1992 рік

The preparation, thermal behaviour, mechanical properties and morphology of a family of binary blends composed of components each containing ionic functionalities are examined. One component is a semicrystalline copolymer, metal-neutralized ethylene-methacrylate (M-EMA), and the other an elastomeric component, metal-neutralized sulphonated ethylene-propylene diene copolymer (M-SEPDM). These polymeric materials contain low levels of ionic groups (~<10 mol%) which are capable of coulombically associating together into microphase-separated regions. These regions contain nonstoichiometric levels of ionic groups. A general characteristic of these blend systems is that the mechanical properties and morphology are directly influenced by the specific composition ratio of rubber to semicrystalline component. Without the associating units on one (or both) of the components, the resulting blends have grossly phase-separated components. The interfacial adhesion is weak, as indicated by poor tensile properties. The inter-relationship between structure and mechanical properties is discussed in terms of changes in the initial spherulitic morphology of the M-EMA component with the addition of increasing levels of the coulombically associating elastomeric component, M-SEPDM.

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A melt-quenched blend of 80wt% poly(vinylidene fluoride) (PVDF) and 20wt% poly(methyl methacrylate) (PMMA) has the fl-crystal form of PVDF, which grows larger on annealing at higher temperature. The internal electric field E i induced by poling in the PVDF/PMMA (80/20) blend was measured using the technique of electrochromic peak shift of dye dissolved in the blend. It was found that E i was of the order of 106 V cm-1 (larger than the poling field), and that Ei was anomalously stable when the sample was annealed at higher temperature, whereas the pyroelectricity decreased above the glass transition temperature. We speculated that the space charge may be related to the anomalous stability of El.

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Blends of poly(methyl methacrylate) (PMMA) and bisphenol-A polycarbonate (PC) having high molecular weights do not form homogeneous mixtures at equilibrium above the glass transition temperature. In this paper, the possibility of developing blends of PMMA with polycarbonates that can be melt processed into homogeneous materials was examined by adding a comonomer to the polycarbonate. Hexafluorobisphenol- A appears to be an extremely effective comonomer for this purpose. The phase behaviour of PMMA blends with hexafluorobisphenol-A polycarbonate (HFPC) and with PC-HFPC copolycarbonates containing various amounts of hexafluorobisphenol-A was determined. The blends of PMMA and HFPC are miscible and do not phase separate prior to thermal decomposition. The phase separation temperatures of PMMA blends with the copolycarbonates increase dramatically as the hexafluorobisphenol-A content increases. Blends of PMMA with copolycarbonates containing 15 wt% hexafluorobisphenol-A or higher have phase separation temperatures above the temperature range required for melt processing. Additionally, the interaction energies for blends of PMMA with PC, bisphenol chloral polycarbonate and PC-HFPC copolymers were calculated from the phase boundaries using the lattice fluid theory and binary interaction model.

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Butyl lithium can be used in place of aluminium alkyls in catalysts of the A1R3/neodymium complex/A1 alkyl halide type. With catalysts consisting of Al alkyl halide/neodymium complex/BuLi, both order of addition and, in particular, the ratio of catalyst components are critical. Polymer with a high cis content can be made from butadiene and isoprene but conversions are lower and more variable than with standard aluminium alkyl-based catalysts, even when high catalyst concentrations are used. The catalyst can be used as a premix or added to mixed feed as separate components. In both cases the catalyst mixture is somewhat heterogeneous and polymerization rates are improved by shaking or stirring during polymerization.

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Profiles of reaction rate as a function of time were obtained for free radical crosslinking polymerizations of ethylene glycol methacrylates and dimethacrylates using differential scanning calorimetry. Copolymerizations of ethylene glycol monomethacrylates with small amounts of dimethacrylate crosslinking agents were studied in addition to homopolymerizations of dimethacrylates. In the former case, the effects of the crosslinking agent, initiator, solvent, and the pendent ethylene glycol chain length were investigated. Typically, a sharp increase in the reaction rate was observed which was attributed to autoacceleration. The time period before the onset of autoacceleration increased and the maximum reaction rate decreased as the solvent concentration or the pendent chain length were increased or the crosslinking agent concentration was decreased. These results were explained by an increase in the mobility of the growing polymer leading to a decrease in the magnitude of the gel effect. Studies of dimethacrylates yielded similar results for the effect of solvent. However, the maximum reaction rate increased when the number of repeating units between the methacrylate functionalities was increased from one to four, but decreased when the number of repeating units was increased from four to nine. Photopolymerization experiments indicated that radicals with significantly different lifetimes might be present in dimethacrylate homopolymerizations

