Transport Properties Of Poly Research Articles

Gas transport properties of poly(arylether bissulfone)s and poly(arylether bisketone)s

AbstractThe transport properties of the poly(arylether bissulfone) based on bisphenol A (PBSF) and the poly(arylether bisketone) s based on bisphenol A (PBK) and bisphenol S (PBK‐S) are reported at 35°C. Comparisons are made with the polysulfone and the polycarbonate also based on bisphenol A to determine the effect of the long, rigid bisketone and bissulfone groups on polymer properties. A direct comparison also is made between PBK and PBSF, which differ only by their ketone and sulfone groups. The bulkier sulfone group increases free volume and Tg more than the ketone group. This results in higher solubility and diffusivity coefficients for the bissulfone versus the bisketone polymer, both of which contribute to higher permeability coefficients. © 1993 John Wiley & Sons, Inc.

A note on the effects of mono-and di-bromination on the transport properties of poly(2,6-dimethylphenylene oxide)

The permeability of poly (2,6-dimethylphenylene oxide) (PPO) to carbon dioxide and methane at 35°C can be increased more than 100% by aryl-bromination, depending on the extent of bromination, whereas, the carbon dioxide/methane permselectivity of the polymer, which ranges from 17–20, is changed only slightly by bromination. The increase in permeability results primarily from a marked increase in the penetrant diffusivity, although the penetrant solubility is also moderately increased by bromination. These results are interpreted in terms of changes in packing density and chain torsional mobility brought about by aryl-bromination of the polymer.

Measurement of transport properties of poly(methylmethacrylate-co-methacrylic acid) ion-containing membranes

Several membranes prepared from poly(methylmethacrylate-co-methacrylic acid) and its Li+ and Zn2+ ionomers were tested for NaCl, creatinine and urea permeability. The permeabilities of the membranes were explained on the basis of pore contents determined from their scanning electron microscope micrographs. All the membranes showed higher permeabilities during the first 2 hours of experimentation. Introduction of Zn2+ ions into the copolymer as crosslinking agent did not have much effect on the membrane properties but the properties of the copolymer were modified.

Transport, magnetic, and optical properties of electrochemically doped poly(1,4-dimethoxy phenylene vinylene).

A coordinated study on electrochemical, magnetic, optical, and transport properties of poly(1,4-dimethoxy phenylene vinylene) (PDMPV) using in situ electrochemical doping techniques is presented. Properties are correlated through a common axis of applied voltage. Electrochemical doping shows \ensuremath{\approxeq}100% Coulombic efficiency up to an applied potential of 3.8 V versus lithium in propylene carbonate electrolyte. Conductivity increases in a reversible manner to a maximum of 250 ${\ensuremath{\Omega}}^{\mathrm{\ensuremath{-}}1}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ and an applied potential of 3.9 V. Potentials in excess of 3.9 V cause an irreversible decrease in conductivity. Spin and charge show a 1:1 relation only to very low doping levels. Two paramagnetic species are produced on doping. A maximum spin concentration is observed at \ensuremath{\approxeq}3.7 V. The ultraviolet--visible--near-infrared spectra of doped PDMPV show at least five absorption bands, at 4.8, 3.7, 2.5, 1.7, and 0.6 eV. The first three bands decrease with doping and the latter two increase. When analyzed by the polaron or bipolaron model, the optical data imply significant symmetry breaking. Contributions to the optical activity from polarons and bipolarons are determined from the EPR results and are found to be different for both peaks, implying greater symmetry-breaking effects for polarons. An electrochemical analysis of EPR results suggests that polaron interaction energies are \ensuremath{\approxeq}0.45 eV greater than those for bipolarons.

Synthesis and transport properties of poly(vinyl alcohol) acrylonitrile/2-hydroxyethyl methacrylate membranes—I. Synthesis of poly(vinyl alcohol) acrylonitrile 2-hydroxyethyl methacrylate graft copolymer

The graft copolymerization of acrylonitrile and hydroxyethyl methacrylate monomers onto poly(vinyl alcohol) backbone using the ceric ion technique was investigated in detail and a high percentage grafting of the monomers onto the backbone was obtained. Another backbone which was investigated was a blend of poly(vinyl alcohol) and polyacrylic acid (PVA-PA). The grafting onto the poly(vinyl alcohol) was found to depend on the concentration of the ceric ion and its acidity and the poly(vinyl alcohol) content. Grafting was observed to proceed very smoothly onto the poly(vinyl alcohol) but was much slower in the poly(vinyl alcohol)/poly(acrylic acid) system. The graft copolymerization was interpreted in terms of an emulsion polymerization in the case of the poly(vinyl alcohol) system. However, grafting did not proceed very readily in the poly(vinyl alcohol)/poly(acrylic acid) blend system, explained by a coagulation which caused the system to react more slowly.

