Surface modification of natural rubber by graft copolymerization of hydrophilic monomers to improve blood compatibility

Abstract

Unvulcanized and vulcanized natural rubber latex films having surfaces grafted with hydrophilic monomers: poly (ethylene glycol) methacrylate (PEGMA), N-vinyl pyrrolidone (Vpy), 2-methacryloyloxyethyl phosphorylcholine (MPC) were prepared by UV-induced graft copolymerization using benzophenone as a photosensitizer. The grafting yield increase of vulcanized NR latex films as a function of time and monomer concentration were of lesser magnitude than ones of the unvulcanized NR latex films. This can be explained as a result of the crosslinked network generated during vulcanization acting as an obstacle to the permeation of the photosensitizer as well as the monomer. An appearance of a characteristic carbonyl stretching in NR latex films after the surface grafting of PEGMA and MPC indicated that the modification has proceeded at least to the sampling depth of ATR-IP (~1-2 µm). According to the water contact angle of the modified NR latex films, the surface grafting density became higher as the grafting time and monomer concentration increased. The completely absence of plasma protein adsorption and platelet adhesion on the densely grafted NR latex films is a strong indication of significantly improved blood compatibility. Results from tensile tests suggest that graft copolymerization does not cause adverse effects on mechanical properties of NR latex films.