Synthesis and characterization of novel jacketed polymers and investigation of their self assembly and application 2

Chapter Part Synthesis, characterization of a series of novel mesogenjacketed polymers and investigation of their selfassembly properties 56 2.2.1 Introduction Based on the previous results, the alkyl chains in the lateral position on the mesogenic core exert a great negative effect on the self-assembly of the jacketed polymers. To overcome this disadvantage, two methods were proposed: one involves shorter alkyl chain to decrease this disturbance; and introduction of polar groups to increase the incompatibility and stability to the microphase separation. We report the synthesis of a series of novel jacketed polymers. Strong electrostatic, weak Van der Wall’s interaction and geometrical effects were incorporated in the substituents attached to the polymer backbone to control the self-assembly of polymer chains in the lattice. The novel polymers were characterized using GPC, DSC, TGA, FTIR, and NMR. The morphology of these polymers on the substrate was studied via AFM, polar optical micrograph. This work shows some characterization about the rigid side chain organization and may provide a new method for designing some supramolecular building blocks to control synthetic polymer function, size and shape. 2.2.2 Experimental section 2.2.2.1 Materials and reagents All reagents and solvents were obtained from commercial sources and used without further purification unless noted otherwise. Tetrahydrofuran (THF) was distilled over sodium and benzophenone under N2 atmosphere. N, N-dimethylformamide (DMF) was dried with molecular sieves (4 Å, Aldrich). Flash column chromatography was performed using silica gel (60-mesh, Aldrich). Dibenzoyl peroxide (BPO) was recrystallized from 57 chloroform-methanol solution as glistening crystals, and used as initiators for polymerization. 2.2.2.2 Instrumentation H NMR, 13C NMR spectra were recorded on a Bruker ACF 300 MHz spectrometer. MS spectra were obtained using a Finnigan TSQ 7000 spectrometer with ESI or EI ionization capabilities. Data from thermogravimetric analyses (TGA) and differential scanning calorimetry (DSC) thermograms were recorded using a TA-SDT2960 and a TA-DSC 2920 at a heating rate of 10 °C min-1 under N2 environment. Gel permeation chromatographic (GPC) analysis were conducted with a Waters 2696 separation module equipped with a Water 410 differential refractometer HPLC system and Waters Styragel HR 4E columns using THF as eluent and polystyrene as standard. The XRD patterns were recorded on an X-ray powder diffractometer with a graphite monochromator using Cu Kα radiator with a wavelength of 1.54 Å at room temperature (scanning rate: 0.05 o/s; scan range 1.5 - 30 o). A Zeiss Axiolab polarized optical microscopy (POM) equipped with a Linkam LTS 350 hot stage was used to observe anisotropic textures. All AFM images were recorded with a Digital Instruments (DI) Multimode SPM IIIa system in contact mode using square pyramidal Si3N4 probes (25 °C, in air). All films were spincoated from polymer solutions in THF (0.5 mg/ml) onto glass slide at 2000 rpm for min. 2.2.2.3 Synthesis Poly (5’-methoxy [1, 1', 4', 4"] terphenyl-2-yl methacrylate) (P01), poly(1,3-bis(5’methoxy [1, 1’, 4’, 1”] terphenyl -2’-yloxy)-2-propyl methacrylate) (P02), poly (5dodecyloxy [1, 1’, 4’, 1”] terphenyl -2-yl methacrylate) (P03), and poly (4-dodecyloxy- 58 2,5-bis(pyrimidin-5-yl)-phenyl-1-yl methacrylate) (P04) were synthesized using the route shown in Scheme 2.2.1 and Scheme 2.2.2: OH OH OCH3 Br Br BrOBn K2CO3/DMF Br NaOH/EtOH Br OH Br CH3I Br OBn OBn OBn OH B(OH)2 H2 Pd/C Pd(PPh3)4/ 2M Na2CO3 H3CO H3CO n BPO/THF O Cl O Et3N O O OCH3 P 01 OH O O O Cl Br Br K2CO3/DMF OR O OCH3 OH OR n BPO/THF O O Et3N OR OR OR OR P 02 R = H3CO Scheme 2.2.1. Synthesis route for monomer and polymers of type P 01 and P 02 59 OH OH Br Br C12H24Br NaOH/EtOH Br Br BnBr K2CO3/DMF Br OH Br OC12H25 iii, 1M HCl OC12H25 OBn 10 B(OH)2 i,n-BuLi ii, B(O-i-Pr)3 THF OBn N Br N N N Pd(PPh3)4/Toluene/EtOH (HO)2B N N 2M Na2CO3 OC12H25 OBn C12H25O 12 11 OH Pd/C O Cl N N Et3N H2 O O N N N N N N C12H25O 13 14 OC12H25 n BPO/THF O O N N N P 03 N OC12H25 OH OBn Br 2M K2CO3 11 Pd/C H2 Pd(PPh3)4/Toluene/EtOH C12H25O C12H25O 16 15 n Et3N BPO/THF O O Cl O O O P 04 17 OC12H25 OC12H25 Scheme 2.2.2. Synthetic route for polymers P 03 and P 04 60 4-Benzyloxy-2, 5-dibromophenol (2) In a 250 ml round-bottom flask with a stir bar was placed 13.4 g of (0.1 mol), 10.4 g K2CO3 (0.075 mol) and 150 ml dry DMF. The mixture was purged with N2 for 20 min, heated to 60 - 70 °C under nitrogen atmosphere. A solution of benzyl bromide 5.6 ml (0.05 mol) in 10 ml absolute ethanol was added dropwise. After finishing the addition, the reaction mixture was stirred for 18 h, allowed to cool to RT and then filtered. The solution was concentrated and poured into water. The pH was adjusted to about 6. The obtained precipitate was recrystalized in ethanol to yield a white powder. Yield: 5.75g (77.9 %). 