unit. 28 On the other hand, some bent-core molecules with Schiff base linkage have also been utilized to blend with conventional nematic LCs to induce or stabilize BPs and decrease the formation temperature of BPs even though they could not exhibit BPs as a single molecular form. 29 It suggested that the bent-core molecules possessing biaxialities and small bend elastic constants could enhance twisting power in the N* phase and stabilize DTC structures. 9,33,34 For instance, Takezoe et al. reported an amorphous BPIII material with a wide thermal range ( 20 K), and a large electrooptical Kerr effect was induced by doping a Schiff base bent-core molecule and a high-helical twisting power (HTP) chiral dopant ISO(6OBA) Meanwhile, Takezoe and Choi et al. incorporated azo linkage into the Schiff base bent-core Scheme 1. Synthetic Route of Rodlike Racemic Schiff Base Mesogens DOI: /acs.jpcb.6b09823 J. Phys. Chem. B 2016, 120,

3 The Journal of Physical Chemistry B Article Table 1. Phase Transition Temperature and Corresponding Transition Enthalpies of Salicylaldimine-Based Mesogens a phase sequence b ( C, ΔH/kJ mol 1 ) compounds cooling heating OH-TI (1.4) N (1.9) SmC 80.1 (3.3) CrG 70.8 (1.0) CrH Cr 86.0 (21.5) SmC (2.5) N (1.3) OH-TI (1.0) N (1.7) SmC 81.2 (1.8) CrG 75.9 (1.4) CrH Cr 82.2 (13.8) SmC (2.1) N (0.8) OH-TI (1.0) N (2.2) SmC 84.3 (2.2) CrG 78.0 (1.4) CrH Cr 84.2 (13.7) SmC (2.2) N (1.2) OH-TII (0.79) N 72.9 (1.51) SmC 52.5 (0.62) CrG 48.5 (0.73) CrH Cr 72.3 (49.4) N (0.7) OH-TII (1.03) N 84.5 (1.45) SmC 61.8 (0.72) CrG 59.3 (0.51) CrH 41.5 (0.81) Cr Cr 47.5 (9.6) CrH (0.6) CrG (0.6) SmC (1.4) N (1.0) OH-TII (0.84) N 72.9 (1.39) SmC 52.6 (0.65) CrG 48.7 (0.73) CrH Cr 62.3 (47.2) SmC 89.6 (1.4) N (0.7) OH-EI (0.86) N 81.8 (1.17) SmC 34.4 (0.05) Cr Cr 65.9 (18.4) SmC 81.3 (1.1) N (0.9) OH-EI (1.06) N 95.1 (1.99) SmC 41.7 (0.31) Cr Cr 77.3 (25.0) SmC 96.0 (2.0) N (1.0) OH-EI (1.07) N (1.64) SmC 51.3 (16.6) Cr Cr 76.1 (25.0) SmC (1.7) N (1.0) OH-EII (0.62) N 54.0 (0.83) SmC <20 Cr Cr 60.4 (28.3) N (0.6) OH-EII (1.06) N 68.5 (1.06) SmC <20 Cr Cr 55.9 (31.0) SmC 68.4 (1.1) N (1.0) OH-EII (0.99) N 76.1 (1.29) SmC 22.7 (0.06) Cr Cr 51.9 (22.0) SmC 76.6 (1.2) N (0.6) a Peak temperature in the DSC profiles obtained during the second heating and cooling cycles at a rate of 3 C min 1. b N, nematic; SmC, smectic C; CrG, soft crystal G; CrH, soft crystal H. structure to obtain a new photoresponsive bent-core molecule. 20 The UV stimulus can convert a chiral nematic phase into a cubic BP through its photoisomerization. However, only a few racemic rodlike Schiff base molecules were utilized to induce BPs. Recently, we prepared a series of chiral and racemic rodlike Schiff base mesogens with tolane moiety. 35 Notably, they possess two specific soft crystal phases that could be confirmed by the polarized optical microscopy (POM) texture and variable-temperature X-ray diffraction (XRD). Additionally, they could be applied in the stabilization of the BP temperature range by adding chiral dopant ISO(6OBA) 2, S811, orr811. In general, BPs can be induced by adding chiral dopant R811 or S811 into racemic salicylaldimine-based mesogens. In addition, BPs are not stabilized in these binary mixture systems composed of the Schiff base mesogens possessing alkynyl linkage and no hydroxyl group. Among these binary mixture systems, the widest temperature range of cubic BP (35 K) can be induced by adding rodlike chiral dopant R811 or S811 into rodlike racemic salicylaldimine-based mesogens. By molecular modeling, it can be suggested that the appearance and temperature range of BPs are affected by the dipole moment and biaxiality of molecular geometry. Accordingly, we demonstrated that the hydroxyl group and the methyl branch in this type of Schiff base mesogen play important roles in the stabilization of BPs. In this work, four series of racemic Schiff base mesogens possessing terminal alkoxy/alkyl chains, two types of linkages between two rigid cores, and a hydroxyl group at the inner-core position were prepared. Subsequently, these Schiff base mesogens are doped with variable ratios of chiral dopants S811 and ISO(6OBA) 2 (Figure 1) to investigate the effect of functional groups on the stabilization of BP. In addition, we also prepared racemic Schiff base compounds H-TII n, H-EI n, and H-EII n, which are structurally similar to their respective salicylaldiminebased analogues in the absence of intramolecular hydrogen bonding, to further investigate the effect of the intramolecular hydrogen bonding between the hydroxyl group and the imine group on the stabilization of BPs in a blending mixture system. Furthermore, to understand the reasons of BP stabilization, we utilize molecular modeling calculation for these types of Schiff base mesogens to find the correlation between BP stabilization and structural variations. 2. EXPERIMENTAL SECTION 2.1. Spectroscopic Analysis. The chemical structure of the target materials was identified by proton nuclear magnetic resonance ( 1 H NMR) spectroscopy using a Bruker Avance DRX 500 NMR spectrometer (Bruker Co., Karlsruhe, Germany). The purity of the final compounds was assessed by thin layer chromatography (TLC) and further confirmed by elemental analysis using a Heraeus Vario EL III analyzer (Elementar Analysenyteme GmbH Co., Hanau, Germany). The carbon and hydrogen analytical data were in agreement with the calculated results within ±1%. Variable-temperature XRD experiments were performed at wiggler beamline BL17A in the National Synchrotron Radiation Research Center, Taiwan. The experimental wavelength is Å, and the sample was packed into a 0.5 mm capillary. A heat gun was equipped at this beamline, and the temperature controller was programmable by a PC with a PID feedback system. The experimental XRD pattern was indexed by the DICVOL program to obtain the crystal system and cell constants DOI: /acs.jpcb.6b09823 J. Phys. Chem. B 2016, 120,

4 The Journal of Physical Chemistry B Article Figure 2. Microphotographs of compound OH-TII 6 : (a) N texture at C, (b) N SmC texture at 73.2 C, (c) SmC texture at 65.0 C, (d) CrG texture at 50.0 C, (e) CrG CrH texture at 48.5 C, and (f) CrH texture at 37.5 C. Table 2. Phase Transition Temperature and Corresponding Transition Enthalpies of Schiff Base Mesogens a phase sequence b ( C, ΔH/kJ mol 1 ) compounds cooling heating H-TII (0.59) N (4.42) SmC (0.06) CrG 81.2 (0.88) CrH CrH 81.3 (0.9) SmC (4.9) N (0.6) H-EI (0.65) N (0.48) SmC 40.0 (13.56) Cr (0.2) Cr 2 Cr 67.4 (21.4) SmC (0.5) N (0.6) H-EI (0.89) N (0.65) SmC 40.1 (20.12) Cr Cr 68.9 (29.0) SmC (0.6) N (0.8) H-EI (0.96) N (0.39) SmC 58.9 (4.65) Cr (27.38) Cr 2 Cr 73.8 (39.0) SmC (0.4) N (0.9) H-EII (0.69) N 72.9 (0.95) SmC 33.3 (0.70) CrG 29.0 (0.29) CrH Cr 64.9 (18.2) SmC (1.0) N (0.6) H-EII (0.71) N 84.1 (0.65) SmC 35.1 (0.65) CrG 28.4(0.20) CrH Cr 57.8 (29.1) SmC 85.0 (0.6) N (0.6) H-EII (0.53) N 90.0(0.65) SmC 38.5(0.45) CrG 28.4 (0.13) CrH Cr 15.6 (0.2) SmC 48.4 (17.1) N (0.4) a Peak temperature in the DSC profiles obtained during the second heating and cooling cycles at a rate of 3 C min 1. b N, nematic; SmC, smectic C; CrG, soft crystal G; CrH, soft crystal H. Table 3. Cell Transformation of the Standard Monoclinic Setting in Compound OH-TII 6 at CrH Phase unit cell a (Å) b (Å) c (Å) α (deg) β (deg) γ (deg) volume standard 25.58(6) 4.393(6) 5.607(8) (1) (7) transformation 4.393(6) 5.607(8) 25.58(6) 96.0(1) (7) hkl index transformation standard (100) (200) (201 ) (301 ) (301) (401 ) (010) (501 ) transformation (001) (002) (01 2) (01 3) (013) (01 4) (101) (01 5) Q value Liquid-Crystalline and Physical Properties. The initial phase sequence and corresponding transition temperature of the compounds were determined by POM. Mesophases were principally identified by the microscopic texture of the materials sandwiched between two glass plates under a crossed polarizing microscope using Nikon Microphoto-FXA optical microscopy in conjunction with a hot stage controlled by a control processor. The phase transition temperatures and the corresponding phase transition enthalpies of compounds were determined by differential scanning calorimetery (DSC) using PerkinElmer Diamond calorimeter under a running rate of 3 C min 1. The Bragg reflection spectra of BPs were examined with a USB2000 spectrometer in reflection mode, and the temperature of the samples was controlled accurately by the hot stage Preparation of Materials. All of the starting materials were purchased from Sigma-Aldrich with purity greater than 99%. TLC was performed using TLC sheets coated with silica; spots were detected by UV irradiation. Silica gel (Merck silica gel 60, mesh) was used for column chromatography. The organic solvents were dried and distilled before use. The Schiff base mesogens were synthesized according to Scheme 1. 1-Ethynyl-4-(alkyloxy)benzene 39 and 1-ethynyl-4-alkylbenzene 40 were synthesized according to the procedure mentioned in the literature. The intermediates, compounds c, and 4-(1- methylheptoxy)aniline were synthesized by our currently DOI: /acs.jpcb.6b09823 J. Phys. Chem. B 2016, 120,

