Paper BI-TuM10
Surface-initiated Vapor Deposition Polymerization of Poly(gamma-benzyl L glutamate): Optimization and Mechanistic Study

Tuesday, November 10, 2009, 11:00 am, Room K

Surface-initiated vapor deposition polymerization (SI-VDP) is a highly effective approach to synthesize grafted polypeptides. In this study, we developed an SI-VDP system having pressure and temperature control to reduce vacuum restriction 1000 times with high grafting efficiency and, thus, were able to synthesize grafted poly(gamma-benzyl L-glutamate)(PBLG) film of 167nm thick under 0.75 mbar. More importantly, we quantitatively investigated mechanistic details of the SI-VDP process including monomer vaporization and reservoir polymerization in the monomer reservoir and monomer condensation and physisorbed and chemisorbed polymerization on the substrate surface. To study the major monomer reservoir processes, we monitored the amount of vaporized monomers and developed a VDP reaction profile (VDPRP) method. We found that the VDPRPs were mostly contributed by the reservoir processes. We also found that characteristic features of the VDPRPs were determined by the monomer heating temperature and proposed possible mechanisms for the feature evolution. To evaluate the major substrate surface processes, we developed a quantitative analysis method using FTIR on both as-deposited PBLGs and chemisorbed PBLGs. Consequently, we were able to propose possible SI-VDP mechanisms leading to the surface-grafted PBLGs that were expected to have either high packing density with mostly α-helix segments or low packing density with a significant amount of both random coil and α-helix segments.