title: Molecular ordering in monolayers of an alkyl-substituted perylene-bisimide dye by attenuated total reflectance ultraviolet-visible spectroscopy.
abstract: Surface-relative orientational parameters were determined for monolayer films of N, N'-ditridecylperylenetetracarboxylic dianhydridediimide (C13-PTCDI) in terms of the relative electronic transition dipole strengths, providing a three-dimensional view of the absorption dipole distribution. In order to obtain a macroscopically ordered film, C13-PTCDI was deposited by (1) horizontal Lang-muir-Blodgett (LB) transfer onto methyl- and phenyl-silanized glass, and (2) vapor deposition onto oriented films of poly(tetrafluoroethylene) (PTFE) on glass. Films of LB-deposited C13-PTCDI were found to be completely isotropic prior to annealing. After annealing, these films remained isotropic in the plane of the substrate while the out-of-plane anisotropy was significantly enhanced. In contrast, films of C13-PTCDI vapor deposited onto oriented poly(tetrafluoroethylene) (PTFE)-modified substrates yielded films with a high degree of both in- and out-of-plane anisotropy. Atomic force microscopy (AFM) images of both the LB- and vapor-deposited films show substantial differences in film morphology and long-range order. These results demonstrate that molecular orientation in C13-PTCDI films can be controlled by varying substrate surface chemistry and post-deposition processing.
authors.affiliation: Department of Chemistry, University of Arizona, Tucson, Arizona 85721, USA.
authors.forename: Walter J
authors.initials: WJ
authors.lastname: Doherty
authors.forename: Adam G
authors.initials: AG
authors.lastname: Simmonds
authors.forename: Sergio B
authors.initials: SB
authors.lastname: Mendes
authors.forename: Neal R
authors.initials: NR
authors.lastname: Armstrong
authors.forename: S Scott
authors.initials: SS
authors.lastname: Saavedra