5 The Journal of Physical Chemistry B Article Figure 3. Variable-temperature XRD measurements of compound OH-TII 6. Figure 4. Microphotographs of compound H-EII 8 : (a) N texture at 91.0 C, (b) N SmC texture at 80.9 C, (c) SmC texture at 67.9 C, (d) CrG texture at 36.0 C, and (e) CrH texture at 24.0 C DOI: /acs.jpcb.6b09823 J. Phys. Chem. B 2016, 120,

6 The Journal of Physical Chemistry B Article Figure 5. Phase diagrams of (a) OH-TI 6, (b) OH-TI 7, and (c) OH-TI 8 when doped with different ratios of chiral dopant S811 at a cooling rate of 0.5 C min 1. BP, N*, SmX*, and Cr indicate blue phase, cholesteric phase, smectic phase, and crystal phase, respectively. Figure 6. Phase diagrams of (a) OH-TII 6, (b) OH-TII 7, and (c) OH-TII 8 when doped with different ratios of chiral dopant S811 at a cooling rate of 0.5 C min 1. Figure 7. Phase diagrams of (a) OH-EI 6, (b) OH-EI 7, and (c) OH-EI 8 when doped with different ratios of chiral dopant S811 at a cooling rate of 0.5 C min 1. reported method. 35 In addition, compounds OH-TI 7 and H- TI 7 have been prepared and characterized according to our previously reported method. Chemical characterization data of new Schiff base mesogens are provided below Synthesis of Racemic Schiff Base Compounds. A mixture of compound a d (0.90 mmol) and 4-(1- methylheptoxy)aniline (1.10 mmol) in mixed solvent of ethanol (10 ml) was refluxed for 4 h. After cooling to room temperature, a yellow precipitate was obtained and collected by filtration. The crude product was further purified by repeated recrystallization from ethanol to give a yellow powder in 80 85% yield. Compound OH-EI 6 : 1 H NMR (CDCl 3 ): δ (ppm) (s, Ar-OH, 1H), 8.61 (s, CH N, 1H), 8.13 (d, Ar-H, 2H, J = DOI: /acs.jpcb.6b09823 J. Phys. Chem. B 2016, 120,

7 The Journal of Physical Chemistry B Article Figure 8. Phase diagrams of (a) OH-EII 6, (b) OH-EII 7, and (c) OH-EII 8 when doped with different ratios of chiral dopant S811 at a cooling rate of 0.5 C min 1. Figure 9. Phase diagrams of (a) H-EI 6, (b) H-EI 7, and (c) H-EI 8 when doped with different ratios of chiral dopant S811 at a cooling rate of 0.5 C min 1. Figure 10. Phase diagrams of (a) H-EII 6, (b) H-EII 7, and (c) H-EII 8 when doped with different ratios of chiral dopant S811 at a cooling rate of 0.5 C min Hz), 7.40 (d, Ar-H, 1H, J = 8.4 Hz), 7.25 (d, Ar-H, 2H, J = 8.8 Hz), 6.97 (d, Ar-H, 2H, J = 8.9 Hz), 6.94 (d, Ar-H, 2H, J = 9.0 Hz), 6.88 (d, Ar-H, 1H), 6.82 (dd, Ar-H, 1H, J = 2.5 Hz, J = 2.0 Hz), (m, OCH, 1H), 4.05 (t, OCH 2, 2H, J = 6.5 Hz), (m, CH 2, CH 3, 21H), 0.91 (m, CH 3, 6H). 13 C NMR (CDCl 3 ): 164.4, 163.6, 162.4, 159.4, 157.6, 154.4, 140.8, 132.7, 132.3, 122.3, 121.2, 117.3, 116.5, 114.3, 112.9, 110.5, 74.3, 68.3, 36.4, 31.8, 31.5, 29.3, 29.0, 25.6, 25.5, 22.6, 19.7, 14.1, FT-IR (KBr): 3421, 2927, 2856, 1720, 1612, 1508, 1464, 1252 cm 1. Elemental analysis for C 34 H 43 NO 5 (%): calcd C, 74.83, H, 7.94, N, 2.57; found C, 74.96, H, 7.70, N, DOI: /acs.jpcb.6b09823 J. Phys. Chem. B 2016, 120,

8 The Journal of Physical Chemistry B Article Table 4. Phase Transitions in Compounds OH-EI n and OH-EII n Doped with Different Ratios of Chiral Dopant ISO(6OBA) 2 at a Cooling Rate of 0.5 C min 1a compound wt % b phase behavior c ΔBP (K) compound wt % b phase behavior c ΔBP (K) OH-EI 6 OH-EI 7 OH-EI 8 5 N* 10 N* 15 N* 5 N* 10 N* XooooY N* XooooY 0.0 XooooY 0.0 OH-EII 6 10 N* XoooY BP XoooY XooooY N* XoooY BP XoooY XooooY N* XooooY 0.0 OH-EII 7 10 N* XooooY XooooY N* XooooY BP XooooY N* XooooY N* 10 N* 15 N* XooooY N* XooooY 0.0 OH-EII 8 10 N* XoooY BP XoooY XoooY a, isotropic; BP, blue phase; N*, chiral nematic. b ±0.5 wt %. c ±0.5 C XooooY N* BP Table 5. Phase Transitions in Compounds OH-EI n and OH-EII n Doped with Different Ratios of Chiral Dopant ISO(6OBA) 2 at a Cooling Rate of 0.5 C min 1a compound wt % b phase behavior c ΔBP (K) compound wt % b phase behavior c ΔBP (K) H-EI 6 H-EI 7 H-EI 8 5 N* XooooY N* 10 N* XooooY BP XooooY 7.1 H-EII 6 10 N* XoooY BP X Y N* XooooY BP XooooY N* X Y 5 N* XooooY N* XooooY ooo ooo XooooY N* XooooY BP XooooY 3.8 H-EII 7 10 N* XooooY N* XoooY BP XooooY N* XoooY BP X Y 5 N* XooooY N* 10 N* XoooY BP XooooY 22.8 H-EII 8 10 N* XoooY BP X Y N* XoooY BP XooooY N* X Y a, isotropic; BP, blue phase; N*, chiral nematic. b ±0.5 wt %. c ±0.5 C ooo XooooY ooo ooo Compound OH-EI 7 : 1 H NMR (CDCl 3 ): δ (ppm) (s, Ar-OH, 1H), 8.62 (s, CH N, 1H), 8.15 (d, Ar-H, 2H, J = 9.0 Hz), 7.41 (d, Ar-H, 1H, J = 8.5 Hz), 7.31 (d, Ar-H, 2H, J = 9.0 Hz), 6.98 (d, Ar-H, 2H, J = 8.5 Hz), 6.94 (d, Ar-H, 2H, J = 9.0 Hz), 6.89 (d, Ar-H, 1H), 6.82 (dd, Ar-H, 1H, J = 2.5 Hz, J = 2.0 Hz), (m, OCH, 1H), 4.06 (t, OCH 2, 2H, J = 6.5 Hz), (m, CH 2, CH 3, 23H), 0.91 (m, CH 3, 6H). 13 C NMR (CDCl 3 ): 164.4, 163.6, 162.4, 159.4, 157.6, 154.4, 140.8, , 132.4, 122.3, 121.2, 117.3, 116.5, 114.3, 112.9, 110.5, 74.3, 68.3, 36.4, 31.8, 31.7, 29.3, 29.1, 29.0, 25.9, 25.5, 22.6, 19.7, FT-IR (KBr): 3423, 2927, 2854, 1728, 1600, 1579, 1466, 1246 cm 1. Elemental analysis for C 35 H 45 NO 5 (%): calcd C, 75.10, H, 8.10, N, 2.50; found C, 75.27, H, 8.14, N, Compound OH-EI 8 : 1 H NMR (CDCl 3 ): δ (ppm) (s, Ar-OH, 1H), 8.62 (s, CH N, 1H), 8.15 (d, Ar-H, 2H, J = 9.0 Hz), 7.41 (d, Ar-H, 1H, J = 8.5 Hz), 7.31 (d, Ar-H, 2H, J = 9.0 Hz), 6.98 (d, Ar-H, 2H, J = 8.5 Hz), 6.94 (d, Ar-H, 2H, J = 9.0 Hz), 6.90 (d, Ar-H, 1H), 6.82 (dd, Ar-H, 1H, J = 2.5 Hz, J = 2.0 Hz), (m, OCH, 1H), 4.06 (t, OCH 2, 2H, J = 6.5 Hz), (m, CH 2 -, CH 3, 25H), 0.91 (m, CH 3, 6H). 13 C NMR (CDCl 3 ): 164.4, 163.6, 162.4, 159.3, 157.6, 154.4, , 132.7, 132.3, 122.3, 121.2, 117.3, 116.5, 114.3, 112.9, 110.5, 74.3, 68.3, 36.4, 31.77, 29.3, 29.2, 26.0, 25.5, 25.1, 22.6, 22.5, 19.7, FT-IR (KBr): 3452, 2925, 2856, 1728, DOI: /acs.jpcb.6b09823 J. Phys. Chem. B 2016, 120,

