1994 рік

The copolymerization behaviour of the adduct of N',N'-dimethylaminopropyl methacrylamide and epichlorohydrin (DMAPMA-Epi) and methyl methacrylate (MMA) was investigated. The reactivity ratios for the MMA (I)/DMAPMA-Epi (2) couple in solution, using various regression methods based on the Mayo-Lewis model, are r 1 --- 1.73 and r2 =0.03. The Q and e values for DMAPMA-Epi are estimated to be 0.23 and - 1.32 respectively. On the basis of the reactivity ratios, theoretical curves for the instantaneous copolymer composition throughout conversion have been calculated

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The behaviour of energy flow in a model chain of amorphous polyethylene is discussed. The rate of energy flow through the backbone of a polyethylene chain was studied as a function of density, stretching force constant and temperature. It is found that the energy flow rate is initially fast and then becomes slower.The dispersion of excitation energy is found to be accelerated by energy transfer through non-bonded interactions. The rate of energy flow is also sensitive 1o the stretch force constant and temperature of the system.

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The polymer pair, poly(vinyl alcohol)/(N-vinyl pyrrolidone) (PVA/PVP), is thermodynamically miscible in the amorphous state, as judged from the detection of a single T~, which is situated between the T~s of the two homopolymers, over the whole range of compositions of the binary blend. The molecular orientation and optical anisotropy induced by uniaxial deformation of the polymer blends were characterized through fluorescence polarization and birefringence measurements. Two series of samples, designated as PVA/PVP-H and PVA/PVP-L, were examined; these were cast as films from aqueous polymer solutions containing a slight amount of a stilbene derivative as a fluorescent probe (the notations H and L indicate whether the molecular weight of the PVP is much higher or lower than that of the PVA). In both series of blends, development of the molecular orientation in the drawn films became gradually suppressed with increasing PVP content. PVA/PVP-H blends acquired a higher orientation than the corresponding PVA/PVP-L blends with the same composition. The optical birefringence of the oriented films, when compared at a given draw ratio for a series of blends, decreased drastically with an increase in the PVP fraction and eventually changed from positive to negative values at a certain fraction. The critical PVP fraction was much lower in the PVA/PVP-H series than in the corresponding series. An explanation for this is presented in terms of an effect of birefringence compensation, due to the positive and negative contributions of oriented PVA and PVP, respectively. The molecular weight dependence of the segmental relaxation of PVP chains in the drawing process and that of the frequency of interpolymer interactions are taken into account in the discussion.

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The ultrasonic degradation of the water-soluble polymers pullulan, poly(ethylene oxide) and polyvinylpyrrolidone was studied at a frequency of 500 kHz. The apparent degradation rate constants are 0.030 for pullulan, 0.076 for poly(ethylene oxide) and 0.032 min- 1 for polyvinylpyrrolidone. The degradation mechanism was analysed by using Glynn's model. The water-soluble polymers used here are degraded with a Gaussian probability by ultrasonic irradiation

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Solutions of poly(2-ethyl-2-oxazoline), PEOX, and poly(2-methyl-2-oxazoline), PMOX, in water and PEOX solutions in several alcohols were characterized by light scattering. The second virial coefficients in water were found to decrease with increasing temperature, reflecting lower critical solution behaviour due to hydrogen bonding. This resulted in negative values of the excess enthalpy Ah ~ and entropy of dilution As E for PEOX and PMOX in water. The magnitudes of Ah E and As E were higher for PMOX than for PEOX. The magnitudes of Ah E and As E for PEOX increased with molecular weight. The second virial coefficients of PEOX in water were systematically lower than in ethanol, isopropanol and n-butanol.

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Based on rheological data, two polyblends of poly(ether sulfone) (PES) and polycarbonate (PC) with a liquid crystalline polymer (LCP) as the dispersed phase were prepared by extrusion. The process of LCP microstructure formation was investigated by studying the morphology of the blend obtained from different sections of the extruder. The deformation of LCP domains is controlled by the viscosity ratio of the dispersed phase to the continuous phase (qa/qm)" LCP domains in LCP/PES blend have been deformed into oriented fibrils, due to a viscosity ratio of 0.0l. A quantitative comparison of LCP droplet sizes before and after the extruder die shows that the morphology of extrudates has been determined before the melt enters the die. After the die, the diameter and length to diameter ratio of LCP fibrils were increased by coalescence and further deformation by the action of extensional flow. The morphology of LCP/PES extrudates after remaining at quiescence within the die for different time intervals indicates that even after a 60 s residence, LCP domains retained their fibrillar structure in the blend and no significant recoiling and breakup of LCP fibril occurred.

