1994 рік

The compatibility behaviour of an epoxidized styrene butadiene three-arm block copolymer ((ESB)3) with chlorinated polyethylene (CPE) at two degrees of chlorination (36 and 48 wt %) and with poly(vinyl chloride) was investigated over the complete composition range. The techniques used were dynamic mechanical analysis, differential scanning calorimetry and tensile testing. The results were compared with epoxidized block copolymer blends of different architectures, studied before: a linear ESB, a branched E(SB), and an SBS. The results indicate that miscibility is reduced along the series ESB>(ESB)3>E(SB) ., at the same level of epoxidation. Additional data on tensile properties on (ESB)3 and E(SB), blends are also reported. A method is also described to obtain epoxidized semicrystalline poly(hydrocarbons), which when blended with CPE showed a T m depression. This allowed the determination of the interaction parameter gl,. of epoxidized poly(hydrocarbon)/chlorinated polymer using the well established method.

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Miscibility of blends of polychloroprene (CR) and poly(alkyl methacrylate)s (PAMAs), such as poly(ethyl methacrylate) (PEMA), poly(isobutyl methacrylate) (PiBMA) and poly(glycidyl methacrylate) (PGMA) prepared by casting from tetrahydrofuran, were investigated by their glass transition temperature behaviours and morphologies. Since the blends of CR and PAMA were incompatible regardless of the different alkyl groups, copolymers of chloroprene and ethyl methacrylate (poly(CP-co-EMA)), isobutyl methacrylate (poly(CP-co-iBMA)) and glycidyl methacrylate (poly(CP-co-GMA)) were prepared as compatibilizers by radical solution copolymerization. Compatibilization effects of those copolymers were studied for the CR/PAMA blends of 50/50 wt% composition. For comparison, the graft copolymers of alkyl methacrylates onto CR were also prepared. The copolymers and graft copolymers showed compatibilizing effects in the blends consisting of each homopolymer, and the copolymers showed better compatibilizing effect than the graft copolymers. It was concluded that the compatibilizing effect of the copolymers in the CR/PAMA blends was more prominent in the order poly(CP-co-GMA)> poly(CP-co-iBMA)>poly(CP-co-EMA).

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We present the first open-circuit-potential (OCP) study of the chemical polymerization of aniline in the presence of various aromatic additives and demonstrate the feasibility of monitoring the polymerization rate by the OCP technique. With (NH4)zS20 8 as oxidant, there are three stages in the OCP-reaction time plots. The time (tl + t2) needed for completion of the first two stages is inversely related to the rate of polymerization. The presence of p-aminodiphenylamine, N,N'-diphenylhydrazine, benzidine and pphenylenediamine reduces the tl +t2 value and therefore increases the rate of polymerization. In contrast, the presence of p-hydroquinone increases the tl + t2 value and thus reduces the polymerization rate. These preliminary results are consistent with the kinetics and mechanism of the electrochemical polymerization of aniline.

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High molecular weight film-forming flexible fluorinated poly(arylene ether benzoxazole)s, which are suitable as gas separation membranes, adhesives and matrix resins, were synthesized in aprotic dipolar solvents such as N-methyl pyrrolidinone via an intermediate poly(hydroxy amide). The cyclodehydration was subsequently achieved at moderate temperatures (e.g. 150-195°C) in solution via an acid-catalysed (p-toluene sulfonic acid or pyridine hydrochloride) process. The water of dehydration could be azeotropically removed in an analogous manner to the well known synthesis of polyimides via intermediate poly(amide acid)s. The fluorinated monomers were bis(arylamino phenol)s based upon either the 6F or a novel 3F connecting link. Oxybis(benzoylchloride) appears to be a particularly attractive comonomer which allows the synthesis of soluble high molecular weight products. The amorphous macromolecules produced highly transparent ductile cast films with glass transition temperature values of about 300°C or higher. Semicrystalline morphologies could also be produced by incorporating more rigid comonomers. The synthetic procedures described herein are considered to be attractive relative to several alternative methods described in the literature for the synthesis of amorphous polybenzoxazoles

