Self-associating networks of poly(methacrylic acid-g-ethylene glycol)

Poly(methacrylic acid-g-ethylene glycol) networks were prepared by the copolymerization of methacrylic acid and poly(ethylene glycol) methacrylate in the presence of a tetraethylene glycol dimethacrylate cross-linking agent. Their swelling characteristics depended on swelling solution pH, swelling temperature, copolymer composition, and network structure. In aqueous swelling solutions at acidic pH, copolymer networks copolymer composition, and network structure. In aqueous swelling solutions at acidic pH, copolymer networks swelled to a much lower extent than homopolymer networks. This behavior was attributed to complex formation between poly(ethylene glycol) and poly(methacrylic acid) segments. Nuclear Overhauser enhancement measurements revealed that graft copolymers formed complexes under a wider range of concentrations and poly(ethylene glycol) molecular weights than the two ungrafted homopolymers. This enhancement in complexation was attributed to elimination of the unfavorable translational free energy change of complexation by covalent attachment of the complexing species.