Poly(vinyl methyl ether) poly(methyl methacrylate) blends using diblock copolymer of styrene and methyl methacrylate as compatibilizer

Blends of poly(vinyl methyl ether) (PVME) and poly(methyl methacrylate) (PMMA) compatibilized by poly(styrene-block-methyl methacrylate) (P(S-b-MMA)) ale studied by FT-IR, DSC, excimer fluorescence spectrometry, and scanning electron microscopy (SEM). In FT-IR measurement the ratio of absorption intensity at 1107 cm(-1) to that at 1085 cm(-1) (I-1107/I-1085) reaches a minimum at about 10wt% block copolymer content. DSC results show that the glass transition temperature of PVME in the blends has a maximum at 10 wt% copolymer content. In plots of the ratio of excimer-to-monomer fluorescence emission intensities (I-E/I-M) VS block copolymer content, I-E/I-M increases rapidly above 10%. Ail these phenomena show that PS block chains penetrate into PVME: domains on addition of block copolymer. Above 10% copolymer content, block copolymer chains tend to form micelles in bulk phase.

Cure processing modeling and cure cycle simulation of epoxy-terminated poly(phenylene ether ketone) .1. DSC characterization of curing reaction

The curing reaction process of epoxy-terminated poly(phenylene ether ketone) (E-PEK) with 4,4'-diaminodiphenyl sulfone (DDS) and hexahydrophthalic acid anhydride (Nadic) as curing agents was investigated using isothermal differential scanning calorimetry (IDSC) and nonisothermal differential scanning calorimetry (DDSC) techniques. It was found that the curing reactions of E-PEK/DDS and E-PEK/Nadic are nth-order reactions but not autoaccelerating. The experimental results revealed that the curing reaction kinetics parameters measured from IDSC and DDSC are not equivalent. This means that, in the curing reaction kinetics model for our E-PEK system, both isothermal and nonisothermal reaction kinetics parameters are needed to describe isothermal and nonisothermal curing processes, The isothermal and nonisothermal curing processes were successfully simulated using this model. A new extrapolation method was suggested. On the basis of this method the maximum extent of the curing reaction (A(ult)) that is able to reach a certain temperature can be predicted. The A(ult) for the E-PEK system estimated by the new method agrees well with the results obtained from another procedure reported in the literature. (C) 1997 John Wiley & Sons, Inc.

Cure processing modeling and cure cycle simulation of epoxy-terminated poly(phenylene ether ketone) .2. Chemorheological modeling

Chemorheology and corresponding models for an epoxy-terminated poly(phenylene ether ketone) (E-PEK) and 4,4'-diaminodiphenyl sulfone (DDS) system were investigated using a differential scanning calorimeter (DSC) and a cone-and-plate rheometer. For this system, the reported four-parameter chemorheological model and modified WLF chemorheological model can only be used in an isothermal or nonisothermal process, respectively. In order to predict the resin viscosity variation during a stepwise temperature cure cycle actually used, a new model based on the combination of the four-parameter model and the modified WLF model was developed. The combined model can predict the resin viscosity variation during a stepwise temperature cure cycle more accurately than the above two models. In order to simplify the establishment of this model, a new five-parameter chemorheological model was then developed. The parameters in this five-parameter model can be determined through very few rheology and DSC experiments. This model is practicable to describe the resin viscosity variation for isothermal, nonisothermal, or stepwise temperature cure cycles accurately. The five-parameter chemorheological model has also successfully been used in the E-PEK systems with two other curing agents, i.e., the diamine curing agent with the addition of a boron trifluride monoethylamine (BF3-MEA) accelerator and an anhydride curing agent (hexahydrophthalic acid anhydride). (C) 1997 John Wiley & Sons, Inc.

