Water-transport properties in polyetherimide blends with a liquid crystal polymer

The effect of the addition of a liquid crystal polymer (Rodrun(R)) on the s orption and transport properties of water through films of a polyetherimide (PEI, Ultem 1000) was investigated. A Cahn electrobalance was employed for measuring the water uptake by the polymer samples. Sorption measurements w ere made with films of PEI, Rodrun, and heterogeneous PEI/Rodrun blends at different water activities at 30 degrees C. In all cases; diffusion and sor ption coefficients decreased when the amount of Rodrun increased. Values of the water-sorption isotherms were adjusted to different models. Permeabili ties for the different samples were indirectly obtained using experimental values of the solubility and diffusion coefficients described above. Furthe rmore, permeabilities of the binary composite material were calculated on t he basis of those of the pure components and some theoretical assumptions c oncerning blend morphology. Results were consistent with a Rodrun structure in the composite intermediate between a fibrillar and a laminar morphology . (C) 1999 John Wiley & Sons, Inc.