title: Surface structure relaxation of poly(methyl methacrylate).
abstract: Surface structure relaxations caused by temperature changes at the free surface of poly(methyl methacrylate) were studied using IR-visible sum-frequency generation (SFG). A polarization-rotating technique was introduced to enhance the sensitivity of SFG for monitoring the surface structure relaxations during a cooling process. A new surface structure relaxation was observed at 67 degrees C. This temperature does not match any known structure relaxation temperatures for the bulk and is 40 degrees C below the bulk glass transition temperature. As expected for a free-surface phenomenon, the surface relaxation temperature was found to be independent of film thickness in the range of 0.1-0.5 microm.
authors.affiliation: Department of Chemistry, University of British Columbia, Vancouver, BC V6T 1Z1, Canada.
authors.forename: Qifeng
authors.initials: Q
authors.lastname: Li
authors.forename: Rui
authors.initials: R
authors.lastname: Hua
authors.forename: Ignatius J
authors.initials: IJ
authors.lastname: Cheah
authors.forename: Keng C
authors.initials: KC
authors.lastname: Chou