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Intermacromolecular complex formation has been studied between polyethyleneimine and methacrylic acid-methacrylamide copolymer in water-dimethylformamide (DMF) mixtures of different compositions. Preferential solvation coefficients (2/C) have been calculated for the various compositions of the solvent mixtures. At a specific composition of the solvent (e.g. 50% water + 50% DMF by volume), the intrinsic viscosity of the copolymer had a maximum value which coincided with the minimum value of 2/C and the minimum value of the reduced viscosity of the complexes. Interpretations have been sought in terms of conformational change of the copolymer and the interpolymer complex at a specific composition of the solvent mixture.

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The phase behaviour of binary blends of copolycarbonates of tetramethyl bisphenol-A and bisphenol-A (TMPC-PC) with copolymers of styrene with acrylonitrile (SAN) or styrene with methyl methacrylate (SMMA) has been examined as a function of composition of each copolymer. The interaction parameters for TMPC-PC blends with each SAN copolymer and each SMMA copolymer were evaluated from the lower critical solution temperature type phase boundary using the lattice fluid theory of Sanchez and Lacombe. From such information for several copolymer compositions, bare interaction parameters for mixing of various monomer unit pairs (AP*) were calculated using a binary interaction model. Additionally, from miscibility maps, Flory-Huggins type energy densities (Bu) have been computed for various monomer unit pairs. The interactions of acrylonitrile with other monomer units (styrene, PC and TMPC) are strongly repulsive in each case while the interactions of MMA with these monomer units are weakly repulsive.

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A new route of attaching phosphites to a (co)polymer chain is described. These copolymers are used for the preparation of a rhodium phosphite hydroformylation catalyst. The catalytic activity of this polymer-bound system is identical to that of the low molecular weight analogue. The catalysts show a high activity towards the hydroformylation of the otherwise unreactive cyclooctene. From spectroscopic and kinetic data, it was found that only one phosphite is coordinated to the rhodium complex in its active form. An equilibrium between this complex and an inactive complex without phosphite ligands, prohibits its use in continuous flow reactors.

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The contact angles 0 of dispersion (D), polar (P) and hydrogen bonding (H) liquids on poly (vinylidene fluoride-co-hexafluoroacetone ) (P (VDF-HFA); HFA content 6.5, 8.3 and 10.4 mol % ) were measured. The critical surface tensions 7c of P(VDF-HFA) were evaluated by the Zisman plot (cos 0 versus 7L), Young-Dupre-Good-Girifalco plot (1 + cos 0 versus 1/7 °"5) and the log(1 + cos 0) versus log(TL) plot. The following results were obtained: the yc values of P(VDF-HFA) evaluated for the P liquids were larger than those for the D and H liquids; the 7o values estimated by the Zisman plot were smaller than those obtained by the other plots; the surface tension Ys values of P(VDF-HFA) revealed a minimum at the HFA content of 8.3 mol%. It was expected that P(VDF-HFA) with HFA = 8.3 mol% induced surface segregation most easily.

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A viscometric analysis of four samples of poly(dihexoxyphosphazene), [N.-.P(R2)-] x with R = -O-(CH2)sCH3, having very different molecular weights has been carried out using benzene as solvent. The results for intrinsic viscosity obtained at 25°C were [~/] = 1.61, 1.09, 0.41 and 0.057 dig -~, respectively, for samples having weight-average molecular weights, determined by light scattering, of 10-5~tw = 22.8, 9.17, 2.45 and 0.26 g mol -~. Although the samples are polydisperse, it is possible to determine the true values of the K and a coefficients appearing in the Mark-Houwink equation [ ~/] = KM", by using the results obtained in a previous analysis performed on a different solvent. The values for K and a for benzene at 25°C are 2.01 x 10-5 and 0.79, respectively. The extrapolation to unperturbed conditions allows the evaluation of the characteristic ratio of dimensions as C, = (r 2 )o/nl 2 = 12.9, in good agreement with the value of 13.2 previously obtained. This agreement validates the hypothesis used for the determination of the K and a coefficients

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