1H NMR (300 MHz, CDCl3, δ ppm) 10.2 (s, OH, 1H), 7.5-7.1, (m, ArH, 7H), 5.2 (s, Ar-CH2-O, 2H). 13C NMR (75.4 MHz, CDCl3, δ ppm) 159.9, 136.9, 135.7, 128.4, 127.6, 113.7 (ArC), 68.8 (O-CH2-Ar). MS (ESI): m/z: 357.9, 267.9, 91.1. Mp: 108 °C. 1-Benzyloxy-2, 5-dibromo-4-methoxy benzene (3) 5.37 g of (0.015 mol), and 100 ml absolute ethanol were added to a 250 ml roundbottom flask, and purged with N2 for 20 min. 0.9 g NaOH was added to the mixture and purged with N2 for another 20 min, heated to 60 °C and 15 ml 2M iodomethane in hexane (0.03 mol) was added dropwise to the solution. After finishing the addition, the reaction mixture was kept stirring for overnight under N2 atmosphere. The reaction mixture was allowed to cool to RT, filtered, concentrated and poured into water. The precipitate was recrystalized from methanol to yield a white powder. Yield: 5.4 g (96.7 %) 1H NMR (300 MHz, DMSO, δ ppm) 7.5-7.3 (m, ArH, 7H). 5.16 (s, O-CH2-Ar, 2H), 3.8 (s, O-CH3, 3H). 13 C NMR (75.4 MHz, DMSO δ ppm) 150.2, 148.9, 136.4, 128.4, 127.9, 127.4, 118.8, 116.9, 110.8, 109.7 (Ar-C), 70.9 (O-CH2-Ar), 56.8 (O-CH3). MS (ESI): m/z: 371.9, 281.9, 91.1. Mp: 106 °C. 61 5’-benzyloxy-2’-methoxy [1, 1’; 4’, 1”] terphenyl (4) A 250 ml round-bottom flask equipped with a condenser was charged with compound (5.58 g, 15 mmol), 5.50 g phenyl boronic acid (45 mmol), 80 ml toluene, 20 ml methanol and 80 ml 2M sodium carbonate solution. The mixture was degassed via cycles, before the catalyst of 0.2g tetrakis (triphenylphosphine) palladium (5 mol%) was added in dark under argon atmosphere. The reaction mixture was heated at 100 °C for 48 h, before being allowed to cool to RT and then filtered. The liquid layer was separated with a separation funnel, and the aqueous layer was extracted with × 100 ml toluene. The toluene layer was combined, washed with 3× 100 ml water and dried over MgSO4. The solvent was then removed with a rotary evaporator, and the resulting crude product was purified using column chromatography on a silica gel column with hexane and dichloromethane (4:1) as the eluant. Yield: 4.6 g (44.3%). 1H NMR (300 MHz, DMSO-d6, δ ppm) 7.64-7.33 (m, ArH, 15 H). 7.12 (s, ArH, H), 7.04 (s, ArH, H), 5.10 (s, O-CH2Ar, H), 3.76 (s, O-CH3, H). 13C NMR (75.4 MHz, DMSO, δ ppm) 150.4, 137.8, 129.3, 129.2, 128.2, 128.0, 127.5, 127.1, 126.9, 116.4, 114.4 (Ar-C), 70.4 (O-CH2-Ar), 58.2 (OCH3). MS (ESI): m/z: 366.2, 275.1, 260.1, 244.1, 202.0, 198.0, 91.1. Mp: 100 °C. 5’-Methoxy [1, 1’; 4’, 1”] terphenyl-2’-ol (5) To a 100 ml round-bottomed flask containing 10 % Pd/C (2.5 g) in 50 ml THF was added compound (4.40 g, mmol), charged with nitrogen, and a balloon filled with H2 was fitted to the flask. The nitrogen was briefly evacuated from the flask, and the H2 gas was charged above the solution. The reaction mixture was stirred for 24 h at ambient temperature and then filtered through a glass frit containing a small layer of celite powder. After the solid was washed with THF × 25 ml, the organic phases were combined and 62 the solvent was removed under reduced pressure to yield a white powder. The resulting crude product was purified by column chromatography on a silica gel column using hexane and ethyl acetate (1:4) as the eluent. Yield: 3.2 g (96.4 %). 1H NMR (300 MHz, CDCl3, δ ppm) 7.54 - 7.43 (m, ArH, 10 H). 7.00 (s, ArH, H), 6.88 (s, ArH, H), 5.0 (b, Ar-OH, H), 3.77 (s, O-CH3, H). 13 C NMR (75.4 MHz, CDCl3, δ ppm) 154.6, 135.5, 128.1, 122.8, 128.2, 128.0, 127.5, 116.4, 114.4 (Ar-C), 18.3 (O-CH3). MS (ESI): m/z: 276.2, 261.1, 200.0, 185.1, 157.1, 128.1, 84.0. Mp: 127.5 °C. 5-Methoxy [1, 1’; 4’, 1”] terphenyl-2-yl methacrylate (6) A 100 ml round bottom flask was charged with triethylamine (3.1 ml, 19.5 mmol), compound (1.8 g, 6.5 mmol) and 30 ml dry THF. This solution was cooled to °C, and added with a solution of methacryloyl chloride (1.3 ml, 13 mmol) in ml THF. After finishing the addition, the reaction mixture was warmed to room temperature and stirred for hr. The mixture was then filtered and the volatile components were removed under reduced pressure. The resulting crude product was dissolved in dichloromethane, washed with sodium bicarbonate solution, followed by water (3 × 50 ml). The organic layer was dried over anhydrous magnesium sulfate and filtered. The excess solvent was removed under reduced pressure to yield the monomer. Yield: 1.23g (93%). 