SYNTHESIS AND PROPELLER-PROPELLER TRANSITION OF OPTICALLY-ACTIVE POLY(DIPHENYL-O-TOLYLMETHYL METHACRYLATE)

Diphenyl-o-tolylmethyl methacrylate (DPTMA) was synthesized and polymerized using initiators of organolithium complexes with (+) - (2S,3S) -dimethoxy-1,4-bis(dimethylamino) butane (DDB) and (-) -sparteine (Sp) as the chiral ligands. DDB was suitable for its complex effective to prepare optically active poly(diphenyl-o-tolylmethyl methacrylate) (PDPTMA) with one-handed helical conformation, whereas only low-molecular weight polymer was formed when Sp was used as ligand due to the repulsive hindrance between the triarylmethyl group and the ligand. A new mutarotation, propeller-propeller transition, was observed for PDPTMA from the optical rotation curves and CD spectra in THF solution. The equivalent period of PDPTMA was estimated to be 14 angstrom based on the x-ray diffraction. (C) 1993 John Wiley & Sons, Inc.

STUDY ON THE RADIATION-INDUCED COPOLYMERIZATION OF ACRYLAMIDE WITH SODIUM ACRYLATE IN AQUEOUS-SOLUTION

In the present work, the mechanism of radiation-induced copolymerization of acrylamide (AM) with sodium acrylate (AANa) in aqueous solution was studied. A method to protect the copolymerization system from the crosslinking and a carbon-carbon mechanism to form gel in copolymerization reaction have been proposed. The condition to prepare the products with different molecular weight, especially with very high molecular weight were found.

IONIC-CONDUCTIVITY AND DYNAMIC MECHANICAL RELAXATION OF A 2-COMPONENT EPOXY NETWORK-LICLO4 ELECTROLYTE SYSTEM

The correlation between mechanical relaxation and ionic conductivity was investigated in a two-component epoxy network-LiClO4 electrolyte system. The network was composed of diglycidyl ether of polyethylene glycol (DGEPEG) and triglycidyl ether of glycerol (TGEG). The effects of salt concentration, molecular weight of PEG in DGEPEG and the proportion of DGEPEG (1000) in DGEPEG/TGEG ratio on the ionic conductivity and the mechanical relaxation of the system were studied. It was found that, among the three influential factors, the former reinforces the network chains, reduces the free volume fraction and thus increases the relaxation time of the segmental motion, which in turn lowers the ionic conductivity of the specimen. Conversely, the latter two increase the free volume and thus the chain flexibility, showing an opposite effect. From the iso-free-volume plot of the shift factor log at and reduced ionic conductivity, it is noted that the plot can be used to examine the temperature dependence of segmental mobility and seems to be useful to judge whether the incorporated salt has been dissociated completely. Besides, the ionic conductivity and relaxation time at constant reference temperature are linearly correlated with each other in all the three cases. This result gives an additional experimental confirmation of the coordinated motion model of the ionic hopping with the moving polymer chain segment, which is generally used to explain the ionic conduction in non-glassy amorphous polymer electrolytes.

THERMODYNAMICS OF POLY(ETHYLENE OXIDE)-POLY(VINYL ACETATE) BLENDS

Heat-of-mixing data, obtained on blends of poly(ethylene oxide) (PEO) with whole and fractionated poly(vinyl acetate) (PVAc), were used to feed Patterson's theory of polymer-polymer miscibility. Negative values of mixing enthalpy, contact-energy term, interaction'' parameter and excess volume were obtained only for blends with the lowest molecular weight PVAc fraction. These results show that miscibility of PVAc with PEO strongly depends on its molecular weight. The calculated unfavourable excess volume term of the Patterson equation is small in comparison with the absolute value of the interaction term. Therefore, miscibility of PEO and low-molecular-weight PVAc is dictated by the weak specific interactions between different repeat units and by the entropic gain in the mixing process.

