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

Chapter Part1 Synthesis and characterization of novel jacketed polymers 32 2.1.1 Introduction The development of synthetic materials with controlled nanostructures is a fascinating area of scientific research in science and engineering. The driving forces arise from areas such as biological, microelectronic material science and development of sensing, actuating, and control devices with components in the nano- or microscale 1. Various chemical synthesis and physical manipulation techniques are under development to meet the challenge of architectural control in nanoscale. Examples include electrodepositing metals inside the pores of commercial membrane, growing polymers in the cavities of inorganic clay and sieves2-3, or self-assembly methods to develop nanostructured materials. Self-assembly of molecules through non-covalent forces including hydrophobic and hydrophilic effects, electrostatic interactions, hydrogen bonding, microphase segregation, and shape of molecules have significant potential for creating such supramolecular structures 4-5 . It is relatively easy to self-assemble macromolecules into ordered morphologies covering several length-scales6. There is growing interest in the precise control of the order of macromolecules in the nano-scale through self-assembly, which may be used in improvement of the material properties, lithographic techniques, chemical sensors and so on. The order of macromolecules depends largely on the primary structure and the segmental interaction of polymers. It is well known that the chain stiffness of polymers offers a method of controlling the spatial arrangement of a polymer chain. This stiffness may contribute to the formation of supramolecular structures and is used to demonstrate the correlation between chemical structure and performance in application. There are usually two ways to make the chain stiff. In one method, the main chain of the 33 polymer is made of rigid, interconnected groups. For example, many rigid - coil block copolymers with helical rods, mesogenic rods, and conjugated rods, have been reported7. Another way is to force the main chain to take a rigid conformation through the attachment of many side groups on the polymer backbone. These polymers can be considered as jacketed polymers and used as building blocks can provide valid access to the construction of interesting architectures5-9. The concept of jacketed polymers was first proposed by Zhou et al.9-11 to describe a new type of liquid crystalline polymers in which the mesogenic units were attached laterally to the main chain via a direct connection or via short spacers. The results of X-ray diffraction9 revealed that the rigid side groups spiral around the backbone of the mesogen - jacketed polymers and the morphological study showed that the polymers have a branded texture similar to that of the semi - rigid main - chain liquid crystalline polymers. The authors suggested that the jacketed polymer’s main chain backbone was forced to take a stiffen conformation due to the steric repulsion between the densely grafted side chains and excluded volume effects. These jacketed polymers often show liquid crystalline properties and allow the creation of highly ordered architecture. Polymacromonomers can also be considered as a kind of jacketed polymers, in which the side group is a flexible polymer chain. Schmidt’s group12 reported the synthesis of polymacromonomers based on polystyrene side chains and a methacrylate main chain. Such polymers adopt the conformation of a cylindrical brush. The study showed that the methacrylate main chain exhibits extremely high chain stiffness in the order of 100 nm for the Kuhn statistical segment length, and it depends on the length of the side chains used. 34 Percec et al. synthesized a series of monodendron - jacketed polymers5, 7, 8, 13-15. They demonstrated a rational control of polymer conformation through self-assembly of monodendritic side - groups. At low degree of polymerization (DP), the conical monodendrons assembled to produce a spherical polymer with random - coil backbone conformation. At high DP, the monodendritic units changed to give a cylindrical polymer with an extended backbone. This correlation between polymer conformation and DP is opposite to that seen in most synthetic and natural macromolecules. This may provide a new method for the design of organized supramolecular materials for nanotechnology, functional films and fibers, and molecular devices. The Schluter group16 have reported the synthesis of poly(p-phenylene) substituted with monodendron side groups, in which the main chain is rigid and