SYNTHESIS AND SURFACE CHARACTERIZATION OF HEPARIN-IMMOBILIZED POLYETHERURETHANES

Novel poly(ether urethanes) containing diester groups in the side chai ns (PU) were synthesized from 4,4'-diphenylmethyl diisocyanate, polyte tramethylene glycol, and diethyl bis(hydroxymethyl)malonate as a chain extender. The surface modification of the PU film was carried out by a hydrolysis reaction, poly(ethylene oxide) (PEO) grafting, and hepari n immobilization, and the surface-modified PUs were then characterized by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, electron spectroscopy for chemical analysis (ESCA), and a contact angle goniometer. The concentration of carboxylic acid group s introduced on the PU surfaces as determined by the rhodamine interac tion method was 61 nmol/cm(2) when treated with 4N NaOH/methanol (1 : 2 v/v) for 30 min and subsequently with a citric acid-methanolic aqueo us solution. The amounts of heparin coupled to the carboxyl groups on the PU surfaces and to the terminus amino groups on the PU-PEO were 0. 92 and 0.84 mu g/cm(2), respectively. There was almost no heparin rele ased from the immobilized surface of a physiological solution for 100 h, thereby indicating the strong stability of immobilized heparin. (C) 1998 John Wiley & Sons, Inc.