A two-step wet chemical method is described for the preparation of spherical silver nanoparticle-decorated flower-shaped zinc oxide (ZnO@Ag) heteronanostructures using a newly designed redoxactive poly(ionic liquid)(PIL), poly(1-vinyl-3-butylimidazolium ascorbate) (P[VBuIm][As]). The first step is the generation of ZnO nanoflower using P[VBuIm][As] in water followed by its decoration with in situ formed Ag nanoparticles (AgNPs) by the reduction of AgNO3 with surface adsorbed ascorbate ion. P [VBuIm][As] plays a triple role as shape-directing-cum-capping agent, mediator for Ag+ reduction and inducing the formation of spherical AgNPs. The composite ZnO@Ag heteronanostructures are thoroughly characterized by FESEM, TEM and XRD. The as-synthesized ZnO@Ag heteronanostructures is found to be excellent composite photocatalyst towards photopolymerization of methyl methacrylate (MMA) to very high-molecular-weight poly(methyl methacrylate) (PMMA) (Ca. similar to 2 x 10(5)) with very high (82%) conversion in bulk and in solution without any photoinitiator under UV light irradiation (lambda(max) = 350 nm). The ZnO@Ag composite is also an efficient photocatalyst for styrene polymerization in bulk and N-iso-propylacrylamide polymerization in water. The photopolymerization with neat ZnO nanoflower catalyst also produces PMMA, but molecular weights are comparatively low with a low conversion. The ZnO@Ag composite photocatalyst is easily isolable by centrifugation after polymerization, is stable and is reusable for four cycles of polymerization of MMA in bulk condition without losing its original activity. (C) 2017 Elsevier Ltd. All rights reserved.