1H NMR (300 MHz, CDCl3, δ ppm) 7.59 - 7.00 (m, ArH, 12 H), 6.1 (s, CH2=C, H), 5.6 (s, CH2=C, H), 3.84 (s, O-CH3, H), 1.9 (s, =C-CH3, H). 13 C NMR (75.4 MHz, CDCl3, δ ppm) 166.5 (C=O), 153.1, 137.5, 135.6, 129.5, 128.8, 128.2, 127.4, 126.8, 124.8, 114.5, 113.3 (Ar-C, C=C), 58.9 (O-CH3), 18.4 (=C-CH3). MS (EI): m/z: 344.2, 303.2, 275.2, 260.2, 215.2. Mp: 82 °C. 63 1, 3-Bis (5-methoxy [1, 1’; 4, 1”] terphenyl-2-yloxy) propan-2-ol (7) To a 250 ml three neck round bottom flask fitted with a reflux condenser, addition funnel and a nitrogen inlet were added 100 ml DMF, compound (2.76 g, 10 mmol) and potassium carbonate (2.8 g, 20 mmol). The mixture was purged with N2 for 30 then stirred at 80 °C for hr under nitrogen atmosphere. A solution of 1,3-dibromo-2propanol (0.41 ml, 4.0 mmol) in ml DMF was added dropwise using a dropping funnel. The reaction mixture was stirred at 80 °C for 12 hr and filtered. The volatile components were removed under reduced pressure and excessive phenol was removed by washing with 2M sodium hydroxide and water (3 × 100 ml). The resulting crude product was purified using column chromatography on a silica gel column with hexane and dichloromethane (2:1) as the eluent. Yield: 1.2 g (49.2 %). 1H NMR (300 MHz, CDCl3, δ ppm) 7.60-6.96 (m, ArH, 20 H), 4.1 (p, J= 5.1 Hz, C-CH(O)-C, 1H), 3.94 (d, J= 4.8 Hz, O-CH2-C, H), 3.82 (s, O-CH3), 2.17 (b, C-OH). 13C NMR (75.4 MHz, CDCl3, δ ppm) 151.2, 149.4, 138.1, 131.3, 130.6, 130.5, 129.4, 128.1, 126.2, 118.2, 117.2, 116.2, 115., 114.5, 114.3, 113.2 (Ar-C), 70.7 (Ar-O-CH2-), 68.6 (HO-CH(C)-), 57.2 (O-CH3). MS (EI): m/z: 608.3, 332.2, 276.2, 261.2, 215.1. Mp: 79 °C. 1, 3-Bis (5’-methoxy [1, 1’; 4’, 1”] terphenyl-2’-yloxy)-2-propyl methacrylate (8) Compound was synthesized according to the procedure described for the synthesis of compound 6. Yield: 1.6 g (72.0%). 1H NMR (300 MHz, CDCl3, δ ppm) 7.56 - 6.85 (m, ArH, 24 H), 6.29 (s, CH2=C, H), 5.8 (s, CH2=C, H), 5.3 (p, J= 6.7 Hz, O-CH(C)-C, H,), 4.05 (d, J= 4.2 Hz, O-CH2-C, H), 3.8 (s, O-CH3, H), 1.9 (s, =C-CH3, H). 13 C NMR (75.4 MHz, CDCl3, δ ppm) 160.5 (C=O), 151.1, 149.4, 137.9, 131.3, 129.4, 127.8, 64 127.1, 116.7, 114.4, 112.9 (Ar-C, C=C), 70.7 (COO-C), 67.6 (Ar-O-C), 56.3 (O-CH3). 18.4 (=C-CH3). MS (EI): m/z: 676.2, 620.2, 564.3, 387.4, 315.2, 300.2, 260.2, 215.2. Mp: 78 °C. Poly(5’-methoxy [1, 1'; 4’, 1"] terphenyl-2-yl methacrylate) (P01) A 25 ml round flask was charged with 1.0 g of compound 6, 0.01 g (1 wt%) of BPO, ml THF and sealed with a rubber septum. The solution was subjected to freeze-pump-thaw cycles, and stirred at 70 °C for 48 h under N2 atmosphere. The crude reaction mixture was precipitated in MeOH. The resulted solid was dissolved in THF, re-precipitated in methanol several times and dried under high vacuum. Yield: 0.8 g (80%). 1H NMR (300 MHz, CDCl3, δ ppm) 7.48 - 7.39 (b, ArH, 12 H), 3.84 -3.76 (b, O-CH3, H), 1.27 (b, CH2-, H), 0.92 (b, -CH3, H). FT-IR (KBr, cm-1): 3055 (ArH stretching), 2930 (-CH2stretching), 1743 (ester C=O stretching), 1601,1514,1479 (Ar, C=C stretching), 1250, 1164, 1098 (C-O-C stretching). Mw: 0.99× 104, Mn: 0.85 × 104 , PD: 1.2. Poly(1, 3-bis (5’-methoxy [1, 1’; 4’, 1”] terphenyl -2’-yloxy)-2-propyl methacrylate) (P02) Polymerization of compound was performed according to the procedure for P01 from 0.8 g of compound 8. Yield: 0.6 g (75%). 1H NMR (300MHz, CDCl3, δ ppm) 7.48- 7.27 (b, ArH, 24 H), 5.35 (b, -CH(O)-, H), 4.08 (b, O-CH2-, H), 3.84-3.76 (b, O-CH3, H), 1.28 (b, -CH2-, H). FT-IR (KBr, cm-1): 3059 (ArH stretching), 2919 (-CH2- stretching), 1725 (ester C=O stretching), 1599, 1514, 1481 (Ar, C=C stretching), 1259, 1183, 1058 (C-O-C stretching). Mw: 1.62 × 104, Mn: 1.02 × 104, PD: 1.6. 2-Benzyloxy-5-dodecyloxy phenyl-1, 4-diboronic acid (11) 65 10 g of compound 10 and 150 ml dry THF were placed in a round-bottom flask. The solution was cooled to -78 °C and 55 ml (0.088 mol) of a 1.6 M solution of butyl lithium in hexanes were added slowly under a nitrogen atmosphere. The solution was warmed to RT and re-cooled to -78 °C, followed by the dropwise addition of triisopropylborate (51 ml) during a period of h. After complete addition, the mixture was warmed to RT, stirred overnight, and mixed with L of deionized water. The organic phase was collected, dried with MgSO4, and filtered. The excess solvent was removed under reduced pressure, and the crude product was re-crystallized from acetone. Yield: 5.7 g (80.0%). 