Surface modification of poly(ethylene terephthalate) angioplasty balloons with a hydrophilic poly(acrylamide-co-ethylene glycol) interpenetrating polymer network coating

An interpenetrating polymer network (IPN) of poly(acrylamide-co-ethylene gl ycol) (p(AAm-co-EG)) hydrogel was covalently grafted to polyethylene tereph thalate (PET) angioplasty balloons to increase surface hydrophilicity and i mprove lubricity. A 2-step graft polymerization protocol was followed to fi rst polymerize and cross-link acrylamide onto the substrate with a photosen sitizer and/or oxygen plasma pretreatment. The effects of varying photo-ini tiation and plasma exposure times were investigated separately and conjunct ively using water contact angles to obtain optimal coating deposition param eters. A poly(ethylene glycol) network was then grafted by swelling the pre existing polyacrylamide network to allow inter-diffusion of the monomer and cross-linker, which were then polymerized by photo-initiation. When the ph oto-initiation time was long enough to reach near gelation, pretreatment of PET with oxygen plasma did not offer significant benefit. X-ray photoelect ron spectroscopy confirmed the presence of both polymer layers and composit ion depth profiles supported the assessment that an interpenetrating networ k was formed. Tensile testing and application of Weibull statistics on unmo dified and modified films indicated that the surface modification approach did not significantly alter the mechanical integrity of the material. These findings indicate that a p(AAm-co-EG) coating can be effectively deposited on PET surfaces without compromising the structural integrity of the subst rate. (C) 2000 John Wiley & Sons, Inc.