Chinese Journal of Polymer Science

A series of sulfonated polybenzimidazoles (sPBI-SF) were prepared from 2,2-bis(4-carboxyphenyl)hexafluoro-propane (BIS-B-AF), 3,3′-disulfonyl-4,4′-dicarboxyldiphenylsulfone (DSDCDPS) and 3,3′-diaminobenzidine (DAB) at various stoichiometric ratio by solution copolycondensation in poly(phosphoric acid). The chemical structure of the resulting sPBI-SF was confirmed by FTIR and ¹H-NMR. The sPBI-SFs with high molecular-weights (M_n = 39400–65500) were soluble in DMF, DMSO or DMAc. Therefore, they could form some transparent and flexible membranes easily by solution casting. The glass-transition temperatures of the acidic form sPBI-SF were in the range from 222°C to 269°C. The extrapolated onset decomposition temperatures were up to 440°C. The sulfonic groups grafted in the PBI chain had higher initial thermal degradation activation energy and exhibited excellent thermal stability. In addition, these membranes with good mechanical properties presented the swelling degree below 12% and the water uptake about 16%. The proton conductivities of sPBI-SF membranes measured by alternating-current impedance spectroscopy attained to 1.64 × 10^-3 S/cm at 70°C.

The oxidative polycondensation reaction conditions of 2-[(2-hydroxyphenyliminomethylbenzylidene)amino-phenol] (2-HPIMBAP) has been accomplished by using air O₂ and NaOCl oxidants in an aqueous alkaline medium between 50–90°C. The optimum reaction conditions of the oxidative polycondensation and the main parameters of the process were established. At the optimum reaction conditions, yield of the products were found to be 67.72% and 61.49% for air O₂ and NaOCl oxidants respectively. The structures of the monomer and oligomer were confirmed by FT-IR, UV-Vis, ¹H-NMR and ¹³C-NMR and elemental analysis. Also, TGA-DTA, SEC techniques and solubility tests were applied for characterization. ¹H-NMR and ¹³C-NMR data show that the polymerization proceeded by the C-C and C-O-C coupling systems of ortho and para positions and oxyphenylene according to -OH group of 2-HPIMBAP. The number-average molecular weight (M_n), weight-average molecular weight (M_w) and polydispersity index (PDI) values of oligo[2-(2-hydroxyphenylimi-nomethylbenzylidene)aminophenol] (oligo(2-HPIMBAP)) were determined. Thermal analyses of oligomer-metal complexes were investigated in N₂ atmosphere between 15–1000°C. Electrical conductivities of oligo(2-HPIMBAP) and oligomer-metal complexes measured with four point technique. Electrical conductivity of the oligo(2-HPIMBAP) was measured, showing that the oligomer is a typical semiconductor. Optical band gaps (E_g) of 2-HPIMBAP, oligo(2-HPIMBAP) and oligomer-metal complex compounds were determined by UV-Vis measurements. The monomer and oligomer were screened for antibacterial activities.

The surface of calcium carbonate (CaCO₃) particles was modified with stearic acid (SA) and the chemical structures of the product were characterized by FT-IR analysis. The interaction between polydimethylsiloxane (PDMS) and CaCO₃ fillers with different surface character was investigated by means of dynamic rheological and bound rubber tests for uncured compounds and mechanical properties measurements for the corresponding vulcanites. The results of dynamic tests indicate that with the increase of SA mass fraction, the span of the linear viscoelastic region broadens and the height of the modulus plateau decreases. The reasons for these are ascribed to that the SA decreases the surface energy of filler particles and weakens their tendency to agglomerate. Moreover, the results of mechanical measurements reveal that the vulcanized compound filled with modified filler has a relative high tensile strength induced by a reinforced interaction between filler and polymer matrix, which is confirmed by the bound rubber tests and transmission electron microscopy (TEM) observations.

Crystallization kinetics of syndiotactic polypropylene (sPP) was observed by light attenuation measurements. The initial stages of temperature dependent sPP crystallization fall in the range of Rayleigh scattering and Rayleigh-Debye-Gans scattering. Initial time and growth time of crystallization were obtained, and the trend of crystallization temperature dependent linear attenuation coefficient on the radius and the index of the refraction of the spherulite were evaluated.

Well-defined star-shaped poly(L-lactide) with six arms (sPLLA) was synthesized via the ring-opening polymerization of L-lactide using dipentaerythritol as initiator and stannous octoate as catalyst in bulk at 125°C. The effects of molar ratios of both monomer to initiator and monomer to catalyst on the molecular weights of as-synthesized sPLLA polymers were in detail investigated. The molecular weights of sPLLA polymers linearly increased with the molar ratio of monomer to initiator, and the molecular weight distribution was narrow (M_w/M_n = 1.04–1.12). However, the molar ratio of monomer to catalyst had no apparent influence on the polymer molecular weight. Moreover, the maximal melting point, the crystallization temperature, and the degree of crystallinity of sPLLA polymers increased with the increasing molecular weight, meanwhile they exhibited a spherulitic morphology. Furthermore, spherical nanoparticles (less than 100 nm) could be generated by direct injection of sPLLA solutions into distilled water, and the average size of nanoparticles could be adjusted through both the macromolecular architecture and the polymer molecular weight, respectively.