1H NMR (300 MHz, DMSO, δ ppm) 7.52 (s, Ar-B(OH)2, H), 7.40(s, ArB(OH)2, H), 7.40-7.17 (m, ArH, H), 5.11 (s, Ar-CH2-O, H), 4.00 (t, J = 4.8, O-CH2C, H), 1.73 (q, J = 6.4 Hz, C(O)-CH2-, H), 1.24 (b, -CH2-, 16 H), 0.85 (t, J = 6.84 Hz, -CH3, H). 13 C NMR (75.4 MHz, CDCl3, δ ppm) 151.5, 145.7, 144.6, 130.7, 126.4, 126.3, 123.4, 121.9, 120.4, 119.7, 111.8, 110.7, 110.5, 109.4 (Ar-C), 66.5 (O-CH2-Ar), 66.2 (O-CH2-), 26.6, 24., 24.2, 24.1, 24.0, 23.9, 23.8, 20.7, 17.4, 8.8 (alkyl C). MS (ESI): m/z: 368.1, 277.1, 200.0, 109.0. Mp: 115 °C. 1-Benzyloxy-4-dodecyloxy-2, 5-di (pyrimidin-5-yl) benzene (12) Compound 12 was synthesized according to the procedure described for the synthesis of compound 4. From 5.2 g (14.1 mmol) of compound 11 and 5.5 g (34.6 mmol) of 5bromopyrimidine was obtained the deserved molecule as white powder. Yield: 4.5 g (60.8%). 1H NMR (300 MHz, CDCl3, δ ppm): 9.18 - 8.91 (m, Ar-H, H), 7.32 - 7.26 (m, ArH, H), 7.06 (s, ArH, H), 6.98 (s, ArH, H), 5.09 (s, O-CH2-Ar, H), 3.98 (t, J = 6.3 Hz, O-CH2-, H), 1.73 (p, J = 7.5 Hz, R(O)-CH2-, H), 1.26 (b, -CH2- 18 H), 0.87 (t, J = 6.7 Hz, -CH3, H). 13C NMR (75.4 MHz, CDCl3, δ ppm): 157.0, 156.7, 150.8, 149.5, 66 131.5, 128.6, 128.2, 127.2, 115.9, 114.6, 106.2 (Ar-C), 71.7, 69.5 (O-CH-), 318, 29.5, 29.4, 29.3, 29.2, 29.1, 29.0, 25.9, 22.6 (-CH2-), 13.9 (-CH3). MS (ESI): m/z: 524.5, 433.4, 355.2, 265.1, 238.1, 91.1. Mp: 132 °C. 4-Dodecyloxy-2, 5-di(pyrimidin-5-yl) phenol (13) Compound 13 was synthesized according to the procedure described for the synthesis of compound 5. Yield: 2.5 g (88.7 %). 1H NMR (300MHz, DMSO, δ ppm): 9.82 (s, Ar-OH, H), 9.15 - 8.94 (m, Ar-H, H), 7.25 (s, ArH, H), 7.03 (s, ArH, H), 4.04 (t, J = 6.3 Hz, O-CH2-, H), 1.62 (p, J = 6.4 Hz, R(O)-CH2-, H), 1.26 (b, -CH2- 18 H), 0.87 (t, J = 6.0 Hz, -CH3, H). 13 C NMR (75.4 MHz, CDCl3, δ ppm): 156.5, 156.3, 149.0, 148.6, 131.5, 131.4 131.2, 124.4, 122.0, 117.5, 114.8, 106.4, 92.4 (Ar-C), 68.8 (O-CH-), 31.2, 28.9, 28.8, 28.7, 28.6, 28.5, 28.4, 25.4, 21.9 20.2 (-CH2-), 13.8 (-CH3). MS (ESI): m/z: 434.3, 226.1, 238.1, 212.1, 158.1, 106.1, 71.1, 57.1. Mp: 170 °C. 4-Dodecyloxy-2, 5-di(pyrimidin-5-yl) phenyl-1-yl methacrylate (14) Compound 14 was synthesized according to the procedure described for the synthesis of compound 6. From the reaction of 2.0 g (4.6mmol) of compound 13 and 1.5 ml (11 mmol) methacryloyl chloride was obtained the desired monomer 14 as light yellow powder. Yield: 0.9 g (38.9%). 1H NMR (300 MHz, CDCl3, δ ppm): 9.22 - 8.87 (m, Ar-H, H), 7.26 (s, ArH, H), 7.04(s, ArH, 1H), 6.22 (s, CH2=C, H), 5.71 (s, CH2=C, H), 4.04 (t, J = 6.6 Hz, O-CH2-C, H), 1.93 (s, =C-CH3, 3H), 1.74 (p, J = 6.7 Hz, R(O)-CH2-, H), 1.24 (b, -CH2- 18 H), 0.89 (t, J = 7.2 Hz, -CH3, H). 13 C NMR (75.4 MHz, CDCl3, δ ppm): 157.9 (C=O), 157.3, 156.7, 156.2, 154.2, 141.5, 134.8, 129.1, 128.2, 125.2, 124.8, 113.5 (ArC, C=C), 69.3 (O-CH-), 31.8, 29.5, 29.4, 29.3, 29.2, 29.1, 28.7, 27.9, 25.8, 22.6 67 (-CH2-), 18.3 (=C-CH3), 13.9 (-CH3). MS (EI): m/z: 502.4, 472.4, 433.4, 334.2, 265.2, 69.0. Mp: 112 °C. Poly(4-dodecyloxy-2, 5-di(pyrimidin-5-yl) phenyl-1-yl methacrylate) (P03) Polymerization of 14 was performed according to the procedure described for P01. Yield: 0.82 g (82 %). 1H NMR (300 MHz, CDCl3, δ ppm): 9.22 - 8.87 (b, ArH, H), 7.26 - 6.40 (b, ArH, H), 3.97 (b, O-CH2-C, H), 1.64 (b, C(O)-CH2-, H), 1.24 (b, CH2- 18 H), 0.89 (b, -CH3, H). FT-IR (KBr, cm-1): 3044 (ArH stretching), 2919 (-CH2stretching), 1736 (ester C=O stretching), 1552, 1412, 1388 (Ar, C=C, C=N stretching), 1259, 1183, 1058 (C-O-C stretching). Mw: 3.13 × 104, Mn: 1.48 × 104, PD: 2.1. Poly(5-dodecyloxy [1, 1’; 4’, 1”] terphenyl -2-yl methacrylate) (P04) Polymerization of 17 was performed according to the procedure described for P01. Yield: 0.6 g (66.7 %). 1H NMR (300 MHz, CDCl3, δ ppm): 7.55 - 6.88 (b, Ar-H, 12 H), 3.89 (b, O-CH2-C, H), 1.83 (b, C(O)-CH2-, H), 1.27 (b, -CH2- 18 H), 0.89 (b, -CH3, 6H). FT-IR (KBr, cm-1): 3068 (ArH stretching), 2933 (-CH2- stretching), 1724 (ester C=O stretching), 1515, 1490, 1472 (Ar, C=C stretching), 1259, 1183, 1058 (C-O-C stretching). Mw: 1.08 × 104, Mn: 0.81 × 104, PD: 1.3. 