Poly solutions transport properties

Membranes and Osmosis. Membranes based on PEI can be used for the dehydration of organic solvents such as 2-propanol, methyl ethyl ketone, and toluene (451), and for concentrating seawater (452—454). On exposure to ultrasound waves, aqueous PEI salt solutions and brominated poly(2,6-dimethylphenylene oxide) form stable emulsions from which it is possible to cast membranes in which submicrometer capsules of the salt solution ate embedded (455). The rate of release of the salt solution can be altered by surface—active substances. In membranes, PEI can act as a proton source in the generation of a photocurrent (456). The formation of a PEI coating on ion-exchange membranes modifies the transport properties and results in permanent selectivity of the membrane (457). The electrochemical testing of salts (458) is another possible appHcation of PEI. 

We have studied a variety of transport properties of several series of 0/W microemulsions containing the nonionic surfactant Tween 60 (ATLAS tradename) and n-pentanol as cosurfactant. Measurements include dielectric relaxation (from 1 MHz to 15.4 GHz), electrical conductivity in the presence of added electrolyte, thermal conductivity, and water self-diffusion coefficient (using pulsed NMR techniques). In addition, similar transport measurements have been performed on concentrated aqueous solutions of poly(ethylene oxide)... 

Manning GS. Limiting laws for equihbrium and transport properties of poly electrolyte solutions. In Seleny E, ed. Charged and Reactive Polymers, Reidel Dordrecht, Boston, 1974 Vol. 1 9-18. 

Figure 5.5 Transport properties of a cation exchange membrane having a cationic polyelectrolyte layer formed by electrodeposition. (A) PNaCa ( ) current efficiency (%) ( ) electrical resistance of the membrane during electrodialysis for 1 h. After solutions containing 0.0416N sodium chloride and poly(3-methylene-N, N-dimethylcyclohexylammonium chloride) of various concentrations had been electrodialyzed, for 60 min at a current density of 10 mA cm 2, as anolyte to electrodeposit the polyelectrolyte on the membrane surface (catholyte was 0.0416N sodium chloride), a 1 1 mixed solution of 0.208N calcium chloride and 0.208 N sodium chloride was electrodialyzed at a current density of 10 mA cmr1 for 60 min (cation exchange membrane NEOSEPTA CH-45T).

White [25] investigated the transport properties of a series of asymmetric poly-imide OSN membranes with normal and branched alkanes, and aromatic compounds. His experimental results were consistent with the solution-diffusion model presented in [35]. Since polyimides are reported to swell by less than 15%, and usually considerably less, in common solvents this simple solution-diffusion model is appropriate. However, the solution-diffusion model assumes a discontinuity in pressure profile at the downstream side of the separating layer. When the separating layer is not a rubbery polymer coated onto a support material, but is a dense top layer formed by phase inversion, as in the polyi-mide membranes reported by White, it is not clear where this discontinuity is located, or whether it wiU actually exist The fact that the model is based on an abstract representation of the membrane that may not correspond well to the physical reality should be borne in mind when using either modelling approach. 

Polyelectrolyte multilayers (PEMs) are very important materials due to having a wide range of application helds such as encapsulation of drugs and enzymes, membrane-based separations, antibacterial coatings, membrane reactors and fuel cells. Polyelectrolyte multilayer (PEM) has a wide range of transport properties, simple deposition and small thickness, so it can be used in separation membranes. Polyelectrolyte concentration, duration and temperature of adsorption, deposition and solution pH are key parameters for specific separations. In addition the number of poly electrolyte layers can alter the properties of poly electrolyte. Poly (styrene sulfonate) (PSS)/poly(diallyldimethylammonium chloride) (PDADMAC) films are utilized in separation membranes. The adsorption of Cu(II) or Fe(III) ions can be carried out with PSS/poly(allylamine hydrochloride) (PAH) membranes. 

ABSTRACT. The poly(3-alkylthiophenes) represent a new generation of conducting polymers, that exhibit both solution and melt processability. These properties open new possibilities for the utilization of conducting polymers in practical applications. Fur eimore, the solubility of these polymers enables the characterization of the physical and chemical structure in greater detail than hitherto have been possible. In this chq)ter we give a brief review of the synthetic routes to the poly(3-alkylthiophenes) as well as an overview of some of the recent results on the physical and chemical characterization of this class of materials. In diis overview we include results on stability properties, transport properties, thermo- and solvatochromism. We also discuss some aspects of the utilization of the poly(3-dkyltiiiophenes) in plications. 

---