1993 рік

Interpenetrating polymer networks (IPNs) composed of hydrophobic polystyrene (PS) and hydrophilic poly(2-hydroxyethyl methacrylate) (PHEMA) were synthesized by a sequential IPN method, and they showed a microphase-separated structure. A common solvent, dimethylformamide, which swells the polymer I network and dissolves monomer II, was used to impregnate monomer II into the network of polymer I. The content of polymer II in the IPNs became large when the crosslink density of polymer I was low and that of polymer II was high. It was found that certain monomer II concentration in the swelling agent existed that maximized the polymer II fraction in the IPN. Contact angle and Fourier-transform infra-red measurements revealed that the polymer II content decreased gradually towards the surface of the IPNs. The gradient composition observed in the IPNs was explained by the polymerization inhibition by oxygen and the thermodynamic effect.

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The protonation of polyemeraldine base (PANI) by diesters of phosphoric acid was studied. Three esters were investigated, namely bis(2-methylpropyl) hydrogen phosphate (DiBHP), bis(2-ethylhexyl) hydrogen phosphate (DiOHP) and its non-branched analogue, bis(n-octyl) hydrogen phosphate (DnOHP). It has been found that DiOHP, in addition to protonation, plasticizes PANI at very low ester contents i.e. for y ~> 0.25 in PANI(DiOHP)y. In PANI(DnOHP)y and PANI(DiBHP)y the plastification starts at y = 0.50 and y = 0.65 respectively. It is clear that the long and branched substituents facilitate plastification. PANI protonated with DiOHP is soluble in common organic solvents such as toluene, chloroform, THF etc. The soluble fraction is enriched in DiOHP as compared with the parent protonated polymer. The existence of the anions originating from the ester in the soluble part of the polymer was confirmed by FTi.r. and 31p n.m.r. studies of the soluble fraction. Free-standing films with a conductivity of 10 S cm 1 can be produced by hot pressing PANI(DiOHP)y at temperatures of 80-140°C. At higher temperatures partial degradation of the complex occurs resulting in a decrease of conductivity with a simultaneous increase of Young's modulus and tensile strength. Blends of DiOHP-plasticized PANI and dioctyl phthalate-plasticized PVC, of excellent mechanical properties, can be prepared by hot pressing at 160c'C.

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Acenaphthalene was copolymerized with acrylamide in water to form poly(acrylamide-co-acenaphthalene) [P(AAm-co-ACE)] with molecular weight ~2 x 106g mol-1. A variety of fluorescence experiments were carried out at 0.8 wt% polymer concentration. Time-resolved fluorescence depolarization measurements gave a mean rotational correlation time for backbone motion of 30 ns. Time-resolved and steady-state fluorescence quenching experiments were carried out using acrylamide as the quencher. In the case of polymer-bound chromophore, we were able to follow the transient effect in the diffusion-controlled quenching process. The mutual diffusion coefficient D characterizing this reaction is a factor of six slower than the self-diffusion coefficient DAA~=9.15 x 10 -6 cm 2 s-1 for acrylamide in water, measured by pulsed gradient n.m.r. We interpret this result to mean that acrylamide diffusion is significantly slower inside the P(AAm) coil than it is in bulk water.

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The effects of the type and amount of surfactant on the overall polymerization features and final product properties for the seeded semicontinuous emulsion terpolymerization of styrene, 2-ethylhexyl acrylate and methacrylic acid were investigated. The emulsifier systems studied included: (i) pure anionic emulsifier (sodium lauryl sulfate); (ii) anionic ethoxylated emulsifier (Alipal CO-436); and (iii) non-ionic emulsifiers of different ethylene oxide chain length (Myrj 45 and Myrj 52). The final latex properties considered were: latex viscosity both prior to and after neutralization, mechanical stability, chemical stability and freeze-thaw stability.