of sterically crowded. The scanning tunneling microscopy (STM) investigations showed that the polymers take rigid rod type conformation. Recent years have seen much progress in the use of rigid components in polymers as building blocks to form interesting supramolecular structures and their intriguing properties are extensively discussed9,10,13. Generally, the rigid components are incorporated on the main chain of the polymers. Further studies are required to understand the properties of jacketed polymers in which the main chain is sterically crowded with laterally attached rigid side chains17-19. Here we report the synthesis of a series of novel jacketed polymers. Constitutes on the polymer backbone are designed to incorporate strong electrostatic, weak Van der Waals interactions, and shape effects, to control the self-assembly of polymer chains in the lattice. The novel polymers were characterized with GPC, DSC, TGA, FTIR, 35 and NMR. This work show characterization about the rigid side chain organization and provide a new method to design novel macromolecular building blocks. 2.1.2 Experimental section 2.1.2.1 Materials and reagents All reagents and solvents were obtained from commercial supplies 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 Å molecular sieves (Aldrich). Flash column chromatography was performed using silica gel (60-120 mesh, Aldrich). 2.1.2.2 Instrumentation Fourier transform infrared (FT-IR) spectra were obtained using a Perkin-Elmer 1616 FT-IR spectrometer as KBr mulls. 1H NMR, 13C NMR spectra were recorded on a Bruker ACF 300 MHz spectrometer. Thermogravimetric analyses (TGA) and differential scanning calorimetry (DSC) traces were recorded using a TA-SDT2960 and a TA-DSC 2920 at a heating rate of 10 °C min-1 under N2 environment. The XRD patterns were recorded on an X-ray powder diffractometer with a graphite monochromator using Cu-Kα radiation with a wavelength of 1.54 Å at room temperature (scanning rate: 0.05 o /s; scan range 1.5-30o). Gel permeation chromatographic (GPC) analyses 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. Melting points (Mp) were obtained on a BÜCHI Melting Point B-540 apparatus and are uncorrected. 36 2.1.2.3 Synthesis. Poly(5’-dodecyloxy-[1, 1’; 4’, 1’’]terphenyl-2’-yl methacrylate) (7a), poly(5’’dodecyloxy [1, 4’; 1’, 1’’; 4’’, 1’’’; 4’’’, 1’’’’] quinquephenyl-2’’-yl methacrylate ) (7b), poly(1, 3-bis (5'-dodecyloxy [1, 1'; 4', 1''] terphenyl-2'-yloxy) propan-2-yl methacrylate) (10a) and poly (1, 3-bis (5''-dodecyloxy [1, 4'; 1', 1''; 4'', 1'''; 4''', 1''''] quinquephenyl-2''-yloxy) propan-2-yl methacrylate) (10b) were synthesized using the following route shown in Scheme 2.1.1: Synthesis of monomers and polymers 2,5-dibromohydroquinone (1) In a 1L round-bottom flask containing a teflon stir bar was placed 110.2 g hydroquinone (1 mol) and 200 ml glacial acetic acid. A solution of 102.7 ml Br2 (0.99 mol) in 150 ml glacial acetic acid was added dropwise to the flask. After finish the addition, the reaction mixture was kept stirring at RT for 12 h, then poured into water. The precipitate was recrystallized in glacial acetic acid to yield a white crystalline solid. Yield: 189.4g (71 %). 1H NMR (300MHz, DMSO-d6, δ ppm): 7.16 (s, Ar-H, H), 5.16 (s, Ar-OH, H). 37 OH OH OH Br2 Br NaOH/Ethanol K2CO3/Ethanol Br Benzylbromide Br OH 12-bromoldodecane OC12 H25 Glacid acetic acid OH OBn Br Br Br OC12 H25 OBn B(OH)2 OH H2 Pd(PPh3)4\toluene\Na2CO3 Pd/C C12H25 C12H25O 5a 4a OBn B(OH)2 Pd(PPh3)4\toluene\Na2CO3 C12H25O 4b H2 OH Pd/C ROH C12H25O 5b CH3 H2C C C O Cl CH3 H2C C CO TEA/THF RO AIBN CH3 H2C C n C O RO OH CH3 H2C C CH3 AIBN Br Br OH Cl C O H2C C C O ROH O DMF/K2CO3 OR OR TEA/THF H2 CH3 C C n C O O OR OR OR OR 10 R= C12H25O a C12H25O b Scheme 2.1.1: Synthesis route for the monomers and polymers 38 2,5-dibromo-4-dodecyloxyphenol (2) 53.6 g of compound (0.2 mol), 12 g NaOH (0.3 mol) and 500 ml absolute ethanol were added to a L round-bottom flask, purged with N2 for 20 min, heated to 50-60 °C under N2 atmosphere and 46 ml bromododecane (0.19 mol) was added dropwise to the solution. After finishing the addition, the reaction mixture was stirred for 18 h. The reaction mixture was allowed to cool to RT and then filtered. The solution was concentrated and poured into dilute HCl. The precipitate was recrystallized in hexane to yield a white powder. Yield: 26.9 g (32.5 %). 1H NMR (300 MHz, CDCl3, δ ppm): 7.24 (s, Ar-H, H), 6.90 (s, Ar-H, H), 5.15 (s, Ar-OH, H), 3.93 (t, J = 6.4 Hz, ArO-CH2-, H), 1.80 (p, J = 6.8 Hz, R(O)-CH2-,2 H), 1.27 (b, -CH2-, 18 H), 0.8 (t, J = 6.0 Hz, -CH3, H). 