A NEUTRON REFLECTOMETRY STUDY OF POLYSTYRENE NETWORK INTERFACES

We have used neutron reflectometry to measure interfacial widths betwe en two polystyrene films, where either one or both films are crosslink ed. The observed interfacial width between two networks is larger than the size expected for ''dangling ends'', which suggests motion of het erogeneous regions of the networks. In the case when one of the networ ks is replaced by a linear polymer, the interfacial profile can be asy mmetric with a diffusion ''front'' of linear polymer penetrating the n etwork to a length scale of up to 200 Angstrom. In the case of a more densely crosslinked network and a high molecular weight linear polymer the interface is symmetric implying negligible penetration.