Approach to cross-linked polynorbornene/ZnO nanocomposites through nitroxide-mediated free radical graft polymerization and in situ hydrolysis

In this study, we reported an alternative strategy for fabricating stable cross-linked poly(butoxymethylenenorbornene-co-norbornene-2-carboxaldehyde)/ZnO (P(BN/NCA)/ZnO) nanocomposite films based on nitroxide-mediated free radical polymerization (NMRP) and in situ hydrolysis. Firstly, the macroinitiator poly(butoxymethylenenorbornene-co-norbornene-2-carboxaldehyde) alkoxyamine (P(BN/NCA)-TIPNO) was synthesized through the attachment of an alkoxyamine to polynorbornene derivative. And then the cross-linked graft copolymers poly(butoxymethylenenorbornene-co-norbornene-2-carboxaldehyde)-g-poly(zinc dimethacrylate) (P(BN/NCA)-g-PZDMA) were prepared using zinc dimethacrylate (ZDMA) and the as-prepared macroinitiator P(BN/NCA)-TIPNO by NMRP. Due to the two CC bonds in each ZDMA molecule, the resulting cross-linked polymer connected the precursor of ZnO nanocrystals and polymer with covalent band, leading to a homogenous distribution of Zn2+ at the molecular level. Finally, ZnO nanocrystals were generated in situ by hydrolyzing the polymer film in NaOH aqueous solution. ZnO nanocrystals were homogeneously dispersed in the cross-linked polymer matrix without aggregation. Compared with the physical blending of non-cross-linked P(BN/NCA)/ZnO nanocomposite film, the cross-linked P(BN/NCA)/ZnO nanocomposite films exhibited good optical properties and photoluminescence (PL) stability owing to the function of cross-linked template.

► An alternative strategy for fabricating stable polynorbornene/ZnO nanocomposite films is proposed.
► The resulting cross-linked structures present homogenous distribution of ZnO in polynorbornene matrix.
► The nanocomposites exhibited excellent optical properties and photoluminescence stability.