Multidimensional benzobisoxazole rigid-rod polymers. I. Preparation and characterization

Two- and three-dimensional rigid-rod polymers containing benzobisoxazole structures were prepared through the polycondensation in polyphosphoric acid of 4-[5-amino-6-hydroxybenzoxazol-2-yl]benzoic acid (ABA) with trimesic acid and 1,3,5,7-tetrakis(4-carboxylatophenyl)adamantane, respectively. Thermal properties of the polymers were determined by differential scanning calorimetry, thermogravimetric/mass spectral analysis, and isothermal aging studies. The multidimensional polymers exhibited lower solution viscosities and lower thermooxidative stabilities than the one-dimensional polymer generated by the homopolymerization of ABA under identical reaction conditions. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 3451–3456, 1997     

Synthesis and photoconductivity study of phthalocyanine polymers. IV. [SiPcNHCH2CH2NH]n

The preparation of a novel polymer of ethylenediamine bridged polymeric silicon phthalocyanine ( I ) with quasi-one-dimensional structure is described. The product was obtained by the condensation polymerization of ethylenediamine and silicon dichloride phthalocyanine (Cl₂SiPc) monomers and was characterized by IR and UV/VIS spectroscopy and elemental analysis. The photoconductivity of the polymer I with the quasi-one-dimensional structure is much better than that of not only the corresponding Cl₂SiPc monomer, but also other phthalocyanine polymers whose molecules are not one-dimensional structures, and showing the one-dimensional effects of molecular structure of increasing photoconductivity. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 959–964, 1997     

Polymers from renewable resources. XXI. Semi-interpenetrating polymer networks based on cardanol-formaldehyde-substituted aromatic compounds copolymerized resins and castor oil polyurethanes: Synthesis,structure, scanning electron microscopy and XRD

Substituted aromatic compounds incorporated–cardanol–formaldehyde novolac resins were synthesized by acid base catalyzed reactions. A number of improved high temperature stable interpenetrating polymer networks (semi-IPNs) were prepared by condensing novolac resins and polyurethanes prepared from castor oil and diisocyanates of varying NCO/OH ratio. The structure of these semi-IPNs were studied using various characterization techniques such as IR, nuclear magnetic resonance (NMR) spectra. The scanning electron microscopy of some of the semi-IPNs have been studied and the morphology has been examined. The samples were subjected to wide angle X-ray diffraction analysis. The degree of crystallinity (X_cr) was computed on the basis of the crystal defect concept, developed by Ruland and Vonk. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3117–3124, 1997     

Water-soluble polymer carriers. Ionically bonded substances with physiological activity

The preparation of water-soluble polymers with physiological activity via ion bonding of low molecular weight physiologically active substances to a polymer carrier has been studied. The conditions for obtaining polymer salts of physiologically active substances with acid properties and amino-containing polymer carrier have been established. The maximum conversion degree has been determined. The polymer salts have been characterized by potentiometric titration, ³¹P-NMR and IR spectroscopy, and elemental analysis. The stability of the salts and the immobilization rate of the low molecular weight physiologically active substances have been investigated. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 1933–1938, 1997     

Synthesis and photovoltaic properties of 2,6‐bis(2‐thienyl) benzobisazole and 4,8‐bis(thienyl)‐benzo[1,2‐B:4,5‐B′]dithiophene copolymers

In an effort to design efficient low‐cost polymers for use in organic photovoltaic cells the easily prepared donor–acceptor–donor triad of a either cis‐benzobisoxazole, trans‐benzobisoxazole or trans‐benzobisthiazole flanked by two thiophene rings was combined with the electron‐rich 4,8‐bis(5‐(2‐ethylhexyl)‐thien‐2‐yl)‐benzo[1,2‐b:4,5‐b′]dithiophene. The electrochemical, optical, morphological, charge transport, and photovoltaic properties of the resulting terpolymers were investigated. Although the polymers differed in the arrangement and/or nature of the chalcogens, they all had similar highest occupied molecular orbital energy levels (?5.2 to ?5.3 eV) and optical band gaps (2.1–2.2 eV). However, the lowest unoccupied molecular orbital energy levels ranged from ?3.1 to ?3.5 eV. When the polymers were used as electron donors in bulk heterojunction photovoltaic devices with PC₇₁BM ([6,6]‐phenyl C₇₁‐butyric acid methyl ester) as the acceptor, the trans‐benzobisoxazole polymer had the best performance with a power conversion efficiency of 2.8%. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 316–324     

