Amphiphilic polymer networks consisting of hydrophilic poly(2-hydroxyethyl methacrylate) (PHEMA) and hydrophobic polyisobutylene (PIB) chains were synthesized from a cationic copolymer of isobutylene (IB) and 3-isopropenyl-alpha,alpha-dimethylbenzyl isocyanate (IDI) prepared at -50 degrees C in dichloromethane in conjunction with SnCl4. The isocyanate groups of this random copolymer, PIB(NCO)(n), were subsequently transformed in situ to methacrylate (MA) groups in the dibutyltin dilaurate-catalyzed reaction with 2-hydroxyethyl methacrylate (HEMA) at 30 degrees C. The resulting PIB(MA)(n) with number-average molecular weight 8200 and average functionality F-n similar to 4 per chain was in situ copolymerized radically with HEMA at 70 degrees C, giving rise to the amphiphilic networks containing 41 and 67 mol % HEMA. PHEMA-PIB network containing 43 mol % HEMA was also prepared by radical copolymerization of PIB(MA)(n) precursor with HENU using sequential synthesis. An amphiphilic nature of the resulting networks was proved by swelling in both water and n-heptane. PIB(NCO)(n) and PIB(MA)(n) were characterized by FTIR spectroscopy, SEC and the latter also by H-1 NMR spectroscopy. Solid state C-13 NMR spectroscopy was used for characterization of the resulting PHEMA-PIB networks. Whereas single glass-transition temperature, T-g = -67.4 degrees C, was observed for the rubbery crosslinked PIB prepared by reaction of PIB(NCO)(n) with water, the PHEMA-PIB networks containing 67 and 41 mol % HEMA showed two T-g's: -70.4 and 102.7 degrees C, and -63 and 107.2 degrees C, respectively. (c) 2006 Wiley Periodicals, Inc.