THERMALLY REVERSIBLE POLYMER LINKAGES .3. COVALENTLY CROSS-LINKED POLY(AZLACTONE)

Research on the azlactone-phenol reaction has been extended to cross-linking chemistry. Poly-(2-vinyl 4,4-dimethyl-2-oxazolin-5-one) was used to synthesize three-dimensional networks using bisphenol cross-linkers. Among the bisphenols considered, only bisphenols containing electron-withdrawing groups at the site para to the phenol hydroxyls cross-link the polymer. The bisphenol 4,4'-(perfluorobutanediyl-1,4-disulfonyl)diphenol was also found to facilitate the reverse reaction in high-boiling solvents, re-forming linear polymer and bisphenol at temperatures below the degradation temperature of the linear polymer. These networks undergo up to 20 or more cycles of cross-linking-de-cross-linking both inside and outside of the drybox.