1993 рік

Amylopectin-sugar mixtures in the ratio of 10:1 have been studied using fructose, glucose, sucrose and xylose. Samples of amylopectin containing glucose in the ratio of 5:1 and fructose in the ratio of 2:1 (amylopectin-sugar) were also prepared. The glass transition as a function of water content was studied using d.m.t.a., d.s.c., pulsed n.m.r, and a three-point bend test. Small amounts of sugar were found to reduce the glass transition temperature of starch in accordance with or in excess of the predictions of a Couchman-Karasz equation. For the sample containing the greatest amount of sugar, less plasticization than predicted was observed; this appeared to be due to a substantial degree of phase separation

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A study has been made of the possible synthesis of metalliferous epoxy chelate polymers (MECPs) by hardening of the diglycidyl ether of bisphenol A (DGEBA) with the chelates of metals (Cu 2+, Co 2 +, Ni 2 +, Zn 2+, Cd 2+, Fe 3? and Mn 4+) and aliphatic amines (ethylenediamine, diethylenetriamine, triethylenetetramine and cyanoethylated diethylenetriamine). The salts of the metals and organic acids have been combined with the amines to produce the chelates both in solvents (acetone, water) and in the absence of solvents. The complex hardeners were identified by elemental analysis and infra-red spectroscopy. The reactivity of the complexes in reactions with DGEBA and its dependence on the structures of the chelates have been investigated. The properties of epoxy polymers modified by metal cations have been studied. MECPs have been found to possess significant strength. The introduction of cations into the epoxy matrices increases the deformation temperature up to 163°C and tensile strength up to 100MPa. The copper-containing polymers exhibit a significant increase in thermal oxidative stability, which becomes comparable with the heat resistance of well known epoxy-anhydride systems

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The high resolution CP/MAS/DD ~aC n.m.r, spectra of bulk, semicrystalline poly(L-lactide) (PLLA) and PLLA confined to the narrow channels of its urea clathrate (PLLA-U) are compared and contrasted to the recently reported CP/MAS/DD spectrum of the crystalline 1:1 stereocomplex (PLLA, PDLA) formed by mixing dilute solutions of PLLA and poly(D-lactide) (PDLA) followed by their cocrystallization. Single resonances are observed for all three carbon types in PLLA-U, while the carbonyl carbons in PLLA* PDLA and all three carbon types in bulk PLLA evidence multiple resonances. Differences in the conformations and packing of PLLA chains in these distinct, ordered solid-state environments are the likely sources of their very different high resolution, solid-state ~3C n.m.r, spectra.

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The glass transition temperature of the soft phase has been studied in blends of multiblock polyetherester (PEE) with multiblock polyesterurethane (PUA) and poly(ether carbonate)urethane (PUC) copolymer. The K 1 and K2 coefficients from the Schneider equation and the q parameter from the modified Kwei equation have been used to monitor the strength of intermolecular interaction. A suggestion for the partial miscibility of the PEE/PUC blends in the soft phase is proposed.

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The influence of the structural fragments (metal cation, ligand and anion) of metal-containing chelate hardeners on the properties of cured diglycidyl ether of bisphenol A (DGEBA), viz. strength, deformation temperature and thermal oxidative stability, has been examined. It has been established that the metal cation has the most effect on the properties of metalliferous epoxy chelate polymers (MECPs), that of the anion being the least. A structural change in a hardener molecule has been found to influence greatly the polymer heat resistance and, to a lesser extent, the compressive strength

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Volume behaviours of 2-acryloyloxyethyl acid phosphate monopolymer gels immersed in methanol water, acetonitrile-water, tetrahydrofuran-water, dioxane-water and dimethylsulfoxide-water mixtures were examined. Polymer gel samples of the same composition but differing in overall concentration all exhibited a discontinuous volume change at an appropriate solvent composition, regardless of change in gel concentration. This could be accounted for by an unchanged interaction between the polymer gel at various concentrations and a solvent mixture at each transition point.

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The order~lisorder transition in a lattice hole model of a polydisperse dense system of semiflexible chain macromolecules is studied within the mean-field approximation and by Monte-Carlo methods. The polymer chains consist of 'stiff' or 'flexible' monomer units which associate at a given density and temperature in the process of reversible equilibrium polymerization. The system goes from an ordered state of parallel infinite rods into a lower density state of differently long disoriented chains at a temperature which is influenced by the chain stiffness and by the ratio between inter- and intrachain interactions. The mechanism of the transition is different from that of Flory and represents rather a polymerization transition.

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The influence of the structural fragments (metal cation, ligand and anion) of metalliferous epoxy chelate polymers (MECPs) on their properties, viz strength, deformation temperature (DT) and thermal oxidative stability, has been examined. Correlations between tensile strength (at) and tensile modulus (Et) and between flexural strength (af) and flexural modulus (Ef), a t = f(Et) and a r = f(E O, have been established. By supposing that, when the conditions at.A = at.B, O'fA. = O'f.B, Et, g = Et,l~ and Ef, A = El, B are fulfilled, where A and B are complex hardeners of partly different structures, the epoxy chelate matrices based on the same oligomer and these complexes have similar structures, the influence of the structural fragments on MECP properties was evaluated. It was found that the effect of chelate structure on the alteration of polymer properties is maximal for thermal oxidative stability(AM is the polymer mass loss after thermal treatment in air), minimal for compressive strength (ac) and decreases in the following order

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2-(3•5-Diethyny•pheny•)-4•4•5•5-tetramethy•-4•5-dihydr•-•H-imidaz••-•-•xy•-3-•xide (1) was polymerized by oxidative coupling to poly(2-(3,5-diethynylenephenyl)-4,4,5,5-tetramethyl-4,5-dihydro-lH-imidazol-1- oxyl-3-oxide) (2), which was characterized by gel permeation chromatography, spectroscopic methods (infrared, ultraviolet, electron spin resonance), transmission electron microscopy and magnetic susceptibility measurements. Samples of polymer 2 obtained by evaporation of the solvent showed the usual paramagnetic properties while those obtained by addition of a non-solvent to a solution exhibited an increase of the magnetic mass susceptibility ~m when the samples were stored at a temperature of 78 K.

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Quaternization of the amino end-groups of telechelic polymers with n-alkyl iodides has been found to modify profoundly the solution behaviour of these materials. In toluene, the relative viscosity increases rapidly with concentration, in a manner dependent on the length of the alkyl substituent of the quaternizing agent. It has been observed that the increase in viscosity can be mitigated by lengthening the alkyl substituent shape. This lessening of viscosity levels off as soon as the alkyl substituent contains more than three carbon atoms. For the longest substituents, the viscosity slightly increases again. The sharpness of the increase in viscosity upon increasing polymer concentration can be significantly reduced in polar solvents. A lower medium polarity appears to promote higher differences in viscosity between quaternized and unquaternized polymers. Empirical equations have also been derived to fit the experimental hydrodynamic behaviour.

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