The synthesis and morphology of grafted semiinterpenetrating polymer networks on the basis of functional prepolymers

Semi-IPNs on the basis of PU prepolymers with carboxylic groups and methacrylic copolymers with tertiary amine groups were synthesized. The influence of the functional group content and of the M_n of polymer components, as well as their ratio, on the morphology and mechanical properties were investigated. The miscibility in the systems was estimated by differential scanning calorimetry (DSC) and by scanning electron microscopy (SEM). The miscibility of components was increased by augmenting the content of the functional groups. By varying the ratio of components, the highest miscibility was found at the isoelectric ratio of functional groups. However, all the investigated IPNs were two-phase systems, due to the segmented structure of PU prepolymers. The lowering of M_n values of the starting components did not improve their compatibility. The mechanical properties of semi-IPNs changed with the increased concentration of functional groups in a way that is typical for ionomers. By physical interactions between functional groups, Young's modulus was most influenced, while the M_n of the polymethacrylic component influenced the tensile strength of IPNs. The compatibility between PU hard segments and the polymethacrylic component found in our experiments led us to the conclusion that the preparation of IPNs of finer morphology would be possible by using PU prepolymers with shorter soft segments. © 1996 John Wiley & Sons, Inc.