Effect of structure on properties of aromatic-aliphatic polybenzimidazoles. II

Polybenzimidazoles (PBI) with p-phenylene and/or cis-vinylene groups in the backbone were prepared from terephthalic acid (T), maleic acid (M), and 3,3′ diamino-benzidine tetrahydrochloride dihydrate (DAB) in poly(phosphoric acid) (PPA). Five polymer samples were prepared by varying the M:T molar ratios in the following order: 1:0, 1:1, 2:1, 1:2, and 1:4. The polymers were characterized by intrinsic viscosity, density, electronic fluorescence, and IR spectra. The effect of composition on the solubility of the polymers in various organic solvents was also investigated. The relative thermal stability of the polymers was evaluated by dynamic thermogravimetry in air and polybenzimidazoles (PBI) with cis-vinylene groups were found to be less stable.     

Polybenzimidazoles: Thermally Stable Materials

Polybenzimidazoles were prepared in poly(phosphoric acid) from isophthalic acid (I), terephthalic acid (T), and 3,3′-di-aminobenzidine tetrahydrochloride dihydrate (DAB). Homo-polymers of I, T, and various IT copolymers have been prepared. The polymers were characterized by viscosity, IR spectra, and nitrogen estimation. The effect of copolymer composition on UV and visible spectra, solubility in various solvents, and density was also investigated. The relative thermal stability of the polymers was evaluated by TGA and DTA.     

Synthesis and investigation of polybenzimidazoles containing alkyl substituents in aromatic nuclei

Polybenzimidazoles have been synthesized from 3,3′-diamino-5,5′-dimethylbenzidine, 3,3′,4,4′-tetraamino-5,5′-dimethyldiphenylmethane, bis(3-amino-4-methylamino)phenylmethane, bis(3-amino-4-methylamino-5-methyl)phenylmethane, and diphenyl esters of adipic, sebacic, isophthalic, and terephthalic acids and 4,4′-dicarboxydiphenyl oxide by solid-phase polyheterocyclization. Properties of the polybenzimidazoles have been studied. The polymers have high thermal stability. They are soluble in a number of organic solvents and give strong, elastic films. Solubility and thermal stability of polybenzimidazoles is determined by the methyl group position in the polymeric chain. The influence of other alkyl substituents on properties of polybenzimidazoles have been investigated. The polymer structure has been studied by infrared and PMR spectroscopy and elemental analysis.     

Bisorthoesters as polymer intermediates. II. A facile method for the preparation of polybenzimidazoles

Aromatic bisorthoesters were found to be good polymer intermediates and could be condensed with aromatic tetramines under mild conditions, in DMSO at 100°C in a relatively short reaction time to give polybenzimidazoles. The hexapropyl orthoesters of terephthalic and isophthalic acid were the preferred aromatic orthoesters because they were relatively easily purified by vacuum distillation to polymer grade intermediates, since they are liquids. Higher orthoesters distill even under good vacuum near or above the decomposition temperature of the orthoester group. Hexaethyl orthooxalate was also used and is a very useful and stable derivative of oxalic acid, which can be used for condensation reactions. These three orthoesters were used for condensations with 3,3′,4,4′-tetraaminobiphenyl, 1,2,3,4-tetraaminobenzene, 3,3′,4,4′-tetraaminobiphenyl ether, and 3,3′,4,4′-tetraaminobenzophenone. All polybenzimidazoles were obtained in high to quantitative yields and with varying molecular weights (η_inh = 0.1?0.8 dl/g), which in some cases were in the fiber forming range.     

A pyrolysis mass spectrometry study of polythiophene copolymers

The thermal behaviour of copolymers of thiophene with decanedioic acid bis-(2-thiophen-3-yl-ethyl)ester (DATE) and terephthalic acid bis-(2-thiophen-3-yl-ethyl)ester (TATE) prepared by potentiostatic polymerization was studied via pyrolysis mass spectrometry. It was determined that the electrolytic films correspond to the related homopolymers. The increase in thermal stability of ester linkages, and evolution of characteristic degradation products of TATE and DATE together with thiophene based products above 400 °C confirmed copolymer formation.     