9 The Journal of Physical Chemistry B Article Figure 11. (a) Typical reflectance profiles of the higher-temperature phase (black line) and the lower-temperature phase (gray line). (b) Temperature dependence of the Bragg reflection wavelength. (c) Microphotographs of the blending mixture system consisting of OH-TII % S811 on cooling at a rate of 0.5 C min , 1574, 1464, 1248 cm 1. Elemental analysis for C 36 H 47 NO 5 (%): calcd C, 75.36, H, 8.26, N, 2.44; found C, 75.48, H, 8.33, N, Compound H-EI 6 : 1 H NMR (CDCl 3 ): δ (ppm) 8.50 (s, CH N, 1H), 8.16 (d, Ar-H, 2H, J = 8.7 Hz), 7.96 (d, Ar- H, 2H, J = 8.6 Hz), 7.33 (d, Ar-H, 2H, J = 8.6 Hz), 7.23 (d, Ar- H, 2H, J = 8.9 Hz), 6.99 (d, Ar-H, 2H, J = 9.1 Hz), 6.93 (d, Ar- H, 2H, J = 8.9 Hz), 4, (m, OCH, 1H), 4.06 (t, CH 2, 2H, J = 6.5 Hz), (m, CH 2, 2H), (m, CH 2, CH 3, 19H), (m, CH 3, 6H). 13 C NMR (CDCl 3 ): 164.6, 163.7, 157.0, 153.2, 144.5, 134.1, 132.3, , 121.2, 116.4, 114.3, 74.3, 68.3, 36.5, 31.8, 31.7, 29.3, 29.1, 29.0, 25.9, 25.5, 22.6, 19.8, FT-IR (KBr): 2925, 2854, 1726, 1602, 1506, 1265, 1163, 1119 cm 1. Elemental analysis for C 36 H 47 NO 4 (%): calcd C, 77.09, H, 8.18, N, 2.64; found C, 77.22, H, 8.27, N, Compound H-EI 7 : 1 H NMR (CDCl 3 ): δ (ppm) 8.50 (s, CH N, 1H), 8.16 (d, Ar-H, 2H, J = 8.8 Hz), 7.96 (d, Ar- H, 2H, J = 8.6 Hz), 7.33 (d, Ar-H, 2H, J = 8.6 Hz), 7.23 (d, Ar- H, 2H, J = 8.8 Hz), 6.99 (d, Ar-H, 2H, J = 9.0 Hz), 6.93 (d, Ar- H, 2H, J = 9.0 Hz), (m, OCH, 1H), 4.06 (t, CH 2, 2H, J = 6.6 Hz), (m, CH 2, 2H), (m, CH 2, CH 3, 21H), (m, CH 3, 6H). 13 C NMR (CDCl 3 ): 164.6, 163.7, 157.0, 153.2, 144.5, 134.1, 132.3, 129.7, 122.2, 121.2, 116.4, , 74.3, 68.3, 36.5, 31.8, 31.7, 29.3, 29.1, 29.0, 25.9, 25.5, 22.6, 19.8, FT-IR (KBr): 2925, 2854, 1726, 1602, 1506, 1265, 1166, 1119 cm 1. Elemental analysis for C 36 H 47 NO 4 (%): calcd C, 77.31, H, 8.34, N, 2.58; found C, 77.42, H, 8.31, N, Compound H-EI 8 : 1 H NMR (CDCl 3 ): δ (ppm) 8.50 (s, CH N, 1H), 8.16 (d, Ar-H, 2H, J = 8.9 Hz), 7.96 (d, Ar- H, 2H, J = 8.7 Hz), 7.33 (d, Ar-H, 2H, J = 8.6 Hz), 7.23 (d, Ar- H, 2H, J = 8.9 Hz), 6.99 (d, Ar-H, 2H, J = 9.0 Hz), 6.93 (d, Ar- H, 2H, J = 8.8 Hz), (m, OCH, 1H), 4.06 (t, CH 2, 2H, J = 6.5 Hz), (m, CH 2, CH 3, 25H), (m, CH 3, 6H). 13 C NMR (CDCl 3 ): 164.6, 163.7, 157.0, 153.2, 144.5, 134.1, 132.3, 129.7, 122.2, 121.2, 116.4, 114.3, 74.3, 68.3, 36.5, 31.8, 29.3, 29.2, 29.1, 25.6, 25.5, 22.6, 22.6, 19.8, FT-IR (KBr): 2925, 2854, 1726, 1602, 1506, 1265, 1163, 1119 cm 1. Elemental analysis for C 36 H 47 NO 4 (%): calcd C, 77.52, H, 8.49, N, 2.51; found C, 77.60, H, 8.33, N, Compound OH-EII 6 : 1 H NMR (CDCl 3 ): δ (ppm) (s, Ar-OH, 1H), 8.63 (s, CH N, 1H), 8.12 (d, Ar-H, 2H, J = 8.2 Hz), 7.42 (d, Ar-H, 1H, J = 8.5 Hz), 7.33 (d, Ar-H, 2H, J = 8.2 Hz), 7.27 (d, Ar-H, 2H, J = 8.7 Hz), 6.94 (d, Ar-H, 2H, J = 8.8 Hz), 6.88 (d, Ar-H, 1H, J = 2.1 Hz), 6.82 (dd, Ar-H, 1H, J = 8.4 Hz, J = 2.1 Hz), (m, OCH, 1H), 2.71 (t, CH 2, 2H, J = 7.7 Hz), (m, CH 2, CH 3, 21H), (m, CH 3, 6H). 13 C NMR (CDCl 3 ): 164.7, 162.4, 159.3, 157.6, 154.3, 149.6, 140.7, 132.7, 130.3, 128.7, 126.7, 122.3, 117.4, 116.5, 113.0, 110.5, 74.3, 36.4, 36.1, 31.8, 31.6, 31.1, 29.1, 28.9, 25.5, 22.6, 19.7, FT-IR (KBr): 3440, 2925, 2850, 1726, 1614, 1508, 1265, 1180, 1119 cm DOI: /acs.jpcb.6b09823 J. Phys. Chem. B 2016, 120,

