New Cross-Linkable Polymers with Huisgen Reaction Incorporating High μβ Chromophores for Second-Order Nonlinear Optical Applications

Abstract

We report herein the synthesis, the functionalization, and the successful radical polymerization of very nonlinear optical (NLO) active push–pull polyene chromophores (CPO). Second, the thermal Huisgen cyclo-addition cross-linking reaction was implemented, and it proved to be fully compatible with a polyene-based push–pull chromophore. Toward this goal, PMMA-co-CPO-3 and two cross-linkable polymers (PCC1-CPO-3 and PCC2-CPO-3) were first prepared and characterized by a modified Teng and Man technique performed in transmission. These first series of polymers were not compatible with the applied poling conditions because an irreversible film degradation was systematically observed at a temperature significantly lower than the cross-linking temperature. Consequently, a second series of polymers was prepared, in which the cross-linking temperature was decreased by functionalizing acetylenic moieties with ester electron withdrawing groups, which decrease the activation energy of the thermal Huisgen cyclo-addition. These new polymers were stable until the cross-linking reaction, and they exhibit bulk electro-optic coefficients (r33) until 41 pm/V at 1.5 μm. Furthermore, it was shown that the Huisgen cross-linking reaction is compatible with such push–pull polyene-based chromophores, and it systematically enhances the stability of the electro-optic activity because chromophore orientation was maintained up to 96 °C against 70 °C for the same uncross-linked polymer.