2.2.3 Results and discussion 2.2.3.1 Synthesis of polymers The polymers were synthesized through radical polymerization from the appropriate monomers. The concentration of initiator BPO was 1.0 mol % based on the amount of the monomer used. The structures of all monomers and polymers prepared in our work were characterized by 1H NMR and FTIR. Figure 2.2.1 illustrates two representative 1H NMR spectra of monomer 14 and polymer P03. In the 1H NMR spectra of monomer 14, for 68 example, the signals appearing in the range of δ 9.22–8.87 correspond to those in pyrimidine ring protons while those at δ 7.26-7.04 are assigned to those in the benzene ring. The double peak at δ 6.22 and 5.71 are characteristic of methacrylic carbon double bond protons. It is noted that in the spectrum of polymer P03, these two signals disappears. The absence of a C=C band at 1640 cm-1 in the FTIR spectrum of P03 also indicates that the monomer has reacted to form a polymer. Figure 2.2.1. 1H NMR spectra of monomer 14 and polymer P03 in CDCl3 2.2.3.2 Thermal analysis The thermal stability of polymers P01-04 in nitrogen was investigated by thermogravimetric analysis (TGA) and the results are given in Figure 2.2.2. All polymers showed a weight loss at 285-305 °C (285 °C for P03, 289 °C for P04, 302 °C for P02 and 69 305 °C for P01). Typically, the polymers P03 and P04 show a two-stage decomposition, wherein the first stage is believed to involve the long alkyl side chains. Thermally induced phase transition behaviors of the polymers were evaluated by differential scanning calorimetry (DSC) in a nitrogen atmosphere. The DSC traces are shown in the Figure 2.2.3. 100 p01 p02 p03 p04 weight percent (%) 80 60 40 20 0 100 200 300 400 500 600 700 800 o Temperature ( C) Figure 2.2.2. TGA traces of P01-P04 measured in a nitrogen atmosphere at a heating rate 10 °C /min. 70 o Tg -3.2 C P04 o o Tiso 108 C Heat flow (W/g) Tg 29.1 C o Tg 52.4 C P03 P02 o Tg 73.2 C -50 50 P01 100 150 200 o Temperature ( C) Figure 2.2.3. Second heating differential scanning calorimetry curves for P01-P04 measured in nitrogen at a heating rate 10 °C /min. P01 exhibits a clear glass transition (Tg) at 73.2 °C while the Tg of P02 decreases to 52.4 °C due to the addition of the flexible link. P03 and P04 show a glass transition at 29.1 °C and – 3.2 °C, respectively. The decrease in Tg from P01-P04 may be due to the increase in the alkyl chain length. On heating, the polymer P03 exhibits a mesophase with an isotropic transition at 108 °C. This mesophase is identified as columnar phase using wide-angle X-ray diffraction measurements (WAXS). A similar transition was not seen in other polymers. It is noticeable that the P03 and P04 are very similar in the chemical structure with only difference in the pyrimidine groups on the rigid core of P03, which may play a significant role in the self-assembly of polymers to form a columnar lattice. 71 2.2.3.3 Mesomorphic Properties and Self-assembled structures 2.2.3.3.1 POM study. The novel polymers were analyzed with polarized optical microscopy to investigate the mesophase of the polymers. Only P03 exhibits an isotropization under polarized optical microscopy and the micrograph is shown in Figure 2.2.4. a b Figure 2.2.4. Polarized optical micrographs of P03 (a) observed at 95 °C on cooling with a 0.5 °C min-1 from isotropic melt, (b) observed at 102 °C on cooling with 0.1 °C min-1 from isotropic melt. When the isotropic liquid of P03 was cooled with a slower rate 0.1 °C min-1, a fibrous texture was formed during cooling (shown in Figure 2.2.4 a) while cooled with a rate of 0.5 °C min-1 to 95 °C, a mosaic texture was formed (shown in Figure 2.2.4b). However, the cooling of the melt of P03 only gave atypical birefringent textures, from which the exact nature of the mesophase was difficult to identify. It is well known that the broad polydispersity of polymers cause some hindrance to form mesophase, which may be the reason for the lack of recognizable textures from these polymers 2. However, with the aid 72 of X-ray diffraction (XRD) measurements, the texture can be associated with a columnar mesophase. 2.2.3.3.2 X-ray diffraction analysis XRD measurements were carried out to collect more information on the molecular arrangements and packing model of a novel polymer series. X-ray diffraction patterns for all polymers are shown in the Figure 2.2.5. The d-spacing distance was derived using the Bragg’s law d = nλ/2sin(θ) (λ = 1.54 Å). The reflection angle 2θ and the distance d are listed in Table 2.2.1. The XRD diffraction pattern of P03 shows two sharp reflections in small angle together with one reflection with low intensity at 2θ = 2.46, 2.88 and 4.91°, from which d spacings of 35.9Å, 30.6 Å and 18.0 Å are derived. It also offers a sharp reflection in the middle angle region and a broad halo at 2θ = 7.42 and 19.9 °, from which d spacings of 11.9 Å and 4.5 Å are derived. P01 affords a sharp reflection in middle angle region and