13 C NMR (75.4 MHz, CDCl3, δ ppm): 150.0, 120.2, 118.4, 116.2, 112.5, 108 (ArC), 70.3 (O-C-), 31.8, 29.6, 29.5, 29.4, 29.2,29.1, 28.9, 23.4, 22.6, 13.9 (-CH2-), 11.3 (-CH3). MS (EI): m/z: 438.2, 436.2. Mp:66 °C. 1-benzyloxy-2, 5-dibromo-4-dodecyloxy benzene (3) In a 1L round-bottom flask was placed 21.8 g compound (0.05 mol), 10.4 g K2CO3 (0.075 mol) and 400 ml absolute ethanol. The mixture was purged with N2 for 20 min, heated to 75°C under the atmosphere of nitrogen. A solution of benzyl bromide 11.9 ml (0.1 mol) in 50 ml absolute ethanol was added dropwise. After finishing the addition, the reaction mixture was kept stirring for 18 h, cooled to RT and filtered. The solution was concentrated and poured into water. The precipitate was recrystallized in ethanol to yield a white powder. Yield: 20.5 g (77.9 %). 1H NMR (300 MHz, CDCl3, δ ppm): 7.47 - 7.32 (m, Ar-H, H), 7.16 (s, Ar-H, H), 7.11 (s, Ar-H, H), 5.07 (s, ArO-CH2-, H), 3.95 (t, J = 6.6 Hz, ArO-CH2-, H), 1.83 (q, J = 6.8 Hz, 2H), 1.27 (b, -CH2-, 18 H), 0.89 (t, J = 6.0 Hz, -CH3, 3H). 13 C NMR (75.4 MHz, CDCl3, δ ppm): 150.5, 149.5, 136.2, 128.5, 128.0, 127.2, 119.3, 118.2, 111.5, 39 111.0 (ArC), 72.0, 70.1 (O-CH-), 32.8, 29.6, 29.4, 29.3, 29.2, 29.0, 25.8, 22.6, 14.0 (CH2-), 11.3 (-CH3). MS (EI): m/z: 526.1, 524.2. Mp: 152 °C. 2’-Benzyloxy-5’-dodecyloxy [1, 1’; 4’, 1’’] terphenyl (4a) 20 A 500 ml round-bottomed flask equipped with a condenser was charged with 10.52 g compound (20 mmol), 7.32 g phenyl boronic acid (60 mmol), 80 ml toluene, 20 ml methanol and 100 ml 2M sodium carbonate solution. The mixture was degassed before the catalyst tetrakis(triphenylphosphine) palladium (1 g, mol%) was added in dark under argon atmosphere. The reaction mixture was heated to 100 °C for 48 h, cooled to RT and filtered. The liquid layer was separated with a separation funnel, and the aqueous layer was extracted with toluene (100 ml × 2). The toluene layer was combined and washed with 3× 100 ml water and dried over MgSO4. The solvent was then removed under reduced pressure, and the resulting crude product was purified using column chromatography on silica gel column with hexane and dichloromethane (4:1) as the eluant. Yield: 4.6g (44.3%). 1H NMR (300 MHz, CDCl3, δ ppm): 7.65 7.29 (m, ArH, 15 H), 7.06 (s, Ar-H, H), 7.00 (s, Ar-H, H), 4.99 (s, ArO-CH2-, 2H), 3.92 (t, J = 6.5 Hz, ArO-CH2-, H), 1.68 (p, J = 6.5 Hz, R(O)-CH2-, H), 1.26 (b, -CH2-, 18 H), 0.8 (t, J = 6.3 Hz, H). 13C NMR (75.4 MHz, CDCl3, δ ppm): 150.7, 149.7, 149.5, 148.3, 148.2, 148.1, 138.3, 138.2, 131.4, 130.7, 129.5, 129.4, 128.3, 127.9, 127.8, 127.5, 127.3, 127.3, 127.1, 126.9, 126.8, 117.4, 116.1 (ArC), 77.8, 69.4(O-CH-), 31.8, 29.6, 29.5, 29.5, 29.3, 29.2, 28.9, 25.9, 22.6, 14.0 (-CH2-), 12.5 (CH3). MS (EI): m/z: 520.6, 429.4, 352.3, 261.1, 215.2, 183.1,83.0. Mp: 76 °C. 2’’-Benzyloxy-5’’-dodecyloxy [1, 4’; 1’, 1’’; 4’’, 1’’’; 4’’’, 1’’’’] quinquephenyl (4b) Compound 4b was synthesized according to the procedure described for the synthesis of 4a. Yield: 4.5 g (33.6 %). 1HNMR (300 MHz, CDCl3, δ ppm): 7.72 - 7.30 (m, Ar- 40 H, 23 H), 7.26 (s, Ar-H, H), 7.07 (s, Ar-H, H), 5.06 (s, ArO-CH2-, H), 3.98 (t, J = 6.3 Hz, ArO-CH2-, 2H), 1.73 (p, J = 6.8 Hz, R(O)-CH2-, 2H), 1.24 (b, -CH2-,18 H), 0.87 (t, J = 6.0 Hz, -CH3, 3H). 13 C NMR (75.4 MHz, CDCl3, δ ppm): 150.8, 149.8, 140.9, 139.8, 139.7, 137.3, 130.9, 130.3, 129.9, 129.8, 128.7, 128.3, 127.6, 127.2, 128.7, 128.7, 128.3, 127.6, 127.1, 127.0, 126.9, 126.7, 126.6, 117.3, 115.9, 98.1 (ArC), 71.9, 69.5 (O-CH), 31.8, 29.6, 29.6, 29.5, 29.3, 29.2, 26.0, 22.6, 14.0 (-CH2-), 11.3 (-CH3). MS (ESI): m/z: 672.4, 581.6, 413.2, 306.2, 289.2, 228.2, 153.1. Mp: 143 °C. 5’-Dodecyloxy [1, 1’, 4’, 1’’] terphenyl-2’-ol (5a) 21 To a 100 ml round-bottom flask containing 10% Pd/C (2.5 g) in 50 ml THF was added 4a (2.6 g, mmol). The flask was charged with nitrogen, and a balloon filled with H2 was fitted to the flask. The nitrogen was briefly evacuated from the flask, and H2 was charged above the solution. The mixture was stirred for 24 h at ambient temperature and filtered through a glass frit containing a small layer of celite powder. After the solid was washed with THF (3 × 25 ml), the organic fractions were combined and the excess solvent was removed under reduced pressure to yield a white powder. Yield: 2.02 g (93 %). 1H NMR (300MHz, CDCl3, δ ppm): 7.42 - 7.40 (m, Ar-H, H), 7.38 - 7.32 (m, Ar-H, H), 4.90 (s, Ar-OH, 1H), 3.88 (t, J = 6.2 Hz, ArO-CH2-, H), 1.67 (p, J = 6.8 Hz, R(O)-CH2-, H), 1.25 (b, -CH2-, 18 H), 0.88 (t, J = 6.6 Hz, H). 