The synthesis and thermotropic liquid crystalline behavior of the novel poly(aryl ether ketone)s containing chloro-side group

The novel poly(aryl ether ketone)s containing chloro-side group were synthesized by nucleophilic substitution reactions of 4,4'-biphenol and chlorohydroquinone with either 4,4'-difluorobenzophenone(BP/CH/DF) or 1,4-bis(p-fluorobenzoyl)benzene (BP/CH/BF) and their thermotropic liquid crystalline properties were characterized by a variety of experimental techniques. The thermotropic liquid crystalline behavior was observed in the copolymers containing 50 and 70% biphenol. Melting transition (Tm) and isotropization transition (Ti) both appeared in the DSC thermograms. A banded texture was formed after shearing the sample in the liquid crystalline state. The novel poly(aryl ether ketone)s had relatively higher glass transition temperature (Tg) in the range of 168 similar to 200 degrees C and lower melting temperature (Tm) in the range of 290 similar to 340 degrees C. The thermal stability (Td) was in the range of 430 similar to 490 degrees C.

Novel poly(aryl ether ketone)s containing various pendant groups .2. Gas-transport properties

The gas transport of hydrogen, oxygen, nitrogen, carbon dioxide, and methane gases in a series of poly(aryl ether ketone)s was examined. These polymer membranes have a wide range of permeability coefficients and permselectivity coefficients, showing excellent gas-transport properties. The enhanced interchain interaction in the polymers due to intermolecular hydrogen bonds and ionic bonds results in a considerable increase in permselectivity but a decrease in permeability. On the contrary, the polymers with bulky arkyl substituents show significantly increased permeability. The causes of this trend are interpreted in terms of the free volume, interchain distance, and glass transition temperature together with the respective contribution of gas solubility and diffusivity to the overall permeability. Of interest is the observation that the ionomer IMPEK-K+, which simultaneously contains bulky isopropyl substituents and pendant carboxylate groups, exhibits over twice higher CO2 permeability and 15% higher CO2/CH4 permselectivity than those of bisphenol-A p'olysulfone (PSF). The possibility of using the new synthesized poly(aryl ether ketone)s in gas separation membrane application is also discussed. (C) 1997 John Wiley & Sons, Inc.

Effect of heat treatment on the parameters of crystal structure and degree of crystallinity of poly(aryl-ether-ether-ketone)

The variations of unit cell parameters and crystallite size of nine PEEK samples treated at various temperatures have been studied by using Wide-Angle X-ray Diffraction (WAXD), The results indicate a decrease in unit cell parameter a,b and c but an increase in crystallite size L(hkl) With the increase beat treatment temperature. Based on X-ray scattering intensity theory and using the graphic multipeak resolution method, the formula of degree of crystallinity (W-c,W-X) for PEEK is derived. The results calculated are compatible with the density measurement and calorimetry.

Ionic conductivity of polymer gel electrolytes based on poly(polyethylene glycol dimethacrylate)

Gel electrolytes have been prepared by thermal polymerization of poly(polyethylene glycol dimethacrylate) (P(PEGD)) in the presence of propylene carbonate (PC) and alkali metal salts, such as LiClO4, LICF(3)SO(3) and LiBF4. The conductivity was studied by means of impedance spectroscopy, and it is found that the temperature dependence of conductivities follow a Arrhenius relationship when the molar percentage of PC is higher than 75% or LiClO4 concentration is lower than 0.9 mol/l. However, when LiCF3SO3 or LiBF4 is used instead of LiClO4 as the salt, the situation is different. For LICF(3)SO(3), the Arrhenius relationship almost holds true for all the salt concentrations studied; while for LiBF4, the Arrhenius equation hardly fits for any salt concentration. The dependence of activation energy on salt concentration is also examined, both for LiClO4 and LiCF3SO3, the values of E(a) tend to reach a minimum value with increasing salt concentration. Copyright (C) 1996 Elsevier Science Ltd.

