Supporting Information. Red-light Controllable Liquid-Crystal Soft Actuators via Low-power Excited Upconversion. Based on Triplet-Triplet Annihilation

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1 Supporting Information Red-light Controllable Liquid-Crystal Soft Actuators via Low-power Excited Upconversion Based on Triplet-Triplet Annihilation Zhen Jiang,,# Ming Xu,,# Fuyou Li, and Yanlei Yu, Department of Materials Science & State Key Laboratory of Molecular Engineering of Polymers, Fudan University, Shanghai , China Department of Chemistry & Institutes of Biomedical Sciences, Fudan University, Shanghai , China. (F. Y. Li); (Y. L.Yu) Synthesis of 9,10- bis(diphenylphosphoryl)anthracene (BDPPA) BDPPA was synthesized according to the previous literatures [S1]. A 100 ml flask was charged with 9,10-dibromoanthracene (672 mg, 2.0 mmol) and 40 ml of dry THF at -78 C. Then n-buli (1.6 M in hexane, 2.5 ml, 4.0 mmol) was added dropwise over 10 min at -78 C under Ar. And the mixture was stirred for 1 h under Ar. After that PPh 2 Cl was added to the residue over 5 min, and the suspension was stirred at room temperature overnight and collected by filtration. The solid was recrystallized from CH 3 Cl/hexane to give a yellow solid BDPPA with 73% yield. Then 2 ml 30% H 2 O 2 was added dropwise into a 100 ml flask charged with 40 ml CH 2 Cl 2 solution of BDPPA (546 mg, 1 mmol) in ice bath. The mixture was stirred for 1 h at 0 C. The reactant was quenched with water, extracted with CH 2 Cl 2 and dried with anhydrous Na 2 SO 4. The residue was purified by column chromatography using silica gel and CH 2 Cl 2 then CH 2 Cl 2 /CH 3 OH (v/v, 9/1) as the eluent to obtain a yellow solid BDPPA (503 mg, 87% yield). 1 H NMR (500 MHz, CD 2 Cl 2 ) δ 8.50 (d, J = 7.0 Hz, 4H), 7.72 (dd, J = 11.7 and 8.1 Hz, 8H), 7.60 (t, J = 7.3 Hz, 4H), 7.51 (d, J = 7.5 Hz, 8H), 7.16 (dd, J = 6.9 and 3.1 Hz, 4H). MALDI-MS m/z: calcd for C 38 H 28 O 2 P 2 : , found: [M]+. S1

2 Measurement of the absolute upconversion luminescence quantum yield (QY UCL ). The absolute QY UCL of the samples in toluene and in polyurethane were measured on fluorescence spectrophotometer with an integrating sphere (Edinburgh, FLS-920). Herein, CW 635-nm laser was used as the excitation source. The equation (S1) that represents the meaning of the absolute QY UCL is used for calculation. [S2] where QY UCL is the upconversion luminescence quantum yield, Em(sample) is the emission intensity, Ex(sample) and Ex(reference) are the detected intensities of excitation lights in the presence of the samples and the references (pure toluene or polyurethane film), respectively. Measurement of the relative upconvesion quantum yield The relative upconversion quantum yield (Φ UCL ) of the sample was determined according to equation (S2) [S3] with methylene blue in methanol as a standard reference (The maximum upconversion quantum yield of 0.5 is directly used as the upper limit). where Φ UCL and Φ std stand for relative upconvesion quantum yield of the sample and fluorescence quantum yield of methylene blue, respectively. A and A std stand for absorbance at 635 nm of the sample and methylene blue, respectively. I UCL and I std stand for integrated UCL intensity of the sample and fluorescence intensity of methylene blue, respectively. n s and n std stand for the solvent refractive index of toluene (for the sample) and methanol (for methylene blue), respectively. According to the equation (S2), the relative upconvesion quantum yield of PtTPBP&BDPPA in deaerated toluene was measured to be 7.3%, with methylene blue in methanol (Φ std = 0.03) [S4] as a standard reference. In our measurement of the absolute and relevant UCL efficiencies, the irradiation power density was 200 mw cm -2 (saturated incident intensity), definitely lies in the linear dependence region, with the consideration of providing the stationary efficiency values. S2

3 Scheme S1. The chemical structures of the reported effective TTA based upconversion systems of PdOEP&DPA and PtTPBP&BODIPY. S3

4 Scheme S2. (a) Synthetic route for azotolane-containing monomer 1. (b) Synthetic route for non-azotolane crosslinker 2. S4

5 Absorbance (a.u.) Wavelength (nm) Figure S1. Absorbance spectra of PtTPBP (green solid line) and BDPPA (orange solid line) respectively, and emission spectrum of BDPPA (blue dotted line). All are normalized to an arbitrary maximum of Fluorescence intensity (a.u.) S5

