1992 рік

Tensile stress and electrical conductivity were studied on gels formed from toluene solutions of a polydiacetylene, poly[ 5,7-dodecadiyn-1,12-diol-bis(n-butoxycarbonylmethyl urethane)], abbreviated to P(4BCMU). The gels exhibited stress-strain curves concave upwards, that is, opposite to the behaviour of ordinary flexible polymer networks. This behaviour indicates that the elasticity is not due to the conformational entropy due to deformation of the stiff ribbon-like P(4BCMU) molecules. The direct current conductivity cdc, the alternating current conductivity Q,, and Young’s modulus E increased with concentration C in proportion to Co.“, C”.89, and Cl.“, respectively. The similarity in the concentration dependences of bdc, g,, and E is explained with a percolation model. The oat was almost independent of frequency in the range of 0.1-100 kHz.

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Poly (arylene ether)s containing 1,3,4-oxadiazole and 1,2,4-triazole units were prepared by the aromatic nucleophilic displacement reaction of bisphenol oxadiazole and bisphenol triazole compounds with activated aromatic dihalides. The polymers exhibited glass transition temperatures (Tgs) ranging from 182 to 242°C and several polymers exhibited melting transitions (Tins) ranging from 265 to 390°C. Inherent viscosities ranged from 1.02 to 3.40 dl g-1 indicating relatively high molecular weights. Thin films exhibited tensile strengths, moduli and elongations at 23°C of 90-1IOMPa, 2.7-3.6GPa and 4-7%, respectively. Titanium-to-titanium tensile shear specimens of a poly(arylene ether 1,3,4-oxadiazole) exhibited tensile shear strengths at 23 and 150°C of 22.1 and 17.9 MPa, respectiv

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A generalized Flory-Huggins theory is utilized to investigate liquid-liquid phase diagrams of quasi-binary polymer solutions and blends, in which one component may be polydisperse. A temperature and concentration dependent Z parameter is employed. It is illustrated that a polymer solution, in which the polymeric component has a Schulz-Zimm molecular weight distribution, may exhibit combined lower critical solution temperature/upper critical solution temperature spinodals and hour-glass cloud-point curves (CPCs). This is a direct consequence of the critical points being offset from the extrema of the CPCs and spinodals for quasi-binary systems, in contrast to true binary systems (such as solutions and blends of monodisperse polymers). Thus, for quasi-binary systems, it may be hazardous to infer the behaviour of spinodals from observations of CPCs or vice versa

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The compatibility behaviour of epoxidized styrene-butadiene (SB) block copolymers of varying architecture with chlorinated polyethylene at two degrees of chlorination (36 and 48 wt%) and with poly(vinyl chloride) was investigated over the complete composition range. The copolymers were two diblock (SB) copolymers differing in their degree of purity and a multiarm block copolymer (SB),. For comparison, data obtained previously with an epoxidized (E) triblock (ESBS) were also used. Other parameters examined were the degree of epoxidation to attain miscibility and the degree of chlorination. The techniques used were dynamic mechanical analysis, differential scanning calorimetry and tensile testing. It was demonstrated that epoxidized SB (ESB) is more miscible with chlorinated polymers than ESBS or E(SB). with the same degree ofepoxidation. Also E(SB). is better in this respect than ESBS. The level of impurities (homopolymers and SBS) accompanying commercial samples of SB did not impair the tensile properties of these blends. The degree of chlorination was found to determine the required degree of epoxidation to obtain a miscible system.

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Well defined poly (styrene-block-2-vinylpyridine) diblock copolymers were prepared by sequential anionic addition. Films were fabricated by casting diblock copolymer solutions on a Teflon sheet or flat glass dish by varying the casting conditions. Morphological results of these ultrathin sections were obtained using a transmission electron microscope. The surface characterization of diblock copolymer films was carried out by X-ray photoelectron microscopy. Both surface and bulk morphologies of these diblock copolymer films ( -50 wt% polystyrene blocks) showed a tendency that alternating lamellar structures of two microphases were oriented with their interfaces parallel to the surface that has contact with air or the substrate. Semiconducting materials were obtained upon exposure of these diblock copolymer films to alkyl halide vapour. As a result, these materials showed electrical anisotropy with conductivity.

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2-Amino-4-(N-alkylanilino)-6-isopropenyl-l,3,5-triazines were synthesized by the reaction of 2-amino-4- anilino-6-isopropenyl-l,3,5-triazine with alkyl bromides in the presence of sodium hydride in dimethyl sulphoxide. The alkyl groups of the monomers were isopropyl, isobutyl, sec-butyl, pentyl, isopentyl, 1-methylbuty! and benzyl. Solution homopolymerization of these monomers and their copolymerization with styrene, methyl methacrylate and methyl acrylate was carried out using azobisisobutyronitrile as an initiator. Copolymerization parameters were determined for these monomers. The glass transition temperature of the resulting polymers depended on the length and the shape of the alkyl side-chain. A polymerization exothermic peak was observed in differential scanning calorimetry curves above the melting point for the monomers. The ceiling temperature (To) and heat of polymerization (AHp) were determined from the exothermic peaks. The influence of branched alkyl groups on T? and AHp is discussed.

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3,2-Thienyl chromium acrylate has been synthesized and its polymerization carried out in the presence of a styrene-arsenic sulphide complex in dimethylformamide at 90 + 0.1°C for 4 h. The reaction order with respect to initiator and monomer revealed essential differences from those assumed using the classical polymerization rate equation. The overall activation energy and the average value of the ratio of the square of the propagation constant to the termination rate constant (k2/kt) are 53.3 kJ mo1-1 and 0.80 x I0- 51 mol- 1 s- 1, respectively.

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Adhesion between filler and matrix has been studied using a model system composed of glass bead filled poly(vinyl chloride) (PVC). Stress-strain and volume-strain tests and scanning electron microscopy revealed that adhesion is improved by grafting poly(methyl methacrylate) (PMMA), which is known to be miscible with the PVC matrix, upon the surface of the glass beads. The best results were obtained when large amounts of grafted PMMA were used, leading to maximum stress of the composite, nearly as high as that of pure PVC.

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Aggregation states and electro-optical properties of a binary mixture by mixing a nematic side chain type liquid crystalline polymer (LCP) and a nematic low molecular weight liquid crystal (LC) have been studied. The nematic LC with a strong polar terminal group was miscible with the nematic LCP having a weak polar terminal group. The binary mixture showed an induced smectic phase over a wide range of mixing concentrations and temperature. The reversible turbid (light scattering)-transparent change was observed upon application of electric fields with low and high frequencies, respectively. Both transparent and turbid states of the binary mixture could be maintained stably even when the electric field was turned off (bistable and reversible light switching). A novel type of electro-optical effect based on light scattering was obtained for the mixture in the induced smectic state.

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This communication is a theoretical re-examination of the method to obtain Avrami parameters directly from non-isothermal crystallization data proposed by Dutta.

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