title: X-ray reflectivity study of ultrathin liquid films of diphenylsiloxane-dimethylsiloxane copolymers.
abstract: Using X-ray reflectivity, we observe drastic differences in the interfacial structure and molecular ordering of diphenylsiloxane-dimethylsiloxane copolymer thin films deposited on hydroxylated versus H-terminated (etched) silicon wafers. We find that substrate type and comonomer ratio determine the conformational arrangements in these liquid films. High-energy bonding between the substrate and the molecules and an increase in rigidity of the molecules due to replacement of methyl groups by phenyl groups leads to a specific molecular ordering at the liquid/solid interface and pronounced density oscillations in this region. The observed structural reorganizations are explained by the interplay and the established balance between the chain flexibility and the polymer-substrate interactions.
authors.affiliation: Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208-3112, USA. g-evmenenko@northwestern.edu
authors.forename: Guennadi
authors.initials: G
authors.lastname: Evmenenko
authors.forename: Haiding
authors.initials: H
authors.lastname: Mo
authors.forename: Sumit
authors.initials: S
authors.lastname: Kewalramani
authors.forename: Pulak
authors.initials: P
authors.lastname: Dutta