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The compatibilizing efficiency of epoxidized styrene-butadiene block copolymers [E(S-b-B)] of varying architecture for the immiscible polystyrene (PS)/chlorinated polymer (CP) blends [poly(vinyl chloride), chlorinated polyethene] was examined. The copolymers were a diblock (ESB), a three-arm star (ESB) 3 and a random ESBR. The techniques applied were dynamic mechanical analysis and tensile testing of specimens prepared from solvent casting. Compatibilizing efficiency was found to depend on the degree of epoxidation of the butadiene unit in the copolymer, which in turn relates to the degree of chlorination of the CP, and also on the CP/PS ratio in the ternary blend and the molecular architecture of the E(S-b-B) compatibilizer. Other things being equal, this efficiency varies as: ESB>(ESB) 3 > ESBR; thus it parallels the behaviour of the E(S-b-B) towards the CP in the binary blends. The same holds true for the degree of epoxidation of the E(S-b-B). This is in agreement with recent theoretical compatibilizing efficiency predictions and relates to the relative strength of the interaction parameters among blend constituents. Use of appropriate values for these parameters allowed the determination of the spinodal, approximating successfully the immiscibility gap of the ternary. This procedure could only be applied to the PS/ESBR/CP system, since ESBR, unlike the other E(S-b-B) copolymers, is not microphase separated.

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2-Hydroxy-3-chloropropyl- and 2-methylthio-l-phenylethyltriphenylphosphonium salts have been used as novel photoinitiators for cationic polymerization of vinyl ethers.

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The enzyme-catalysed condensation polymerization of 11-hydroxyundecanoic acid in hexane with the lipase from Candida cylindracea is reported. Molecular weights up to 35 000 are attained. A time course study of the polymerization process reveals that oligomers are formed relatively rapidly and that these oligomers then condense to generate higher molecular weight polyesters

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This paper presents an investigation of the morphology of blends containing 5 wt% styrene butadiene diblock copolymer in a high-molecular-weight polystyrene matrix. Different samples of these blends were prepared by melt compounding in an extruder and by solvent casting. Transmission electron microscopy was used to determine their morphology. The extruded blend contained well dispersed, disc-shaped micelles of the diblock. The morphology of the solvent-cast blend was strikingly different, with onion-skinned structures of diblock copolymer that spanned up to several micrometres. However, upon annealing at 200'C, the morphology of the extruded blend and of the solvent-cast blend evolved towards the same relaxed state. The micelles became more spherical, grew in size and slowly agglomerated into cluster formations. The kinetics of this evolfition were observed for the extruded blend. Micelle growth and clustering rates at 200°C and also at 180°C were determined by characterizing their size, shape and spatial distribution. The micelles became more spherical quickly and formed clusters over a longer time period. The changes in micelle shape became apparent in blends annealed at 180°C for as little as 5 min. The micelle clustering, however, was only evident in the blends annealed at 200°C. The rate of clustering was quantified by plots of nearest-neighbour distributions at different times. Analysis of these plots indicates a diffusion mechanism for the clustering. The results seem to support theoretical assertions of Semenov on dynamics of block-copolymer micelles in a high-molecular-weight polymer matrix.

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Stress and strain distributions around the crack tip of rolled high-density polyethylene have been analysed using the two-dimensional finite element method. Mechanical parameters from two samples were used. The highly anisotropic sample showed distinct differences in Young's moduli and yield stresses versus various off-axis angles while the sample of low anisotropy showed high moduli and yield stresses in both the roll and the transverse direction. Calculated results revealed a strong relation between the stress distributions at the crack front and the anisotropy of the materials. The sample with high anisotropy showed intense stress distributions coincident with the chain axis. In contrast, stress distributions of the sample with low mechanical anisotropy were less affected by the alignment of the chain axis. From experiment, kinky deformation was observed for some cases. Comparison of the experimental with the calculated results threw light on the mechanism of formation of a kink band during restretching ofanisotropic polymers

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The electro-optical coefficient r33 and refractive index of films of poly(y-benzyl-L-glutamate) and the p-nitro, p-fluoro and p-trifluoromethyl derivatives were determined as a way to assess the non-linear optical behaviour of these organic polymers. The p-fluoro-7-benzyl and p-trifluoromethyl-~,-benzyl ester polymers are new materials synthesized for this study. The electro-optical coefficient r33 = 5.2 X 10- 2 pm V- 1 for the unsubstituted polymer, 13.9 x 10 -2 pm V -1 for the p-nitro polymer, 3.0 x 102 pmV -~ for the p-fluoro polymer, and 1.6 x 10- 2 pm V- 1 for the p-trifluoromethyl polymer. The refractive indices, at a wavelength of 488 nm, of films of the polymer were determined to be 1.60, 1.61, 1.59, and 1.70, respectively, for the unsubstituted polymer and the p-nitro, p-fluoro, and p-trifluoromethyl derivatives. The frequency dependence of the dielectric constant, from 10 kHz to 4 MHz, for each of the polymer films was also determined. The waveguiding and other properties of each of the polymers were assessed in terms of the polymer structu

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