10 The Journal of Physical Chemistry B Article Figure 12. (a) Typical red-shift reflectance profiles during the cooling process. (b) Temperature dependence of the Bragg reflection wavelength. (c) Microphotographs of the blending mixture system OH-EI % S811 upon cooling at a rate of 0.5 C min 1. Elemental analysis for C 34 H 43 NO 4 (%): calcd C, 77.09, H, 8.18, N, 2.64; found C, 77.02, H, 8.10, N, Compound OH-EII 7 : 1 H NMR (CDCl 3 ): δ (ppm) (s, Ar-OH, 1H), 8.63 (s, CH N, 1H), 8.12 (d, Ar-H, 2H, J = 8.3 Hz), 7.42 (d, Ar-H, 1H, J = 8.5 Hz), 7.33 (d, Ar-H, 2H, J = 8.3 Hz), 7.27 (d, Ar-H, 2H, J = 8.8 Hz), 6.94 (d, Ar-H, 2H, J = 9.0 Hz), 6.88 (d, Ar-H, 1H, J = 2.3 Hz), 6.82 (dd, Ar-H, 1H, J = 8.4 Hz, J = 2.3 Hz), (m, OCH, 1H), 2.71 (t, CH 2, 2H, J = 7.7 Hz), (m, CH 2, CH 3, 23H), 0.90 (t, CH 3, 6H, J = 6.9 Hz). 13 C NMR (CDCl 3 ): 164.7, 162.4, 159.3, 157.6, 154.3, 149.6, 140.7, 132.7, 130.3, 128.7, 126.7, 122.3, 117.4, 116.5, 112.9, 110.5, 74.3, 36.4, 36.1, 31.8, 31.1, 29.3, 29.2, 29.1, 25.5, 22.6, 22.5, 19.7, FT-IR (KBr): 3440, 2924, 2852, 1726, 1614, 1508, 1265, 1180, 1119 cm 1. Elemental analysis for C 35 H 45 NO 4 (%): calcd C, 77.31, H, 8.34, N, 2.58; found C, 77.36, H, 8.39, N, Compound OH-EII 8 : 1 H NMR (CDCl 3 ): δ (ppm) (s, Ar-OH, 1H), 8.63 (s, CH N, 1H), 8.12 (d, Ar-H, 2H, J = 8.1 Hz), 7.42 (d, Ar-H, 1H, J = 8.4 Hz), 7.33 (d, Ar-H, 2H, J = 8.2 Hz), 7.27 (d, Ar-H, 2H, J = 8.8 Hz), 6.94 (d, Ar-H, 2H, J = 8.9 Hz), 6.89 (d, Ar-H, 1H, J = 2.1 Hz), 6.82 (dd, Ar-H, 1H, J = 8.4 Hz, J = 2.2 Hz), (m, OCH, 1H), 2.71 (t, CH 2, 2H, J = 7.7 Hz), (m, CH 2, CH 3, 25H), 0.90 (t, CH 3, 6H, J = 6.8 Hz). 13 C NMR (CDCl 3 ): 164.9, 157.0, 156.9, 153.1, 149.6, 144.5, 134.1, 130.3, 129.7, 128.7, 126.6, 122.2, 122.3, 116.4, 74.3, 36.5, 36.1, 31.8, 31.8, 31.1, 29.4, 29.3, 29.2, 25.5, 22.6, 22.6, 19.8, FT-IR (KBr): 3440, 2924, 2852, 1726, 1614, 1508, 1267, 1180, 1119 cm 1. Elemental analysis for C 36 H 47 NO 4 (%): calcd C, 77.52, H, 8.49, N, 2.51; found C, 77.43, H, 8.41, N, Compound H-EII 6 : 1 H NMR (CDCl 3 ): δ (ppm) 8.50 (s, CH N, 1H), 8.13 (d, Ar-H, 2H, J = 8.2 Hz), 7.96 (d, Ar- H, 2H, J = 8.6 Hz), 7.33 (dd, Ar-H, 4H, J = 8.5 Hz, J = 1.9 Hz), 7.23 (d, Ar-H, 2H, J = 8.8 Hz), 6.93 (d, Ar-H, 2H, J = 8.8 Hz), (m, OCH, 1H), 2.72 (t, CH 2, 2H, J = 7.7 Hz), (m, CH 2, CH 3, 21H), (m, CH 3, 6H). 13 C NMR (CDCl 3 ): 164.9, 157.0, 156.9, 153.1, 149.6, 144.5, 134.1, 130.3, 129.7, 128.7, 126.6, 122.2, 122.1, 116.4, 74.3, 36.5, 36.1, 31.8, 31.6, 31.1, 29.3, 28.9, 25.5, 22.6, 22.5, 19.8, FT-IR (KBr): 2925, 2850, 1728, 1606, 1504, 1273, 1198, 1110 cm 1. Elemental analysis for C 34 H 43 NO 3 (percent): calcd C, 79.49, H, 8.44, N, 2.73; found C, 79.35, H, 8.48, N, Compounds H-EII 7 : 1 H NMR (CDCl 3 ): δ (ppm) 8.50 (s, CH N, 1H), 8.13 (d, Ar-H, 2H, J = 8.1 Hz), 7.96 (d, Ar- H, 2H, J = 8.7 Hz), 7.33 (dd, Ar-H, 4H, J = 8.6 Hz, J = 1.75 Hz), 7.23 (dd, Ar-H, 2H, J = 8.5 Hz, J = 0.6 Hz), 6.93 (d, Ar-H, 2H, J = 8.8 Hz), (m, OCH, 1H), 2.71 (t, CH 2, 2H, J = 7.7 Hz), (m, CH 2, CH 3, 23H), 0.90 (t, CH 3, 6H, J = 6.8 Hz). 13 C NMR (CDCl 3 ): 164.9, 157.0, 156.9, 153.1, 149.6, 144.4, 134.1, 130.3, 129.7, 128.7, 126.6, 122.2, 122.1, 116.4, 74.3, 36.5, 36.1, 31.8, 31.7, 31.1, 29.3, 29.2, 29.1, 25.5, 22.6, 22.6, 19.7, FT-IR (KBr): 2925, 2850, 1738, 1610, 1502, 1257, 1198, 1057 cm 1. Elemental analysis for C 35 H 45 NO 3 (%): calcd C, 79.66, H, 8.59, N, 2.65; found C, 79.53, H, 8.41, N, DOI: /acs.jpcb.6b09823 J. Phys. Chem. B 2016, 120,

11 The Journal of Physical Chemistry B Article Figure 13. (a) Temperature dependence of the Bragg reflection wavelength. (b) Microphotographs of the blending mixture consisting of OH-EII % S811 during the cooling process at a rate of 0.5 C min 1. Compounds H-EII 8 : 1 H NMR (CDCl 3 ): δ (ppm) 8.50 (s, CH N, 1H), 8.13 (d, Ar-H, 2H, J = 8.1 Hz), 7.96 (d, Ar- H, 2H, J = 8.5 Hz), 7.33 (dd, Ar-H, 4H, J = 8.0 Hz, J = 0.9 Hz), 7.23 (d, Ar-H, 2H, J = 8.7 Hz), 6.93 (d, Ar-H, 2H, J = 8.8 Hz), (m, OCH, 1H), 2.71 (t, CH 2, 2H, J = 7.7 Hz), (m, CH 2, CH 3, 25H), 0.90 (t, CH 3, 6H, J = 6.8 Hz). 13 C NMR (CDCl 3 ): 164.9, 157.0, 156.9, 153.1, 149.6, 144.5, 134.1, 130.3, 129.7, 128.7, 126.6, 122.2, 122.3, 116.4, 74.3, 36.5, 36.1, 31.8, 31.8, 31.1, 29.4, 29.3, 29.2, 25.5, 22.6, 22.6, 19.8, FT-IR (KBr): 2922, 2854, 1726, 1608, 1506, 1265, 1178, 1119 cm 1. Elemental analysis for C 36 H 47 NO 3 (%): calcd C, 79.81, H, 8.74, N, 2.59; found C, 79.62, H, 8.89, N, Compounds OH-TI 6 : 1 H NMR (CDCl 3 ): δ (s, Ar- OH, 1H), 8.60 (s, CH N, 1H), 7.48 (d, Ar-H, 1H, J = 8.4 Hz), 7.33 (d, Ar-H, 2H, J = 8.4 Hz), 7.27 (d, Ar-H, 2H, J = 8.4 Hz), 7.15 (s, Ar-H, 1H), 7.07 (dd, Ar-H, 1H, J = 7.8 Hz, J = 1.2 Hz), 6.94 (d, Ar-H, 2H, J = 8.4 Hz), 6.89 (d, Ar-H, 2H, J = 8.4 Hz), (m, OCH*, 1H), 3.99 (t, OCH 2, 2H, J = 6.6 Hz), (m, CH 2, CH 3, 21H), 0.91 (m, CH 3, 6H). 13 C NMR (CDCl 3 ): 160.7, 159.5, 159.2, 157.7, 140.8, 133.3, 131.7, 127.7, 122.4, 122.2, , 119.1, 116.5, 114.7, 114.6, 92.0, 88.0, 74.3, 68.1, 36.5, 31.8, 31.6, 29.3, 29.2, 25.7, 25.5, 22.6, 19.7, FT-IR (KBr): 3444, 2932, 2858, 2206, 1602, 1516, 1496, 1287, 1245 cm 1. Elemental analysis for C 35 H 43 NO 3 (%): calcd C, 79.96, H, 8.24, N, 2.66; found C, 79.87, H, 8.16, N, Compound OH-TI 8 : 1 H NMR (CDCl 3 ): δ (s, Ar-OH, 1H), 8.61 (s, CH N, 1H), 7.48 (d, Ar-H, 1H, J = 8.4 Hz), 7.33 (d, Ar-H, 2H, J = 8.4 Hz), 7.27 (d, Ar-H, 2H, J = 8.4 Hz), 7.15 (s, Ar-H, 1H), 7.07 (dd, Ar-H, 1H, J = 8.4 Hz, J = 1.2 Hz), 6.94 (d, Ar-H, 2H, J = 8.4 Hz), 6.89 (d, Ar-H, 2H, J = 8.4 Hz), (m, OCH*, 1H), 4.00 (t, OCH 2, 2H, J = 6.6 Hz), (m, CH 2, CH 3, 25H), 0.90 (m, CH 3, 6H). 13 C NMR (CDCl 3 ): 160.7, 159.5, 159.2, 157.7, 140.8, 133.3, 131.7, 127.7, 122.4, 122.2, 119.7, 119.1, 116.5, 114.7, 114.6, 92.0, 88.0, 74.3, 68.1, 36.5, 31.8, 31.6, 29.3, 29.2, 25.7, 25.5, 22.6, 19.7, FT-IR (KBr): 3436, 2929, 2856, 2206, 1615, 1517, 1496, 1288, 1245 cm 1. Elemental analysis for C 37 H 47 NO 3 (%): calcd C, 80.25, H, 8.55, N, 2.53; found C, 80.36, H, 8.66, N, Compound OH-TII 6 : 1 H NMR (CDCl 3 ): δ (ppm) (s, Ar-OH, 1H), 8.61 (s, CH N, 1H), 7.47 (d, Ar-H, 2H, J = 8.1 Hz), 7.34 (d, Ar-H, 1H, J = 8.0 Hz), 7.28 (d, Ar-H, 2H, J = 7.2 Hz), 7.18 (d, Ar-H, 2H, J = 8.0 Hz) 7.16 (d, Ar-H, 1H, J = 1.1 Hz), 7.08 (dd, Ar-H, 1H, J = 7.8 Hz, J = 1.4 Hz), 6.94 (d, Ar-H, 2H, J = 8.8 Hz), (m, OCH, 1H), 2.63 (t, OCH 2, 2H, J = 7.8 Hz), (m, CH 2, CH 3, 21H), 0.90 (t, CH 3, 6H, J = 6.8 Hz). 13 C NMR (CDCl 3 ): 160.7, 159.2, , 143.9, 140.8, 131.7, 128.5, 127.5, 122.4, 122.3, 112.0, 119.9, 119.3, 116.5, 92.0, 88.6, 74.3, 36.5, 36.0, 31.8, 31.7, 31.2, 29.3, 28.9, 52.5, 22.6, 19.7, FT-IR (KBr): 3682, 2957, 2924, 2856, 2243, 1616, 1520, 1467, 1380, 1244 cm 1. Elemental analysis for C 35 H 43 NO 2 (%): calcd C, 82.47, H, 8.50, N, 2.75; found C, 82.51, H, 8.43, N, Compound OH-TII 7 : 1 H NMR (CDCl 3 ): δ (ppm) (s, Ar-OH, 1H), 8.61 (s, CH N, 1H), 7.47 (d, Ar-H, 1H, J = 8.0 Hz), 7.34 (d, Ar-H, 2H, J = 7.9 Hz), 7.28 (d, Ar-H, 2H, J = 7.1 Hz), 7.18 (d, Ar-H, 2H, J = 8.2 Hz), 7.16 (d, Ar-H, 1H, J = 1.0 Hz) 7.08 (dd, Ar-H, 1H, J = 7.9 Hz, J = 1.3 Hz), 6.94 (d, Ar-H, 2H, J = 8.8 Hz), (m, OCH, 1H), 2.63 (t, OCH 2, 2H, J = 7.7 Hz), (m, CH 2 -, CH 3, 24H), DOI: /acs.jpcb.6b09823 J. Phys. Chem. B 2016, 120,