Studies on polyepichlorohydrin-based polyurethane/poly(MMA-co-St) IPNs

Interpenetrating polymer networks of polyepichlorohydrin-based polyurethane/poly(MMA-co-St) have been prepared with simultaneous mettled by changing the weight fraction of MMA(W-MMA) in copolymer of MMA with styrene. The IPNs have been studied by DSC, TEM and dynamic mechanical spectroscopy(DMS). The results show that the IPNs have only one T-g, when W-MMA is greater than 0. 6. But when W-MMA IMA is less than 0. 4, the IPNs have two T(g)s, and phase separation is observed on TEM. The phenomenon is explained according to the solubility parameters(delta) and the fraction of hydrogen bond(delta(h)) of P (MMA-co-St). The study reveals that there is a close correlation among the delta, domain size and mechanical properties of PU (PECH)/P(MMA-co-St) IPN.

TERBIUM P-NITROBENZOATE HYDRATE

There are no discrete molecules of the title compound, catena-poly[{triaquaterbium-tris-beta-(p-nitro-benzoato)-O,O':O;O:O,O';O:O'-aqua(p-nitroben-zoato-O,O')terbium}-bis-mu-(p-nitrobenzoato-O:O') hydrate], [Tb2(C7H4NO4)6(H2O)5], in the crystal structure.

GAS PERMEABILITIES OF POLY(TRIMETHYLSILYLPROPYNE) MEMBRANES SURFACE MODIFIED WITH CF4 PLASMA

Surface fluorination of poly (trimethylsilylpropyne) (PTMSP) membranes by CF4 plasma was studied. The surface fluorination of the membranes was carried out in an atmosphere of CF4 in a capacitively coupled discharge apparatus with external electrodes. Dramatic increase in selectivity (P(O2)/P(N2)) was observed. The effect of fluorination conditions such as duration of treatment and discharge power on the permeabilities of the membranes was studied. X-ray photoelectron spectrometric data of modified PTMSP membranes showed a drastic alternation in the surface layer. The P(O2) and P(O2)/P(N2) of the membranes were observed to be dependent on the F/C atomic ratio. At F/C > 1, the P(O2/P(N2) value of the membranes could be more than four.

STUDY ON OPTICAL-ROTATORY OF HELIX POLYMER POLY(TRIPHENYLMETHYL METHACRYLATE)

The optical rotatory of helix polymer poly(triphenylmethyl methacrylate) (PTrMA) has been studied. The specific rotation of PTrMA is related with the length of helical chain linearly, while P(n)BAR<6 and P(n)BAR greater-than-or-equal-to 15. When P(n)BAR greater-than-or-equal-to 15, [alpha]D/20 = 1.6 P(n)BAR + 290-degrees. The contribution of each repeating unit to [alpha]D/20 is 1.6-degrees. In the 300-600 nm region, the ORD of PTrMA obeys both the Drude equation and Moffitt equation. The relationship between the [alpha]D of PTrMA and the solvent, concentration and temperature has also been investigated.

C, N and P regeneration by a detritivorous fish, Liza haematocheila T. & S.: effects of temperature, diet and body size

Detritus, as a nutrients reservoir, affects the trophic structure and dynamics of communities and supports a greater diversity of species and longer food chains. Detritivorous fish is an important organism to regenerate the nutrients from sediments. Despite the numerous studies on the nutrients cycle in fish, only a few attempts have been made to quantify the regenerating ability. In the present study, we chose the common detritivorous fish redeye mullet as the research object. Redeye mullet is also a common poly-culture fish in China. Diet, including a commercial diet mostly used in aquaculture and a home-made diet with contents close to detritus, was used and considered as a fixed factor. Temperature was also considered as a fixed factor as much research has shown that temperature has significant effects on fish metabolism. Moreover, body size was regarded as a covariate under analysis of covariance. Three key nutrients, namely carbon, nitrogen and phosphorus, were used to measure the nutrient-regenerating ability of redeye mullet under laboratory conditions. The results showed that the nutrient regeneration in percent of the consumption decreased with increasing temperature. Carbon and nitrogen regeneration of redeye mullet fed on commercial diet was lower than those of the home-made diet group, while the opposite was found for phosphorus. In each group, the amount of regenerated nutrients increased linearly with body size. Fed on the home-made diet, 5-g fish at 25 degrees C can regenerate 210.822 mg C, 37.533 mg N and 0.727 mg P per day.