13 C NMR (75.4 MHz, CDCl3, δ ppm): 150.1, 146.3, 142.7, 140.7, 137.9, 137.2, 132.0, 131.8, 131.7, 131.2, 129.4, 129.1, 128.9, 127.8, 127.3, 126.9, 118.0, 115.3, 98.1 (ArC), 69.6 (O-CH-), 31.8, 29.6, 29.5, 29.5, 29.3, 29.2, 29.2, 25.9, 22.6, 14.1 (-CH2-), 13.9 (-CH3). MS (ESI): m/z: 430.2, 262.2, 149.0, 66.0. Mp: 61 °C. 5’’-Dodecyloxy [1, 4’; 1’, 1’’; 4’’, 1’’’; 4’’’, 1’’’’] quinquephenyl-2’’-ol (5b) 41 Compound 5b was synthesized according to the procedure described for the synthesis of 5a. From 4.3 g of 4b was obtained 3.5 g of white powder. Yield: 3.4 g (93 %). 1H NMR (300 MHz, CDCl3, δ ppm): 7.73 - 7.46 (m, Ar-H, 18 H), 7.26 (s, Ar-H, H), 7.07 (s, Ar-H, H), 5.10 (s, Ar-OH, H), 3.94 (t, J = 6.5 Hz, ArO-CH2-, H), 1.72 (p, J = 6.7 Hz, -CH2-, H), 1.24 (b, -CH2- 18 H), 0.89 (t, J= 4.0 Hz, H). 13C NMR (75.4 MHz, CDCl3, δ ppm): 150.3, 146.3, 140.9, 129.8, 129.2, 128.8, 128.7, 127.8, 127.5, 127.1, 127.0 126.9, 126.5, 120.6, 118.8, 115.3, 98.1, 89.6 (ArC), 69.6 (O-CH), 31.8, 29.6, 29.5, 29.5, 29.3, 29.2, 28.8, 27.6, 26.0, 22.6 (-CH2-), 13.9 (-CH3). MS (ESI): m/z: 582.4, 414.3. Mp: 146 °C. 5’-Dodecyloxy [1, 1’, 4’, 1’’] terphenyl-2’-yl methacrylate (6a) Triethylamine (1.5 ml, 11 mmol) and compound 5a (2.15 g, mmol) were dissolved in a 50 ml dry THF placed in a 100 ml round-bottom flask. This solution was cooled with ice, and a solution of methacryloyl chloride (1 ml, 10 mmol) in ml THF was added dropwise. After finishing the addition, the reaction mixture was stirred at room temperature for hr, filtered and the volatile components were removed under reduced pressure. The resulting crude product was dissolved in dichloromethane, washed with sodium bicarbonate solution and followed by water (3 × 50 ml), and the organic layer was dried over anhydrous magnesium sulfate. Filtered the solution, and the solvent was removed under reduced pressure to yield the monomer. Yield: 1.7 g (68 %). 1H NMR (300 MHz, CDCl3, δ ppm): 7.65 -7.28 (m, Ar-H, 10 H), 7.21(s, ArH, H), 7.03 (s, Ar-H, H), 6.22 (s, CH2=C-, H), 5.65 (s, CH2=C-, H), 4.02 (t, J = 6.4 Hz, ArO-CH2-, H), 2.0 (s, =C-CH3, H), 1.68 (p, J = 6.9 Hz, R(O)-CH2-, H), 1.25 (b, -CH2-, 18 H), 0.90 (t, J = 6.6 Hz, -CH3, H). 13C NMR (75.4 MHz, CDCl3, δ ppm): 171 (C=O), 153.8, 141.2, 137.1, 136.6, 135.8, 134.6, 134.5, 133.8, 130.6, 129.3, 128.9, 128.8, 128.6, 128,6, 128.5, 126.6, 124.6, 114.5, (ArC, C=C), 62.9 (O- 42 CH-), 31.8, 29.6, 29.5, 29.4, 29.1, 29.0, 26.0, 25.9, 25.5, 21.1 (-CH2-), 18.2, 14.0 (CH3). MS (EI): m/z: 498.5, 430.5, 330.3, 289.2, 261.2. Mp: 45 °C. 5’’-Dodecyloxy [1, 4’; 1’, 1’’; 4’’, 1’’’; 4’’’, 1’’’’] quinquephenyl-2’’-yl methacrylate (6b) Monomer 6b was synthesized according to the procedure described for the synthesis of 6a. From 2.2 g (3 mmol) of compound 5b was obtained 1.28 g of 6b. Yield: 1.28 g (64.1 %). 1H NMR (300 MHz, CDCl3, δ ppm): 7.73 - 7.36 (m, Ar-H, 18 H), 7.24 (s, Ar-H, H), 7.04 (s, Ar-H, H), 6.18 (s, CH2=C-, H), 5.65 (s, CH2=C-, H), 3.98 (t, J= 6.5 Hz, ArO-CH2-, H), 2.02 (s, C=C-CH3, H), 1.73 (p, J = 6.6 Hz, R(O)-CH2-, H), 1,26 (b, -CH2-, 18 H), 0.87 (t, J = 6.7 Hz, -CH3, 3H). 13 C NMR (75.4 MHz, CDCl3, δ ppm): 166 (C=O), 150.3, 146.3, 140.9, 129.8, 129.1, 128.8, 128.7, 127.8, 127.5, 127.1, 127.0 126.9, 126.5, 120.7, 118.7, 115.2, 98.1, 89.6 (ArC), 69.4 (O-CH),31.8, 29.6, 29.5, 29.4, 29.2, 29.1, 28.7, 27.5, 26.0, 22.6 (-CH2), 18.4, 14.0 (-CH3). MS (EI): m/z: 650.4, 581.4, 482.2, 413.1, 69.1. Mp: 115 °C. Poly(5’-dodecyloxy [1, 1’, 4’, 1’’] terphenyl-2’-yl methacrylate) (7a) Monomer 6a (1.5 g, mmol) and 2, 2’-azobisisobutyronitrile (AIBN) (0.02 g, 0.01 mmol, 0.3 mol%) were dissolved in 20 ml dry THF. Purged with nitrogen for 30 min, heated to 70-80 ºC and stirred for 18 h under nitrogen flush. The polymer 7a was isolated via precipitation from methanol. Yield: 1.22 g (81 %). 1H NMR (300MHz, CDCl3, δ ppm): 7.66 - 7.32(b, Ar-H, 10 H), 7.07-7.00(b, Ar-H, H), 3.95(b, ArOCH2- H), 1.75-1.65(b, R(O)-CH2-, H), 1,24(b, -CH2-, 18 H), 0.87(b, -CH3, H). FT-IR (KBr, cm-1): 3030 (ArH stretching), 2928 (-CH2- stretching), 1724 (ester C=O stretching), 1515, 1478, 1390, 1370 (Ar, C=C stretching), 1268, 1165, 1020 (C-O-C stretching). 43 Poly(5’’-dodecyloxy [1, 4’; 1’, 1’’, 4’’, 1’’’; 4’’’, 1’’’’] quinquephenyl-2’’-yl methacrylate ) (7b) Polymer 7b was synthesized according to the procedure described for the synthesis of 7a. From 1.0 g of monomer 6b was obtained 0.52g of polymer 7b. Yield: 0.52g (52%). 1H NMR (300MHz, CDCl3, δ ppm): 7.66 - 7.32(b, Ar-H, 18 H), 7.07 - 6.87(b, Ar-H, H), 3.90(b, ArO-CH2-, H), 1.75-1.65(b, R(O)-CH2-, H), 1,24(b, -CH2-, 18 H), 0.87(b,-CH3, H). FT-IR (KBr, cm-1): 3067 (ArH stretching), 2920 (-CH2stretching), 1724 (ester C=O stretching), 1626, 1602, 1527 (Ar, C=C stretching), 1268, 1150, 1020 (C-O-C stretching). 