Gas transport in poly(vinylidene fluoride): Effects of uniaxial drawing and processing temperature

AbstractThis paper reports on the gas sorption and transport properties of poly(vinylidene fluoride) (PVF2) and on the effects uniaxial drawing and processing temperature have on these properties. Sorption and transport were first examined for “as‐received” commercial Kynar PVF2 film at 35°C. This film was 54% crystalline by weight. Solubility, diffusion, and permeability coefficients were measured for He, H2, Ar, O2, N2, CH4, and CO2. The solubility coefficient and the diffusion coefficient D were correlated with the Lennard–Jones potential and mean molecular diameter of the gas, respectively. Uniaxial drawing of PVF2 films was performed up to a draw ratio of 3.7 and over the temperature range 75–140°C. Transport properties were correlated with the extent of draw and drawing temperature. The permeability P and D were found to significantly decline with uniaxial drawing; the magnitude of this effect was dependent on both the drawing temperature and the molecular size of the penetrant considered. Roduetions in P and D became progressively more pronounced with increasing molecular diameter and with decreasing drawing temperature (down to a limit of about 75°C), which reflects an increase in effectiveness of drawing at low temperatures. PVF2 films annealed above 75°C showed an increase in P and D as opposed to the effect of drawing. The solubility of various gases in PVF2 was not found to be sensitive to processing treatments such as drawing and annealing, in agreement with the relatively small changes observed in free volume. PVF2 films subjected to various treatments were characterized by DSC, density, birefringence, and dynamic mechanical measurements. Gas transport measurements appear to provide a more sensitive and hence more viable measure of the effectiveness of drawing than these other techniques. Drawing PVF2 in the melt state was found to increase P and D, in contrast with the effects observed for solid‐state drawing. The results have been interpreted in terms of existing theories on morphology and microstructure in semicrystalline polymers.

Conformation and transport properties of poly(alkylene phosphate)—A synthetic analogue of natural teichoic acids—I. Hypercoiled to extended coil state transition in poly(1,3-propylene phosphate)

The pH-induced conformational transition of poly(1,3-propylene phosphate) (PPP) in an aqueous solution has been investigated by the potentiometric method. It has been found that PPP undergoes a cooperative macroconformational transition upon changing the fraction of dissociated phosphate groups from 0.3 to 0.4. The standard free energy for the transition from a hypothetical hypercoiled form to a loosely coiled form was estimated to be 565 J/mol.

Conformation and transport properties of poly(alkylene phosphate)—A synthetic analogue of natural teichoic acids—II. Conductivity percolation in poly(vinyl chloride)-poly(1,3-propylene phosphate) membranes

The electrical conductivity of poly(vinyl chloride)-poly(1,3-propylene phosphate) membranes was measured as a function of ionic polymer content and its ionic state. The results are discussed by applying the percolation conductivity theory and considering the conformational transition upon neutralization of PPP. It was found that the critical volume fraction of PPP in membranes of 0.06 did not depend on an ionic form of polymer. A critical exponent ( t) predicted by the percolation theory was found to be 1.64 for the membrane in its sodium form and 1.04 in its hydrogen form. The value t = 1.04 is below the theoretical value of t, i.e. 1.6 ± 0.2, for conductor/insulator systems. This effect may result from the reduced conductivity of PPP after the transition from extended coil to the hypercoiled state in the ionic polymer.

Effects of whole blood interfacial interactions on potassium ion transport through poly(2-hydroxyethylmethacrylate) membranes.

Transport chamber experiments were conducted to elucidate the role of surface-oriented blood cell/serum protein interactions in modulating the potassium ion (K+) transport properties of poly (2-hydroxyethylmethacrylate) (pHEMA) membranes. The effects were achieved by carefully exposing one side of pHEMA membranes to freshly drawn whole blood for a period of 10 min. A simple steady-state diffusion model is presented and verified for both the control and experimental membranes. The results indicate that the presence of blood components rapidly decreases the rate of K+ transport to a new steady-state value which is described by a surface area multiplication factor of γT≃0.60. This observation is useful in the design of medical devices for biomedical electroanalysis and haemodialysis, where ion transport is the main function. This transport chamber approach is flexible and useful in measuring the effects of various microenvironmental manipulations to simulate variousin vivo conditions.

The structure and transport properties of poly(methacrylic acid) in aqueous solution

AbstractDiffusion and anisotropic electrical conductivity measurements have been used to investigate the structure of poly(methacrylic acid) in aqueous solution at various degrees of neutralization. Both kinds of measurement indicate that the polyion chain opens from a coiled to an extended configuration as the chain is neutralized. In addition it was found that, at low concentrations, the opening of the chain is a two‐step process, whereas at higher concentrations the mechanism involves a single step.

Spin resonance, hall effect, and transport properties of poly(N‐vinyl carbazole)—iodine complex

AbstractThe results and interpretations of Hall effect, resistivity, electron spin resonance, Dember effect, and thermoelectric measurements on the poly(N‐vinyl carbazole)—iodine complex are presented. The existence of a charge‐transfer state in this system is demonstrated by three independent techniques: (1) the variation of resistivity with iodine content; (2) study of unpaired spin concentration; (3) optical absorption measurements. Many complexes have high impedances that have prohibited heretofore measurement of fundamental characteristics such as Hall mobility. The development of an AC technique9 for the measurement of the Hall effect in materials of high resistivity and low mobility has permitted the measurement of the Hall mobility in compressed pellets of poly(N‐vinyl carbazole) complexed with iodine (impedance ∼1 megohm). It is believed that the Hall mobilities are the first to be reported for a charge‐transfer complex. A discrepancy in the sign of the majority carriers is observed: the Hall coefficient is negative, the Seebeck coefficient is positive. The Dember voltage supports n‐type conduction as found in the Hall effect. It is suggested that this sign discrepancy can be resolved by consideration of surface states. The concentration of carriers deduced from Hall measurements is four orders of magnitude smaller than the unpaired spin concentration. The mechanism of conduction proposed invokes a hopping process in which a localized electron in an unpaired spin state makes phonon‐assisted jumps from site to site.