MORPHOLOGIES OF SEMI AND FULL INTERPENETRATING POLYMER NETWORKS BY NUCLEAR-MAGNETIC-RESONANCE RELAXATION-TIMES

Full and semi interpenetrating polymer networks, IPNs, formed with a n etwork of polyurethane (PU), and either a crosslinked poly(methyl meth acrylate), PAc, or a linear polystyrene, PS, were synthesized with the aim of obtaining homogeneous materials. As already shown in a previou s paper, the degree of phase dispersion in such materials depends on t he synthesis method. The purpose of the n.m.r. investigations is to es timate the degree of mixing of the polymer in such networks, together with the synthesis parameters. The n.m.r. lineshape evolution of the P U/PAc IPNs with temperature allowed us to conclude that the PAc and PU networks are more intimately mixed in the sequential mode. In this pa per, the measurements of the spin-lattice relaxation times in the rota ting frame and the Goldman-Shen experiment are used to confirm previou s results, and to give an estimation of the degree of mixing of the tw o networks in the matrix and of the size of the inclusions of PS in th e simultaneous IPN. Following the same protocol, different semi-1 IPNs of PU/PS are examined in order to relate the amount of PS added to th e reaction medium with the degree of advancement of the phase separati on. Nodules of pure PS are seen for some samples but they do not corre spond to those observed by SEM.