engleski

ESR-spin labelling study of semi-interpenetrating networks and polymer mixtures based on functionalized polyurethanes and polymethacrylates

Semi-interpenetrating polymer networks, SIPNs, and polymer mixtures (1:1 mass ratio) based on segmented polyester polyurethane, PU, with carboxylic groups and methacrylic copolymer, PM, with tertiary amine groups were prepared. Electron spin resonance, ESR, spin label method was used to study the effect of functional groups concentration on the segmental motion, motional transitions and phase separation. The concentration of functional groups varied from 0 to 0.45 mmol g-1. From the temperature dependent composite ESR spectra of PU labelled component motional heterogeneity was deduced. Restriction of segmental motion of PU segments in the PU/PM mixtures increases with the augmentation of functional groups content due to the additional noncovalent interactions. The critical concentration (0.35 mmol g-1) above which the motional restriction decreases is observed. The effect of functional groups is discussed in terms of the change of local packing density. According to the fractions of the slow component and temperatures of motional transitions SIPNs reveal better interpenetration and interactions of both polymer components. Additional functional groups contribute to a very strong influence of restricted PM chains on the PU hard segments.

Semi-interpenetrating polymer networks ; Polyurethanes ; Polymethacrylates ; ESR ; Motional heterogeneity

nije evidentirano