6 (a) UCL intensity (a.u.) Concentration ratio C BDPPA /C PtTPBP (b) UCL intensity (a.u.) Wavelength (nm) Ratio of C BDPPA /C PtTPBP Figure S2. (a) UCL spectra of the toluene solution of PtTPBP&BDPPA at different molar ratios of BDPPA (concentration of PtTPBP is fixed at M). (b) Integrated UCL intensity of the PtTPBP&BDPPA system as a function of increasing concentration of the BDPPA under selective excitation with CW 635-nm laser (power density = 200 mw cm -2 ) in deaerated toluene. The function of TTA-UCL intensity to molar ratio presents an approximate parabolic curve, and the ratio of 150 lying at the acme was chosen as the best concentration ratio that used throughout the experiment. S6

7 Figure S3. (a) BDPPA molecular and the optimized ground state geometry of the compound. Calculated by DFT at the B3LYP/6-31G/LanL2DZ level using Gaussian 09W. (b) Frontier molecular orbitals of BDPPA based on the optimized ground state geometry of the compound. Calculated by DFT at the B3LYP/6-31G/LanL2DZ level using Gaussian 09W. The transition involved in S 0 T 1 (oscillator strength is f = No spin orbital coupling was considered in the calculation) is HOMO LUMO (CI = ). The calculated S 0 /T 1 energy gap is 1.60 ev (773 nm). Toluene was used as solvent in the calculation. S7

8 1 BDPPA* E PtTPBP ππ* hν 635 nm 1.95 ev ISC PtTPBP 3 ππ* TTET 3 BDPPA* TTA 1.61 ev 1.60 ev 3 BDPPA* 3 BDPPA* 2.64 ev GS Scheme S3. Qualitative Jablonski diagram illustrating the sensitized TTA upconversion process between PtTPBP (sensitizer) and BDPPA (annihilator). To understand the UCL process of PtTPBP&BDPPA, the energy level of BDPPA was investigated. The BDPPA molecule exhibits blue fluorescence emission at 470 nm (2.64 ev) with its triplet state at 1.60 ev (Figure S3), therefore its singlet excited state is lower in energy than two times of its triplet state (3.20 ev). Importantly, the triplet state at 1.60 ev of BDPPA is lower than that of the sensitizer PtTPBP (1.61 ev), [S5] thus exactly satisfying the energy requirement for an efficient TTA based upconversion system. A possible TTA-UCL process between PtTPBP and BDPPA is shown in Scheme 2. Upon selective excitation at 635 nm (1.95 ev), the PtTPBP molecule is excited to its singlet state and then undergoes immediate intersystem crossing (ISC) to its triplet excited state. After ensuing fast triplet-triplet energy transfer (TTET) process from PtTPBP to BDPPA, TTA occurs between two generated triplet BDPPA molecules, bringing about one BDPPA molecule in its singlet excited state, which leads to delayed intense UCL emission at 470 nm when it returns to ground state. S8

9 Figure S4. Continuous kinetic scan of the upconversion luminescence intensity of the PtTPBP&BDPPA system upon excitation with CW 635-nm laser (power density = 200 mw cm -2 ). The photostability of the PtTPBP&BDPPA system was measured by kinetic spectroscopy scan. No significant change in the UCL emission was observed when the degassed PtTPBP&BDPPA toluene solution was continuously irradiated by the CW 635-nm laser (200 mw cm -2 ) for 60 min, suggesting excellent photostability of PtTPBP&BDPPA. S9

10 (a) Absorbance Wavelength (nm) (d) (e) Absorbance ' 1' 2' Wavelength (nm) (b) (c) Fluorescence intensity (a.u.) Wavelength (nm) (f) UCL intensity (a.u.) ' 1' 2' Wavelength (nm) Figure S5. The photostability of the BDPPA solution (a-c) and PtTPBP&BDPPA system (d-f). (a, d) The absorption spectra of the samples. (b, e) The photographs of the samples. (c) The fluorescent emission spectra of the BDPPA samples. (f) The UCL spectra of the PtTPBP&BDPPA system. 0: The newly prepared BDPPA solution; 1: BDPPA kept in darkness for one week; 2: BDPPA kept in the indoor circumstance for one week. 0 : The newly prepared PtTPBP&BDPPA system; 1 : The PtTPBP&BDPPA system kept in darkness for one week; 2 : The PtTPBP&BDPPA system kept in the indoor circumstance for one week. The long-term stability experiments of BDPPA as well as PtTPBP&BDPPA were carried out in darkness and indoor circumstance, respectively. As shown in Figure S5, the absorption and emission of BDPPA as well as PtTPBP&BDPPA displayed no obvious change over one week. This result revealed that the chromophores used in our study were of high chemical stability and ensured the maintenance of their chemical properties as we were carrying out our entire study. S10

11 Figure S6. Schematic layout of the UV-Vis absorption measurement system. The excitation laser beam path and the UCL emission pathway are shown in red and blue, respectively. Under the irradiation of CW 635-nm laser, PtTPBP&BDPPA solution in cell 3 was firstly excited to generate TTA-UCL, which was employed to irradiate the toluene solution of LC monomer 1 in cell 4. And then changes in absorption spectra corresponding to triggered photoisomerization of the azotolane moieties of LC monomer 1in cell 4 were measured with spectrophotometer. S11