New high-tensile thermally stable copolymers of poly(p-phenylene-1,3,4-oxadiazole)

A one-stage method is developed for the synthesis of new irregular copolymers of poly(p-phenylene-1,3,4-oxadiazole), whose polymer chain contains a 5,5-dioxodibenzothiophenylene fragment. The polymer synthesis is performed through direct copolymerization of terephthalic acid, 5,5-dioxodibenzothiophen-3,7-dicarboxylic acid, and hydrazine sulfate in oleum at an elevated temperature. The introduction of 13.5–17% structural fragments of 5,5-dioxodibenzothiophene into a copolymer macromolecule makes it possible to improve the thermal stability and fire-resistance of fibers and films produced on their basis and to achieve a 30% increase in breaking strength and a fivefold greater breaking extension relative to those values for a homopolymer based on terephthalic acid.     

Synthesis and characterization of block copolymers having liquid crystalline behaviour

A series of four block copolymers based on aromatic acetoxy-polysulphone (Ac-PSF), terephthalic acid (TPA), m-phthalic acid (MPA), acetoxy-benzoic acid (Ac-HBA), and a di(acetoxy)bisphenol monomer were synthesized. Their structures were determined by IR, thermal mechanical analyses and solubility tests. They all exhibit liquid crystalline behaviour.     

Polyamide-imides

A novel preparation of polyamide-imides from diphenylmethane diisocyanate and trimellitic anhydride in N-methylpyrrolidone is described. Partial substitution of trimellitic anhydride with either maleopimaric acid, terephthalic acid, or by various di-anhydrides permitted a correlation of structure with solution stability and thermal properties. Heat resistance improved with increasing imide content of the polyamide-imide. Almost all solutions advanced in viscosity on storage at room temperature. The least stable solutions were those that deviated the most from 50–50 amide-imide. However, the viscosity changes depended somewhat on the type of modifying ingredient. For example, polyamide-imides modified by substitution of 10% PMDA (pyromellitic anhydride) or BPDA (benzophenone tetracarboxylic acid dianhydride) were less stable than those modified with 10% (cyclopentanetetracarboxylic acid dianhydride) CPDA or THFDA (tetrahydrofuran-2,3,4,5-tetracarboxylic acid dianhydride). The use of excess reagent and of monofunctional chain stopper was investigated as a means of controlling solution stability.     

Novel copolyesters based on poly(alkylene dicarboxylate)s: 1. Thermal behavior and biodegradation of aliphatic-aromatic random copolymers

In order to improve the thermal and mechanical properties of the poly(butylene 1,12-dodecanedioate), some novel aliphatic-aromatic random copolyesters have been prepared by starting from 1,4-butanediol and different molar ratio of 1,12-dodecanedioc acid and terephthalic acid. The samples were characterized by ¹H NMR and the molecular structure was correlated with the crystalline phase present, the level of crystallinity, the glass transition temperature, the mechanical behavior, and the biodegradability. In particular, the copolymer containing the 70 mol% of PBT repeating units notably improves the thermal and mechanical properties of the poly(butylene 1,12-dodecanedioate) towards those of PBT and maintains a very high thermal stability, but loses the biodegradability of the poly(alkylene dicarboxylate). Therefore, for this class of aliphatic-aromatic copolymers the chemical composition must be carefully chosen to reach a compromise between good thermal and mechanical performances and biodegradability, according to the necessity.     

