Some rheological properties of an interpolymer complex formed in the mixtures of aqueous solutions of poly(acrylic acid) and methyl cellulose are investigated. In a diluted state, the complex exhibits polyelectrolyte properties, and in the shear field, it flows like a pure poly(acrylic acid) solution. From the experimental data obtained from the mixture flow in a longitudinal field, an effective relaxation time was calculated. It turned out to be higher than that for the initial components. The deviation of the experimental values of the viscosity from the calculated additive ones allowed us to determine the critical molecular weight of the poly(acrylic acid) below which the complex is not formed: M cr Ϸ 6 ϫ 10 4 , which is one order of magnitude higher than for the mixtures of spatially complementary macromolecules. The increase of the total polymer concentration in the mixture first leads to an increase of the complex size. Further increase of the polymer concentration and transition to the semidiluted state decreases the complex size and also decreases its solubility in water.

Chitosan + poly(ethylene oxide) mixtures and films prepared from these mixtures were studied by rheological, absorption of solvent vapors, SANS, and mechanical testing methods. At a stoichiometric chitosan:poly(ethylene oxide) monomer:monomer composition, the mechanical properties of chitosan + poly(ethylene oxide) film are the best as compared with those of the initial components or of other compositions. This film composition is shown to be less heterogeneous. Chitosan and poly(ethylene oxide) are proved to be slightly incompatible polymers. This is supposed to induce the two components to align and to order at their stoichiometric composition, leading to the improvement in the mechanical properties. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1114–1122, 2002; DOI 10.1002/app.10319

Poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) membranes are attractive due to high permeability for gases; however, the selectivity of these membranes is insufficient. In this work, the gas selectivity was improved without significant loss of the permeability. For this purpose, PPO was modified via incorporation of the branched copolyimide filler–grafted copolyimide (PI‐g‐PMMA) with polymethyl methacrylate (PMMA) side chains. Two series of mixed self‐supporting PPO/PI‐g‐PMMA films (with variation of the filler content) were prepared and studied as gas separation membranes. The length of the polymide (PI) chain and the density of PMMA grafting were the same in both series, however, in one series the grafted chains contained 50 MMA units, and in the other 150 units. The intermolecular interactions between the PPO matrix and the PI‐g‐PMMA fillers were investigated using viscometry, infrared (IR) spectroscopy, and scanning electron microscopy. The compatibility of the polymer components is limited; however, for both series, the contents of the respective filler are found, which ensures phase segregation only in a microscale. Therefore, the mechanical properties of the films allow their use as gas separation membranes. It is shown that the degree of the segregation as well as the mechanical and gas transport properties of the membranes depend on the length of the PMMA chains, and the membranes with filler‐containing shorter branches (50 MMA units) show better selectivity.

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