Molecular composite fibers from rigid rod polymers and thermoset resin matrixes

Fibers consisting of a rigid rod polymer and thermoset resin matrices were prepared. Poly(benzo-[1,2-d : 5,4-d′]bisoxazole-2,6-diyl)-1,4-phenylene} (PBO) in polyphosphoric acid (PPA) was blended with isophthaloyl bis-4-benzocyclobutene (1) or 2,6-bis-4-benzocyclobutene benzo[1,2-d: 5,4-d′]bisoxazole (2), and fibers were spun from these dopes. As-spun fibers that did not show phase segregation between the two components as examined with an optical microscope, were soluble in methanesulfonic acid (MSA). After heat treat-ment, the fibers swelled but did not dissolve in MSA. A fiber cross section of heat-treated PBO-1 fiber showed well-dispersed benzocyclobutene polymer domains of 200–500 Å by transmission electron microscopy (TEM). Films cast from MSA solutions of PBO and 2 were homogeneous, and TEM of heat-treated fiber showed only one phase. A molecular composite fiber was made. Some of these fibers showed 20–30% improvement in compressive strength over unmodified PBO fiber. © 1995 John Wiley & Sons, Inc.     

Synthesis and Characterization of Poly(p-phenylene benzobisoxazole)/Poly(pyridobisimidazole) Block Copolymers

Poly(p-phenylene benzobisoxazole)/poly(pyridobisimidazole) block copolymers (PBO-b-PIPD) were prepared by introducing poly(pyridobisimidazole) (PIPD) moieties into the main chains of poly(p-phenylene benzobisoxazole) (PBO) in order to enhance its photostability. PBO and copolymer fibers were directly prepared from the polymerization solutions by dry-jet wet-spinning. Chemical structures and molecular chains arrangement of the block copolymers were characterized by Fourier transform infrared (FTIR) spectroscopy, solid-state ¹³C-NMR and wide angle X-ray diffraction (WAXD). Thermal stability of the copolymers was investigated by thermogravimetric analysis (TGA) in nitrogen. Thin films of PBO and copolymers were cast from methanesulfonic acid (MSA) solutions. Both the films and fibers were exposed to UV light to determine their photostability. Changes in the chemical structures and surface morphologies of the films were characterized by FTIR spectra and scanning electronic microscopy (SEM), respectively. After UV light exposure, the retention of strength for copolymer fibers is improved compared to PBO fibers. The results revealed that copolymers suffered less photodegradation in comparison with homopolymer. The mechanism for the improved photostability of the copolymers was discussed.     

Synthesis and characterization of fully aromatic thermotropic liquid‐crystalline copolyesters containing m‐hydroxybenzoic acid units

A series of fully aromatic copolyesters based on p‐acetoxybenzoic acid (p‐ABA), hydroquinone diacetate (HQDA), terephthalic acid (TPA), and m‐acetoxybenzoic acid (m‐ABA) were prepared by a modified melt‐polycondensation reaction. The copolyesters were characterized by DSC, thermogravimetric analysis, ¹H NMR, polarized optical microscopy, X‐ray diffraction, and intrinsic viscosity measurements. The copolyesters exhibited nematic liquid‐crystalline phases in a broad temperature range of about 150 °C, when the content of linear (p‐ABA, HQDA, and TPA) units was over 67 mol %. DSC analysis of the anisotropic copolyesters revealed broad endotherms associated with the nematic phases, and the melting or flow temperatures were found to be in the processable region. The flow temperatures and crystal‐to‐nematic and nematic‐to‐isotropic transitions depend on the type of linear monomer units, and these transitions increased as the content of the p‐ABA units increased, as compared to the HQDA/TPA units. When the content of the p‐ABA units increased, as compared to other linear units (HQDA and TPA), the intrinsic viscosity and degree of crystallinity of the copolyesters also increased, implying a higher reactivity for p‐ABA in the p‐ABA/HQDA/TPA/m‐ABA polymer system. The aromatic region in the ¹H NMR spectra of the copolyesters containing equal molar compositions of p‐ABA, HQDA, and TPA units were sensitive to the sequence distribution of aromatic rings. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3263–3277, 2001     