New Unsaturated Biodegradable Poly(ester amide)s Composed of Fumaric Acid,L-leucine and α,ω-Alkylene Diols

The synthesis of α-amino acid L-leucine (Leu) based high-molecular-weight and biodegradable unsaturated poly(ester-amide)s (PEAs) was reported. Amino acid L-phenylalanine (Phe) was used to synthesize some copolymers for a comparative study. The syntheses of three types of new unsaturated PEA polymers were explored – (i) Unsaturated PEA homopolymers (UPEAs) composed of fumaric acid, aliphatic diol and one alpha-amino acid: L-Leu or L-Phe; (ii) L-Leu-based unsaturated-saturated copolymers (USPEAs) composed of aliphatic diol, fumaric and saturated fatty diacid, and (iii) L-Leu- and L-Phe-based copolymers (co-UPEAs) composed of 100% fumaric acid, aliphatic diol and combinations of both amino acids. Many of the targeted unsaturated polymers were soluble in common organic solvents and showed good film-forming property. The unsaturated PEA polymers were further chemically modified into functional derivatives and subjected to thermal and photochemical transformations (curing) that substantially expand material properties and, hence, the scopes of potential applications as absorbable surgical devices and drug carriers.     

新型磺化聚苯并咪唑的合成及性能

以对苯二酚及对氟苯甲腈为原料, 合成了1,4-二(4-羧基苯氧基)苯, 再经磺化反应合成了1,4-二(4-羧基苯氧基)苯-2-磺酸钠(BCPOBS-Na), 并以4,4'-二羧基二苯醚(DCDPE)作为非磺化二酸单体与3,3'-二氨基联苯胺反应合成了一系列磺化聚苯并咪唑(SPBI). 通过红外光谱、 核磁共振及热重分析等手段对聚合物的结构及性能进行了分析. 研究了聚合物的特性黏度、 溶解性、 成膜性及聚合物薄膜的力学性能.     

Synthesis and characterization of novel polybenzimidazoles containing 4-phenyl phthalazinone moiety

A novel series of homo- and copoly(phthalazinone benzimidazole)s were synthesized from various stoichiometric mixtures of 4-(4-(4-(4-carboxyphenoxy)phenyl)-1-oxophthalazin-2(1H)-yl)benzoic acid (CPPBC) and isophthalic acid (IPA) with 3,3′-diaminobenzidine (DAB) by solution polycondensation in polyphosphoric acid (PPA). The structures of the obtained polymers were characterized by FT-IR and ¹H NMR. The obtained polybenzimidazoles were found to be soluble in aprotic polar solvents such as N-methyl-2-pyrolidinone (NMP), N,N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO) and m-cresol, without the addition of inorganic salts. The inherent viscosities of the polybenzimidazoles were in the range of 1.10–2.05 dL/g. All of the polymers show amorphous nature as evaluated by WAXD. These polymers have high glass transition temperatures (T_gs) in the range of 398–408 °C. Thermogravimetric analysis exhibit that these polybenzimidazoles containing 4-phenyl phthalazinone moiety have excellent thermal stability with the temperatures for 5% and 10% weight loss of the polymers ranging from 516 to 594 °C and 560 to 672 °C, respectively.     

Phosphorus-containing polybenzimidazoles prepared by reaction of bis(p-carboxyphenoxymethyl)methylphosphine oxide with aromatic tetramines

Two types of polybenzimidazoles (phosphorus- and phosphorus and chlorine containing) are synthesized from bis(p-carboxyphenoxymethyl)methylphosphine oxide or its chlorine-containing analogue and aromatic tetramines in polyphosphoric acid. The structures of the new polybenzimidazoles are determined with the aid of model compounds and i.r. and u.v. spectroscopy. The polymers possess comparatively high thermal stability and resistance to ignition.     

Synthesis and characterization of novel polybenzimidazoles bearing pendant phenoxyamine groups

A novel aromatic diacid, 3, 5‐dicarboxyl‐4′‐amino diphenyl ether, containing pendant phenoxy amine group was synthesized. Homo‐ and co‐polybenzimidazoles containing different content of pendant phenoxyamine groups were synthesized by condensation of 3,3′‐diaminobenzidine with this acid and a mixture of this acid and isophthalic acid in different ratio in polyphosphoric acid. Copolybenzimidazoles with structural variations were also synthesized based on this acid and pyridine dicarboxylic acid, terephthalic acid, adipic acid, or sebacic acid. The polymers have good solubility in polar aprotic solvents and strong acids and they form tough flexible films by solution casting. The polymers were characterized by different instrumental techniques (FTIR, TGA, DSC, XRD, etc.) and for solvent solubility, mechanical properties, inherent viscosity, and proton conductivity. The inherent viscosities of the polymers vary in the range of 0.62–1.52 dL/g. They have high thermal stability up to 475–506 °C (IDT) in nitrogen, high glass transition temperatures (T_g) ranging from 313 to 435 °C and good tensile strength ranging from 58 to 125 MPa. Proton conductivity of homo polymer is 3.72 × 10^?3 S/cm at 25 °C and 2.45 × 10^?2 S/cm at 200 °C © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5776–5793, 2008     