RADIATION STABILITY OF PTFE WITH DIFFERENT CRYSTALLINITY

In this work, the effects of radiation on polytetrafluoroethylene (PTFE) samples with different crystallinity were studied. Using Suwa's equation for calculating the number-average molecular weight of PTFE, the radiation-induced reduction in molecular weight was followed and the G values for scission of PTFE were also obtained on the basis of the changes in molecular weight. The G(scission) for as-polymerized PTFE was 2.15 +/- 0.01, whereas for sintered sample, which has a relative low crystallinity, G(scission) = 6.0 +/- 0.14.

STATISTICAL THERMODYNAMICS OF POLYDISPERSE POLYMERS

A statistical thermodynamics theory of polydisperse polymers based on a lattice model of fluids is formulated. Pure polydisperse polymer can be completely characterized by three scale factors and the molecular weight distribution of the system. The equation of state does not satisfy a simple corresponding-states principle, except for a polymer fluid of sufficiently high molecular weight. The relationships between thermal expansion coefficient alpha and isothermal compressibility beta with reduced variables are also predicted.

THE RADIATION STABILITY OF PERFLUOROALKOXY RESIN

By examining the changes in melting temperature, heat of fusion, tensile strength and ultimate elongation at 150-degrees-C, and weight loss, radiation effects on perfluoroalkoxy resins (PFA) were investigated. The results show that at the temperatures used here the predominant effect caused by radiation on PFA is degradation of the molecular weight. The radiation stability is much better than that of polytetrafluoroethylene, however.

RADIATION STABILITY OF PTFE IRRADIATED UNDER VARIOUS CONDITIONS

As a typical example of a polymer degraded by radiation, the radiation stability of PTFE was observed to depend upon irradiation conditions. Increases in irradiation temperature and crystallinity were found to increase its radiation stability whereas increase in the concentration of oxygen in the system over a certain range was observed to have little effect on radiation-induced reactions of PTFE as measured by changes in number-average molecular weight, melting temperature and crystallinity.

STATISTICAL THERMODYNAMICS OF A LATTICE FLUID - PURE POLYMER

A statistical thermodynamics theory of a polydisperse polymer based on a lattice model of a fluid is formulated. The pure polydisperse polymer is completely characterized by three scale factors and the distribution law of the system. The equation of state does not satisfy a simple corresponding state principle, except for the polymer fluid with sufficiently high molecular weight.

COMPARATIVE-ANALYSIS OF GLYCOPROTEIN AND GLYCOLIPID COMPOSITION OF VIRULENT AND AVIRULENT STRAIN MEMBRANES OF MYCOPLASMA-HYOPNEUMONIAE

The glycoproteins and glycolipids from membranes of virulent strain Z and avirulent strain M of Mycoplasma hyopneumoniae have been compared. The proteins and the glycoproteins were identified by SDS-polyacrylamide gel electrophoresis and concanavalin A-biotin labeling, respectively. The membrane preparation contained approximately 34 protein bands with molecular weights between 20 KD and 100 KD. The concanavalin A-biotin system reacted with a glycoprotein of a molecular weight of approximately 28,000 from avirulent strain M and did not react with the correspondent band from virulent strain Z. The membrane glycolipids of both strains consisted of monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG), and the percentages of 16:0, 18:0, and 18:1 fatty acids comprised more than 80% of the total fatty acids of membrane glycolipids. The 18:0 fatty acid of MGDG in avirulent strain M was twofold higher than that of virulent strain Z.

CRYSTALLIZATION OF POLY(ARYL-ETHER-ETHER-KETONE)S BLENDS

The crystallization and melting behaviour of poly(aryl-ether-ether-ketone) (PEEK) in blends with another polymer of the same family containing a bulky pendant phenolphthalein group (PEK-C) have been investigated by thermal methods. The small interaction energy density of the polymer pair (B = -8.99 J/cm3), evaluated from equilibrium melting point depression, is consistent with the T(g) data that indicate partial miscibility in the melt. Two conjugated phases are in equilibrium at 430-degrees-C: one is crystallizable and contains about 35 wt% of PEK-C; the other, containing only 15 wt% of PEEK, does not form crystals upon cooling and it interferes with the development of spherulites in the sample. The analysis of kinetic data according to nucleation theories shows that crystallization of PEEK in the explored temperature range takes place in Regime III and that a transition to Regime II might be a consequence of an increase in the amount of non-crystallizable molecules in the PEEK-rich phase. A composition independent value of the end surface free energy of PEEK lamellae has been derived from kinetic data (sigma-e = 40 +/- 4 erg/cm2) in excellent agreement with previous thermodynamic estimates. A new value for the equilibrium melting temperature of PEEK (T(m)-degrees = 639 K) has been obtained; it is about 30-degrees-C lower than the commonly accepted value and it explains better the "memory effect" in the crystallization from the melt of this high performance polymer.

