title: Cross-linking-induced permanently perpendicular helix orientation in surface-grafted polyglutamate films.
abstract: Using a chemical cross-linking procedure, surface-grafted polyglutamate films with a permanently perpendicular helix orientation were prepared. A surface-grafted alpha-helical polyglutamate film containing polymerizable side groups was synthesized by ring-opening terpolymerization of 50 molar% gamma-methyl-L-glutamate N-carboxyanhydride (NCA), 30% gamma-stearyl-L-glutamate NCA and 20% gamma-4-vinylbenzyl-L-glutamate NCA initiated from a silicon substrate functionalized with primary amino groups. The average tilt angle of the end-grafted helices in this film is approximately 66 degrees , indicating a nearly parallel helix orientation with respect to the substrate surface. After swelling of the grafted terpolyglutamate film in stearyl methacrylate and subsequent radical cross-linking, the average helix tilt angle decreases to about 11 degrees, indicating an almost perpendicular helix orientation. The film thickness increases accordingly from 151 A before to approximately 390 A after cross-linking. Extensive solvent treatment of the cross-linked film shows that the perpendicular helix orientation is permanent.
authors.affiliation: Department of Polymer Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands.
authors.forename: Jeroen
authors.initials: J
authors.lastname: Luijten
authors.forename: Daan Y
authors.initials: DY
authors.lastname: Groeneveld
authors.forename: Gerard W
authors.initials: GW
authors.lastname: Nijboer
authors.forename: Eltjo J
authors.initials: EJ
authors.lastname: Vorenkamp
authors.forename: Arend J
authors.initials: AJ
authors.lastname: Schouten