Reversible Addition−Fragmentation Transfer Polymerization in Nanosized Micelles Formed in Situ

Abstract

The reversible addition−fragmentation transfer (RAFT) polymerizations of 4-vinylpyridine (4VP) in tetrahydrofuran (THF) and in cyclohexane with RAFT agent, dithiobenzoate-terminated polystyrene (PS−SC(S)Ph), involve one polymerization rate (Rp = 0.083 mol L-1 h-1) and two stages of polymerization (Rp = 0.164 and 0.0024 mol L-1 h-1 before and after 5 h), respectively. The polymerization of 4VP and divinylbenzene (less than 10% relative to 4VP) in THF led to gelation, but the polymerization in cyclohexane displayed clear solution consistently throughout polymerization, and kinetic studies showed sudden decrease of polymerization rate and sharp increase of molecular weight at around 5 h. Polymerization was followed by gel permeation chromatography (GPC) and the combination of GPC and multiangle laser light scattering (MALLS). The results show the formation of micelles with PS as shell and poly(PVP-co-DVB) as core by microphase separation; the micelles' size increased fast around 5 h polymerization, and then ...