Vapor Deposition−Polymerization of α-Amino Acid <i>N</i>-Carboxy Anhydride on the Silicon(100) Native Oxide Surface

Abstract

In this study, we introduce a novel dry process for surface deposition−polymerization of vapor phase α-amino acid N-carboxy anhydride (NCA) from a surface-immobilized initiator layer. In particular, the NCA of γ-benzyl-l-glutamate is initiated from (1-aminopropyl)triethoxysilane-modified silicon(100) native oxide substrates to form poly(γ-benzyl-l-glutamate) (PBLG). The progress of the reaction is monitored by the thickness change measured with ellipsometry, the surface composition is analyzed by X-ray photoelectron spectroscopy, the secondary conformation is characterized by attenuated total reflection Fourier transform infrared spectroscopy, and the surface roughness is examined by atomic force microscopy. Under an optimal reaction condition with temperature from 95 to 125 °C in vacuo, PBLG films of 40 nm thickness have been prepared in 4 h with surface roughness rms within 3.5 nm. All films above 4 nm thickness adopt the α-helical conformation.