12 Figure S7. Changes in the absorption spectra of the toluene solution of LC monomer 1 ( M) upon direct irradiation with 635-nm laser (power density = 200 mw cm -2 ). S12

13 Storage modulus (Mpa) Temperature (K) Figure S8. DMA temperature sweeps of the compression molded film of polyurethane. Plots depict the storage modulus (black line) and loss tangent (blue line) of the polyurethane film. Tan δ at 223K and tan δ at 283 K are attributed to the glass transition of soft segment phase and hard segment phase in the polyurethane film, respectively. Tan δ S13

14 (a) UCL intensity (a.u.) Content of PtTPBP&DPPOA 1 wt 2 wt 3 wt 4 wt 5 wt (b) Wavelength (nm) 1.5 UCL intensity (a.u.) Content of PtTPBP&DPPOA (wt ) Figure S9. (a) UCL spectra of the polyurethane films containing different concentrations of PtTPBP&BDPPA. (b) Integrated UCL intensity of the PtTPBP&BDPPA-containing polyurethane film as a function of increasing concentration of the PtTPBP&BDPPA under CW 635-nm excitation (power density = 200 mw cm -2 ). In terms of obtaining the optimal UCL performance of PtTPBP&BDPPA-containing polyurethane film, 4 wt of PtTPBP&BDPPA was the best content in the polyurethane film that was then used for the preparation of assembly film. S14

15 Figure S10. The photoluminescence emission spectrum of the upconverting polyurethane film (containing 4 wt PtTPBP&BDPPA, molar ratio of PtTPBP and BDPPA = 1:150) upon 635-nm excitation (power density = 200 mw cm -2 ). Selective excitation at 635 nm, the PtTPBP molecule is excited to its singlet state and then undergoes immediate intersystem crossing to its triplet excited state, leads to the generation of long-lived phosphorescence at 766 nm. S15

16 Intergrated UCL intensity 10 6 Slope= Slope= Power density (mw cm -2 ) Figure S11. TTA-UCL property of the upconverting polyurethane film. Integrated UCL intensity from part Figure 4 plotted as a function of incident light power density. S16

17 Figure S12. Continuous kinetic scan of the UCL intensity of the polyurethane film containing 4 wt PtTPBP&BDPPA (molar ratio of PtTPBP and BDPPA = 1:150) upon CW 635-nm excitation (power density = 200 mw cm -2 ). S17

18 (a) Analyzer θ Polarizer Rubbing direction θ = 0 θ = 45 (b) Cooling Heat flow (W/g) Heating Temperature ( o C) Figure S13. (a) Polarizing optical micrographs and (b) DSC thermograms of the azotolane-containing CLCP film. S18

19 Turn off the laser Figure S14. Photograph of the assembly film bending toward the light source in response to 635-nm laser (200 mw cm -2 ) and retaining the bent state after switching off the laser, and then the bent film reverted to the flat state after heated to 80 C. Thickness of each layer in the assembly film: 15 µm of upconverting film and 27 µm of CLCP. S19

20 Figure S15. Photographic frames of the square-shaped composite film: (a) the monodomain composite film bent toward the light source along the rubbing direction of the polyimide alignment layers; (b) the bending direction of the square-shaped polydomain composite film is random due to its inhomogeneous alignment of the mesogens in the macroscopic scale. The irradiation source was CW 635-nm laser (power density = 200 mw cm -2 ). Thickness of each layer in the assembly film: 15 µm of upconverting film and 27 µm of CLCP. S20

21 Figure S16. Bending time for the composite film to bend by 30 as a function of the 635-nm laser power density in the range of mw cm -2. Thickness of each layer in the assembly film: 15 µm of upconverting film and 27 µm of CLCP. Movie 1. Bending of the composite film upon irradiation of CW 635-nm laser. Movie 2. Unbending of the blank CLCP film upon irradiation of CW 635-nm laser. Reference: [S1] (a) Yip, J. H. K.; Prabhavathy, J. Angew. Chem. Int. Ed. 2001, 40, (b) Fei, Z. F.; Kocher, N.; Mohrschladt, C. J.; Ihmels, H.; Stalke, D. Angew. Chem. Int. Ed. 2003, 42, [S2] Boyer, J. C.; van Veggel, F. Nanoscale 2010, 2, [S3] (a) Demas, J. N.; Crosby, G. A. J. Phys. Chem. 1971, 75, (b) Jankus, V.; Snedden, E. W.; Bright, D. W.; Whittle, V. L.; Williams, J. A. G.; Monkman, A. Adv. Funct. Mater. 2013, 23, (c) Monguzzi, A.; Tubino, R.; Hoseinkhani, S.; Campione, M.; Meinardi, F. Phys. Chem. Chem. Phys., 2012, 14, [S4] Olmsted III, J. J. Phys. Chem. 1979, 83, [S5] (a) Singh-Rachford, T. N.; Castellano, F. N. Inorg. Chem. 2009, 48, (b) Singh-Rachford, T. N.; Castellano, F. N. J. Phys. Chem. Lett. 2010, 1, S21