Direct condensation polymerization of N-alkylated p-aminobenzoic acid, in which methyl, propyl, butyl, pentyl, heptyl, octyl and also heptadecyl substituents were provided as the alkyl group, was performed using hexachloroethane, triphenylphosphine and pyridine as condensation reagents. Pale-yellow N-alkylated poly(p-benzamide) (PABAn) polymers, wbelow n is the variety of carbon atoms of the alkyl side chain, were derived in 46–87% yields via an inherent viscosity of 0.06–0.65 per 100 ml g−1 (conc. H2SO4, 30 °C). The frameworks of PABAn were established utilizing infrared, nuclear magnetic resonance and also elemental evaluation. PABAn with long alkyl side chains (n>3) showed great solubility in chlorocreate, as well as conc. H2SO4 and m-cresol. The glass shift temperature (Tg) of PABAn measured by differential scanning calorimeattempt gradually reduced with an increase in the size of the alkyl group. The endothermic height corresponding to melting was observed for PABAn with n=3, 4, 5 and also 17 on DSC profiles. The wide-angle powder X-ray scattering of the polymer samples shown that PABAn polymers via n=0, 1, 3, 4, 5 and also 17 were crystalline polymers. X-ray scattering prorecords proved PABAn with n=3, 4 and 5 crystallized in an orthorhombic lattice, whereas PABA1 crystallized in a monoclinic lattice. PABA17 crystallized in hexagonal packing at the long side chain via an interplanar spacing of 4.2 Å.

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Comb polymers are advantageous products because of the different solid-state lutz-heilmann.infos of main chains and also side chains, which mostly afford long-array phase-segregated frameworks.1, 2 Crystalline primary chain via amorphous side chain3, 4, 5, 6, 7, 8, 9, 10, 11 comb polymers and amorphous primary chain through crystalline side chain12, 13, 14, 15, 16, 17, 18 ones have been studied broadly and reviewed in terms of their chemistry19, 20 and also physical properties.21 The activity of crystalline segments is variably inhibited by the amorphous portion; hence, formation of various segregated frameworks is often oboffered from similar products. The ‘crystalline–crystalline’ comb polymers,22, 23, 24, 25 especially those with aromatic main chain polymers,26, 27, 28, 29 are of interemainder because packing of the bulky fragrant polymer major chain deserve to be adjusted by varying the crystallinity of side chains. As the first instance, Kevlar, poly(p-phenylene terephthalamide), was functionalized via direct hydrocarbons of 3, 4, 7, 12 and also 18 carbon atoms via metalation of poly(p-phenylene terephthalamide) utilizing sodium hydride (level of substitution (DS) was 86–99%, inherent viscosity (ηinh) 0.06–0.14), and also the packing mode was investigated for the resulting comb polymers, which were all amorphous other than for the polymer with C18H37 side chains.30 Poly(3-n-alkyl-4-oxybenzoate)s (PAOBA)s through alkyl side chains varying from 1 to 18 carbon atoms were ready and their phase properties completely investigated.31 The framework and thermal shift from crystalline to mesophase of PAOBA with brief alkyl chains, such as propyl groups, was regulated by the rigid-rod primary chain, whereas those of PAOBA having actually longer alkyl chains were regulated by the lutz-heilmann.info of side chains. N-Alkylated poly(p-benzamide) (PABAn, DS >96%) (from 10 to 18 carbon atoms) was additionally ready by the metalation approach, and their packing structure was investigated.32 In comparison to the high crystallinity of PAOBA, all PABAn polymers, other than for the one with the 18-carbon alkyl chain, were amorphous bereason of bulky aromatic rings and also reasonably sporadic semicrystalline alkyl chains. We intended that well-characterized PABAn need to load easily in a various create on polymerization of a completely alkylated monomer via a side chain containing a number of carbon atoms varying from 1 to 17. Therefore, this examine focused on the preparation of high-molecular-weight PABAn from N-alkylated p-aminobenzoic acid and investigation of the packing that occurred on varying the length of alkyl side chains.