Polymer-supported reagents. II. Kinetics of esterification of acrylic acid with n-butanol using polymer supported titanium tetrachloride as catalyst

Crosslinked poly(4-vinylpyridine-co-styrene) was prepared and functionalized with titanium tetrachloride to afford the corresponding poly(4-vinylpyridine-co-styrene)-titanium tetrachloride complex. This insoluble functionalized polymer-supported catalyst shows good catalytic activity for esterification reactions. In this article, the kinetics of esterification of acrylic acid with n-butanol is reported. The rate of formation of product depends on many experimental parameters, viz., stirring speed, concentration of acrylic acid, catalyst amount, temperature, percent active site, percent crosslinking, and mesh size of the polymer catalyst. The reaction rates were found to increase with increase in the stirring speed, concentration of acrylic acid, catalyst amount, and temperature, and decreases with increasing percentage crosslinking and mesh size of the polymer beads. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 727–733, 1997     

Fiber property and structure development of polyester blend fibers reinforced with a thermotropic liquid‐crystal polymer

Ternary blend fibers (TBFs), based on melt blends of poly(ethylene 2,6‐naphthalate), poly(ethylene terephthalate), and a thermotropic liquid‐crystal polymer (TLCP), were prepared by a process of melt blending and spinning to achieve high‐performance fibers. The reinforcement effect of the polymer matrix by the TLCP component, the fibrillar structure with TLCP fibrils of high aspect ratios, and the development of more ordered and perfect crystalline structures by an annealing process resulted in the improvement of the tensile strength and modulus for the TBFs. An increase in the apparent crystallite size with the spinning speed was attributed to the development of larger crystallites and more ordered crystalline structures in the annealed TBFs. The birefringence and density of the TBFs increased with increasing spinning speed, the TBFs becoming more oriented and the crystal packing becoming more enhanced. The molecular orientation was an important factor in determining the tensile strength and modulus of the TBFs. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 395–403, 2004     

Phase behavior of modified montmorillonite– poly(ϵ‐caprolactone) nanocomposites

The thermal behavior and overall isothermal crystallization kinetics of a series of organophilic modified montmorillonite–poly(?‐caprolactone) nanocomposites were investigated. In general, the thermal behavior was influenced more by the type of dispersion than by the clay content. For nanocomposites in which silicate platelets were predominantly dispersed in the polymer matrix to give exfoliated structures, the thermal properties were improved with respect to those of neat poly(?‐caprolactone), whereas in those cases in which simply intercalated structures were attained, the thermal properties regularly decayed as the clay content increased. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1321–1332, 2004     

Potential switching of optical properties in polymer electrolytes

The electric field dependence of the optical properties of a series of anion-conducting polymer electrolytes at an ITO–electrolyte interface was investigated. A change in reflectance and refractive index of polymer electrolytes [poly(ethyl methacrylate)]₁₈(Bu₃SnX)₃Bu₄NX where X = Cl, Br, and SCN was observed. This was ascribed to anion accumulation/depletion in the interfacial region. Shorter response times were observed for electrolytes with higher conductivities, illustrating the interrelationship between these two phenomena. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2057–2062, 1997     

Observations on the thermoreversible gelation of two-directional arborols in water–methanol mixtures

Reversible gels of two-directional cascade polymers with hydrophilic groups covalently attached by an hydrophobic center chain were studied by light and small-angle X-ray scattering, differential scanning calorimetry, and freeze-fracture transmission electron microscopy. The long, self-assembled fibers interact side-by-side over extended regions to form bundles. A given fiber may participate in several bundles, thus forming a three-dimensional gel network. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2787–2793, 1997     

