Crosslinking of poly(ethylene glycol) with divalent metal salts of mono(hydroxyethyl) phthalate,anhydride, and bisepoxide

Poly(ethylene glycol)s (PEG) were crosslinked with divalent metal salts of mono(hydroxyethyl) phthalate, anhydride, and bisepoxide to give metal-containing cured rubbers. As the anhydride, hexahydrophthalic anhydride was used, and bisphenol A diglycidyl ether was the bisepoxide used. As for the physical properties of the cured rubbers obtained, the rubbers containing Mg showed much better physical properties than those containing Ca. In addition, the rubbers with high hard block contents and high overall crosslinking densities exhibited high tensile strength and Shore A hardness, and so did the rubbers having a high degree of crystallinity of the PEG soft block. The occurrence of crystallization became easy as the soft block length became longer and the soft block content became higher, or as the crosslinking density of the hard block became lower. The PEG-based rubbers showed much higher water absorption than the previously reported poly(propylene glycol)-based rubbers, due to the much higher hydrophilicity of the PEG block. Resistance to chemical attack and stress–relaxation are also discussed.