12 The Journal of Physical Chemistry B Article Figure 14. (a) Temperature dependence of the Bragg reflection wavelength and (b) typical POM texture of BPs at different temperatures for the blending mixture consisting of H-EI % S811 during the cooling process at a rate of 0.5 C min (m, CH 3, 6H). 13 C NMR (CDCl 3 ): 160.6, 159.2, 157.7, 143.9, 140.7, 131.7, 128.5, 127.4, 122.4, 122.3, 119.9, 119.8, 119.2, 116.5, 91.9, 88.6, 74.3, 36.41, 35.9, 31.8, 31.2, 29.3, 29.2, 29.1, 25.5, 22.6, 22.6, 19.7, FT-IR (KBr): 3672, 2956, 2925, 2851, 2203, 1615, 1506, 1467, 1380, 1244 cm 1. Elemental analysis for C 36 H 45 NO 2 (%): calcd C, 82.65, H, 8.66, N, 2.67; found C, 82.75, H, 8.50, N, Compounds OH-TII 8 : 1 H NMR (CDCl 3 ): δ (ppm) (s, Ar-OH, 1H), 8.61 (s, CH N, 1H), 7.47 (d, Ar-H, 1H, J = 8.0 Hz), 7.34 (d, Ar-H, 2H, J = 8.1 Hz), 7.28 (d, Ar-H, 2H, J = 7.2 Hz), 7.18(d, Ar-H, 2H, J = 8.1 Hz), 7.16 (d, Ar-H, 1H, J = 1.0 Hz), 7.08 (dd, Ar-H, 1H, J = 7.9 Hz, J = 1.3 Hz), 6.94 (d, Ar-H, 2H, J = 8.8 Hz), (m, OCH, 1H), 2.63 (t, OCH 2, 2H, J = 7.8 Hz), (m, CH 2 -, CH 3, 25H), (m, CH 3, 6H). 13 C NMR (CDCl 3 ): 160.6, 159.2, 143.9, 140.7, 131.6, 128.5, 127.4, 122.3, 122.3, 119.9, 119.8, 119.2, 116.5, 91.9, 88.6, 74.3, 36.4, 35.3, 31.8, 31.7, 31.2, 29.4, 29.2, 25.5, 22.6, 22.5, 19.7, FT-IR (KBr): 3672, 2954, 2920, 2848, 2209, 1615, 1506, 1496, 1380, 1243 cm 1. Elemental analysis for C 37 H 47 NO 2 (%): calcd C, 82.64, H, 8.81, N, 2.60; found C, 82.80, H, 8.85, N, Compound H-TII 6 : 1 H NMR (CDCl 3 ): δ (ppm) 8.49 (s, CH N, 1H), 7.87 (d, Ar-H, 2H, J = 8.2 Hz), 7.61 (d, Ar- H, 2H, J = 8.3 Hz), 7.47 (d, Ar-H, 2H, J = 8.1 Hz), 7.24 (dd, Ar-H, 2H, J = 2.4 Hz, J = 2.3 Hz), 7.18 (d, Ar-H, 2H, J = 8.2 Hz), (dd, Ar-H, 2H, J = 2.5 Hz, J = 2.2 Hz), (m, OCH, 1H), 2.63 (t, OCH 2, 2H, J = 7.8 Hz), (m, CH 2, CH 3, 21H), (m, CH 3, 6H). 13 C NMR (CDCl 3 ): 157.2, 144.4, 143.8, 135.6, 131.6, 131.5, 128.6, , 126.1, 122.3, 120.1, 119.4, 92.0, 88.7, 74.3, 36.5, 36.0, 31.8, 31.7, 31.2, 29.3, 29.0, 25.6, 22.6, 19.8, FT-IR (KBr): 3436, 2929, 2856, 2206, 1615, 1517, 1496, 1288, 1245 cm 1. Elemental analysis for C 35 H 43 NO (%): calcd C, 85.14, H, 8.78, N, 2.84; found C, 85.27, H, 8.92, N, Theoretical Calculation. All density functional theory (DFT) calculations were performed in the Gaussian09 package. 41 The calculation strategy is based on our previous report. 35 The coordinates used for geometry optimization of all Schiff base compounds were initially built in the Avogadro program 42 and then optimized by long-range-corrected hybrid functional CAM-B3LYP 43 in the G09 program. The basis sets of 6-311G(d,p) were used to calculate the dipole moment and polarizability. To compare the dipole moments of all molecules, the origin was set at the center of the phenyl ring, the x axis was parallel to the longitudinal direction, and the z axis was perpendicular to the phenyl plane. The molecular structures, dipole moments, and isosurface plots of the molecular orbitals were generated using GaussView RESULTS AND DISCUSSION 3.1. Phase Transition Behaviors and X-ray Powder Diffraction Study of Schiff Base Mesogens. As shown in Table 1, the phase transition temperatures and enthalpies of four series of salicylaldimine-based mesogens were determined by DSC (Figure 1S) and POM. Compounds OH-TI n and OH- TII n with alkynyl linkage exhibit phase sequence isotropic () nematic (N) smetic C (SmC) soft crystal G (CrG) soft crystal H (CrH). Figure 2a exhibits a schlieren texture at the appearance of the nematic phase for compound OH-TII 6 upon cooling. On further cooling, a striated texture or transition bar is observed at phase transition, indicating the DOI: /acs.jpcb.6b09823 J. Phys. Chem. B 2016, 120,

13 The Journal of Physical Chemistry B Article Figure 15. (a) Temperature dependence of the Bragg reflection wavelength and (b) typical POM texture of BPs at different temperatures for the blending mixture consisting of OH-EI % ISO(6OBA) 2 during the cooling process at a rate of 0.5 C min 1. characteristic transition of the nematic to the smectic C phase (Figure 2b). The SmC phase can be characterized by the schlieren texture of four brush singularities (Figure 2c). After the SmC phase disappears, the soft crystal G phase exhibits a mosaic texture and retains the schlieren characteristics of the SmC phase (Figure 2d). On further cooling, mosaic terrace-like relief with larger domains immediately appears (CrH), as shown in Figure 2e. 45,46 The smectic phase and the soft crystal assignments of these Schiff base compounds were also confirmed by XRD measurements. Figure 3b shows that lattice constants a and c in the hexagonal phase (CrG) are 5.15 and Å, respectively. The weak and wide angle peak q3 becomes sharper from the SmC phase to the CrG phase, which may indicate that the packing of mesogenic molecules is getting more ordered. From Figure 3c, the XRD pattern can be indexed by a monoclinic crystal system with cell constants a = 25.58(6) Å, b = 4.393(6) Å, c = 5.607(8) Å, and β = 96.0(1). To correlate the phase transition from a hexagonal to a monoclinic system, this standard unit-cell setting can be transformed into a = 4.393(6) Å, b = 5.607(8) Å, c = 25.58(6) Å, and α = 96.0(1). The cell constants of CrH at 34 C indicate slight distortion in comparison with that of CrG at 50 C. The indexation of both standard and transformation settings is listed in Table 2. However, salicylaldimine-based mesogens OH-EI n and OH-EII n possessing a more-flexible ester linkage between two rigid cores exhibit phase sequence N SmC Cr. In addition, their phase transition temperatures are lower than those of OH-TI n and OH-TII n. Table 3 shows the phase transition temperatures and enthalpies of three series of racemic Schiff base mesogens H-TII n, H-EI n, and H-EII n without hydroxyl groups. Compound H-TII 6 with alkynyl linkage and a terminal alkyl chain shows the same phase sequence as that shown by compound H-TI 7. Notably, compounds H-EII n with ester linkage and terminal alkyl chains also exhibit two soft crystal G and H phases in addition to N and SmC phases. The temperature-dependent XRD patterns obtained from the powder sample of compound H-EII 8 are shown in Figure S6. Figure S6a shows a layered structure with a periodicity, d-spacing, Å and the molecular width, w 0, 4.55 Å, indicating the packing characteristics of the smectic C phase of H-EII 8. In addition, Figure 4d shows that H-EII 8 at 36 C retains the schlieren texture of the SmC phase and exhibits mosaic patches, implying the characteristics of the hexagonal CrG phase with cell constants a =5.18 Å and c = Å. 35 On further cooling, the characteristics of the schlieren texture disappear and an irregular grain boundary emerges in the POM texture as the characteristic of soft crystal H (Figure 4e). The XRD patterns of CrH can be indexed by a monoclinic crystal system with cell constants a = 28.72(4) Å, b = 2.621(2) Å, c = 5.276(6) Å, and β = 94.67(9). This standard unit cell can be transformed into a = 2.621(2) Å, b = 5.276(6) Å, c = 28.72(4) Å, and α = 94.67(9). The indexation of both standard and transformation settings are listed in Table S1. The cell constants of CrH indicate that the molecular packing becomes more ordered with roughly half of cell volume in comparison with that of CrG at 34 C. On the basis of the results of POM textures, DSC (Figure S1f), and XRD patterns (Figure S6), it can be inferred that Schiff base mesogens H-EII n with ester linkage possess soft crystal G and H phases DOI: /acs.jpcb.6b09823 J. Phys. Chem. B 2016, 120,

