Crystallization Behavior of Poly(tetrahydrofuran-b-methyl methacrylate) Diblock Copolymer

Crystallization behavior of a series of newly synthesized poly (tetrahydrofuran-b-methyl methacrylate) diblock copolymer has been studied by differential scanning calorimetry (DSC) and X-ray scattering and diffraction techniques. The results show that the

EXCIMER FLUORESCENCE STUDY ON THE MISCIBILITY OF POLY(VINYL METHYL-ETHER) AND STYRENE-BUTADIENE STYRENE TRIBLOCK COPOLYMER

The excimer fluorescence of a triblock copolymer, styrene-butadiene-styrene (SBS) containing 48 wt% polystyrene was used to investigate its miscibility with poly(vinyl methyl ether) (PVME). The excimer-to-monomer emission intensity ratio I(M)/I(E) can be used as a sensitive probe to determine the miscibility level in SBS/PVME blends: I(M)/I(E) is a function of PVME concentration, and reaches a maximum when the blend contains 60% PVME. The cloud point curve determined by light scattering shows a pseudo upper critical solution temperature diagram, which can be attributed to the effect of PB segments in SBS. The thermally induced phase separation of SBS/PVME blends can be observed by measuring I(M)/I(E), and the phase dissolution process was followed by measuring I(M)/I(E) at different times.

SYNTHESIS AND MOLECULAR-STRUCTURE OF (CH3CP)2YB.DME AND ITS CATALYTIC ACTIVITY FOR THE POLYMERIZATION OF METHYL-METHACRYLATE

The complex of (CH3Cp)2Yb . DME (DME = dimethoxyethane) has been synthesized by the reduction with metallic sodium of the corresponding chloride (CH3CP)2YbCl. (CH3CP)2Yb . DME crystallized from DME in the monoclinic space group Cm, with cell constants a = 11.068(3), b = 12.338(4), c = 12.479(4) angstrom; beta = 100.51(2)-degrees, V = 1675(l) angstrom3, and D0 = 1.66 g/cm3 for Z = 4. Least-squares refinement of 1420 unique observed reflections led to final R of 0.0487. This complex can be used as a catalyst for the polymerization of methyl methacrylate (MMA).

THE EFFECT OF MOBILITY OF MOLECULES ON RADIATION-INDUCED CHAIN SCISSION AND RACEMIZATION OF ISO-POLY(METHYL METHACRYLATE)

The radiation-induced chain-scission and racemization of isotactic poly(methylmethacrylate)(iso-PMMA) in amorphous and semi-crystalline state as well as in solution have been studied with nuclear magnetic resonance and molar mass deter-mination. It is shown that the chain-scission is dominant for iso-PMMA in dilute solution while the racemization reaction is not favorable in this case. On the contrary, the racemization is favorable when iso-PMMA was irradiated in its crystalline state while chain-scission is not. Such experimental results could be well explained by the mobility of molecules and "cage effect". The hypothesis, we proposed previously that the chain-scission, racemization and recombination are in competition and the final result depends on the state of molecular motion at which iso-PMMA was irradiated, has been verified verified once again.

THE COMPATIBILITY AND CRYSTALLIZATION OF THE MIXTURES OF POLY (TETRAHYDROFURAN-b-METHYL METHACRYLATE) DIBLOCK COPOLYMER WITH POLYVINYL CHLORIDE HOMOPOLYMER

The compatibility and crystallization behaviour of the mixtures of poly (tetrahydrofuran-methyl methacrylate) diblock copolymer (PTHF-b-PMMA) with polyvinyl chloride has been studied. We found that the compatibility of these blends, in which there is special interaction between the homopolymer and the PMMA block of the copolymer, is much better than that of the AB/A type blends; and that the crystallization rate and crystallinity of PTHF microdomain changed greatly due to the swollen by PVC homopolymer. In this paper, these changes in cryatallization are well explained according to the theories of block copolymer blends and the density gradient model presented by JIANG Ming.

SYNTHESIS AND CRYSTAL-STRUCTURE OF NEODYMIUM COMPLEX OF 1-METHYL-1, 4, 7, 10-TETRAAZACYCLODODECANE

The complex [Nd(L)(CH3CN)(CF3SO3)3] has been synthesized. Where L = 1-methyl-1, 4, 7, 10-tetraazacycldodecane. The crystal structure of the complex has been determined by a four-circle X-ray diffractometer to a final deviation factor B value of 0.0370 and R(w) value of 0.0385 respectively. The crystal is triclinic system, space group P1BAR with a = 0.8738(2), b = 1.2870(3), c = 1.2900(3) nm, alpha = 85.63(2), beta = 87.25(2), gamma = 78.30(2)-degrees, V = 1.41571 (60) nm3, Z = 2, D(c) = 1.92 g/cm3. The neodymium ion is eight-coordinated to forming a distorted square antiprism.

MUTUAL ENTANGLEMENTS IN POLY(VINYL ACETATE) POLY(METHYL ACRYLATE) INTERPENETRATING POLYMER NETWORKS

An equation has been derived for the equilibrium swelling of sequential interpenetrating polymer networks (IPNs), which exhibit a single glass transition temperature and the two components are considered to be compatible. The properties of the equilibrium swelling and elastic modulus of sequential poly(vinyl acetate)/poly(methyl acrylate) IPNs have been discussed according to the derived equation and the Siegfried-Thomas-Sperling formula of the elastic modulus for homo IPNs. In both fully swollen and bulk states, there was favourable evidence for added physical crosslinks in poly(vinyl acetate)/poly(methyl acrylate) IPNs. The Binder-Frisch theory is also discussed.