New unsaturated polyesters as injectable drug carriers

New unsaturated polyesters of poly(fumaric acid-glycol-sebacic acid) copolymers and poly(maleic anhydride-glycol-sebacic acid) copolymers were prepared by melt polycondensation of the corresponding mixed monomers: sebacic anhydride, fumaric acid or maleic anhydride and glycol. Methyl-methacrylate (MMA) was used as crosslinker and dimer acid was used as thinner.In vitro studies showed that those copolymers are degradable in phosphate buffer at 37 °C and poly(fumaric acid-glycol-sebacic acid) has proper drug release rate as drug carriers. The biocompatibility of poly(fumaric acid-glycol-sebacic acid) copolymers under mice skin was also evaluated; macroscopic observation and microscopic analysis demonstrated that the copolymer is biocompatible and well tolerated in vivo. The injected poly(fumaric acid-glycol-sebacic acid) [molar ratio M_{fumaric acid}:M_glycol:M_{sebacic acid} = 1.75:2.20:0.25] containing 5% adriamycin hydrochloride (ADM) in the mice bearing Sarcoma-180 tumor exhibited a good antitumor efficacy. The volume doubling time (VDT) (18 ± 2.5 days) of the tumor growth by this treatment was longer than that (7 ± 0.9 days) by the subcutaneous injection of ADM.     

Contribution to the study of the mechanism of curing of unsaturated polyester resins

The mechanism of copolymerization of monomethyl and dimethyl maleates and fumarates with styrene was studied by analysis of the conformation of the acid units of the resulting copolymers. The absorption bands for C?O stretching and OH stretching in the spectra of the copolymers are fully identical. They are quite different from the spectra of the copolymers obtained from maleic anhydride and styrene that are subsequently treated with absolute methanol to give the monoester which is then esterified with diazomethane to give the diester. The acid units of the copolymers derived from maleic anhydride exist in a gauche configuration; copolymers derived from fumaric units exist in a trans conformation. The identity of copolymers derived from maleic units with those derived from fumaric units but not with those derived from maleic anhydride indicates that the first step in the copolymerization of the maleic units is an isomerization to fumaric units, which are actually the genuine comonomers.     

Studies on thermotropic liquid crystalline polymers. XVI. Synthesis and properties of fully aromatic poly(amide-ester)s with naphthalene structures

A series of novel, fully aromatic high-molecular-weight poly(amide-ester)s was prepared by the direct polycondensation from terephthalic acid (TPA) and 2,6-naphthalene dicarboxlic acid (NDC) with various aromatic diols and diamines in the presence of diphenyl chlorophosphate (DPCP), LiCl, and pyridine. The structures and thermal properties of these synthesized poly(amide-ester)s were examined by FTIR, wide-angle x-ray diffraction (WAXD), differential scanning calorimetry (DSC), thermal polarized optical microscope, thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA). The effects of the kinds of the aromatic diols and diamines (bisphenyl units, naphthalene, and (un)substituted phenylene structures) on the thermal properties of the synthesized poly(amide-ester)s were investigated in this study. Strong interchain interactions were induced by using a 50:50 molar ratio of the amide groups to the ester groups, and, thus, no LC properties but good thermal stabilities were found in all of the synthesized poly(amide-ester)s containing naphthalene, substituted hydroquinone, or bisphenol segments in this study. However, another series of poly(amide-ester)s with a molar ratio of diamine to diol of 20:80 exhibited excellent mesophase stabilities, with various molar ratio of terephthalic acid (TPA) to 2,6-naphthalene dicarboxlic acid (NDC). © 1996 John Wiley & Sons, Inc.     