a broad peak at 2θ = 7.52 and 20.2°, from which a d spacing of 11.8 and 4.4 Å is derived. For P02 and P04, the diffraction patterns only exhibit one broad peak at 2θ = 20.1o and 20.2 o, and no sharp peaks were observed indicating the absence of long-range ordering in the polymer lattice. It is noted that polymer P03 afforded X-ray reflections in the small angle region, which indexed as (100), (101), (200) of the 2D rectangular columnar structure with the lattice constants a = 3.59 nm and c = 5.89 nm3, 4. P03 and P01 both show a sharp reflection at about 2θ = 7.5 o with a d = 11.9 Å. It is believed that the jacketed polymer chains adopt a somewhat extended conformation with the cylindrical symmetry 4. P03 and P01 are very similar in chemical structure except that the P03 has a long flexible alkyl chain attached in the middle of the 73 rigid core. So it is reasonable to assign this reflection from the rigid cylindrical core of P01 or P03. The diameter of the cylindrical rigid core is about 12 Å. A broad peak at wide-angle region about 20 ° observed for all the polymers can be attributed from the disordered arrangement of mesogenic groups 5. o 35.9 A o o 11.9 A Relative Instensity (a. u.) 30.6 A o 18.0 A o 4.5 A P03 o 11.8 A P01 p04 P02 10 15 20 25 2-theta (degree) Figure 2.2.5. X-ray diffraction patterns of polymer P01, P02, P03 and P04 Table 2.2.1. Peak Angles (°) and d Spacings (Å) for the Polymers Polymer 2θ1°/ d1 Å 2θ2°/ d2Å 2θ3°/ d3 Å 2θ4°/ d4 Å 2θ5°/ d5 Å P03 2.46/35.9 2.88/30.6 4.91/18.0 7.42/11.9 19.80/4.5 P01 7.52/11.8 20.1/4.4 P02 20.1/4.4 P04 20.2/4.4 74 2.2.3.3.3 AFM analysis By using atomic force microscopy (AFM), the self-assembly of the novel jacketed polymers was examined. AFM analyses were performed on spin-coated films. Only the films from P03 showed some ordered packing on the substrates. The AFM images from P03 are displayed in Figure 2.2.6. a b Figure 2.2.6. AFM images (contact mode) of film on glass slide by spin-coated from a solution of P03 (0.5 mg/ml) in THF (a) 10× 10 µm, (b) 5× µm. The image displays a well-ordered fibrous structure, which is characteristic of the selfassembly of cylindrical rods6-8. The jacketed polymer P03 has laterally attached side rigid mesogenic groups, which are much bigger than the repeating units of the polymer backbone. It is believed that the jacketed polymer backbone was forced to take a rigid conformation due to the steric repulsion between the densely grafted side chains and excluded volume effects. Therefore, The polymer chains can be seen as thick rods 5, 9, 10. AFM images from P03 demonstrate the cylindrical self-assembling properties of the jacketed polymer packed on the surface. The diameter of fibers is about 60 nm - 100 nm. 75 The mechanism for self-assembly of the novel jacketed polymer needs further investigation, and it is believed that the individual polymer chains aggregate to form a thick fiber. In view of the DSC, X-ray diffraction, and AFM results, the following scheme for the 2D rectangular columnar mesophase is suggested: the polymer backbone and the mesogenic units of the rigid cylindrical core are organized into 2D rectangular columnar cell whereas the flexible alkyl chains attached to the mesogenic units were filled in the cell. Figure 2.2.7. Schematic representation of rectangular columnar structures of the novel jacketed polymer. 2.2.3.4 Influence of the pyrimidine functional groups and the alkyl chains on the self-assembly of the jacketed polymer It is interesting to compare the self-assembly of polymer P01, P02, P03 and P04 based on the results from DSC, POM, X-ray diffraction and AFM analysis. The bulky polymer P04 only shows a glass transition in DSC and X-ray diffraction results show that the 76 polymer P04 takes an amorphous conformation, which is in contrast to the normal mesogen-jacketed polymers. In small liquid crystalline molecules, it is believed that if the alkyl chains are grafted in the lateral position at the rigid core, the ordered arrangement of the molecules is strongly disturbed 11-12 . In polymer P04, the flexible alkyl group is attached to the lateral position of the terphenyl rigid rods, which are parallel to the polymeric backbone. This causes disturbance to the ordered arrangement of the polymers. For polymer P01, there are no alkyl chains grafted in the lateral position resulting ordered arrangement as confirmed by the X-ray diffraction patterns. However no long-range order was observed in the lattice, which might be due to the lack of the driving force from the micro-separation between the rigid and flexible segments13, 