Multidimensional benzobisoxazole rigid-rod polymers. II. Processing,characterization, and morphology

A high-torque rheometer was used to facilitate the polycondensation of 4-[5-amino-6-hydroxybenzoxazol-2-yl]benzoic acid (ABA) with trimesic acid and 1,3,5,7-tetrakis(4-carboxylatophenyl)adamantane to yield two- and three-dimensional benzobisoxazole polymers, respectively. Although the resultant polymer dopes exhibited improved homogeneity compared to polymer dopes previously prepared in glassware, improved polymer solution viscosities were not achieved. Fibers spun from the two- and three-dimensional polymers did not show a significant increase in compressive strength compared to fibers of the linear or one-dimensional benzobisoxazole polymer derived from the homopolymerization of ABA. Morphological studies of the polymer fibers and films by wide-angle X-ray scattering and scanning electron microscopy strongly indicated more lateral disorder and a more isotropic character for the three-dimensional structures compared to the one-dimensional structures. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 3457–3466, 1997     

Ionic conductivity of conjugated water-soluble rigid-rod polymers

Poly[(1,7-dihydrobenzo[1,2-d:4,5-d′] diimidazole-2,6-diyl)-2-(2-sulfo)-p-phenylene], a conjugated rigid-rod polymer, was derivatized with pendants of propane-sulfonated ionomers. The derivatized rigid-rod polymer was soluble in aprotic solvents as well as in water for isotropic solutions that were processed into isotropic films. Direct-current electrical conductivity σ of the films was measured using the four-probe technique. Room-temperature σ as high as 2.9 × 10^?4S/cm was achieved on pristine isotropic films without using dopants. When the rigid-rod polymer concentration exceeded 25 wt %, the isotropic solution could be transformed into a liquid-crystalline solution that allowed deformations to be applied to produce anisotropic films. Significant increase in σ was obtained in a sheared film along both the parallel direction (∥) and the transverse direction (⊥) with a σ_∥/σ_⊥ = 5. Additionally, enhanced σ was realized in films heat-treated at about 100°C, in the derivatized polymer with higher molecular weight from dialysis, and in substituting the sulfonated ion Na⁺ by H⁺ in the pendants of the polymers. Constant-voltage measurements were applied to the polymers to monitor the σ stability for ascertaining the nature of the conductivity. No electronic contribution in σ was detected. Instead, a monotonically decreasing σ was consistently observed indicative of ionic conductivity. © 1993 John Wiley & Sons, Inc.     

Structure and electrical conductivity of ion-implanted rigid-rod and ladder polymers

Isotropic and oriented thin films of rigid-rod, rigid-rod pseudo-ladder, and ladder polymers were ion-bombarded with ⁸⁴Kr⁺ to a dose of 4 × 10¹⁶ ions/cm². The bombardment was conducted at two conditions: one at 190 keV energy with 0.12 μA/cm² current density and the other at 200 keV energy with 2.0 μA/cm² current density. With the low current density, the polymers developed a uniform ion-bombarded layer of about 0.35 μm at the surface. This layer showed an electrical conductivity on the order of 10^?3s/cm at ambient conditions, an enhancement of 6 to 9 orders of magnitude from the pristine polymers. The enhanced conductivity was found to decrease to 10^?6s/cm after the implanted krypton was removed by heating under reduced pressure. It suggests that the enhanced conductivity was due to a synergistic effect of structural change of the polymers and chemical doping by the im-planted ions. With the high current density, most polymer films, except that of rigid-rod pseudo-ladder poly(p-(2,5-dihydroxy) phenylene benzobisthiazole) (DPBT), developed an additional fibrous network structure over the uniform ion-bombarded layer. The comparable conductivity, 53 to 157 s/cm, measured for the various ion-bombarded films in-dicated that neither the molecular structure, rigid-rod or ladder, nor the molecular packing order, isotropic or oriented, constituted significant effect on the conductivity of ion-bombarded polymers. Since krypton could not be detected in the polymers ion-bombarded with high current density, the enhanced conductivity was attributed to the structural change of the polymers. The DPBT films ion-bombarded with high current density showed holes of micron size, probably due to the decomposition of hydroxy pendents from the rigid-rod backbone. © 1993 John Wiley & Sons, Inc.     