Tuning the molecular properties of polybenzimidazole by copolymerization

In the present work, a series of novel random polybenzimidazole (PBI) copolymers consisting of m- and p-phenylene linkages are synthesized from various stoichiometric mixtures of isophthalic acid (IPA) and terephthalic acid (TPA) with 3,3',4,4'-tetraaminobiphenyl (TAB) by solution copolycondensation in polyphosphoric acid (PPA). The resulting copolymers are characterized by different techniques to obtain their molecular properties parameters. The monomer concentration in the polymerization plays an important role in controlling the molecular weight of the polymer. Surprisingly, a simple change in the dicarboxylic acid architecture from meta (IPA) to para (TPA) increases the molecular weight of the copolymers, which is maximum for the para homopolymer. The low solubility of TPA in PPA is found to be the dominating factor for obtaining the higher molecular weight polymer in the case of the para structure. FT-IR study shows that the introduction of the para structure enhances the conjugation along the polymer chain. The positive deviation of the copolymer composition from the feed ratio is due to the higher reactivity ratio of TPA than IPA, which is obtained from proton NMR studies. The incorporation of the para structure in the chain enhances the thermal stability of the polymers. The para homopolymer shows 59 degrees C lower glass transition temperature compare to the meta homopolymer indicating enhancement of the flexibility of the polymer chain due the introduction of the p-phenylene linkage in the backbone. The T(g) of the copolymers shows both positive and negative deviation from the expected T(g) calculated by the Fox equation. The enhanced conjugation of the polymer chains also influences the photophysical properties of the polymers in solution. All the PBI polymers exhibit strong fluorescence in dimethylacetamide solution. As expected, that all the polymers are amorphous in nature reveals that the copolymerization does not influence the packing characteristics of the PBI chains.     

Studies on biodegradability of copolymers of lactic acid, terephthalic acid and ethylene glycol

The copolymers were synthesized by the condensation of lactic acid, terephthalic acid and ethylene glycol. Synthesized copolymers were characterized for various properties such as acid value, hydroxyl value and number average molecular weight, etc. The copolymers were analyzed by FTIR. Copolymers were biodegraded by different fungal species such as Aspergillus sp., Mucor sp., Alternaria sp. and Rhizopus sp., etc. The extent of biodegradation was examined by weight loss and scanning electron microscopy. Biodegradation of copolymer with greater amount of lactic acid was faster than the biodegradation of copolymer with lesser amount of lactic acid.     

Wholly aromatic thermotropic liquid crystalline polyesters of 2-(α-phenylisopropyl)hydroquinone; copolymers with 1,1′-biphenyl-4,4′-diol and 2,6-dihydroxynaphthalene

Two series of new aromatic copolyesters have been synthesized and their properties including liquid crystallinity have been studied. The first series was synthesized by polymerizing mixtures of diacetates of 2-(α-phenylisopropyl)hydroquinone and 1,1′-biphenyl-4,4′-diol with terephthalic acid, and the second by polymerizing mixtures of diacetates of 2-(α-phenylisopropyl)hydroquinone and 2,6-dihydroxynaphthalene with terephthalic acid. These polyesters were characterized by differential scanning calorimetry, thermogravimetric analysis, wide-angle X-ray diffractomerty, and optical microscopy. The glass transition temperatures of the first series decrease from 167 to 138°C as one increases the content of the 1,1′-biphenyl-4,4′-diol unit to 50 mol %. The T_g values of the second series are slightly higher than those of the first series, and appear to be less dependent on their composition. The degree of crystallinity of the first series decreases rapidly by copolymerization, much faster than that of the second series. The melting points of the first series copolymers are significantly lower than those of the second series. All of the copolyesters reported in this investigation form nematic melts. The initial decomposition temperatures of the copolymers were higher than 450°C. It was confirmed that thermal stability of the homopolyester, PIBPL-1.00, containing the isopropylidene units is significantly improved when compared with that carrying benzylic hydrogens. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2777–2786, 1997