1,3-Bis (5'-dodecyloxy [1, 1'; 4', 1''] terphenyl-2'-yloxy)-propan-2-ol (8a) 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 5a (4.3 g, 10 mmol) and potassium carbonate (2.1 g, 20 mmol). Under nitrogen flush, the mixture was heated to 80 °C and stirred for hr. A solution of 1,3-dibromo-2-propanol (0.8 ml, 3.5 mmol, d 2.12) in 25 ml DMF was added dropwise. 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 with column chromatography on a silica gel column using hexane and dichloromethane (10:1) as the eluant. Yield: 2.2 g (68.7 %). 1H NMR (300 MHz, CDCl3, δ ppm): 7.59 - 7.29(m, Ar-H, 20 H), 6.94(s, Ar-H H), 6.92(s, Ar-H, H), 4.05(m, R-CH-O, 1H), 3.93(m, O-CH2-, H), 3.91(m, ArO-CH2-, H), 2.03(s, Ar-OH, H), 1.68(b, R(O)-CH2-, H), 1.25(b, -CH2-, 36 H), 0.88(t, J = 6.7 Hz, -CH3, H). 13C NMR (75.4 MHz, CDCl3, δ/ppm): 154.2, 146.3, 140.9, 129.8, 129.1, 128.8, 128.6, 127.8, 127.4, 127.1, 127.0 126.9, 126.5, 120.6, 118.7, 115.2, 98.1, 89.6 (ArC), 69.6, 69.4, 69.2 (-O-CH2-), 31.8, 44 29.6, 29.5, 29.4, 29.3, 29.2, 29.1, 25.9, 22.5, 14.4 (-CH2-), 13.99 (-CH3). MS (ESI): m/z: 916.7, 486.4, 430.3, 262.3. 1, 3-Bis (5''-dodecyloxy [1, 4'; 1', 1'', 4'', 1'''; 4''', 1''''] quinquephenyl-2''-yloxy) propan-2-ol (8b) Compound 8b was synthesized according to the procedure described for the synthesis of 8a. From 4.0 g of compound 5b was obtained 1.7 g compound 8b. Yield: 1.7 g (60.7 %). 1H NMR (300 MHz, CDCl3, δ ppm): 7.68 - 7.36(m, ArH, 36 H), 7.10(s, ArH, H), 7.04(s Ar-H, H), 4.16(b, R-CH(O)-R, 1H), 4.06(m, O-CH2-, 4H), 3.95 (b, ArO-CH2-, H), 3.48(b, Ar-OH, H), 1.68(b, R(O)-CH2-, 4H), 1.23(b, -CH2-, 38 H), 0.87(t, J = 6.7 Hz, H). 13 C NMR (75.4 MHz, CDCl3): 150.3, 146.3, 140.9, 129.8, 129.1, 128.8, 128.6, 127.8, 127.4, 127.1, 127.0 126.9, 126.5, 120.6, 118.7, 115.2, 98.1, 89.6 (ArC), 69.6, 69.4, 69.1 (O-CH-), 31.8, 29.6, 29.5, 29.4, 29.25, 29.2, 28.7, 27.5, 26.0, 22.6 (-CH2-), 13.9 (-CH3). MS (ESI): m/z: 1220.5. Mp: 151 °C. 1, 3-Bis (5'-dodecyloxy [1, 1'; 4', 1''] terphenyl-2'-yloxy)-2-propyl methacrylate (9a) Monomer 9a was synthesized according to the procedure described for the synthesis of 6a. From 3.1 g of compound 8a (2 mmol) was obtained 1.2 g of 9a. Yield: 1.2 g (54 %). 1H NMR (300MHz, CDCl3, δ ppm): 7.65 -7.29 (m, Ar-H, 20 H), 6.94 (s, ArH, H), 6.92 (s, Ar-H, H), 6.10 (s, CH2=C-, H), 5.56 (s, CH2=C-, H), 5.35 (p, J = 5.1 Hz, R(O)-CH-R(O), H), 4.06 (d, J = 5.8 Hz, O-CH2-R(O), 4H), 3.91 (t, J= 6.6 Hz, ArO-CH2-, H), 2.02 (s, C=C-CH3, H), 1.68 (b, R(O)-CH2-, H), 1.25 (b, CH2-, 36 H), 0.87 (t, J = 7.0 Hz, -CH3, H). 13 C NMR (75.4 MHz, CDCl3, δ ppm): 166.5 (C=O), 153.8, 146, 140.9, 137, 135.5, 134.4, 127.7, 126.4, 126.2, 126.0, 125.6, 124.9, 122.0, 120.66, 118.78, 117.7, 98.1, 89.6 (ArC, C=C), 70.2, 69.4, 66 (O-CH2-), 45 31.82, 29.57, 29.53, 29.45, 29.35, 29.22, 29.16, 25.96, 22.58 (-CH2-), 18.4, 14.2 (CH3). MS (SI): m/z: 984.9, 541.5, 469.5, 262.4. Mp: 65 °C. 1, 3-Bis (5''-dodecyloxy [1, 4'; 1', 1''; 4'', 1'''; 4''', 1''''] quinquephenyl-2''-yloxy) 2-propyl methacrylate (9b) Monomer 9b was synthesized according to the procedure described for the synthesis of 6a. From 0.9g of compound 8a (0.75 mmol) was obtained 0.72 g of 9b. Yield: 0.72 g (85 %). 1H NMR (300 MHz, CDCl3, δ ppm): 7.68 - 7.36 (m, Ar-H, 36 H), 7.10 (s, Ar-H, H), 7.04 (s, Ar-H, H), 6.21 (s, CH2=C-, H), 5.63 (s, CH2=C-, H), 5.33(p, J = 4.8 Hz, R(O)-CH-R(O), H), 4.05 (d, J = 4.5 Hz, O-CH2-R(O), H), 4.06 (t, J = 6.8 Hz, ArO-CH2-, H), 2.0 (s, C=C-CH3, H), 1.68 (p, J = 6.9 Hz, R(O)-CH2-, H), 1.23 (b, Ar-H, 38 H), 0.87 (t, J = 6.7 Hz, H). 13 C NMR (75.4 MHz, CDCl3, δ ppm): 166.5 (C=O), 150.3, 146.3, 140.9, 129.8, 129.1, 128.8, 128.6, 127.8, 127.4, 127.1, 127.0, 126.9, 126.5, 120.6, 118.7, 115.2, 98.1, 89.6 (ArC, C=C), 70.2, 69.4, 66 (OCH2-), 31.8, 29.6, 29.5, 29.4, 29.2, 29.1, 28.7, 27.5, 26.0, 22.6 (-CH2-), 18.2,13.9 (CH3). MS (ESI): m/z: 1289.0. Mp: 60 °C. Poly(1, 3-bis (5'-dodecyloxy [1, 1'; 4', 1''] terphenyl-2'-yloxy)-2-propyl methacrylate) (10a) Polymer 10a was synthesized according to the procedure described for the synthesis of 7a. From 1.0g of monomer 9a (0.1 mmol) was obtained 0.67 g of white powder. Yield: 6.7 g (67 %). 1H NMR (300 MHz, CDCl3, δ ppm): 7.55 - 7.33 (b, Ar-H, 20 H), 6.93 - 6.87 (b, Ar-H, H), 5.21 (b, R(O)-CH-R(O), H), 4.10 - 3.87 (b, O-CH2-, 8H), 1.84 (b, R(O)-CH2-, H), 1,60 (b, -CH2-, H), 1.25 (b, -CH2-, 36 H), 0.88 (b, -CH3, 9H). FT-IR (KBr, cm-1): 3073 (ArH stretching), 2928 (-CH2- stretching), 1720 (ester C=O stretching), 1545, 1515, 1470, 1390(Ar, C=C stretching), 1204, 1140, 1058 (CO-C stretching). 46 Poly(1, 3-bis (5''-dodecyloxy [1, 4'; 1', 1''; 4'', 1'''; 4''', 1''''] quinquephenyl-2''yloxy)-2-propyl methacrylate) (10b) Polymer 10b was synthesized according to the procedure described for the synthesis of 7a. From 0.8 g of monomer 9b (0.6 mmol) was obtained 0.5 g of 10b. Yield: 0.5 g (62.5 %). 