GRAFTING OF POLYURETHANE SURFACES WITH POLY(ETHYLENE GLYCOL)

Films of a commercial poly (ether urethane), Pellethane 2363-80AE, wer e prepared through solvent casting from dimethyl formamide. The films were grafted with poly (ethylene glycol) (PEG) by a two-step procedure . In the first step, the film surfaces were treated with hexamethylene diisocyanate in toluene in the presence of triethylamine as a catalys t. In the second step, PEG 1500 was allowed to react in toluene with s urface bound isocyanate groups. It was shown by ATR-IR, XPS, and conta ct angle measurements that the grafted surfaces were mainly composed o f PEG, and that they were strongly hydrophilic. It was also shown that unreacted PEG was entrapped in the material, which influenced its mec hanical and thermal properties. Extraction of the films with toluene e liminated the entrapped PEG, and the hydrophilicity as well as the PEG coverage of the surface decreased. However, a subsequent treatment wi th aqueous NaCl solution induced a molecular restructuring of the surf ace, increasing the amount of grafted PEG at the surface to a value cl ose to the original one. (C) 1993 John Wiley & Sons, Inc.