Synthesis and properties of new crystalline poly(arylene ether)s containing pendant benzoyl groups

Poly(arylene ether)s ( 3 ) containing pendant benzoyl groups were prepared by the aromatic substitution reaction of 2,5-difluoro-4-benzoylbenzophenone (2) with hydroquinone ( 1a ) and methylhydroquinone ( 1b ) in the presence of potassium carbonate in N,N-dimethylacetamide. The polycondensation proceeded smoothly at 165°C and produced poly(arylene ether)s with inherent viscosities up to 0.8 dL/g. The polymer ( 3b ) derived from methylhydroquinone was quite soluble in common organic solvents and could be processed into uniform films from solutions. On the other hand, the polymer ( 3a ) derived from hydroquinone was only soluble in pentafluorophenol and methanesulfonic acid and had a high crystallinity. These polymers showed 10% weight losses at around 420 and 490°C in nitrogen. Polymer 3b also showed good tensile strength and tensile moduli. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 605–611, 1997     

In situ polymerization and characterization of graphene oxide‐co‐poly(phenylene benzobisoxazole) copolymer fibers derived from composite inner salts

A facile and efficient strategy for preparing well dispersed graphene oxide (GO)‐co‐Poly(phenylene benzobisoxazole) (PBO) copolymer fibers was carried out by direct in situ polycondensation of composite inner salts. The composite inner salts were achieved to improve the dispersivity, solubility, reactivity, and interfacial adhesion of GO in PBO polymer matrix. The structure and morphology of GO‐co‐PBO copolymer fibers have been characterized. It was demonstrated that GO were covalently incorporated with PBO molecular chains and dispersed considerably well in PBO fiber even the GO reach to 3 wt %. Meanwhile, the tensile modulus, tensile strength and thermal stability of GO‐co‐PBO copolymer fibers increased considerably with GO. The mechanism and theoretical calculation of GO enhanced PBO fiber were also discussed. The main reasons for the improvement on performance of PBO fiber should be attributed to good dispersion GO in PBO matrix and covalent bonding networks at the interface between GO and PBO molecular chains. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Blends of bisphenol-A polycarbonate and acrylic polymers: II. PC/acrylic copolymers as a new route for compatibilization

An acrylic polymer containing acid and anhydride units, referred to as reactive polyglutarimide (RPGI), has been used to react with PC. The reaction has been previously determined as an acidolysis of the carbonate bond which breaks the PC chain in two parts. One of those two parts remains free while the other one is grafted on the acrylic backbone. We have found that the anhydride units could also react with the carbonate bonds. In this case the PC macromolecule would also be broken in two parts, which would, however, both be grafted on the acrylic backbone. The reaction has been performed in solution in order to keep good contact between the reacting units. The influence of temperature and concentration on the grafting ratio has been studied. The best experimental conditions were determined in order to obtain a grafted copolymer where the acrylic backbone only supports, on the average, one PC side chain through acid reaction or two PC chains through anhydride reaction. Indeed, these two types of reactions could not be isolated. The efficiency of this copolymer as emulsifier has been studied in solution cast blends as well as in melt mixed blends. The copolymer strongly affects the microstructure in solution cast blends where films containing 30 wt % of PC have become transparent. However, the dispersed phase size of solvent cast blends could be highly influenced by the casting conditions related to solvent trapping. In melt mixed samples, the copolymer also reduces significantly the dispersed phase size, but no transparent blends have been observed so far. These results were compared with those given in the literature describing the efficiency of a synthesized copolymer which has a more complicated structure. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 735–747, 1997     

Hyperbranch‐polyethyleniminated functional polymers. I. Synthesis,characterization of novel ABA type of dumbbell‐like polyethyleniminated polyoxypropylenediamines,and their complexing properties with copper(II) ions in aqueous solution

