Self-Initiated Free Radical Grafting of Styrene Homo- and Copolymers onto Functionalized Graphene

Herein we report on the solvent-free free radical grafting of styrene homo- and copolymers onto functionalized graphene nanosheets without requiring initiator addition. The key intermediate is an organophilic stearylamine-modified graphite oxide (Stearyl-GO), containing both olefinic unsaturation and stable graphene radicals. According to the online tracking of the C-centered graphene radicals by time-resolved EPR spectroscopy, the graphene radical concentration markedly increases during the early stage of polymerization and is depleted as the viscosity builds up with progressing styrene conversion. “Grafting-to” by addition of polystyrene radicals to graphene and “grafting-from” by graphene-initiated free radical polymerization afford high graft yields, as determined by ultracentrifugal separation of polystyrene-grafted functionalized graphene (PS-g-FG) from the styrene homopolymer byproduct. The addition of TEMPO enables control of the further grafting yields by a controlled radical “grafting-from” poly...