14. Polymer P02 did not show any characteristic peaks in X-ray or DSC investigations. For polymer P03, DSC, X-ray diffraction results indicate a columnar lattice structure and an ordered pattern on the substrate (AFM). Between P03 and P04, there are no significant differences in the chemical structure, except that the polymer P03 bears terminal pyrimidine groups on the aromatic core. This clearly demonstrates that the pyrimidine groups at the terminal ends play an important role in the self-assembly of the polymer P03, probably due to polarization effect. In polymer P03, the terminal polar groups (pyrimidine groups) on the aromatic rigid core may contribute to the incompatibility between the lateral alkyl chains and the polymer backbone. Moreover, the pyrimidine groups also provide additional sites for intermolecular interactions, for example hydrogen bond, electronic interaction, through which mesophase stabilization was achieved. Similar observations were seen in the small liquid crystal molecules using this approach 15-18. 77 2.2.4 Conclusion A new series of mesogen-jacketed polymers comprised of laterally attached aromatic mesogenic units with the alkyl chains grafted in the lateral position were synthesized. Results from this study show that the polymers with short alkyl chains (P01, P02) or with long alkyl chains in lateral position of mesogenic units (P04) are short of long-range order, only the polymers incorporated with rigid side chains bearing pyrimidine groups on the aromatic rigid core can exhibit mesophase. X-ray diffraction and AFM studies indicate that the polymer P03 can self-organize into a cylindrical structure with longrange order inside a rectangular columnar structure. The study on the structure-property relationship of the polymers based on the pyrimidine functional groups and the alkyl chains led us to understand the driving force for the self-organization of the jacketed polymers. It is believed the alkyl chains grafted in the lateral position on the aromatic rigid core of the jacketed polymer cause a disturbance to the self-assembly of the jacketed polymers. However, the polar groups (pyrimidine groups) not only helped to increase the incompatibility between the alkyl chains and the polymer backbone, but also provided additional cohesive intermolecular forces. Both effects resulted in the formation of ordered packing from the polymer P03. This study could afford information to the designation for the building blocks for the self-assembling materials. Reference 1. Miyaura, N.; Suzuki, A. Chem. Rev. 1995, 95, 2457-2483. 2. Percec, V.; Ahn, C.; Bera, T.; Ungar, G.; Yeardley, D. T. P. Chem. Eur. J. 1999, 5(3), 1070-1083. 78 3. Ponomaenko, S.; Boiko, N.; Shibaev, V.; Richardson, R.; Whitehouse, I.; Rebrov, E.; Muzafarov, A. Macromolecules 2000, 33, 5549-5558. 4. Lee, M. H.; Jang, D.; Kang, Y.; Zin, W. Adv. Mater. 1999, 11, 1018-1021. 5. Yin, X.; Ye, Chun, Ma, X.; Chen, E.; Qi, X.; Duan, X.; Wan, X.; Cheng, S. Z. D.; Zhou, Q. F. J. Am. Chem. Soc. 2003, 125, 6854-6855. 6. Leclere, P.; Calderone, A.; Marsitzky, D.; Francke, V.; Geerts, Y.; Mullen, K.; Bredas, J.; Lazzaroni, R. Adv. Mater. 2000, 1042-1046. 7. Wang, H.; Wang, H.-H.; Urban, V.; Littrell, K.; Thiyagarajan, P.; Yu, L. J. Am. Chem. Soc. 2000, 122, 6855-6861. 8. Ajayaghosh, A.; George, J. J. Am. Chem. Soc. 2001, 123, 5148-5149. 9. Zhou, Q. F.; Li, H. M.; Feng, X. D. Macromolecules 1987, 20,233. 10. Zhang, D.; Liu, Y.; Wan X.; Zhou, Q. F. Macromolecules 1999, 32,4494-4496. 11. Hildebrandt, F.; Schroter, J.; Tschierske, C.; Kleppinger, R.; Wendorff, J. Angew. Chem. Int. Ed. Engl. 1995, 34 (15), 1631-1633. 12. Cheng, X.; Das, M.; Diele, S.; Tschierske, C. Angew. Chem. Int. Ed. Engl. 2002, 41 (21), 4031-4035. 13. Chen, W.; Wunderlich, B. Macromol. Chem. Phys. 1999, 200, 283-311. 14. Tschierske, C. J. Mater. Chem. 1998, 8(7), 1485-1508. 15. Schroter, J.; Tschierske, C.; Wittenberg, M.; Wondorff, J. J. Am. Chem. Soc. 1998, 120, 10669-10675. 16. Kolbel, M.; Beyersdorff, T; Cheng, X.; Tschierske, C.; Kain, J.; Diele, S. J. Am. Chem. Soc. 2001, 123, 6809-6818. 79 17. Prehm, M.; Cheng, X.; Diele, S.; Das, M. K.; Tschierske, C. J. Am. Chem. Soc. 2002, 124, 12072-12073. 18. Prehm, M.; Diele, S.; Das, M. K.; Tschierske, C. J. Am. Chem. Soc. 2003, 125, 614-615. 80 [...]... o 4.5 A P03 o 11.8 A P01 p04 P 02 5 10 15 20 25 2- theta (degree) Figure 2. 2.5 X-ray diffraction patterns of polymer P01, P 02, P03 and P04 Table 2. 2.1 Peak Angles (°) and d Spacings (Å) for the Polymers Polymer 2 1°/ d1 Å 2 2 / d2Å 2 3°/ d3 Å 2 4°/ d4 Å 2 5°/ d5 Å P03 2. 46/35.9 2. 