Grafting density of oligo-bottle-brushes on silicon surface: effect of mole fraction of RAFT agent-functionalized alkenes in mixed self-assembled monolayers

The purpose of the study is to prepare of novel oligo-(N-(2-hydroxypropyl) methacrylamide)-g-poly(lactic acid) bottle-brushes with different grafting density on the silicon surface. Firstly, the mixtures of 9-decen-1-ol (DO, functional interconnection molecule) and 1-undecene (UD) molecules were attached to the hydrogen-terminated silicon surface by UV irradiation under molecular self-assembly conditions. Secondary, 4-cyano-4-(propylsulfanylthiocarbonyl) sulfanylpentanoic acid RAFT agent was immobilized onto DO molecules by ester reaction, followed by the interface-mediated RAFT polymerization of pre-synthesized N-[(2-hydroxypropyl) methacrylamide]-g-poly(lactic acid) macromonomer. The systematic control of the RAFT agent-functionalized alkene concentration afforded by the mixed self-assembled monolayers on the silicon surface enabled the grafting density and the average distance between grafting points of the polymer chains to independently control. The phase image taken with atomic force microscopy has shown that the silicon surfaces were coated with the bottle-brushes.