Poly(γ-benzyl-L-glutamate) Peptides Confined to Nanoporous Alumina: Pore Diameter Dependence of Self-Assembly and Segmental Dynamics

Nanorods consisting of the polypeptide poly(γ-benzyl-L-glutamate) (PBLG) were synthesized in nanoporous anodic aluminum oxide (AAO) hard templates with pore diameters ranging from 25 to 400 nm. The AAO was immersed in a 1 vol % solution of dried and distilled 3-aminopropyltriethoxysilane (APTES) in anhydrous ethanol for 6 h, rinsed with anhydrous ethanol, sonicated, and finally baked at 120°C under argon for 20 min. The polymerization of the infiltrated BLG-NCA into the pores of the AAO proceeded overnight at 110°C under vacuum (1-2 mbar). After the removal of residual material from the top surface of the AAO with sharp blades, the samples were again heated to 100°C under vacuum for 3 days. A distinct change of the dynamic behavior rather than a gradually increasing interphase contribution was observed. The temperature dependence of segmental dynamics became significantly weaker than in case of bulk PBLG, and the effective glass temperature was reduced by as much as 50 K.