Towards controlled cationic polymer growth from inorganic oxide defects: Directing the mechanism of polystyrene grafting from g-irradiated silica

Most studies on surface-initiated controlled polymerizations for the synthesis of polymeric covalent organic-inorganic hybrid materials focus on chemical methods requiring specific modifications of the inorganic substrate. Few mechanistically-aware approaches have been undertaken towards exploiting the reactivity of defects induced by physical techniques such as ionizing radiations or UVeVis light. Within this framework, we take grafted polymerization of styrene from g-irradiated silica as a mechanistic testing ground where para- and diamagnetic silica defects are present, and polymerization proceeds through both radical and cationic mechanisms, resulting in a bimodal molecular weight distribution. We show that these mechanistic intricacies can be sorted out by resorting to the chemical arsenal developed in the last decades for controlled polymerizations. Specifically, we obtained a silicapolystyrene grafted material by cationic grafting from at 30 C, a unimodal molecular weight distribution, and a relatively high molecular weight (Mn ¼ 7.4 kDa) with a PDI of 1.68.