INTERPENETRATING POLYMER NETWORK (IPN) AS A PERMANENT JOINT BETWEEN THE ELEMENTS OF A NEW-TYPE OF ARTIFICIAL CORNEA

The combination at the interface between two chemically identical poly mers was investigated by light and electron (scanning, transmission) m icroscopy. The polymers constitute elements of a new type of artificia l cornea in which the peripheral skirt is made from spongy poly(2-hydr oxyethyl methacrylate) (PHEMA) and the central optical zone from homog eneous, transparent PHEMA. Their two-phase combination along the bound ary fulfill formally the requirements for an interpenetrating polymer network (IPN). The procedure for the manufacture of prosthesis was des cribed in detail. Thin and ultrathin sections excised from the interfa ce region were investigated using microscopic techniques. Light micros copy allowed the measurement of the diffusion path length of transpare nt PHEMA into sponge, which was approximately 0.5 mm. Transmission ele ctron microscopy revealed a cellular-like morphology as well as larger segregated zones, which indicated network interpenetration on a molec ular level and also a relatively poor miscibility of the two polymers despite their identical chemical structure. The latter was interpreted as a result of the submicroscopic restraints imposed by polymer I (sp onge) upon polymer II. This study provides evidence that the interface combination of the prosthetic elements should be regarded as a gradie nt homo-IPN. This system offers a union between elements much stronger than those previously reported in artificial corneas. (C) 1994 John W iley & Sons, Inc.