MORPHOLOGY AND DYNAMIC MECHANICAL-PROPERTIES OF AB CROSS-LINKED POLYMERS BASED ON POLYURETHANES

Polyoxypropylene glycol (PPG) (or castor oil) and toluene diisocyanate (TDI) were mixed, and the prepolymer polyurethane (PU) (I) was formed. Vinyl-terminated polyurethane (II) was prepared from (I), and hydroxyethyl acrylate, AB crosslinked polymers (ABCPs) were synthesized from (II) and vinyl monomers such as styrene, methyl methacrylate, vinyl acetate, etc. The dynamic mechanical properties and morphology of ABCPs were measured. The ABCPs based on PPG have double glass transition temperatures (T(g)) on the sigma-vs. temperature curves. They display a two-phase morphology with plastic components forming the continous phase and PU-rich domains forming the separated phase on the electron micrographs. Irregular shapes and a highly polydisperse distribution of PU-rich domain sizes were observed. The crosslink density of ABCPs has a notable effect on the morphology and properties. The average diameter of the PU-rich domains depends on the molecular weight of prepolymer PPG. The highly crosslinked structures will produce large numbers of very small domains. ABCPs based on castor oil show a single T(g) relaxation on the dynamic mechanical spectra. The compatibility between the two components is much better in ABCPs based on castor oil than in those based on PPG, because there is a high crosslink density in the former. Comparison of the dynamic mechanical spectra of ABCP and interpenetrating networks (IPN) based on castor oil with similar crosslink density and composition imply that the two components in ABCP are compatible whereas microphase separation occurs in IPN. An improvement in the compatibility is achieved by the crosslinking between the two networks.

COMPARISON OF THE BEHAVIOR OF CYCLIC AND LINEAR POLYSTYRENE IN DILUTE-SOLUTION

Using a low angle laser light scattering photometer, the second virial coefficients (A2) of both cyclic and linear polystyrene were determined in cyclohexane, toluene and methyl ethyl ketone (MEK) solutions. From the data obtained in cyclohexane solution the theta-temperature of cyclic polystyrene was determined to be 30-degrees-C. In toluene solution A2 of cyclic polystyrene is smaller than that of linear polystyrene with the same molecular weight, but in MEK the values are similar.

WATER-SOLUBLE AND AMPHIPHILIC POLYMERS .7. SYNTHESIS AND CHARACTERIZATION OF A NOVEL COMB-TYPE AMPHIPHILIC POLYMER PAMC16S

A novel comb-like amphiphilic polymer, poly (2-acrylamidohexadecylsulfonic acid) (PAMC16S), was synthesized by free radical polymerization of the corresponding amphiphilic monomer in 1,4-dioxane-water mixed solvents. Depending on the ratio of water/dioxane in the solvent, the reaction proceeded by either precipitation polymerization or micellar polymerization. The molecular weight of the polymer obtained under similar conditions decreased and subsequently increased with the increase of water content in the mixed solvent. The polyion nature of PAMC16S was confirmed by viscosity data of ethanolic solutions. In addition, the polymer was characterized by solubility, IR, TG and wide angle X-ray diffraction methods.

SOLUBLE POLY-(O,M)-TOLUIDINE

The soluble poly-o-toluidine (POT) and poly-m-toluidine (PMT) have been success- fully prepared under controlled conditions of polymerization and post-treatment, and characterized by IR, VPO and elemental analysis. It is found that the soluble and insol- uble polymers obtained with two different methods (Ⅰ and Ⅱ) have the similar conduc- tivity and molecular chain structure. VPO measurement shows that the number average molecular weight (Mn) of soluble polymers is about 3000. The mole ratio o...