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The mechanical, elastic and viscoelastic properties of an elastomer are affected by the addition of carbon black. Incorporation of carbon black into an elastomeric matrix increases tensile strength, the complex dynamic modulus and hysteresis among other properties. Dynamic mechanical properties of elastomers filled with polymeric and non-polymeric fillers can be described in terms of certain mechanical models proposed by Takayanagi. In the case of a two-component series model, equations have been developed to predict the individual strain in each phase when testing under position control. Utilizing the loss modulus and the square of the dynamic strain amplitude of each phase, it is possible to calculate the hysteresis in each section. Based on the assumption that the model hysteresis is a weighted average of individual hysteretic contributions, the energy loss per cycle of the series model may be predicted. This approach is also utilized in the case of a two-component parallel model

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Water-soluble polymers such as poly (acrylic acid ) (PAA), poly (methacrylic acid ) (PMAA), poly (ethylene oxide) (PEO) and poly(vinyl pyrrolidone) (PVP) form interpolymer complexes with secondary bonds. These solid amorphous complexes, blends and mechanical mixtures of component polymers have been studied and the results have been compared. The structures have been analysed using differential scanning calorimetry and ~3C cross-polarization/magic-angle spinning nuclear magnetic resonance, and the molecular mobility has been studied using 1H relaxation measurements. The interaction between component polymers affects the molecular motion. T~pH and T m show the molecular-level mixing in complexes and partial mixing in blends. The glass transition of the PMAA-PVP complexes indicates the dominant role of PMAA in the complex. This conclusion is supported by T~H and T~p H measurements

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Novel epoxy resins containing zinc, chromium and copper have been synthesized by reacting acrylates of these metals with bisphenol-A and excess epichlorohydrin. Parameters, such as epoxide equivalent weight, hydroxyl content and viscosity, increase as a function of concentration of metals. The resins, characterized by i.r., SEM, n.m.r., laC n.m.r, and cured with polyamide at room temperature for 24 h and 80°C for 2 h, have improved thermal stability, chemical resistance and electrical conductivity as compared to unmodified epoxy resin. The results have been explained by the assumption that the metal(s) form a complex with bisphenol-A.

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The dynamic mechanical properties of poly(benzyl methacrylate) (PBzMA), and poly(cyclohexylmethyl methacrylate) (PCHMMA) were studied. In order to show the fl relaxation in both polymers and the 7 relaxation in PBzMA, the derivative of the real part of the complex modulus dE'/dTwas calculated, which is proportional to T-2E". A detailed study of the 7 relaxation spectra of PCHMMA in terms of activation free energy distribution was performed.

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The diffusion of small molecules in polymers was measured using Fourier transform infra-red-attenuated total reflection (FTi.r.-a.t.r) spectroscopy, a new approach which allows one to study liquid diffusion in thin polymer films in situ. The system used to test this technique was the diffusion of liquid water in polyacrylonitrile (PAN). The diffusion coefficients that were measured were in good agreement with those reported in the literature for high-activity water vapour in PAN. The test also demonstrated both the reproducibility and accuracy of FTi.r.-a.t.r. experiments for measuring the diffusion coefficient. The diffusion coefficient and the amount of water sorbed at equilibrium appear to be dependent on the temperature at which the films were treated. The method described here shows great potential for elucidating penetrant-penetrant and penetrant-polymer interactions during the diffusion process owing to the spectroscopic nature of the technique.

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This paper describes the synthesis of a novel series of poly(ether imide)s formed as isomeric pairs of polymers by interchanging the diol and diamine derived units. The polymers contained units having flexible and stiff hinges and groups to hinder segmental rotation. Most polymers were soluble in a variety of solvents, which allowed them to be characterized and cast into membranes. Permeabilities to carbon dioxide and methane and glass transition temperatures were determined. Consideration of structure-property relations showed the properties of the polymers to be sensitive to the position of the structural units within the polymer. The polymers showed a linear relationship between permeabilities to the two gases. There was a strong trend between high permeability and high glass transition temperature, suggesting that rigid polymers incapable of inefficient packing lead to highly permeable membranes and that such factors were enhanced by the presence of bulky substituents.

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