1H NMR (300 MHz, CDCl3, δ ppm): 7.60 - 7.37 (b, Ar-H, 36 H), 6.93 6.87 (b, Ar-H, H), 5.34 (b, R(O)-CH-R(O), 1H), 4.4-3.97 (b, O-CH2-, 8H), 1.84 (b, R(O)-CH2-, H), 1,60 (b, -CH2-, H), 1.25 (b, -CH2-, 36 H), 0.88 (b,-CH3, H). FTIR (KBr, cm-1): 3030 (ArH stretching), 2928 (-CH2- stretching), 1720 (ester C=O stretching), 1545, 1526, 1480 (Ar, C=C stretching), 1268, 1165, 1115 (C-O-C stretching). 2.1.3 Results and discussion 2.1.3.1 Synthesis of polymers The polymers were synthesized through radical polymerization from the appropriate monomers. The concentration of initiator AIBN was 0.5 mol % based on the amount of the monomer used. The molecular weight of polymer 7a, 7b, 10a, and 10b were estimated by GPC using a solution of polymers in THF. The results are shown in Table 2.1.1. Table 2.1.1. Number–average (Mn) and weight-average (Mw) molecular weight of polymers Polymer Mn Mw PD 7a 0.56 × 104 0.69 × 104 1.2 7b 0.42 × 104 0.68 × 104 1.6 10a 0.75 × 104 1.20× 104 1.6 10b 0.60 × 104 1.10× 104 1.8 The molecular weights of these polymers are low compared with unsubstitued PMMA. This result may be due to the structure of our monomers. In the monomer, 47 the conjugated side chain group is much larger than the methacrylate carbon-carbon double bond. This will result in a big steric hindrance when radical polymerization is carried out. The double bonds must react before the radical center is quenched. In our case, all the monomers have a large side group and form a very sterically crowded environment. This leads to the separation of radical centers and thereby retards the rate of polymerization. It is difficult to obtain a high molecular-weight polymer through normal radical polymerization. Recently, there are some published reports about the polymerization of the macromonomers through radical polymerization. The new strategy is to increase the concentration of the initiator and the monomers22. 2.1.3.2 NMR and FTIR analysis The structures of all monomers and polymers prepared in our work were characterized by 1H NMR and FTIR. Figure 2.1.1 illustrates two representative 1H NMR spectra of monomer 6a and polymer 7a. In the 1H NMR spectra of monomer 6a, for example, the signals appearing in the range of δ 7.75 –6.94 correspond to those in aromatic protons. The double peak at δ 6.22 and 5.65 are characteristic of methacrylic carbon double bond protons. It is noted that in the spectrum of polymer 7a, these two signals disappears. The structure of the polymers was characterized by means of infrared spectroscopy (IR). The spectrum of polymer 7a is shown in Figure 2.1.2 as an example. The IR spectrum shows typical peaks for aromatic hydrogen stretching at 3030 cm-1 and alkyl hydrogen stretching at 2928 cm-1. The peak of 1724 cm-1 is attributed to the ester group C=O. The strong peaks at 1204 cm-1, 1140 cm-1, 1058 cm1 region are assigned to C-O stretches. The absence of a C=C band at 1640 cm-1 indicates that the monomer has been polymerized completely. 48 Figure 2.1.1. 1H NMR spectra of 6a and 7a in CDCl3 Figure 2.1.2. The FT-IR spectrum of polymer 7a in KBr 49 2.1.3.3 Thermal properties The thermal stability of the novel polymers in nitrogen atmosphere was evaluated by thermogravimetric analysis (TGA), which is given in Figure 2.1.3. Polymer 7a showed a weight loss at 258 °C at a heating rate of 10 °C /min. Polymer 7b also showed a weight loss starting at 175 °C while polymer 10a and 10b showed a weight loss at a higher temperature, 230 °C and 245 °C, respectively. Two significant changes in the slopes of the degradation curves can be observed for the polymers. This two-step decomposition resulted from the special structures of the polymers. The polymers is composed with two components, one is the polymer methacrylate backbone, which decompose at 200-300 °C. 10b 100 10a Weight lose (%) 7b 7a 200 400 600 o Temperature ( C) Figure 2.1.3. TGA traces of polymer 7a, 7b, 10a, and 10b measured in nitrogen atmosphere The polymers were also characterized using differential scanning calorimetric (DSC) at a heating rate of 10 °C /min, which is shown in Figure 2.1.4. A glass transition was observed at about –3.2 °C for polymer 7a. The DSC plots of polymer 10a, 7b and 10b 50 showed a Tg at 4.5 °C, 34.3 °C and 74.5 °C respectively. With the increase of the phenyl group, the Tg of the polymer increases. Tg=74.5 C 10b Heat Flow Tg=34.3 C 7b Tg=4.5 C 10a Tg=-3.2 C 7a 100 200 o Temperature ( C) Figure 2.1.4. DSC traces of polymer 7a, 7b, 10a, and 10b measured in nitrogen atmosphere 2.1.3.4 X-ray analysis XRD measurements were used to characterize the polymer lattice. The X-ray diffraction profiles of the four polymers are similar. Figure 2.1.5 shows the XRD patterns of polymer 10a and 10b as representative. Polymer 10a shows a broad peak at 18.5 ° while polymer 10b shows a peak at 21.5°. No higher order peak is detected, indicating polymers appear to have poor lattice structure. The bulk polymer is considered to take an amorphous nature. 