Measurements

Fourier transcreate infrared (IR) spectra were measured through a Jasco IR-5500 (Jasco, Tokyo, Japan) by transmittance absorption spectroscopy (KBr tablet method). The molecular mass of polyamides (weight average (Mw)) was figured out making use of a Viscotek T60A gel permeation chromatograph (Viscotek, Houston, TX, USA) equipped through a three detector system: refractive index, light scattering detector and viscometer detector. The scattering angles, dn/dc (refractive index increment) and also sample concentrations were collection to be 90.0, 0.185 and also 1.0 mg ml−1, respectively. Separation was brought out through Tosoh HLC-8120 GCOMPUTER (Tosoh, Tokyo, Japan) utilizing a consecutive polystyrene gel column (TSK-GEL GMHHR-M and GMHHR-N) at 40 °C and eluted with tetrahydrofuran (THF) at a circulation rate of 1.0 ml min−1. Nuclear magnetic resonance (NMR) was percreated on a Bruker AC-400P spectrometer (Bruker BioSpin K.K., Yokohama, Japan) at 400 MHz for 1H and also at 100 MHz for 13C measurements. Deuterated chlorocreate (CDCl3) was provided as a solvent via tetramethylsilane as an interior recommendation. Thermal analyses were lugged out on a Seiko thermal analyzer (Seiko Instruments Inc., Chiba, Japan) (SCC 5200 system) at a heating price of 10 °C min −1 for thermogravimetric evaluation (by TG/DTA 320) under air or nitrogen. Differential scanning calorimeattempt (DSC) was percreated on a Shimadzu DSC-60 (Shimadzu Corporation, Kyoto, Japan) at a heating rate of 20 °C min−1 under nitrogen. The packing settings of a number of polymers in the crystalline phase were examined by wide-angle X-ray powder diffractivity (WAXD) dimensions making use of a Rigaku R-axis Rapid diffractometer (Rigaku Corporation, Tokyo, Japan) equipped through a graphite monochromator, via CuKα radiation at 45 kV and 200 mA. The layer structure of comb polymers was characterized with a small-angle X-ray scattering (SAXS) instrument (M18XHF, MAC Science, Bruker AXS K.K., Yokohama, Japan) consisting of an 18-kW rotating-anode X-ray generator through a Cu targain (wavesize, λ=0.154 nm) operated at 50 kV and 300 mA. This instrument included a pyrographite monochromator, pinhole collimation mechanism (φ=0.3, 0.3, 1.1 mm), vacuum chamber for the scattered beam path and a two-dimensional imaging plate detector (DIP-220). The sample-to-detector distance was readjusted to 710 mm. The expocertain time for each sample was 30 min. For SAXS dimensions, a sample of ∼1-mm thickness was inserted in the sample holder so that its place remained unreadjusted.

Reagents

p-Aminobenzoic acid ethyl ester and also p-(N-methylamino)benzoic acid were purchased from Wako Pure Chemical Industries (Osaka, Japan) and TCI Chemical Indusattempt (Tokyo, Japan), respectively, and also provided as obtained. Dry pyridine was purchased from Kanto Chemical (Tokyo, Japan) and also provided under nitrogen. Hexamethylphosphorous triamide was dried over calcium hydride and distilled under lessened push. The various other reagents and solvents were supplied as got.

Synthesis of p-(N-propylamino)benzoic acid

Into a three-necked flask equipped through a reflux condenser, a thermometer and a three-means stopcock was included p-aminobenzoic acid ethyl ester (79.3 g, 0.480 mol) under nitrogen. Hexamethylphosphorous triamide (222 ml) was then included and the mixture was stirred until the solid was entirely liquified at 20 °C. 1-Iodopropane (42.9 g, 0.252 mol) was then added to this solution, and also the mixture was stirred at 130 °C for 4 h. The resultant mixture was poured into water (1 l), and also the precipitate was waburned with methanol/water (1:5 v/v)-combined solvent to rerelocate the residual solvent and salt. The solid was gathered by filtration, purified by recrystallization from methanol and also dried in vacuo at 80 °C for 12 h to offer p-(N-propylamino)benzoic acid ethyl ester as yellow needles. Yield: 46.5 g (88.9%); m.p.: 70–73 °C; IR (KBr): ν 3373 (N-H), 3063 (aromatic C-H), 2964 (aliphatic C-H), 1676 (ester C=O), 1343 (Ar-N), 1173 (C-O) cm−1; 1H NMR (CDCl3, 400 MHz): δ 1.00 (t, 3H, CH3), 1.36 (t, 3H, CH3), 1.65 (m, 2H, CH2), 3.13 (t, 2H, CH2), 4.11 (s, 1H, NH), 4.31 (q, 2H, CH2), 6.53 (d, 2H, ArH), 7.86 (d, 2H, ArH) p.p.m.; 13C NMR (CDCl3, 100 MHz): δ 11.6, 14.5, 22.5, 45.2, 60.1, 111.3, 118.4, 131.5, 152.1, 166.9 p.p.m. The resulting p-(N-propylamino)benzoic acid ethyl ester (38.3 g, 0.185 mol) was inserted in a 500-ml two-necked flask equipped through a reflux condenser. Potassium hydroxide (56.8 g, 0.923 mol) and ethanol (450 ml) were added to this flask and also heated to 90 °C. After 7 h, the reaction mixture was poured into water, and also the pH of the solution was changed to be around 4 through hydrochloric acid. The precipitate was built up, wamelted with water, recrystallized through methanol and dried in vacuo at 80 °C for 12 h to provide the title compound as yellow needles. Yield: 21.2 g (64.1%); m.p.: 164–169 °C; IR (KBr): ν 3377 (N-H), 3058 (fragrant C-H), 2961 (aliphatic C-H), 1663 (C=O), 1313 (Ar-N), 1171 (C-O) cm−1; 1H NMR (CDCl3, 400 MHz): δ 1.01 (t, 3H, CH3), 1.66 (q, 2H, CH2), 3.15 (t, 2H, CH2), 6.55 (d, 2H, ArH), 7.91 (d, 2H, ArH); 13C NMR (CDCl3, 100 MHz): δ 11.5, 22.5, 45.1, 111.3, 117.0, 132.3, 152.7, 172.2 p.p.m.; anal. calcd for C10H13NO2: C, 67.02; H, 7.31; N, 7.82%; found: C, 66.92; H, 7.26; N, 7.88%.

