ATRP grafting of oligo(ethylene glycol) methacrylates from gold surface - Effect of monomer size on grafted chain and EO unit densities

摘要

Oligo(ethylene glycol) methacrylate (OEGMA) was grafted from Au surface via surface-initiated atom-transfer radical polymerization (s-ATRP). The initiator density was adjusted by the mole fractions of surface-attachable ATRP initiator and diluting agent. Three OEGMA monomers of M_r 300, 475, and 1100 were used. The Au surfaces before and after modification were characterized by water contact angle and ellipsometry. The effect of monomer M_r and initiator density on surface chain density and EO unit density was investigated. It was found that at low initiator density (mole fraction of initiator of 2%-5%), poly(OEGMA) grafts had comparable surface chain density independent of OEGMA M_r. However, at high initiator density (mole fraction of initiator >10%), poly(OEGMA)noo had obviously lower chain densities than poly(OEGMA)3oo and poly(OEGMA)475, which could be attributed to the size difference of the monomers. The short chain length and low surface chain density of poly(OEGMA)noo resulted in its relatively low surface EO unit density.