14 The Journal of Physical Chemistry B Article Figure 16. Optimized molecular structures of Schiff base mesogens (a) OH-TII 7, (b) H-TII 7, (c) OH-EI 7, (d) H-EI 7, (e) OH-EII 7, and (f) H-EII 7 together with their corresponding molecular dimensions and dipole moments indicated by the blue arrows Investigation of the BP Ranges in the Binary Mixture Containing Chiral Dopant S811. According to our previous report, 35 BPs could be induced significantly after 30.0 wt % of chiral dopant S811 is added into the racemic salicylaldimine-based mesogen OH-TI 7. We attempt to evaluate the addition ratios of chiral dopant S811 for assessing the BP range and investigate the effect of the functional groups of racemic Schiff base mesogens on BP ranges (Figures 5 10). Figure 5a shows that when the alkoxy chain is shortened to six carbons for the racemic Schiff base mesogen with alkynyl linkage (OH-TI 6 ), the widest BP range ( 35 K) can be induced by adding only 30.0 wt % S811 and suppressed by more than 30.0 wt % addition. When the alkoxy chain is extended to seven and eight carbons (OH-TI 7 and OH-TI 8 ), the addition ratio of the chiral dopant for the broad BP range is higher than 35.0 wt % S811 (Figure 5b,c). In comparison with OH-TI n, compounds OH-TII n possessing alkyl chains exhibit more narrow BP ranges and lower BP formation temperatures DOI: /acs.jpcb.6b09823 J. Phys. Chem. B 2016, 120,

15 The Journal of Physical Chemistry B Table 6. Correlations of the BP Range with the Differences of Biaxiality, Modulus of Dipole Moments, and Polarizability in Optimized Schiff Base Mesogens with Alkynyl Linkage alkynyl linkage compound OH-TI 7 OH-TII 7 H-TI 7 H-TII 7 dipole moment (D) polarizability W 1 (Å) a W 2 (Å) b W 1 /W L (Å) c BP range (K) with 30 wt % S BP range (K) with 10 wt % ISO(6OBA) 2 a W 1 : width along the short axis parallel to the middle phenyl ring. b W 2 : width along the short axis normal to the middle phenyl ring. c L: length along the long axis. Article For the series of compounds OH-TII n possessing alkyl chains, the widest BP range (ca. 22 K) that exists in the blending mixture consists of 60.0 wt % OH-TII 7 and 40 wt % S811 (Figure 6b). The DSC thermogram of this mixture during cooling and heating processes is shown in Figure S7. On cooling from an isotropic liquid, a broad peak around 73 C can be seen due to the isotropic BP transition and an obvious pattern at 44 C represents the transition from the BP to the chiral nematic phase. More broad BP ranges ( 28 K) can be observed in the DSC thermogram with a slow cooling rate (1 K min 1 ). As a result of having more-flexible ester linkage, compounds OH-EI n also show narrower BP ranges and lower BP formation temperatures than those of OH-TI n. Notably, the termination temperatures of BPs are very close to room temperature (ca. 35 C) after 40.0 wt % of S811 is added into compounds OH-EII n possessing alkyl chains and more-flexible ester linkage (Figure 8b,c). On the other hand, we previously demonstrated that the hydroxyl group in the rodlike Schiff base mesogen with alkynyl linkage plays an important role in the stabilization of BPs. Therefore, compounds H-TI n and H-TII n possessing alkynyl linkage show no BP even in highly chiral systems. However, it is particularly interesting that BPs can be induced and stabilized when both Schiff base mesogens H-EI n and H-EII n possessing ester linkage are blended with chiral dopant S811. The addition ratios of S811 for the appearance of BP are lower in the blending mixture containing Schiff base mesogens than those in mixtures containing salicylaldiminebased mesogens. However, the widest BP ranges of H-EI n and H-EII n (ca. 12 K) are narrower than those of OH-EI n and OH- EII n in the blending mixture containing chiral dopant S811 (Figures 9 and 10). In addition, the HTPs of some Schiff base mesogens were induced by 4% of the blending mixture (60 wt % Schiff base mesogen and 40 wt % S811) in a host nematic LC (5CB) at room temperature. The helical pitch and HTP are summarized in Figure S8 and Table S2. The HTP (4.38 μm 1 ) in the blending mixture containing 60 wt % Schiff base mesogen OH-EI 7 and 40.0 wt % S811 (ΔBP = 12.9 K) is similar to that (4.37 μm 1 ) in the blending mixture containing 60 wt % Schiff base mesogen OH-EI 7 and 40.0 wt % S811 (no BPs). It means that the stabilization of BPs for racemic Schiff base mesogens in the binary mixture systems is not correlated with the HTP. Furthermore, the BP temperature range in the cooling process is broader than that in the heating process (Figures S9 S13). It can be inferred that the hydroxyl group in the Schiff base mesogen could enhance the viscosity of the blending mixture system to easily cause the supercooling effect and induce a relatively slow phase transition Investigation of the BP Ranges in the Binary Mixture Containing Chiral Dopant ISO(6OBA) 2. We also utilize a high-htp (55.2 μm 1 ) chiral dopant, ISO(6OBA) 2,to investigate the effect of the functional groups of these Schiff base mesogens on BP ranges in highly chiral systems. Likewise, Schiff base mesogens possessing alkynyl linkage show no BP in this higher-chirality system. For Schiff base mesogens possessing ester linkage and hydroxyl groups, Tables 4 and 5 show that only OH-EI 7, OH-EII 6 and OH-EII 8 exhibit cubic BPs after wt % ISO(6OBA) 2 is added. The widest cubic BP range with more than 25 K can be observed when compound OH-EI 8 is mixed with 15 wt % ISO(6OBA) 2. In the case of Schiff base mesogens possessing ester linkage and no hydroxyl group, cubic BPs can be induced after 10 wt % of ISO(6OBA) 2 is added into each of them. Notably, the widest cubic BP range with more than 30 K can be induced by adding 15 wt % ISO(6OBA) 2 into compound H-EI 6 even though the formation temperature of BP is higher. Furthermore, compounds H-EII n possessing alkyl chains show lower formation temperatures of BPs than those for compounds H- EI n possessing alkoxy chains when the same ratio of chiral dopant is added. Figure S15 exhibits a DSC thermogram of the blending mixture composed of H-EI 6 (85 wt %) and ISO(6OBA) 2 (15 wt %) during cooling processes. Similar to that in the binary mixture containing chiral dopant S811, more broad BP ranges can be observed in the DSC thermogram due Table 7. Correlations of the BP Range with the Differences of Biaxiality, Modulus of Dipole Moments, and Polarizability in Optimized Schiff Base Mesogens with Ester Linkage ester linkage compound OH-EI 7 OH-EII 7 OH-EII 8 OH-EI 77 H-EI 7 H-EII 7 H-EII 8 H-EI 77 dipole moment (D) polarizability W 1 (Å) a W 2 (Å) b W 1 /W L (Å) c BP range (K) with 30 wt % S BP range (K) with 10 wt % ISO(6OBA) a W 1 : width along the short axis parallel to the middle phenyl ring. b W 2 : width along the short axis normal to the middle phenyl ring. c L: length along the long axis DOI: /acs.jpcb.6b09823 J. Phys. Chem. B 2016, 120,

