Amphiphilic Conetworks. IV. Poly(methacrylic acid)-/-Polyisobutylene and Poly(acrylic acid)-/-Polyisobutylene Based Hydrogels Prepared by Two-Step Polymer Procedure. New pH Responsive Conetworks

This article describes the synthesis and characterization of new amphiphilic polymer conetworks containing hydrophilic poly(methacrylic acid) (PMAA) or poly(acrylic acid) (PAA) and hydrophobic polyisobutylene (PIB) chains. These conetworks were prepared by a two-step polymer synthesis. In the first step, a cationic copolymer of isobutylene (IB) and 3-isopropenyl-alpha,alpha-dimethylbenzyl isocyanate (IDI) was prepared. The isocyanate groups of the IB-IDI random copolymer were subsequently transformed in situ to methacrylate (MA) groups in reaction with 2-hydroxy-ethyl methacrylate (HEMA). In the second step, the resulting MA-multifunctional PIB-based crosslinker, PIB(MA)(n), with an average functionality of approximately four methacrylic groups per chain, was copolymerized with methacrylic acid (PMAA) or acrylic acid (AA) by radical mechanism in tetrahydrofuran giving rise to amphiphilic conetworks containing 31-79 mol % of MAA or 26-36 mol % of AA. The synthesized conetworks were characterized with solid-state C-13-NMR spectroscopy and differential scanning calorimetry. The amphiphilic nature of the conetworks was proven by swelling in both aqueous media with low and high pH and n-heptane. The effect of varying pH on the swelling behavior of the synthesized conetworks is presented. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1284-1291, 2009