Preparation and viscoelastic behavior of methacrylate ionomers crosslinked by titanium(IV) and zirconium(IV)

Ionomers of poly(methyl methacrylate-co-methacrylic acid) crosslinked by titanium(IV) (Ti4+) and zirconium(IV) (Zr4+) ions were prepared, and their structures, optical absorption and viseoelastic properties were investigated. IR measurement revealed that tetravalent metal ions were coordinated by -COO- groups of deprotonated methacrylic acid and functioned as crosslinkers. The coordination of-COO- to the Ti4+ especially brought about strong UV absorption below 360-370 nm owing to charge transfer. Dynamic mechanical thermal analysis (DMTA) showed storage modulus (E') below glass transition temperature (T-g) and a peak temperature of tan delta for every ionomer not to increase regardless of metal ion content. This was attributed to residual alcohols. E' above T-g increased with metal ions content, and DMTA for every ionomer was measured up to 350 degreesC. Crosslinking by tetravalent metal ions thus greatly improves heat resistance of host polymers.