RAFT GRAFTING POLYMERIZATION OF MMA/St FROM SURFACE OF SILICON WAFER

Abstract

Polystyrene(PSt),polymethylmethacrylate(PMMA) and copolymers(poly(MMA-co-St)) were grafted from silicon wafer via RAFT agent that was anchored to the surface.X-ray photoelectron spectroscopy showed that while the polymers were successfully grafted,the control of polymer molecular weight(MW) behaved very differently.The Si-PMMA system yielded MW much higher than the theoretically targeted,broad molecular weight distribution and low grafting density(ca.0.03 chains/nm2).In contrast,the Si-PSt system gave MW close to the theoretical value with polydispersities around 1.3.The grafting density increased to 0.21 chains/nm2.In Si-poly(MMA-co-St) system,the polymer layer thickness increased linearly with monomer conversion and molecular weight of free polymer in solution,suggesting that the RAFT copolymerization grafting of MMA and St from silicon wafer was well controlled.The MW was close to the theoretical value.The grafting density reached 0.31 chains/nm2,which was higher than those obtained in their homo-polymerizations.