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MOotional heterogeneity and phase separation of semi-interpenetrating networks and polymer mixtures based on polyurethanes and polymethacrylates

The motional heterogeneity and phase separation of semi-interpenetrating networks (SIPNs) and polymer mixtures (1:1 mass ratio) based on segmented polyester polyurethane (PU) with carboxylic groups and methacrylic copolymer (PM) with tertiary amino groups were studied by the electron spin resonance (ESR) spin label method. The concentration of functional groups incorporated in both prepolymers varied from 0 to 0.45 mmol g- 1. The ESR spectra of in-chain spin labelled PM component were used to characterise the heterogeneity of segmental motion and transitions due to the additional polymer interactions imposed by complementary functional groups. The results were deduced from the temperature dependent ESR spectra. Occurrence of the fast component in the ESR spectra of SIPNs and mixtures indicates that a part of labelled PM segments are plasticized by the PU soft segments. The fraction of the fast and slow component was related to the complex polymer-polymer interaction or extent of miscibility. Restrictions of segmental motion of PM chains increase with functional groups concentration and above certain concentration (0.25 mmol g- 1) PM segments in the network assess faster motion suggesting a change in the local packing density and domain structure. An increased miscibility and disorganisation of the ordered domains are confirmed by the loss of spherulitic morphology and crystallinity at higher functional groups concentration. PU/PM mixtures reveal similar motional behaviour as SIPNs of the same composition. However, the differences in the fractional amount of fast and slow motions confirm better interpenetration and interaction of the two polymers in the SIPNs. The results of motional heterogeneity and polymer interactions were complemented with the Tgs.

semi-interpenetrating networks; polymer mixtures; ESR

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