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.

CONFORMATION OF PHENYL RINGS IN THE HELICAL CHAIN POLYMER POLY(TRIPHENYLMETHYL METHACRYLATE)

The conformation of phenyl rings in the side groups of the helical chain polymer poly(tripenyl-methyl methacrylate) (1) in solution was studied by spectroscopic methods. According to the Raman spectrum the phenyl rings of 1 and triphenylmethyl methacrylate in solution have the same depolarization ratio at 1002 cm-1. The electronic spectra (ultraviolet and fluorescence) of 1 are similar to those of model substances, except for the "red shift" of the spectra of about 5 nm. It was concluded that the phenyl rings can rotate around the phenyl-C bond.

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.

An in-situ modified sol-gel process for monolith catalyst preparation used in the partial oxidation of methane

An in-situ modified sol-gel method for the preparation of a Ni-based monolith-supported catalyst is reported. With the presence of a proper amount of plasticizer and binder, and at an optimized pH value, the stable boehmite sol was modified with metal ions (Ni, Li, La) successfully without distinct growth of the particle size. Monolith-supported Ni-based/gamma-Al2O3 catalysts were obtained using the modified sol as the coating medium with several cycles of dip-coating and calcination. Combined BET, SEM-EDS, XRD and H-2-TPR investigations demonstrated that the derived monolith catalysts had a high specific surface area, a relatively homogeneous surface composition, and a high extent of interaction between the active component and the support. These catalysts showed relatively stable catalytic activities for partial oxidation of methane (POM) to syngas under atmospheric pressure. The monolith catalysts prepared by this sol-gel method also demonstrated an improved resistance to sintering and loss of the active component during the reaction process.

Modification of a poly(methyl methacrylate) injection-molded microchip and its use for high performance analysis of DNA

Inexpensive and permanently modified poly(methyl methacrylate)(PMMA) microchips were fabricated by an injection-molding process. A novel sealing method for plastic microchips at room temperature was introduced. Run-to-run and chip-to-chip reproducibility was good, with relative standard deviation values between 1-3% for the run-to-run and less than 2.1% for the chip-to-chip comparisons. Acrylonitrile-butadiene-styrene (ABS) was used as an additive in PMMA substrates. The proportions of PMMA and ABS were optimized. ABS may be considered as a modifier, which obviously improved some characteristics of the microchip, such as the hydrophilicity and the electro-osmotic flow (EOF). The detection limit of Rhodamine 6G dye for the modified microchip on the home-made microchip analyzer showed a dramatic 100-fold improvement over that for the unmodified PMMA chip. A detection limit of the order of 10(-20) mole has been achieved for each injected phiX-174/HaeIII DNA fragment with the baseline separation between 271 and 281 bp, and fast separation of 11 DNA restriction fragments within 180 seconds. Analysis of a PCR product from the tobacco ACT gene was performed on the modified microchip as an application example.

Electrochromatographic evaluation of a silica monolith capillary column for separation of basic pharmaceuticals

A silica-based monolithic capillary column was prepared via a sol-gel process. The continuous skeleton and large through-pore structure were characterized by scanning electron microscopy (SEM). The native silica monolith has been successfully employed in the electrochromatographic separation of beta-blockers and alkaloids extracted from traditional Chinese medicines (TCMs). Column efficiencies greater than 250000 plates/m for capillary electrochromatography (CEC) separation of basic compounds were obtained. It was observed that retention of basic pharmaceuticals on the silica monolith was mainly contributed by a cation-exchange mechanism. Other retention mechanisms including reversed-phase and normal-phase mechanisms and electrophoresis of basic compounds also played a role in separation. A comparison of the differences between CEC and capillary zone electrophoresis (CZE) separation was also discussed.