2.1.3.5 Polarized optical microscopy study The thermotropic liquid crystal polymers possess an intrinsic optical anisotropy (double refraction). Depending on the orientation of the liquid crystals, different textures may be observed, and used for identification of the liquid crystal phase. Figure 2.1.6 shows the photomicrograph of the liquid crystalline state of the 51 monomer 9a. The monomer 9a forms a liquid crystalline state at 110 ° C while its melt point is about 78 °C. A typical texture of nematic phase is observed. However, after polymerization, the polymer showed a Tg transition with no liquid crystalline phase. Intensity (a.u.) 400 10a 200 10b 10 20 30 2-Theta Figure 2.1.5. WAXS profiles of the polymer 10a and polymer 10b at room temperature Figure 2.1.6 Polarized optical micrograph of monomer 9a, taken at 110 °C 52 It is well known that the main chain of jacketed polymers may take a rigid conformation due to the steric repulsion between the densely grafted side chains and excluded volume effects. Such polymers show similar properties of semi-rigid or rigid main chain polymers. DSC traces can show special entropy changes accompanied by a transition from anisotropic liquid to isotropic liquid. The same strategy is taken in the design of our polymer structure on which big conjugated phenyl groups are incorporated in the side chain and force the main chain to take a rigid conformation. However, all polymers did not show a liquid crystalline phase. Only Tg changes were observed in the DSC data. It is also confirmed that the polymers appeared to have an amorphous conformation from the X-ray diffraction studies. It is believed that in small liquid crystalline molecules, if the alkyl chains are grafted in the lateral position at the rigid core, the order arrangement of the molecules is strongly disturbed 23, 24. In our polymers, the flexible alkyl chains are also attached to the lateral position of the terphenyl rigid rod, which has a great steric effect on the alignment of the calamitic cores. At the same time the lateral alkyl chains are incompatible to the aromatic cores whereas it is completely compatible with the backbone. This tendency also gives rise the disturbance to the ordered arrangement of the polymers. Therefore no order appears in the bulky polymer 7a and 7b. The disturbance is so strong that the polymer 10a and 10b still appear amorphous even when the rigid core increases to pentaphenyl groups, which is believed to create ordered packing. Based on our preliminary results, two methods are proposed to solve the problem. First, novel jacketed polymer without the alkyl chains may induce some packed order. Second, the repulsive interaction between some polar and non-polar units can be incorporated on the side chains so that the microseparation is enhanced in the selfassembly of the novel polymers. 53 2.1.4 Conclusion A series of novel jacketed polymers were synthesized, and characterized using GPC, DSC, TGA, FTIR, NMR, and X-ray diffraction studies. The results indicate that the novel jacketed polymers take an amorphous conformation and results from DSC and POM analysis showed no liquid crystalline properties. Reference 1. Lee, M.; Cho B.; Zin, W. Chem. Rev. 2001,101, 3869-3892. 2. Gin, D. F.; Gray, D.; Smith, R. Synlett. 1999, 10, 1509-1522. 3. Klok, H.; Lecommandoux, S. Advanced Materials 2001, 13, 1217. 4. Sheiko, S.; Moller, M. Chem. Rev. 2001, 101, 4099-4123. 5. Percec, V.; Schluter, A. D.; Ungar, G.; Cheng, S. Z. D.; Zhang, A. Macromolecules 1998, 31, 1745-1762 6. Tew, G.; Pralle, M.; Stupp, S. I. 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Karakaya, B.; Claussen, W.; Gessler, K.; Saenger, W.; Schluter, A. D. J. Am. Chem. Soc., 1997, 119, 3296-3301. 17. Arehart, S.; Pugh, C. J. Am. Chem. Soc. 1997, 119, 3027-3037. 18. Gopalan P.; Ober C. K. Macromolecules 2001, 34, 5120-5124. 19. Gopalan, P.; Zhang, Y.; Li, X.; Wiesner, U.; Ober, C. K. Macromolecules 2003, 36, 3357-3364. 20. Miyaura, N.; Suzuki, A. Chem. Rev. 1995, 95, 2457-2483. 21. Baxter, B.; Gin, D. Macromolecules 1998, 31, 4419-442. 22. Percec, V.; Ahn, C.-H; Barboiu, B. J. Am. Chem. Soc. 1997, 119, 1297812979. 23. Hildebrandt, F.; Schroter, J.; Tschierske, C.; Kleppinger, R.; Wendorff, J. Angew. Chem. Int. Ed. Engl. 1995, 34 (15), 1631-1633. 24. Cheng, X.; Das, M. K.; Diele, S.; Tschierske, C. Angew. Chem. Int. Ed. Engl. 2002, 41 (21), 4031-4035. 