A novel series of liquid crystalline copolyesters with T-shaped two-dimensional mesogenic unit and crown ether cycle of cis-4,4′-bis(4-hydroxyphenylazo)dibenzo-18-crown-6 was prepared via solution condensation polymerization from 4,4′-(α,ω-hexanedioyloxy)dibenzoyl dichloride (M₁), 2-(4′-ethoxyphenyl)hydroquinone (M₂) and cis-4,4′-bis(4-hydroxyphenylazo)dibenzo-18-crown-6 (M₃). The molecular weights of copolyesters are not high, and the intrinsic viscosity [η] of copolyesters ranges from 0.29–0.43. The monomers' structures were identified by elemental analysis, IR, UV, ¹ H-NMR, MS, etc. All the copolyesters are yellowish powders and insoluble in THF and CHCl₃ at room temperature except CP-9. The properties of copolyesters were investigated by using GPC, [η], DSC, TG, WAXD and POM. It was found that all the copolyesters entered into liquid crystalline phase when they were heated to above their melting temperature (T_m). The threaded texture and schlieren texture of nematic phase can be observed on POM. Their T_m and isotropic temperature (T_i) decrease gradually, while thermal stability increase with varying the content of T-shaped two-dimensional mesogenic unit in the copolyesters.

In order to create a functionalized biodegradable polymer for vascular tissue engineering application, poly(DL-lactide-co-RS-β-malic acid) (PDLLMAc) was synthesized. PDLLMAc was obtained after hydrogenolysis of poly(DL-lactide-co-RS-β-benzyl malolactonate) (PDLLMA), which was from the ring-opening polymerization of DL-lactide (DLLA) and RS-β-benzyl malolactonate (MA) using stannous octoate as catalyst. The copolymers were characterized by ¹H-NMR, FTIR, GPC and DSC. The tensile strength and water uptake of the copolymers were measured. In copolymerization, the proportion of MA in the derived copolymers was lower than that in the feeding dose, a consequence of its lower reactivity. The molecular weight of the copolymers decreased with increasing MA content. The protective benzyl groups were completely removed in hydrogenolysis. The glass transition temperature (T_g) of the protected copolymers decreased with increasing MA content. The mechanical strength test showed that the tensile strength of PDLLMA decreased while elongation increased with MA content increasing, and the tensile strength increased and elongation decreased with increasing malic acid content in PDLLMAc for the formation of hydrogen bonding. The water uptake showed that more hydrophilic malic acid adsorbed more water in PDLLMAc. In order to test the reactivity of functional pendant groups, bioactive RGD peptide was immobilized on the functionalized polymer film surface and smooth muscle cells (SMCs) were cultured on it. The results showed that the functionalized copolymer was biocompatible and could be potentially applied in vascular tissue engineering.

Controlled polymerization of N-n-propylacrylamide was achieved by atom transfer radical polymerization (ATRP) in a N,N-dimethylformamide-water mixture (50 vol%) at room temperature with methyl 2-chloropropinonate as initiator and CuCl/tris(2-dimethylaminoethyl)amine as the catalytic system in a ratio of 1:1:1. High molecular weight homopolymers (up to 3.7 × 10⁴) with narrow molecular weight distribution (less than 1.2) were obtained. The living character of the polymerization was further demonstrated by self-blocking experiment. An inverse molecular weight dependence of the cloud point of narrow-dispersed poly(N-n-propylacrylamide) aqueous solution was determined by turbidimetry and differential scanning calorimetry, especially for the low molecular weight samples.

Novel fluorene-based poly(aromatic diacetylene)s have been synthesized by CuCl-catalyzed oxidative coupling of aromatic diynes. New aromatic diynes 2,7-diethynyl-9,9-bis(triphenylamine)fluorene (M₁) is synthesized by multistep reactions. The structures and properties of the polymers are characterized and evaluated by IR, NMR, TGA, UV, photoluminescence (PL), and cyclic voltammetry analyses. These polymers possess good thermal stability. All the polymers are completely soluble in common solvents such as toluene, THF, chloroform, and dichloromethane. The polymers exhibit strong blue photoluminescence in solution and green photoluminescence in the solid state. The polymer containing triphenylamine-substituted fluorene has lower oxidation potential (-5.45 eV) than the previous polyfluorenes (-5.80 eV).