16 The Journal of Physical Chemistry B to the slow cooling rate (1 C min 1 ). On cooling from an isotropic liquid, a small peak around 117 C can be seen due to the isotropic BP transition and an obvious sharp pattern at 81 C represents the transition from the BP to the chiral nematic phase Reflection Measurements of BP Transition. To confirm the characteristics of cubic BPs, selective reflection for some of these BP blending mixtures was investigated (Figures 11 15). Figure 11a,b exhibits that only a single reflection band around 450 nm can be observed in the higher-temperature range in the blending mixture consisting of OH-TII % S811 similar to that for OH-TI 7, indicating that BPII exists in the high-temperature range of the BP In addition, another reflection band appears around 500 nm on lowering the temperature down to 45 C and exhibits an obvious red shift from 497 to 586 nm during the cooling process (Figure 11b), implying the characteristics of BPI that is caused by the multilattice plane orientations of the different platelet domains, showing two broader and lower peaks in the lower-temperature range of the BP. 50 In comparison, a sharper and higher reflectance peak can be observed in the higher-temperature range of the BP due to relatively uniform alignment. In addition, Figure 11b illustrates that the temperature range of BPII is wider than that of BPI. However, compound OH-TI 7 possessing an alkoxy chain exhibits that the temperature range of BPII is narrower than that of BPI under the same chirality conditions. 33 Similarly, OH-EI 6 possessing an alkoxy chain also likely exhibits BPI in comparison with OH-EII 6 possessing alkyl chains in the blending mixture system containing chiral dopant S811 (Figures 12 and 13). For compounds OH-EI 6 and OH- EII 6 with ester linkage, BPII reflection bands are located around 420 nm and their maximum reflection bands of BPI were observed around 530 nm. All reflection bands of compounds OH-EI 6 and OH-EII 6 were blue-shifted, and especially the maximum reflection band of BPI showed an approximately 60 nm blue shift in comparison with that of compounds OH-TI 7 and OH-TII 7 possessing alkynyl linkage. It means that the conjugation and rigidity of alkynyl linkage in the case of Schiff base mesogens are better than those of the alkynyl linkage in the salicylaldimine-based mesogens. In the case of Schiff base mesogens H-EI 6 (Figures 14 and S17) and H-EII 6 (Figures S18 and S19), only a single reflection band was observed around 420 nm both after heating and cooling processes, indicating that only BPII is present in the blending mixture system composed of Schiff base mesogens and chiral dopants S811. In addition, POM and Bragg reflection observations indicate that only BPII phase can be observed after both cooling and heating processes in the blending mixture system composed of Schiff mesogens and chiral dopants S811. Accordingly, it can be suggested that salicylaldimine-based mesogens possessing alkoxy chains and hydroxyl groups exhibit a larger supercooling effect in the binary mixture system containing chiral dopant S811 in comparison with salicylaldimine-based mesogens possessing alkyl chain. However, BPII exists in the blending mixture system composed of chiral dopants ISO(6OBA) 2 both on heating and cooling processes such as Figures 15 and S21 exhibit only a single reflection band located and remained around 500 and 400 nm on the cooling and on heating process, respectively, in the blending mixture consisting of OH-EI 7 and 15 wt % ISO(6OBA) 2 during the BP ranges. Consequently, it is likely that less supercooling effect is present in the binary mixture consisting of these Schiff base mesogens and chiral Article Figure 17. Molecular structure and phase sequence of compounds OH-EI 77 and H-EI 77. dopant ISO(6OBA) 2 in comparison with that in the mixture containing chiral dopant S Investigation of the Factors Affecting BP Stabilization by Theoretical Simulation. According to our recent report, 35 the results of DFT calculation for these Schiff base mesogens can provide more insight into the influence of the structural variations of Schiff base mesogens upon BP stabilization. To avoid the shortcomings of conventional DFT for the calculation of electronic properties in π- conjugated systems, the range-corrected functional, CAM- B3LYP, 56 was applied to obtain the stable molecular structure, dipole moment, and polarizability. The optimized molecular structures together with the vector of dipole moments are displayed in Figure 16. The correlations of the BP range with the differences of biaxiality, modulus of dipole moment, and polarizability in optimized Schiff base mesogens are shown in Tables 6 and 7. The detailed information of each component of the dipole moment, polarizability, and the energy of HOMO and LUMO is listed in Table S3. On the basis of the HOMO and LUMO displayed in Figure S24, all of the Schiff base molecules with alkynyl linkage indicate similar electron distributions in frontier orbitals. To simplify the description, the central, left, and right phenyl rings are labeled as C, L, and R, respectively. The electron distribution on HOMO of compound OH-TII 7 or H-TII 7 possessing alkynyl linkage is extended from the L to R. However, the electron distribution on HOMO of ester-linkage compound (e.g. OH-EI 7, H-EI 7, OH-EII 7, and H-EII 7 ) is extended from C to R. To explain the difference of the BP range for these Schiff base mesogens in a binary mixture system, their biaxialities, dipole moments, and polarizabilities are further investigated and compared. Compound OH-TII 7 possessing alkyl chain shows that the values of both short axes ( and 4.30 Å) perpendicular to the long axis are similar to those of compounds OH-TI 7 having alkoxy chain. In addition, compound OH-TII 7 exhibits a larger dipole moment (3.54 D) in comparison with that of compound OH-TI 7 (2.21 D). However, compound OH-TII 7 shows smaller polarizability (500.83) than that of compound OH- TI 7 (509.84); thus, the BP range of OH-TII 7 (7.2 K) in the blending mixture with 30 wt % S811 is narrower than that of OH-TI 7 (13.9 K) under the same chirality conditions. Furthermore, Schiff base mesogens H-TI 7 and H-TII 7 that possess alkynyl linkage but no hydroxyl group show no BP in the blending mixture system even though H-TII 7 has a lager dipole moment (2.34 D). On the other hand, we found that no BP is present in the blending mixture composed of chiral dopant ISO(6OBA) 2 and racemic Schiff base mesogens possessing alkynyl linkage even though these mesogens possess larger dipole moments and polarizabilities. However, BPs can be induced in the blending mixture composed of chiral dopant ISO(6OBA) 2 and its chiral homologues according to our previous report. In the case of salicylaldimine-based mesogens DOI: /acs.jpcb.6b09823 J. Phys. Chem. B 2016, 120,

17 The Journal of Physical Chemistry B with ester linkage, Table 7 displays that OH-EI 7 with larger polarizability (465.55) exhibits a wider BP range than OH-EII 7 (458.12) in the binary mixture systems containing chiral dopant S811 (30 wt %) or ISO(6OBA) 2 (10 wt %). In addition, OH- EII 8 with a larger dipole moment (2.80 D) and polarizability (469.80) also shows a wider BP range than OH-EII 7 under the same chirality conditions. The similar trends can be observed in the blending mixture composed of Schiff base mesogens without hydroxyl groups, such as Schiff base mesogen H-EI 7 possessing larger dipole moment (2.94 D) and polarizability (457.91) exhibits a wider BP range than H-EII 7. When the Schiff base mesogens possessing ester linkage are doped with chiral dopant ISO(6OBA) 2, no BP can be induced in the blending mixture composed of compound H-EII 7 probably due to the smaller dipole moment (2.79 D) and polarizability (450.13) of H-EII7. When the alkyl chain is extended to eight carbons, the polarizability (462.43) of Schiff base mesogen H- EII 8 slightly increases. Thus, the BP (17.4 K) emerges after H- EII 8 is doped with 10 wt % ISO(6OBA) 2 even though its dipole moment (2.57 D) decreases. Notably, compound H-EI 7 possesses a larger dipole moment than that of other Schiff base mesogens and thus exhibits a wider BP range (24.5 K) under this higher-chirality condition. In addition, to confirm the effect of the methyl branch of the terminal chain on BP stabilization in racemic Schiff base mesogens with ester linkage, we also prepared homologues OH-EI 77 and H-EI 77 that possess two linear heptoxyl chains shown in Figure 17 according to the previously reported literature. 57,58 We found that only N* and/ or chiral smectic phases appeared when compounds OH-EI 77 and H-EI 77 were doped with the appropriate amount of chiral dopant S811 or ISO(6OBA) 2. Accordingly, our results reveal that the dipole moment and polarizability are the most important factors affecting BP stabilization, in addition to the methyl branch of the terminal chain in racemic Schiff base mesogens. 4. CONCLUSIONS In summary, we prepared four series of rodlike racemic Schiff base mesogens possessing two different alkyl chains, two types of linkages, and the hydroxyl group at the salicylaldimine core position. The mesophases of these Schiff base mesogens were confirmed by variable-temperature XRD and the characteristic texture of POM. Subsequently, they can be applied for inducing cubic BPs in simple binary mixture systems. In general, the cubic BPs could be observed and their temperature range is larger than 20 K when wt % chiral dopant S811 is added into the rodlike racemic salicylaldimine-based mesogens. The widest temperature range of the cubic BP (35 K) can be observed in the binary mixture composed of wt % S811 and the racemic salicylaldimine-based mesogen possessing alkynyl linkage. However, no BP can be induced when S811 is doped into racemic Schiff base mesogens possessing alkynyl linkage. Interestingly, wide BP ranges can also be induced by adding only 10 wt % of chiral additive ISO(6OBA) 2 with a high HTP into the racemic Schiff base mesogen possessing ester linkage. We utilized the temperature dependence of the Bragg reflection and POM to confirm the phase transition between BPII and BPI. By the measurement of Bragg reflection, it can be observed that salicylaldimine-based mesogens easily exhibit BPI in the binary mixture containing chiral dopant S811 during the cooling process. In addition, only BPII can be induced during the heating process. However, only BPII can be observed in all binary mixtures composed of Schiff base mesogen and S811 or Article ISO(6OBA) 2 during both the heating and cooling processes. It means that salicylaldimine-based mesogens easily exhibit a larger supercooling effect than that of Schiff base mesogens. Therefore, the expansion of the BP temperature range could preliminarily be attributed to the viscosity effect of the hydroxyl group in the salicylaldimine-based mesogens. On the basis of molecular modeling and our experimental results, it can be suggested that the large values of biaxiality, polarizability, and dipole moment of molecular geometry are useful to induce a broad BP range. This work built a preliminary correlation between the molecular structure of rodlike Schiff base mesogens and BP stabilization. More related Schiff base mesogens applied in BPLCs will be studied and reported in the future. ASSOCIATED CONTENT *S Supporting Information The Supporting Information is available free of charge on the ACS Publications website at DOI: /acs.jpcb.6b DSC measurement of all Schiff base mesogens on heating and cooling recycle (Figures S1 and S4); microphotographs of compounds OH-EI 8 and H-TII 6 (Figures S2 and S3); variable-temperature XRD measurements for compound H-TII 6 and H-EII 8 (Figures S5 and S6); cell transformation of standard monoclinic setting in Schiff base mesogens (Table S1); DSC curves of OH-TII 7 blended with 40.0 wt % S811 (upon cooling at a rate of 1 C min 1 ) (Figure S7); measurements of helical pitch and HTP of the binary mixture system composed of 60 wt % racemic Schiff base and 40 wt % S811 by Cano s Wedge method (Figure S8); helical pitch and HTP for some of blending mixtures (Table S2); comparison of BP temperature range for the blending mixture system composed of Schiff base mesogens and different amounts of chiral dopant S811 in heating (red line) and cooling processes (blue line) (Figures S9 S13); DSC curves of H-EI 6 blended with 15.0 wt % ISO(6OBA) 2 (upon cooling at a rate of 1 C/min) (Figure S14); data of the Bragg reflection spectra for the blending mixture systems containing chiral dopant S811 during the cooling and heating processes (Figures S15 S19); data of the Bragg reflection spectra for the blending mixture systems containing chiral dopant ISO(6OBA) 2 (Figures S20 S23); HOMO and LUMO of compounds (a) OH-TII 7, (b) H-TII 7, (c) OH-EI 7, (d) H-EI 7, (e) OH-EII 7, and (f) H-EII 7 (Figure S24); DFT calculated HOMO, LUMO, energy gap, dipole moment components, μ x, μ y, μ z, and modulus (μ) for the biphenyl compounds (Table S3) (PDF) AUTHOR INFORMATION Corresponding Authors * chchhuang@ttu.edu.tw. Tel: (C.- C.H.). * ijuihsu@mail.ntut.edu.tw. Tel: # 2420 (I.-J.H.). ORCID Chiung-Cheng Huang: Notes The authors declare no competing financial interest DOI: /acs.jpcb.6b09823 J. Phys. Chem. B 2016, 120,