55 [...]... some polar and non-polar units can be incorporated on the side chains so that the microseparation is enhanced in the selfassembly of the novel polymers 53 2.1.4 Conclusion A series of novel jacketed polymers were synthesized, and characterized using GPC, DSC, TGA, FTIR, NMR, and X-ray diffraction studies The results indicate that the novel jacketed polymers take an amorphous conformation and results... to increase the concentration of the initiator and the monomers22 2.1.3.2 NMR and FTIR analysis The structures of all monomers and polymers prepared in our work were characterized by 1H NMR and FTIR Figure 2.1.1 illustrates two representative 1H NMR spectra of monomer 6a and polymer 7a In the 1H NMR spectra of monomer 6a, for example, the signals appearing in the range of δ 7.75 –6.94 correspond to... 1165, 1115 (C-O-C stretching) 2.1.3 Results and discussion 2.1.3.1 Synthesis of polymers The polymers were synthesized through radical polymerization from the appropriate monomers The concentration of initiator AIBN was 0.5 mol % based on the amount of the monomer used The molecular weight of polymer 7a, 7b, 10a, and 10b were estimated by GPC using a solution of polymers in THF The results are shown in... room temperature Figure 2.1.6 Polarized optical micrograph of monomer 9a, taken at 110 °C 52 It is well known that the main chain of jacketed polymers may take a rigid conformation due to the steric repulsion between the densely grafted side chains and excluded volume effects Such polymers show similar properties of semi-rigid or rigid main chain polymers DSC traces can show special entropy changes accompanied... at δ 6.22 and 5.65 are characteristic of methacrylic carbon double bond protons It is noted that in the spectrum of polymer 7a, these two signals disappears The structure of the polymers was characterized by means of infrared spectroscopy (IR) The spectrum of polymer 7a is shown in Figure 2.1.2 as an example The IR spectrum shows typical peaks for aromatic hydrogen stretching at 3030 cm-1 and alkyl... 0 Tg=-3.2 C 0 7a 100 200 o Temperature ( C) Figure 2.1.4 DSC traces of polymer 7a, 7b, 10a, and 10b measured in nitrogen atmosphere 2.1.3.4 X-ray analysis XRD measurements were used to characterize the polymer lattice The X-ray diffraction profiles of the four polymers are similar Figure 2.1.5 shows the XRD patterns of polymer 10a and 10b as representative Polymer 10a shows a broad peak at 18.5 ° while... peak of 1724 cm-1 is attributed to the ester group C=O The strong peaks at 1204 cm-1, 1140 cm-1, 1058 cm1 region are assigned to C-O stretches The absence of a C=C band at 1640 cm-1 indicates that the monomer has been polymerized completely 48 Figure 2.1.1 1H NMR spectra of 6a and 7a in CDCl3 Figure 2.1.2 The FT-IR spectrum of polymer 7a in KBr 49 2.1.3.3 Thermal properties The thermal stability of the... observed for the polymers This two-step decomposition resulted from the special structures of the polymers The polymers is composed with two components, one is the polymer methacrylate backbone, which decompose at 200-300 °C 10b 100 10a Weight lose (%) 7b 7a 0 200 400 600 o Temperature ( C) Figure 2.1.3 TGA traces of polymer 7a, 7b, 10a, and 10b measured in nitrogen atmosphere The polymers were also... the novel polymers in nitrogen atmosphere was evaluated by thermogravimetric analysis (TGA), which is given in Figure 2.1.3 Polymer 7a showed a weight loss at 258 °C at a heating rate of 10 °C /min Polymer 7b also showed a weight loss starting at 175 °C while polymer 10a and 10b showed a weight loss at a higher temperature, 230 °C and 245 °C, respectively Two significant changes in the slopes of the... photomicrograph of the liquid crystalline state of the 51 monomer 9a The monomer 9a forms a liquid crystalline state at 110 ° C while its melt point is about 78 °C A typical texture of nematic phase is observed However, after polymerization, the polymer showed a Tg transition with no liquid crystalline phase Intensity (a.u.) 400 10a 200 0 10b 10 20 30 2-Theta Figure 2.1.5 WAXS profiles of the polymer 10a and polymer . the pores of commercial membrane, growing polymers in the cavities of inorganic clay and sieves 2-3 , or self- assembly methods to develop nanostructured materials. Self- assembly of molecules. understand the properties of jacketed polymers in which the main chain is sterically crowded with laterally attached rigid side chains 17-19 . Here we report the synthesis of a series of novel jacketed. primary structure and the segmental interaction of polymers. It is well known that the chain stiffness of polymers offers a method of controlling the spatial arrangement of a polymer chain.