New polymer syntheses. LXXV. 2,5-biaryloxyterephthalic acids and rigid-rod polyaramides derived from them

Several 2,5-bisaryloxyterephthalic acids were prepared by a new method, namely arylation of diethyl-2,5-bistrimethylsiloxyterephthalate. Rigid-rod polyaramides were prepared by polycondensation of silylated diamines with a terephthaloylchloride with two diphenylsulfone side chains. Another polyamide was prepared from 2,5-bis(4′-cyanophenoxy) terephthalic acid and 1,4-diaminobenzene. None of these polyaramides is meltable and their solubilities differ largely. A copolymer of 1,4-diaminobenzene and 3,3′-dimethoxybenzidine is soluble in various organic solvents including polar vinyl monomers. © 1994 John Wiley & Sons, Inc.     

New aromatic benzazole polymers. I. Benzobisthiazole and benzobisoxazole polymers with main-chain triarylamino units

Thermally stable, nonrigid-rod poly(benzobisthiazoles), (R)TPA-PBZT , where R = H, Me, NMe₂, and OH, and poly(benzobisoxazoles), (R)TPA-PBO , where R = Me, NMe₂ containing electron-rich triarylamine groups with various para-substituents (Rs) on the pendent phenyl ring, were synthesized from either 2,5-diamino-1,4-benzenedithiol dihydrochloride or 2,4-diamino-1,5-benzenediol dihydrochloride and the respective triarylamine-based dinitrile or diacid monomer in polyphosphoric acid. Whereas (R)TPA-PBZT polymers were obtained in moderate molecular weights, analogous (R)TPA-PBO polymers were only prepared in low molecular weights. No lyotropic behaviors, characteristic of the unmodified rigid-rod benzazole polymers, as evidenced by the absence of either stir opalescence or birefringence under crosspolarizers, were observed for these homopolymers at about 10 wt % polymer concentration. Among these polymers, only (Me)TPA-PBZT and (NMe₂)TPA-PBZT formed cast films with good mechanical integrity. In their pristine state, their film conductivity values were in the range of 10⁻¹⁰–10⁻⁹ S/cm at room temperature. Upon exposure to iodine vapor, their conductivities were increased to the maximal values of 5.0 × 10⁻⁵ S/cm ( (Me)TPA-PBZT ) and 4.1 × 10⁻⁴ S/cm ( (NMe₂)TPA-PBZT ). © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 1909–1924, 1997     

Spectroscopic study of rigid-rod polymers. I. Structures of model compounds

Poly(p-phenylene benzbisoxazole) and poly(p-phenylene benzbisthiazole) belong to the class of extended-chain, rigid-rod polymers possessing high modulus, high strength, and good thermal and oxidative resistance. Fibers and films of these polymers are processed from anisotropic solutions in strong acids such as methane sulfonic acid or polyphosphoric acid. The electronic absorption and vibrational spectra of the model compounds have been investigated in order to characterize the structures in the solid state and in nonprotonic solvents. The dramatic intensity differences in the spectra obtained have been interpreted by variations in the dihedral angle between the plane of the phenyl group and the plane of the central heterocyclic ring which affect the resonance configuration between the two rings.     

Synthesis,characterization, and properties of colorless rigid-rod poly(benzobisthiazole) derived from bicyclo[2.2.2]octane

Polycondensation in polyphosphoric acid of 2,5-diamino-1,4-benzene dithiol dihydrochloride with bicyclo[2.2.2]octane-1,4-dicarboxylic acid, as well as the corresponding dimethyl ester or diacid chloride, led to rigid-rod benzobisthiazole polymers. Colorless and soluble polymers with intrinsic viscosities as high as 30.6 dL/g (methanesulfonic acid, 30°C) were obtained. The ultraviolet-visible spectrum of a polymer film cast from methanesulfonic acid under reduced pressure displayed no absorptions in the visible range (400–900 °m). The polymer was thermooxidatively stable up to 420°C in air as determined by thermogravimetric analysis. Fibers spun from a lyotropic polyphosphoric acid solution exhibited a tensile strength of 300–450 Ksi, a modulus of 26 Msi, and a compressive strength of 53 Ksi. Wide-angle X-ray scattering patterns of polymer fibers indicated a 3-dimensional crystal structure rather than a nematic liquid crystal structure. © 1994 John Wiley & Sons, Inc.     