Synthesis of p-(N-butylamino)benzoic acid

The title compound was all set in a manner comparable to that defined over. The solid was gathered by filtration, purified by recrystallization from methanol and dried in vacuo at 80 °C for 12 h to provide pale-yellow needles. Yield: 1.36 g (74.0%); m.p.: 149–155 °C.

Synthesis of p-(N-pentylamino)benzoic acid

The title compound was prepared in a manner similar to that defined above. The solid was collected by filtration, purified by recrystallization from methanol and dried in vacuo at 80 °C for 12 h to give colorless needles. Yield: 18.6 g (68.0%). m.p.: 132–133 °C.

Synthesis of p-(N-heptylamino)benzoic acid

The title compound was prepared in a manner equivalent to that described over. The solid was collected by filtration, purified by recrystallization from methanol and dried in vacuo at 80 °C for 12 h to offer colorless needles. Yield: 11.3 g (75.0%). m.p.: 107–122 °C.

Synthesis of p-(N-octylamino)benzoic acid

The title compound was all set in a manner similar to that described above. The solid was accumulated by filtration, purified by recrystallization from methanol and dried in vacuo at 80 °C for 12 h to result in yellow needles. Yield: 13.6 g (84.0%); m.p.: 117–125 °C.

Synthesis of p-(N-heptadecylamino)benzoic acid

The title compound was all set in a manner comparable to that defined above. The solid was gathered by filtration, purified by recrystallization from methanol and also dried in vacuo at 80 °C for 12 h to cause white needles. Yield: 9.60 g (64.0%); m.p.: 126–127 °C.

Synthesis of poly(p-benzamide) (PABA0)

Into a three-necked flask equipped via a reflux condenser, a three-method stopcock and also a thermometer were added lithium chloride (10.5 g, 0.247 mol, 4 wt% to the solution), N-methyl-2-pyrrolidone (200 ml) and also pyridine (50 ml). The mixture was stirred until the solid was dissolved. p-Aminobenzoic acid (13.7 g, 0.100 mol) was then included to the flask, followed by triphenylphosphine oxide (31.3 g, 0.100 mol) in one percentage. The flask was heated to 100 °C, and also the mixture was stirred for another 6 h. The resulting heterogeneous solution was poured into methanol (1 l) and stirred for 5 h. The precipitate was gathered, waburned through hot water and dried in vacuo at 220 °C for 24 h to give the title compound. Yield: 11.4 g (95.0%); ηinh=1.18 per 100 ml g−1 (0.5 g per 100 ml in conc. H2SO4, 30 °C); IR (KBr): ν 3446 (N-H), 1669 (C=O), 1315 (Ar-N), 1177 (amide C-N) cm−1; anal. calcd for (C7H5NO)n: C, 70.58; H, 4.23; N, 11.76%; found: C, 69.33; H, 4.75; N, 10.96%.

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Usual procedure of the direct polymerization of N-alkylated monomers: synthesis of N-methylated poly(p-benzamide) (PABA1)

Into a three-necked flask equipped via a reflux condenser, a three-means stopcock and also a thermometer, were included p-(N-methylamino)benzoic acid (4.55 g, 30.1 mol), triphenylphosphine (9.44 g, 36.0 mmol) and also pyridine (30 ml). The mixture was stirred till the solid was liquified. Hexachloroethane (8.52 g, 36.0 mmol) was then included to this solution and the mixture was refluxed for 24 h. After the solution was cooled to room temperature, it was poured right into methanol/hydrochloric acid and stirred for 5 h. The precipitates were built up, stirred in hot methanol for 12 h and dried at 220 °C for 24 h to give the title compound. Yield: 2.22 g (55.6%); ηinh=0.61 per 100 ml g−1 (0.5 g per 100 ml in H2SO4, 30 °C); IR (KBr): ν 3051 (N-H), 2923 (aliphatic C-H), 1645 (C=O), 1368 (Ar-N), 1175 (amide C-N) cm−1; anal. calcd for (C8H7NO)n: C, 72.16; H, 5.30; N, 10.52%; found: C, 71.49; H, 5.29; N, 10.39%.