Morphologies of semi and full interpenetrating polymer networks by nuclear magnetic resonance relaxation times

Full and semi interpenetrating polymer networks, IPNs, formed with a network of polyurethane (PU), and either a crosslinked poly(methyl methacrylate), PAc, or a linear polystyrene, PS, were synthesized with the aim of obtaining homogeneous materials. As already shown in a previous paper, the degree of phase dispersion in such materials depends on the synthesis method. The purpose of the n.m.r. investigations is to estimate the degree of mixing of the polymer in such networks, together with the synthesis parameters. The n.m.r. lineshape evolution of the PU/PAc IPNs with temperature allowed us to conclude that the PAc and PU networks are more intimately mixed in the sequential mode. In this paper, the measurements of the spin-lattice relaxation times in the rotating frame and the Goldman—Shen experiment are used to confirm previous results, and to give an estimation of the degree of mixing of the two networks in the matrix and of the size of the inclusions of PS in the 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 the reaction medium with the degree of advancement of the phase separation. Nodules of pure PS are seen for some samples but they do not correspond to those observed by SEM.