抗紫外老化聚对苯撑苯并二噁唑(PBO)纤维的制备与表征

通过化学添加2,5-二羟基对苯二甲酸(DHTA)共聚,以及添加金红石型纳米TiO2物理共混的方法,制备了聚对苯撑苯并二噁唑(PBO)的抗紫外改性纤维.考察了纤维的力学性能、特性粘度及表面形貌在紫外老化过程中的变化,并结合PBO纤维紫外加速老化后的红外分析,对PBO纤维的光老化机理进行了初步研究.结果表明,本实验所制备的DHPBO纤维以及DHPBO/n-TiO2纤维的抗紫外老化能力明显高于PBO纤维,并且金红石型纳米TiO2对PBO的抗紫外改性效果要优于有机紫外吸收剂(2,2'-(1,2-乙烷二基)双(4,1-亚苯基)双苯并噁唑).     

Chain conformation of rod-like polymers in the melt: Small-angle neutron scattering of poly(benzoyl paraphenylene)

The chain conformation of a rigid rod polymer, poly(benzoyl paraphenylene), is determined in the melt using small-angle neutron scattering. The coherent scattering cross-section from blends of partially deuterated and hydrogenous poly(benzoyl paraphenylene) agree well with ideal rod scattering for q > 0.02 Å⁻¹, indicating that the polymer chains are highly extended. Comparison of the results to a single chain-scattering function for chains of arbitrary stiffness yield a persistence length of ca. 130 Å. Pure component scattering at the lowest scattering lengths indicate that the melt is not molecularly homogenous, but is comprised of domains, potentially reflecting localized groupings of chains with similar backbone orientation. Furthermore, this mesoscopic structure depends on the processing history of the polymer in the melt state. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2449–2459, 1998     

The effect of concentration,temperature, and molecular weight on the dynamics of rigid-rod molecules in semi-dilute solutions

The dynamics of rigid-rod-like molecules are studied using rheo-optical techniques. Measurements of flow birefringence as a function of shear rate are utilized to understand the scaling behavior of rotational diffusivity with respect to concentration and temperature. The concentration scaling exponent increases with increasing concentration and the scaling laws are valid in narrow concentration windows. The Doi-Edwards (DE) scaling law D_r ∼ c⁻², holds at very high concentrations (cL³ > 150). The concentration scaling exponent decreases dramatically with increasing temperature at concentrations, cL²d > 1. Scaling of rotational diffusivity, with respect to temperature and solvent viscosity in the semidilute regime, does not follow the predictions of DE theory (and related caging ideas). On the contrary, a model proposed by Fixman was found to explain both the temperature and concentration dependence of the rotational diffusivity. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36 : 181–190, 1998     

Preparation and characterization of polymers with oxadiazole on the side chain

Three styrene-type monomers having an oxadiazole group were prepared. The monomers were polymerized by a radical initiator into high molecular weight polymer. Polymers were soluble in many organic solvents such as chloroform, benzene and tetrahydrofuran. Polymer films were amorphous and transparent and showed no change after several months of preparation. The polymer had two reduction potentials around −2 V versus Ag/AgCl electrode. The polymer film dispersed with N,N,N′, N-tetraphenyldiaminobiphenyl (TPD) showed electroluminescence due to the exciplex with TPD. © 1997 John Wiley & Sons, Ltd.     