88/30.6 4.91/18.0 7. 42/ 11.9 19.80/4.5 P01 7. 52/ 11.8 20 .1/4.4 P 02 20.1/4.4 P04 20 .2/ 4.4 74 2. 2.3.3.3 AFM analysis By using atomic... O-CH2-, 2 H), 1.73 (p, J = 7.5 Hz, R(O)-CH2-, 2 H), 1 .26 (b, -CH2- 18 H), 0.87 (t, J = 6.7 Hz, -CH3, 3 H) 13C NMR (75.4 MHz, CDCl3, δ ppm): 157.0, 156.7, 150.8, 149.5, 66 131.5, 128 .6, 128 .2, 127 .2, 115.9, 114.6, 106 .2 (Ar-C), 71.7, 69.5 (O-CH-), 318, 29 .5, 29 .4, 29 .3, 29 .2, 29 .1, 29 .0, 25 .9, 22 .6 (-CH2-), 13.9 (-CH3) MS (ESI): m/z: 524 .5, 433.4, 355 .2, 26 5.1, 23 8.1, 91.1 Mp: 1 32 °C 4-Dodecyloxy -2, ... 31.8, 29 .5, 29 .4, 29 .3, 29 .2, 29 .1, 28 .7, 27 .9, 25 .8, 22 .6 67 (-CH2-), 18.3 (=C-CH3), 13.9 (-CH3) MS (EI): m/z: 5 02. 4, 4 72. 4, 433.4, 334 .2, 26 5 .2, 69.0 Mp: 1 12 °C Poly(4-dodecyloxy -2, 5-di(pyrimidin-5-yl) phenyl-1-yl methacrylate) (P03) Polymerization of 14 was performed according to the procedure described for P01 Yield: 0. 82 g ( 82 %) 1H NMR (300 MHz, CDCl3, δ ppm): 9 .22 - 8.87 (b, ArH, 6 H), 7 .26 -... 92. 4 (Ar-C), 68.8 (O-CH-), 31 .2, 28 .9, 28 .8, 28 .7, 28 .6, 28 .5, 28 .4, 25 .4, 21 .9 20 .2 (-CH2-), 13.8 (-CH3) MS (ESI): m/z: 434.3, 22 6.1, 23 8.1, 21 2.1, 158.1, 106.1, 71.1, 57.1 Mp: 170 °C 4-Dodecyloxy -2, 5-di(pyrimidin-5-yl) phenyl-1-yl methacrylate (14) Compound 14 was synthesized according to the procedure described for the synthesis of compound 6 From the reaction of 2. 0 g (4.6mmol) of compound 13 and. .. Hz, C(O)-CH2-, 2 H), 1 .24 (b, -CH2-, 16 H), 0.85 (t, J = 6.84 Hz, -CH3, 3 H) 13 C NMR (75.4 MHz, CDCl3, δ ppm) 151.5, 145.7, 144.6, 130.7, 126 .4, 126 .3, 123 .4, 121 .9, 120 .4, 119.7, 111.8, 110.7, 110.5, 109.4 (Ar-C), 66.5 (O-CH2-Ar), 66 .2 (O-CH2-), 26 .6, 24 ., 24 .2, 24 .1, 24 .0, 23 .9, 23 .8, 20 .7, 17.4, 8.8 (alkyl C) MS (ESI): m/z: 368.1, 27 7.1, 20 0.0, 109.0 Mp: 115 °C 1-Benzyloxy-4-dodecyloxy -2, 5-di (pyrimidin-5-yl)... CDCl3, δ ppm): 9 .22 - 8.87 (m, Ar-H, 6 H), 7 .26 (s, ArH, 1 H), 7.04(s, ArH, 1H), 6 .22 (s, CH2=C, 1 H), 5.71 (s, CH2=C, 1 H), 4.04 (t, J = 6.6 Hz, O-CH2-C, 2 H), 1.93 (s, =C-CH3, 3H), 1.74 (p, J = 6.7 Hz, R(O)-CH2-, 2 H), 1 .24 (b, -CH2- 18 H), 0.89 (t, J = 7 .2 Hz, -CH3, 3 H) 13 C NMR (75.4 MHz, CDCl3, δ ppm): 157.9 (C=O), 157.3, 156.7, 156 .2, 154 .2, 141.5, 134.8, 129 .1, 128 .2, 125 .2, 124 .8, 113.5 (ArC,... 6.88 (b, Ar-H, 12 H), 3.89 (b, O-CH2-C, 2 H), 1.83 (b, C(O)-CH2-, 2 H), 1 .27 (b, -CH2- 18 H), 0.89 (b, -CH3, 6H) FT-IR (KBr, cm-1): 3068 (ArH stretching), 29 33 (-CH2- stretching), 1 724 (ester C=O stretching), 1515, 1490, 14 72 (Ar, C=C stretching), 125 9, 1183, 1058 (C-O-C stretching) Mw: 1.08 × 104, Mn: 0.81 × 104, PD: 1.3 2. 2.3 Results and discussion 2. 2.3.1 Synthesis of polymers The polymers were synthesized... spectra of monomer 14 and polymer P03 in CDCl3 2. 2.3 .2 Thermal analysis The thermal stability of polymers P01-04 in nitrogen was investigated by thermogravimetric analysis (TGA) and the results are given in Figure 2. 2 .2 All polymers showed a weight loss at 28 5-305 °C (28 5 °C for P03, 28 9 °C for P04, 3 02 °C for P 02 and 69 305 °C for P01) Typically, the polymers P03 and P04 show a two-stage decomposition, wherein... Å and 4.5 Å are derived P01 affords a sharp reflection in middle angle region and a broad peak at 2 = 7. 52 and 20 .2 , from which a d spacing of 11.8 and 4.4 Å is derived For P 02 and P04, the diffraction patterns only exhibit one broad peak at 2 = 20 .1o and 20 .2 o, and no sharp peaks were observed indicating the absence of long-range ordering in the polymer lattice It is noted that polymer P03 afforded... backbone and the mesogenic units of the rigid cylindrical core are organized into 2D rectangular columnar cell whereas the flexible alkyl chains attached to the mesogenic units were filled in the cell Figure 2. 2.7 Schematic representation of rectangular columnar structures of the novel jacketed polymer 2. 2.3.4 Influence of the pyrimidine functional groups and the alkyl chains on the self- assembly of the jacketed . 131 .2, 124 .4, 122 .0, 117.5, 114.8, 106.4, 92. 4 (Ar-C), 68.8 (O-CH-), 31 .2, 28 .9, 28 .8, 28 .7, 28 .6, 28 .5, 28 .4, 25 .4, 21 .9 20 .2 (-CH 2 -), 13.8 (-CH 3 ). MS (ESI): m/z: 434.3, 22 6.1, 23 8.1, 21 2.1,. 66 131.5, 128 .6, 128 .2, 127 .2, 115.9, 114.6, 106 .2 (Ar-C), 71.7, 69.5 (O-CH-), 318, 29 .5, 29 .4, 29 .3, 29 .2, 29 .1, 29 .0, 25 .9, 22 .6 (-CH 2 -), 13.9 (-CH 3 ). MS (ESI): m/z: 524 .5, 433.4, 355 .2, 26 5.1,. 31.8, 29 .5, 29 .4, 29 .3, 29 .2, 29 .1, 28 .7, 27 .9, 25 .8, 22 .6 67 (-CH 2 -), 18.3 (=C-CH 3 ), 13.9 (-CH 3 ). MS (EI): m/z: 5 02. 4, 4 72. 4, 433.4, 334 .2, 26 5 .2, 69.0. Mp: 1 12 °C. Poly(4-dodecyloxy -2,