A XE-129 NMR-STUDY ON AN IONOMERIC POLYMER BLEND SYSTEM

The morphology of an ionomeric polymer blend consisting of an amino-si licone copolymer and zinc neutralized sulfonated polystyrene (ZnSPS) h as been studied using proton spin diffusion and small angle X-ray scat tering (SAXS). The extent of reaction between the two components in th e blend was monitored by C-13 CP MAS spectroscopy. All three types of experiment point to domain sizes in the nanometer range. Xe-129 MMR wa s used to study exchange by translational diffusion between domains. A single xenon resonance was detected in temperatures ranging from 25 d egrees C to - 90 degrees C, and the chemical shift followed a weighted average of the isolated polymer shifts consistent with the small doma in sizes. Pulse field gradient Xe-129 NMR was used to determine the ef fective diffusion constants in the amino silicone starting material an d the blend. The diffusion constant of xenon in poly(styrene) is known , allowing for comparison of the predictions of effective diffusion co nstants in the blend based on the values in the constituents of the bl end. Simple two-site exchange equations incorrectly predict that diffu sion in the blend would be dominated by the constituent with slow diff usion. The blend diffusion constant is close to the value of the amino silicone or the constituent with fast diffusion which is correctly pr edicted for a rapid exchange solution of the diffusion equation. (C) 1 998 Elsevier Science B.V. All rights reserved.