Rigid-rod polymers with polysiloxane side chains. I. Synthesis and characterization of rigid-rod polyimides with polysiloxane side chains and their compatibility with linear polysiloxanes

Rigid-rod aromatic polyimdies having polydimethylsiloxane side chains were prepared for the purpose of dispersing rigid-rod molecules in silicone matrices for molecular reinforcement. The polyimides were obtained by imidizing the polyamide-acids bearing the side chains either thermally or chemically, which were synthesized by reacting 4,4′-diaminobiphenyl-terminated polysiloxane macromonomers with pyromellitic dianhydride in THF. The polyamide-acid films obtained by removing the solvent were soluble in THF, but the polyimides were insoluble in any common solvent. The polyimides showed no melting transition below 350°C on DSC analysis, at which temperature the side chain started decomposing. Although all the polyimides were anisotropic as observed by a polarizing microscope, x-ray diffraction analysis suggested the presence of only limited chain organization. Blends with linear polydimethylsiloxanes were prepared by casting the THF solution containing the polyamide-acid and the polydimethylsiloxane, followed by solvent evaporation and thermal imidization. With relatively longer side chains, the polyimides were proved to be compatibilized with polydimethylsiloxanes. © 1994 John Wiley & Sons, Inc.     

Quinone-amine polymers. XII. Synthesis and characterization of novel polymers from 2-phenylbenzoquinone and aliphatic diamines

In order to study the effect of the presence of phenyl groups in poly (amino-quinone) (PAQ) polymers, several novel poly(amino-2-phenylbenzoquinone) (PhPAQ) polymers have been prepared from 2-phenylbenzoquinone and aliphatic diamines, such as 1,6-diaminohexane, 1,8-diaminooctane, 1,12-diaminodod+++++, and 1,4-diaminocyclohexane. Prior to the polymerization, 2-phenylbenzoquinone was generated in situ from 2-phenylhydroquinone in the presence of calcium hypochlorite as the oxidizing agent in dichloromethane. All of the polymers synthesized have been characterized with respect to their corresponding model compounds. It was also found that unlike their analogous PAQ polymers, PhPAQ polymers were highly soluble in many common organic solvents because of the presence of phenyl groups in their polymer backbone. © 1994 John Wiley & Sons, Inc.     

Degradable polymer blends. I. Screening of miscible polymers

Blends of biodegradable polymers having properties distinct from the individual polymer components, and that are suitable for use as carriers of pharmaceutically active agents, were prepared from two or more polyanhydrides, polyesters, and mixtures of polyanhydrides and low molecular weight polyesters. The blends have different properties than the original polymers, providing a mean for altering the characteristics of the polymeric matrix without altering the chemical structure of the component polymers. Aliphatic, aromatic, and copolymers of polyanhydrides were miscible in each other and formed less crystalline compositions with a single melting point which was lower than the melting point of the starting polymers. The polyesters: poly(lactide-glycolide), poly(caprolactone), and poly(hydroxybutyric acid) presented some miscibility in each other. However, the polyanhydrides were immiscible with the polyesters resulting in a complete phase separation both in solution or in melt mixing. Only low molecular weight polyesters (in the range of 2000) of lactide and glycolide, mandelic acid, propylenefumarate, and caprolactone presented some miscibility with polyanhydrides. Similarly, poly(orthoester) and hydroxybutyric acid polymers formed a uniform mixture with the anhydride polymers which had the two melting points of the original polymers. Drug release from polymer blends composed of poly(hydroxybutyric acid) or low molecular weight poly(lactic acid) with poly(sebacic anhydride) (PSA) showed a constant release of drug for periods from 2 weeks to several months as a function of the PSA content in the blend. Increasing the content of PSA, a fast degrading polymer, increases the release rate from the blend. © 1993 John Wiley & Sons, Inc.     

Antimicrobial polymers containing melamine derivatives. I. Preparation and characterization of chloromelamine‐based cellulose

A reactive melamine derivative, 2‐amino‐4‐chloro‐6‐hydroxy‐s‐triazine (ACHT), was synthesized through the controlled hydrolysis of 2‐amino‐4,6‐dichloro‐s‐triazine. The reaction was characterized with Fourier transform infrared study and elemental analysis. ACHT could react with cotton cellulose at room temperature with a cold‐pad‐batch treatment process. Upon chlorination reactions, the amino group of covalently bound ACHT could be transformed into an N‐halamine structure, providing potent, durable, and rechargeable antimicrobial activities against both gram‐negative and gram‐positive bacteria. The chlorination mechanism and the structure–property relationship of the treated samples were further examined. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3818–3827, 2004     

Synthesis and characterization of a new benzobisoxazole/thiophene derivative polymer and the effect of the substituent on the push/pull properties