ELECTROCHEMICAL-BEHAVIOR OF N-METHYL-N'-HEXADECYLVIOLOGEN MONOLAYERS ON SILVER ELECTRODES - EFFECTS OF COUNTERIONS

N-Methyl-N'-hexadecylviologen (C16MV) has been the subject of several electrochemical and spectroelectrochemical studies which characterized the species present in various redox states for C16MV monolayers on silver electrode surfaces. Both self-assembled monolayers (SA) and Langmuir-Blodgett (LB) transferred systems have been studied. These indicated inconsistencies regarding the presence or absence of splitting of the first reduction peak in its cyclic voltammogram (CV). The present study demonstrates the important influence of the specific anionic species present in the supporting electrolyte. Splitting may or may not take place, depending on the size and relative strength of the adsorption of specific anions contributed by the supporting electrolyte. Small, strongly adsorbing anions such as iodide produced peak splitting in the CV of C16MV monolayers; bulky but weakly adsorbing anions such as perchlorate may disrupt the ordered structure of monolayers but produce no splitting. Ancillary data provided by surface enhanced Raman spectroscopy (SERS) was consistent with the electrochemical measurements.

DYNAMIC SCALING AND FRACTAL BEHAVIOR OF SPINODAL PHASE-SEPARATION IN POLYMER MIXTURES OF POLY(METHYL METHACRYLATE) WITH POLY(STYRENE-CO-ACRYLONITRILE)

Dynamic scaling and fractal behaviour of spinodal phase separation is studied in a binary polymer mixture of poly(methyl methacrylate) (PMMA) and poly(styrene-co-acrylonitrile) (SAN). In the later stages of spinodal phase separation, a simple dynamic scaling law was found for the scattering function S(q,t):S(q,t) approximately q(m)-3S approximately (q/q(m)). The possibility of using fractal theory to describe the complex morphology of spinodal phase separation is discussed. In phase separation, morphology exhibits strong self-similarity. The two-dimensional image obtained by optical microscopy can be analysed within the framework of fractal concepts. The results give a fractal dimension of 1.64. This implies that the fractal structure may be the reason for the dynamic scaling behaviour of the structure function.

DYNAMIC SCALING OF THE STRUCTURE-FUNCTION FOR SPINODAL DECOMPOSITION IN CRITICAL AND NONCRITICAL MIXTURES OF POLY(VINYL ACETATE) POLY(METHYL METHACRYLATE)

The dynamics of phase separation in a binary polymer blend of poly(vinyl acetate) with poly(methyl methacrylate) was investigated by using a time-resolved light-scattering technique. In the later stages of spinodal decomposition, a simple dynamic scaling law was found for the scattering function S(q, t)(S(q, t) approximately I(q, t)): S(q, t)q(m)-3 S approximately (q/q(m)). The scaling function determined experimentally was in good agreement with that predicted by Furukawa, S approximately (X) approximately X2/(3 + X8) for critical concentration, and approximately in agreement with that predicted by Furukawa, S approximately (X) approximately X2/(3 + X6) for non-critical mixtures. The light-scattering invariant shows that the later stages of the spinodal decomposition were undergoing domain ripening.

RADIATION-INDUCED CROSS-LINKING OF POLY(METHYL METHACRYLATE)-POLY(ETHYLENE OXIDE) BLEND

Radiation-induced crosslinking of poly(methyl methacrylate) (PMMA)-poly(methylene oxide) (PEO) blends was studied. It was found that PMMA in PMMA-PEO blend can be crosslinked in the range of certain doses (1 approximately 20 x 10(4) Gy) and composition (PMMA% = 30 approximately 70) under the absence of oxygen. Moreover, it was also found that the crosslinking degree of PMMA in the blend in which the content of PMMA is 70% is the largest. The crosslinking degree of PMMA in the blend is closely related with the polymer miscibility. The crosslinking degree of the blend prepared at 60-degrees-C is far higher than one at ambient temperature.

INVESTIGATION OF PHASE SEPARATION BEHAVIOR IN POLY (METHYL METHACRYLATE)/POLY (STYRENE-CO-ACRYLONITRILE) MIXTURES WITH PULSED NUCLEAR MAGNETIC RESONANCE

Thermally induced phase separation in the mixture of poly (methyl methacrylate) (PMMA) with poly(styrene-co-acrylonitite (SAN) has intern studied with pulsed nuclear magnetic resonance(NMR) in single spin-lattice retaxation time T-1 of the eornpatibl. mixture two T-1 corresponding to those of PM MA-rich and SAN-rich comairis. Meanwhile, both T-1 gradually changing with annealing time provides the direct evidence that the phase separation takes place with a decomposition mechanism. Diffusion coeffieient was to lac negative, indicating an uphal diffusion characteristics, The basic parameters governing its kinetics were estimated using NMR date which were in good agreement with those evaluated from time-resolved light scattering experiments for a 60/40(PMMA/SAN) mixture annealed at 180.0 degrees C.