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Spin probe study of semi-interpenetrating polymer networks based on polyurethane and polymethacrylate functional prepolymers

The motional transition and heterogeneity of semi-interpenetrating networks (SIPN) based on polyurethane (PU) with carboxylic groups and methacrylic copolymer (PM) with tertiary amine groups were studied by the electron spin resonance (ESR) – spin probe method. The concentration of functional groups in both prepolymers varied from 0 to 0.45 mmol g-1. Spin probed SIPN shows that the temperature dependent spectra are sensitive to polymer interactions imposed by functional groups. These interactions determine free volume distribution in the matrix and temperature at which motional transition takes place. The fraction of free volume increases with functional groups concentration and reaches its maximum at 0.25 mmol g-1. Further increase of functional groups concentration reduces free volume. The results of the networks with strong interactions are discussed in terms of the interference of the plasticising effect of the PU component and the formation of possible cluster cross-links which restrict segmental motions.

semi-interpenetrating polymer networks ; functional groups ; ESR ; spin probe

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