The improvement of biocompatibility of polyurethanes was investigated. The results demonstrate that the blood compatibility of polyurethanes can be further improved by just simply mixing with the fluorinated phosphatidylcholine poly(carbonate urethane)s (FPCPCUs). The solution blending was done by mixing poly(ether urethane) (PEU) with FPCPCU in different compositions. An increased blood compatibility of the blend films was observed with the increase of FPCPCU content, and when FPCPCU content reached to 40 wt% (40FPCPCU film), 6 times and 23 times decrease of platelet adhesion number have been achieved, compared with that of FPCPCU and PEU, respectively. More interestingly, the blend films showed even better blood compatibility than that of FPCPCU. DSC, AFM and XPS were used to characterize the miscibility and surface structure of the blends film. The largely improved blood compatibility was rationalized based on the combined effect of phase separation between PEU and FPCPCU and the formation of surface nanostructures induced by segregation of FPCPCU at the surface.

The pH-sensitive P(AA-co-NVP)/clay hydrogels were prepared with the monomers of acrylic acid (AA) and N-vinyl-2-pyrrolidone (NVP) based on γ -ray irradiation technique. The influence of pH values of buffer solutions and contents of clay and NVP on the equilibrium swelling ratio (SR) and compressive properties of the hydrogels was investigated in detail. The results of swelling property tests showed that, with the increase of clay content, the SR of hydrogels increases in the same buffer solution, and the SR of hydrogels with different contents of HTMAB-clay is higher than that of P(AA-co-NVP) hydrogels without clay. When the content of clay is 15%, the SR of P(AA-co-NVP)/clay hydrogel is 201 at pH = 9.8, which is 1.23 times of that of the P(AA-co-NVP) hydrogel (164). In addition, the SR of P(AA-co-NVP)/clay hydrogel is higher than that of PAA/clay hydrogel in the same solution. The compressive properties of the hydrogel were also examined. The results showed that the compressive properties of the P(AA-co-NVP)/clay hydrogels were improved distinctly as compared to those of the conventional hydrogels without clay. When the content of clay is 15%, the compression strength of the P(AA-co-NVP)/clay hydrogel is 23 times of that of the P(AA-co-NVP) hydrogel.

Two series of aromatic-aliphatic random copolyesters (PEBTOXS) with diverse diol ratios have been synthesized by direct melting polycondensation. Two kinds of diols (glycol (EG) and 1,4-butanediol (BD)) are used in combination in order to adjust crystallization and tensile properties, and three kinds of diacids (dimethyl terephthalate (DMT), diethyl oxalate (DEOX), and sebacic acid (SA)) are involved. ¹H-NMR spectra quantify both composition and structure, and show that the final contents in copolyesters appropriate to the feed ratio. Average sequence lengths of six polyester units are calculated based on the analyses of ¹H-NMR spectra and copolyester structure. The results reveal that the average sequence lengths of sebacate related units increase with the increasing content of sebacic acid in copolyesters, while those of oxalate related units show a slight rise. Decreases of average sequence length are found for all terephthalate units, which may be because of the restriction of rigid aromatic units in reactions.

A series of conjugated copolymers derived from 9-ethylhexyl-2,7-carbazole (Cz) and 4,7-di(4-hexylthien-2-yl)-2,1,3-benzothiadiazole (DHTBT) was synthesized by Suzuki polycondensation. The photo- and electro-luminescent properties of these polymers were investigated. Efficient energy transfer from the Cz segment to the DHTBT unit occurs even if the DHTBT content as low as 1 mol%. PL emission was red-shifted significantly from 645 nm to 700 nm with the increase in DHTBT content by 1–50 mol%. PL efficiencies decreased with the increase in DHTBT content in the polymers from 55% for PCzDHTBT1 gradually down to 7% for PCzDHTBT50. EL emission of these polymers red-shifted from 640 nm to 690 nm when the DHTBT content increased from 1 mol% to 50 mol%. The highest external quantum efficiency was 1.67% for PCzDHTBT25 with the maximum luminescence of 870 cd/m² in the device configuration of ITO/PEDOT:PSS/polymer/PFN/Ba/Al. The enhancement of device performances could be due to the improved electron injection by inserting the amino-containing polyfluorene (PFN) layer. These polymers are promising candidates as a red emitter in the full-color polymer light emitting diodes (PLEDs).

Chloro(5,10,15,20-tetraphenyl-porphyrinato)-aluminum/tetraethylammonium bromide (Et₄NBr) in combination with bulky Lewis acid was used for the copolymerization of CO₂ and cyclohexene oxide (CHO). Bulky Lewis acid having substituents at the ortho positions of the phenolate ligands, like methylaluminum bis(2,6-di-tert-butyl-4-methylphenolate), significantly shortened the induction period and raised the catalytic activity, the corresponding turnover frequency reached 44.9 h^-1 in 9 h, which was 23.8% higher than that from (TPP)AlCl/Et₄NBr binary catalyst. The resulting polycarbonate has carbonate linkage over 93% with number average molecular weight of (4.5–6.5) × 10³ and polydispersity index below 1.10.