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The solubility properties of amorphous poly[2,2-dicyano-l-[2-(2-(methacryloyloxy)ethyldimethylammonio)- ethoxy]-ethenolate] (zwitterionic lateral group of/~ = 25.9 D) investigated in 43 solvents of widely differing polarity may be interpreted in terms of solvent molar refractivity (dispersion interactions), dipole moment (dipolar interactions), basicity (donor-acceptor interactions with the ammonium site) and hydrogen-bonddonating power (hydrogen bonding to the anionic site). In dimethylformamide, representative of strongly dipolar aprotic media, the phase diagram is characterized by a lower critical solution temperature corresponding to a lower 0 temperature of about 65.8 + 1 °C. Coil expansion at 25°C, as derived from intrinsic viscosity measurements, is an increasing function of the concentration of added lithium salts (~< 1.5 tool 1-1), and the order of anion efficiency is CI- > Br- > I- > C10?. In trifluoroethanol, representative of weakly associated and strongly protic solvents, the addition of tetramethylammonium salts (~< 1 mol 1-1) results in coil expansion only in the case of the more polarizable C10? and I- anions, while CI- and Br- promote chain collapse. The hydrophobic polyzwitterion becomes water soluble at 25°C only in the presence of high salt concentrations, such as NaSCN > 2.5 mol 1-1, ZnC12 > 5 mol 1-1, C2HsNH~-NO 3 > 6 tool 1-1, and the phase diagram is characterized by an upper critical solution temperature strongly dependent on salt concentration (dT/d[NaSCN] =-70°Clmol - 1). In strongly acidic media, such as concentrated H2SO 4, HC104 aqueous solution (40-60 wt%) or methanesulfonic acid, partial protonation of the anionic sites transforms the polyzwitterion into a water soluble cationic polyelectrolyte.

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A clear ferroelectric transition of first-order type is observed in poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) random copolymers with TrFE contents higher than 20% and lower than 40%. This structural phase transition which takes place in the crystalline regions of the polymeric material has been analysed using neutron diffraction under hydrostatic pressure for three copolymer compositions: 80/20, 70/30 and 60/40. The P-Tphase diagrams have been determined in the ranges 0.1-300 MPa, 300-500 K both upon heating and upon cooling, and several thermodynamic parameters have been evaluated for the different crystalline phases: compressibility and thermal expansion coefficients, enthalpies of transition, etc. For the middle composition (70/30) the ferroelectric transition temperature Tc is well separated from the melting temperature Tm of the paraelectric phase and both transition temperatures increase with increasing pressure: dTc/dP = 0.38 K MPa- 1 and dT~/dP = 0.25 K MPa- t. For the 80/20 composition the Curie temperature Tc is closer to the melting temperature Tin, and under increasing pressure the two transition lines are expected to merge at a triple point (P*~500 MPa, T*~560 K), above which a single line corresponds to the melting of the ferroelectric phase. For the 60/40 composition a new 'low temperature disordered' phase appears and coexists with the ferroelectric phase but with a volume fraction which depends on temperature and thermal history.

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A solid-state electrochromic device, which shows excellent performances in terms of colour contrast and response time, has been realized. A solid polymer electrolyte based on a combination of a lithium salt and a chain-extended polyepoxide has been sandwiched between a tungsten oxide electrochromic material (WO3) and an activated nickel oxide (LixNiO) counter-electrode

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The crystalline fl-form of ethylene/propylene random and block copolymers was obtained by crystallizing in the presence of a two-component fl-nucleator. The influence of converting the crystalline copolymers from the c~-form to the fl-form on the drawing behaviour and impact strength was studied. The results show that the fl-phase copolymer has higher impact strength, slightly lower yield strength and a higher degree of stress whitening than the ~-phase copolymer. A stretching-induced or impact-induced fl-~ transformation in parallel with micro-crazing was also noticed

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