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20 Electronic Supporting Information Effect of the Functional Groups of Racemic Rodlike Schiff Base Mesogens on the Stabilization of Blue Phase in Binary Mixture Systems Chiung Cheng Huang,* a Zong Ye Wu, a Bing Han Sie, a We Hao Chou, a Yu Chang Huang, a Mei Ching Yu, a Bo Hao Chen, b I Jui Hsu,* b Lai Chin Wu c and Jey-Jau Lee c a Department of Chemical Engineering, Tatung University, Taipei 104, Taiwan a chchhuang@ttu.edu.tw a Tel.: b Department of Molecular Science and Engineering, National Taipei University of Technology, Taipei 106, Taiwan b ijuihsu@ntut.edu.tw b Tel.: # 2420 c National Synchrotron Radiation Research Center of Taiwan, Hsinchu 300, Taiwan S1

21 (a) (b) (c) (d) (e) (f) Figure S1. The DSC measurements of all racemic Schiff base mesogens on heating and cooling recycle. S2

22 (a) (b) (c) (d) Figure S2. Microphotographs for compound OH-EI 8 (a) N texture at C; (b) N-SmC texture at C; (c) SmC texture at 70.1 C (d) Cr texture 36.9 C (a) (b) (c) (d) Figure S3. Microphotographs for compound H-TII 6. (b) N texture at C; (b) SmC texture at C; (c) CrG texture at 96.0 C (c) CrH texture 78.0 C S3

23 m.p. Heating N Heat Flow Endo Up CrH SmC and CrG N Cooling Temperature( ) Figure S4. The DSC measurement of compound H-TII 6 on heating (red line) and cooling (blue line) recycle. (a) (b) (c) Figure S5. The variable temperature XRD measurements for compound H-TII 6 S4

24 (a) (b) (c) Figure S6. The variable temperature XRD measurements for compound H-EII 8 S5

25 Table S1. Cell transformation of standard monoclinic setting in Schiff base mesogens. Compound H-EII 8 RT` H-TII 6 60 C H-TII 6 RT OH-TII 6 RT Unit cell Standard Transformation Standard Transformation Standard Transformation Standard Transformation a (Å) 28.72(4) 2.621(2) 29.10(2) 4.577(4) 30.56(3) 5.277(3) 28.61(2) 7.268(4) b (Å) 2.621(2) 5.276(6) 4.577(4) 10.19(1) 5.277(3) 10.29(1) 7.268(4) 5.847(4) c (Å) 5.276(6) 28.72(4) 10.19(1) 29.10(2) 10.29(1) 30.56(3) 5.847(4) 28.61(2) α (º) (9) (1) (1) (1) β(º) 94.67(9) (1) (1) (1) γ(º) Volume (Å 3 ) (2) (2) (5) (5) (5) (5) (3) (3) Standard Transformation Q value Standard Transformation Q value Standard Transformation Q value Standard Transformation Q value (100) (001) (100) (001) (100) (001) (100) (001) (200) (002) (200) (002) (200) (002) (200) (002) (101) (011) (501 ) (01 5) (110) (101) (300) (003) (201) (012) (102 ) (02 1) (601 ) (01 6) (400) (004) (301) (013) (202) (022) (111 ) (11 1) (001) (010) (401 ) (01 4) (302 ) (02 3) (011) (110) (101) (011) hkl index (401) (014) (601 ) (01 6) (311 ) (11 3) (600) (006) transformation (210) (102) (501) (015) (401 ) (01 4) (601) (016) (411 ) (11 4) (111) (111) (211) (112) (511 ) (11 5) (211) (112) (800) (008) (800) (008) (501) (015) (511 ) (11 5) (403 ) (03 4) (120) (201) (312 ) (12 3) (710) (107) (220) (202) (420) (204) S6

26 Figure S7. DSC curves of OH-TII 7 blended with 40.0 wt% S811 (with rate of 1 C /min upon cooling). S7

27 Measurements of helical pitch and helical twisting power of binary mixture system composed of 60 wt% racemic Schiff base and 40 wt% S811 by Cano s Wedge method. The helical pitch (p) was evaluated by measuring the distance (a) between Cano lines as follows: p = 2a tanθ, where θ is the angle of the wedge of the cell. In this experiment, the cell s tanθ is , the concentration of the chiral dopant c is 4%. Figure S8. Cano s Wedge method to measure the helical pitch of binary mixture system composed of 60 wt% racemic Schiff base and 40 wt% S811. Table S2. Helical pitch and helical twist power (HTP) in the mixture consisting of 4 wt% blending mixture (60 wt% Schiff base mesogens + 40 wt% S811) and 96 wt% 5CB at room temperature blending mixture Helical pitch/µm HTP/µm wt% OH-EI wt% S wt% H-EI wt% S S8

28 (a) (b) (c) Figure S9. The comparison of BP temperature range for the blending mixture system composed of OH-TII n and different amount of chiral dopant S811 in heating (red line) and cooling processes (blue line). S9

29 (a) (b) (c) Figure S10. The comparison of BP temperature range for the blending mixture system composed of OH-EI n and different amount of chiral dopant S811 in heating (red line) and cooling processes (blue line). S10

30 (a) (b) (c) Figure S11. The comparison of BP temperature range for the blending mixture system composed of OH-EII n and different amount of chiral dopant S811 in heating (red line) and cooling processes (blue line). S11

31 (a) (b) (c) Figure S12. The comparison of BP temperature range for the blending mixture system composed of H-EI n and different amount of chiral dopant S811 in heating (red line) and cooling processes (blue line). S12

32 (a) (b) (c) Figure S13. The comparison of BP temperature range for the blending mixture system composed of H-EII n and different amount of chiral dopant S811 in heating (red line) and cooling processes (blue line). S13

33 Figure S14. DSC curves of H-EI 6 blended with 15.0 wt% ISO(6OBA) 2 (with rate of 1 C/min upon heating and cooling). S14

34 (a) (b) (c) BPII 64.0 C BPII 65.0 C BPII 66.8 C Figure S15. (a) Typical blue-shift reflectance profiles during cooling process. (b) Temperature dependence of the Bragg reflection wavelength. (c) Microphotographs for the blending mixture consisting of OH-TII 7 +40% S811during heating process with a rate of 0.2 C min -1. S15

35 (a) (b) BPII 84.5 C BPII 87.2 C BPII 89.0 C Figure S16. (a) The temperature dependence of the Bragg reflection wavelength (b) typical POM texture of BPs at different temperature for the blending mixture consisting of OH-EI % S811 during the heating process with a rate of 0.2 C min -1. S16

36 (a) (b) BPII 93.0 C BPII 94.5 C BPII 96.0 C Figure S17. (a) The temperature dependence of the Bragg reflection wavelength. (b) typical POM texture of BPs at different temperature for the blending mixture consisting of H-EI % S811 during the heating process with a rate of 0.5 C min -1. S17

37 (a) (b) BPII 65.0 C BPII 70.2 C BPII 72.0 C Figure S18 (a) The temperature dependence of the Bragg reflection wavelength. (b) typical POM texture of BPs at different temperature for the blending mixture consisting of H-EII % S811 during the cooling process with a rate of 0.5 C min -1. S18

38 (a) (b) BPII 66.5 C BPII 68.0 C BPII 69.5 C Figure S19. (a) The temperature dependence of the Bragg reflection wavelength. (b) typical POM texture of BPs at different temperature for the blending mixture consisting of H-EII % S811 during the heating process with a rate of 0.5 C min -1. S19

39 (a) (b) BPII C BPII C BPII C Figure S20. (a) The temperature dependence of the Bragg reflection wavelength. (b) typical POM texture of BPs at different temperature for the blending mixture consisting of OH-EI % ISO(6OBA) 2 during the heating process with a rate of 0.5 C min -1. S20

40 (a) (b) BPII 53.0 C BPII 60.0 C BPII 75.0 C Figure S21. (a) The temperature dependence of the Bragg reflection wavelength. (b) typical POM texture of BPs at different temperature for the blending mixture consisting of OH-EII % ISO(6OBA) 2 during the cooling process with a rate of 0.5 C min -1. S21

41 (a) (b) BPII 87.0 C BPII 95.3 C BPII C Figure S22. (a) The temperature dependence of the Bragg reflection wavelength. (b) typical POM texture of BPs at different temperature for the blending mixture consisting of H-EI % ISO(6OBA) 2 during the cooling process with a rate of 0.5 C min -1. S22

42 (a) (b) BPII C BPII C BPII C Figure S23. (a) The temperature dependence of the Bragg reflection wavelength. (b) typical POM texture of BPs at different temperature for the blending mixture consisting of H-EI % ISO(6OBA) 2 during the heating process with a rate of 0.2 C min -1. S23