Conducting polymer synthesis of a new benzobisoxazole/thiophene derivative is reported. The conjugated co-polymer presents the lowest bandgap (1.78 eV) reported for a neutral benzobisoxazole/thiophene polymer. Electrochemical polymerization is carried out by cyclic voltammetry, and the new conducting polymer is characterized by Raman spectroscopy and X-ray photoelectron spectroscopy. The results indicate that the coupling of the monomer unit occurs at the 2,2′ positions of the thiophene ring. Theoretical studies in derivatives of this family of compounds are conducted to validate the effect on the bandgap modulation due to the change in the substituent on the phenyl moiety of the monomer. The comparison between experimental and theoretical properties shows the substituents impact on the optical properties of the system, and its viability to be used in sensors.     

Synthesis and characterization of silicate polymers

In this work an inorganic polymer is developed based on Elkem microsilica and potassium hydroxide. Using experimental data and the partial charge model a model for the gelation is suggested based on the hydrolysis and condensation reactions occurring during synthesis. In addition the optimal composition of the binder system was determined using compressive strength test and solubility experiments. Based on partial charge calculations and experimental data for the hydroxide concentration and the viscosity obtained in this study it is suggested that the polymerization of the inorganic polymer is determined by the concentration of silica species. It was found that the alkalinity has a crucial effect on the condensation process. The optimal potassium hydroxide concentration used in the synthesis of the inorganic polymer was found to be around 3.5 M, which resulted in a compressive strength of the product in the region of 50 MPa.     

Preparation and characterization of novel molecularly imprinted polymers based on thiourea receptors for nitrocompounds recognition

Molecularly imprinted polymers (MIPs) for the recognition of nitro derivatives are prepared from three different (thio)urea-bearing functional monomers. The binding capability of the polymers is characterized by a batch binding experiment. The imprinting factors and affinity constants (K) of the imprinted polymers exhibit the same tendency as the binding constants (K_a) of the functional monomers to the target substance in solution. Not only nitrofurantoin is efficiently bound by these MIPs but also a broad spectrum of other nitro compounds is bound with at the intermediate level, addressing that these (thio)urea-based monomers can be utilized to prepare a family of MIPs for various nitro compounds, which can be applied as recognition elements in separation and analytical application.     

Polyether azomethines. I. Synthesis and characterization

Six new polyether azomethines were synthesized by melt and solution polycondensation of six different diamines with 4,4′-[1,4-phenylene bis(oxy)] bisbenzaldehyde. The polymers synthesized by solution method are yellow to white in color and had inherent viscosities up to 0.59 dL/g in concentrated H₂SO₄. The polymers obtained by melt condensation show higher viscosity. Except polymer IV , others are insoluble in common organic solvents. The polymers were characterized by IR, x-ray, elemental analysis, and DSC study. The thermal stability of the polymers was evaluated by TGA and IGA study. Polymers I-III are highly thermally and thermooxidatively stable and exhibit no appreciable decomposition up to 420°C both in air and nitrogen atmosphere. It was shown that the curing of the polyazo-methines takes place by opening up of the ? CH?N? linkages at higher temperature. The electrical conductivities of the virgin and iodine doped polymers were as high as 10^?11?10^?16 and 10^?6?10^?8S cm^?1, respectively, at 30°C. Electronic spectra of the undoped polymers ( I-III ) indicated a large bathochromic shift of the ? – ?^* absorptions band (376 nm) due to ? C?N? bonds of the model compound. This can be attributed to extensive delocalization of the electrons along the polymer chain. © 1995 John Wiley & Sons, Inc.     

Liquid chromatography of synthetic polymers under limiting conditions of insolubility. I. Principle of the method

A novel liquid chromatographic procedure is presented. It is based on differences in the transport velocities of the fast-moving, pore-excluded macromolecules and slow-progressing, pore-permeating small molecules of an auxiliary liquid. A barrier of small molecules selectively decelerates certain kind of macromolecules while other kind remains unhindered. As a result, polymers of different nature are efficiently separated. In this new approach, the barrier is formed by a zone of a non-solvent injected immediately before the sample solution. The resulting method is denoted liquid chromatography under limiting conditions of insolubility.