Postfunctionalization of polyoxanorbornene via sequential Michael addition and radical thiol-ene click reactions

We demonstrated the successful postfunctionalization of poly(oxanorbornene imide) (PONB) with two types of double bonds using sequential orthogonal reactions, nucleophilic thiol-ene coupling via Michael addition and radical thiol-ene click reactions. First, the synthesis of PONB with side chain acrylate groups is carried out via ring-opening metathesis polymerization and nitroxide radical coupling reaction, respectively. Subsequently, the resulting polymer having two different orthogonal functionalities, main chain vinyl and side chain acrylate, is selectively modified via two sequential thiol-ene click reactions, nucleophilic thiol-ene coupling via Michael addition and photoinduced radical thiol-ene. The orthogonal reactivity of two diverse double bonds, vinyl and acrylate functionalities, for the abovementioned consecutive thiol-ene click reactions was first demonstrated on the model compound.