Preparation of covalent pseudo two-dimensional. polymers in water by free radical polymerization

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1 Supporting Information Preparation of covalent pseudo two-dimensional polymers in water by free radical polymerization Zili Li a, Miao Tang a, Jingwen Dai a, Taisheng Wang a, Zhisheng, Wang a, Wei Bai* b, Ruke Bai* a a CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei, , P. R. China b Department of Chemistry, University of Tennessee, Knoxville, TN 37996, United States 1. Methods and methods 1.1. Materials Most of the chemical reagents were purchased from Sinopharm Chemical Reagent Co., Ltd. were utilized as received unless indicated otherwise. 1,1,3,3-Tetramethylguanidine (TMG) was purchased from TCI chemicals, and distilled under reduced pressure. Potassium peroxydisulfate (KPS) was recrystallized from deionized water, and then dried at room temperature under vacuum. Acryloyloxethyltrimethylammonium chloride (DAC) was purchased from Jinpin chemicals (80% water solution). All other chemicals were analyticalgrade reagents and used directly without further purification Sample characterization. All NMR spectra were recorded on a Bruker AVANCEII spectrometer (resonance frequency of 400 MHz for 1 H and 13 C) operated in the Fourier transform mode with TMS as internal standard. Multiplets are entitled as s (singlet), bs (broad singlet), d (duplet), t (triplet), m 1

2 (multiplet), and given values are positioned in the centre of a peak. High-resolution mass spectra (HRMS) were recorded on a BRUKER microtof-qii spectrometer with ESI mode unless otherwise stated. Fourier transform infrared (FT-IR) spectra were recorded in the spectral range from 4000 to 400 cm -1 with Thermo Nicolet UV-Vis spectra of solutions were recorded with a Shimadzu UV 3600 UV-Nir-NIR spectrometer at room temperature. XRD patterns were recorded by using a Philips X Pert Pro Super diffractometer with Cu Kα radiation (λ = Å). Atomic force microscopy (AFM) images were recorded with a Veeco DI Innova in tapping mode on coated SiO 2 /Si-wafer pieces. The morphologies of the 2D polymers were characterized by transmission electron microscopy (TEM) using a JEOL transmission electron microscope operated at 200 kv. High-resolution TEM (HRTEM) and selected area electron diffraction (SAED) images were taken using FEI Talos F200X or JEM-2100F transmission electron microscope. The samples were prepared by placing a droplet of solution onto a carbon-coated copper grid followed by air-drying. The field emission scanning electron microscope (SEM) images were performed on copper grids (size of 7.5 µ m 7.5 µ m) by using a FEI Sirion-200 SEM. TGA measurements were carried out on a TA Q5000IR thermogravimetric analyzer (TA Instruments). Samples of about 5 mg were heated from room temperature to 650 C at a heating rate of 10 C/min under a nitrogen atmosphere. Tensile stress strain tests were performed on columnar samples with a diameter of 6 mm by using a ZBC pendulum impact tester (Shenzhen SANS Test Machine Company, China) apparatus at a speed of 10 mm min Synthetic procedures H 2 N NH 2 O O O acetonitrile r.t. HO O O H N H N O O OH Synthesis of compound MAB. To a Schlenk tube was added a solution of benzidine (1.842 g, 10 mmol) in MeCN (100 ml) 2

3 at room temperature followed by the drop wise addition of maleic anhydride (3 g, 30 mmol), precipitates were formed immediately. After stirring for 24 h, yellow solids were filtered and washed with MeCN (3.774 g, 98.2%). The compound was used without further purification. The physical data for MAB: 1 H NMR (400 MHz, CD 3 SOCD 3 ): δ (s, 2H,COOH), δ (s, 2H, CONH), δ 7.69 (d, J = 7.7 Hz, 4H, Ar), δ 7.69 (d, J = 7.6 Hz, 4H, Ar), δ 6.47 (d, J = 6.5 Hz, 2H, double bond), δ 6.34 (d, J = 6.3 Hz, 2H, double bond); 13 C NMR (400 MHz, CD 3 SOCD 3 ); δ 166.8, 163.1, 137.7, 134.9, 131.5, 139.4, 126.5, 119.8; MS (ESI) m/z: Calcd for C 20 H 16 N 2 O 6 [M + H] , found m/z Synthesis of 4-vinylbenzyl trimethylammonium chloride 4-Vinylbenzyl trimethylammonium chloride was prepared according to the previous report 1. To a stirred solution of 4-vinylbenzyl chloride (4 ml, 28.3 mol) in round bottom flask equipped with mechanical stirring device, an aqueous solution of trimethylamine (7.6 g, 42.5 mmol) was added. The mixture was stirred for three days at 0 C. The solution was washed with ethylether four times, and then extracted three times with chloroform. The combined chloroform solvent was evaporated to yield the quaternized product. 1 H NMR (400 MHz, D 2 O): 7.59 (d, 2H, Ar), 7.48(d, 2H, Ar), 6.83 (q, 1H, CH=CH 2 ), 5.60 (d, 1H, CH=CH 2 ), 5.42 (d, 1H, CH=CH 2 ), 4.46 (s, 2H, CH 2 ), 3.05 (s, 9H, CH 3 ) Formation of 2D supramolecular sheets by self-assemble of bola-amphiphilic monomer MAB with TMG In a typical procedure, MAB (20 mg, 52.6 µmol) was dispersed in 10 ml water and sonicated 30 min, then TMG (13.5 µl, µmol) was added to the dispersion and sonicated for another 5 min, the solution turned transparent immediately. The aqueous solution of the MAB-TMG was standing for 24 h without stirring at room temperature. Finally, the solution 3