Novel ABA‐type dumbbell‐like water‐soluble copolymers [D230(EI)₄, D400(EI)₄, and D400(EI)₈] were synthesized by introducing ethylenimine (EI) groups into both sides of polyoxypropylenediamines via a simple in situ ethylamination of polyoxypropylenediamine with 2‐chloroethylamine hydrochloride. The structures of the resultant polymers were identified by Fourier transform infrared spectroscopy and ¹H NMR. The percentages of primary, secondary, and tertiary amine present were determined by the potentiometric titration method after treatments with the appropriate chemicals of salicylaldehyde and acetic anhydride. The surface tension and solubilizing behavior of pyrene in the presence of these polymers in aqueous medium were also investigated, and the efficiency to reduce the surface tension and solubilizing behavior of pyrene depends on the attachments of EI to polymer backbone. The chelating properties of these polymers were examined quantitatively by ultraviolet–visible (UV–vis) spectroscopy in the presence of Cu²⁺ ions in aqueous solution, and continuous variation analysis revealed that the most stable complex is formed at the normality ratio of [N]/[Cu²⁺] = 3.0. UV–vis spectroscopy and transmission electron microscopy were used to evaluate the dumbbell‐like water‐soluble copolymer, D400(EI)₈, as a stabilizer for preparing colloidal noble metal nanoparticles (Au and Pt) in aqueous solution. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1360–1370, 2003     

Photolytic transformation of aryl benzobisoxazole and aryl benzobisthiazole compounds into carbon dioxide

Solid‐state aryl benzobisoxazole and aryl benzobisthiazole compounds photolyzed in the presence of O₂ undergo cleavage to produce benzobisoxazoles (or benzobisthiazoles), benzonitriles, and benzamides. A very high percentage of the carbon atoms in one of the two segments from chain cleavage are converted to CO₂. This very unusual observation has been carefully confirmed by gas chromatography/mass spectroscopy analysis of the gaseous components in the photolysis vessel before and after photolysis, labeling experiments, and the correlation of the mass reduction in photolyzed polymers and the amount of CO₂ that evolves. The rate of CO₂ generation is used to compare the relative photostability of aryl benzobisoxazole and aryl benzobisthiazole model compounds, films, and fibers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1868–1877, 2007     

Self-organization and polyolefin nucleation efficacy of 1,3:2,4-di-p-methylbenzylidene sorbitol

Recent studies have demonstrated that addition of a small quantity of dibenzylidene sorbitol (DBS) to a molten polymer may result in a physical gel if conditions permit the DBS molecules to self-organize into a three-dimensional network composed of highly connected nanofibrils. If the polymer crystallizes, DBS may also serve as a nucleating agent, promoting the formation of spherulites, especially in commercially important polyolefins such as polypropylene. We examine the thermal and mechanical properties, as well as the morphological characteristics, of an isotactic polypropylene copolymer with 3 wt % ethylene upon addition of less than 1 wt % of 1,3:2,4-di-p-methylbenzylidene sorbitol (MDBS). From dynamic rheological measurements, pronounced complex viscosity increases, attributed to MDBS nanofibril network formation, are observed at concentration-dependent temperatures above the melting point of the nucleated copolymer. Transmission electron micrographs of RuO₄-stained sections confirm the existence of MDBS nanofibrils measuring on the order of 10 nm in diameter and, at higher concentrations, fibrillar bundles measuring up to about 200 nm across and several microns in length. The addition of MDBS at different concentrations is also found to promote increases in optical clarity, yield strength, tensile strength, and ultimate elongation of modified copolymer formulations. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 2617–2628, 1997     

Hybrid polystyrene based electrospun fibers with spin‐crossover properties

We have succeeded in the preparation of electrospun fibers of polystyrene incorporating a metallo‐organic polymer of [Fe (II) (4‐octadecyl‐1,2,4‐triazole)₃(ClO₄)₂]n. The obtained fibers have diameters in the range 2–4 µm and show the characteristic spin‐crossover transition associated with the metallo‐organic polymer. The structure of both, polystyrene and the metallo‐organic polymer, in the fibers was also studied. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 814–821