4 was transferred to a dialysis tube (molecular weight cutoff, 7000) and dialyzed against deionized water for 48 h Preparation of covalent pseudo 2D polymer by radical polymerization. In a typical procedure, the solution of supramolecular 2D sheets prepared by self-assembly of MAB-TMG solution without dialysis was used for the polymerization. Sodium p- styrenesulfonate (SSS, 43.4 mg, µmol) was added into the solution of the supramolecular 2D sheets, and subsequently potassium peroxydisulfate (KPS, 0.28 mg, 1.05 µmol) as initiator was added. The mixture was deoxygenated by three cycles of freeze-pumpthaw, the polymerization reaction was conducted at 70 C in an oil bath for 24 h. After the reaction was quenched, the solution was transferred to a dialysis tube (molecular weight cutoff, 7000) and dialyzed against deionized water for 48 h to obtain the covalent 2D polymers MAB-TMG-PSS. Copolymerization of the supramolecular 2D sheet with other comonomers is similarly performed as described above. For preparation of 2D polymers on large scale, the polymerization was performed in a three-necked bottle at the same concentration. MAB (1 g, 2.63 mmol) was dispersed in 200 ml water and sonicated 30 min, then TMG (667 µl, 5.26 mmol) was added and sonicated for another 5 min. The aqueous solution of the MAB-TMG was stood for 24 h without stirring. Sodium p-styrenesulfonate (2.17 g, 10.5 mmol) and potassium peroxydisulfate (14.2 mg, 52.5 µmol) was respectively added into the solution of the supramolecular 2D sheets. After deoxygenated with N 2 for 10 min, the polymerization reaction was conducted at 70 C in an oil bath for 24 h under N 2 atmosphere. The polymerization was quenched, then the solution was concentrated and dialyzed against deionized water for 48 h to obtain the covalent 2D polymers on gram-scale (yield : 2.29 g). To examine the molar ratio of the bola-amphiphilic monomer MAB to the comonomer SSS, avoiding the influence of the TMG concentrations, the 2D polymers were was dialyzed in 1 M hydrochloric acid solution for 48 h to remove the TMG from the polymer and then 4

5 dried to constant weight. Elemental analysis: C, 54.76, N, 3.45, S, Preparation of the 2D polymer sheets based composite hydrogel Composite hydrogels were prepared by in-situ polymerization of acryloyloxethyltrimethylammonium chloride (DAC) in a solution of the covalent 2D polymer sheets MAB-TMG-PSS. Firstly, a certain amount of the 2D polymers sheets were dispersed in 2 ml water in a tube and sonicated for 5 min. Then an aqueous solution containing acrylamide, N, N'-methylenebis(acrylamide) (MBA), N, N, N', N'-tetramethylethylenediamine (TEMDA) was added under N 2 atmosphere in an ice bath. After degassing for 5 min, an aqueous solution of potassium persulfate was added to the flask with syringe. The polymerization was carried out at room temperature for 48 h to obtain a hydrogel rod with a diameter of 4 mm. Table 1 shows the data for preparation of the composite hydrogels. Table S1. Compositions of the composite hydrogels Hydrogel DAC MAB-TMG-PSS MBA TEMDA KPS (µl) (mg) (mg) (µl) (mg) PDA PDA PDA Supplementary figures 5

6 Figure S1 1 H NMR spectrum of MAB. Figure S2 13 C NMR spectrum of the MAB. 6

7 Figure S3 HRMS spectrum of MAB. The small peak at m/z refers to the diprotonated species [M+2H] +. Figure S4 1 H NMR spectrum of 4-vinylbenzyl trimethylammonium chloride in D 2 O. 7

8 Figure S5 TEM images of different aggregates by self-assembly of MAB with different bases. 8

9 Figure S6 TEM images of supermolecular sheets (MAB-TMG) with different concentration; 0.5 mg/ml (a), 1 mg/ml (b), 5 mg/ml (c), 10 mg/ml (d). Figure S7 (a) TEM image of 2D polymer sheets (MAB-TMG-PSS, 5 mg/ml); photograph of 9

10 the 2D polymer MAB-TMG-PSS in water after polymerization (b) and (c) 2D polymer solids. The 2D polymer sheets could be obtained on gram-scale of 2.29 g through three-necked bottle. Figure S8 TEM iamges of 2D polymer sheets obtained from the polymerization of supramolecular 2D nanosheet with sodium 4-styrenesulfonate at different reaction time. Figure S9 TG curve of 2D polymer sheets MAB-TMG-PSS and supermolecular sheets MAB- TMG in N 2 atmosphere. Thermal properties of the 2D polymer sheets were also investigated and the thermogravimetric (TG) curve of the MAB-TMG-PSS was recorded in N 2 atmosphere. The weight loss below 100 C was attributed to evaporation of the adsorbed water and the loss of TMG could be observed above 200 C. The backbone of the 2D polymer began to 10

11 decompose beyond 300 C, indicating the 2D polymer sheet has high thermal stability. Figure S10 TEM images of 2D polymer sheets with different comonomers. The comonomers are shown on the left and the corresponding covalent 2D polymer sheets (1 mg/ml) on the right. 11

12 3. Supplementary references Figure S11 Photograph of the as prepared composite hydrogels. [1] Bo Qiu, Bencai Lin, Lihua Qiu and Feng Yan J. Mater. Chem., 2012, 22,