title: Highly oriented tunable wrinkling in polymer bilayer films confined with a soft mold induced by water vapor.
abstract: The authors report the formation of highly oriented wrinkling on the surface of the bilayer [polystyrene (PS)/poly(vinyl pyrrolidone) (PVP)] confined by a polydimethylsiloxane (PDMS) mold in a water vapor environment. When PVP is subjected to water vapor, the polymer loses its mechanical rigidity and changes to a viscous state, which leads to a dramatic change in Young's modulus. This change generates the amount of strain in the bilayer to induce the wrinkling. With a shape-controlled mold, they can get the ordered wrinkles perfectly perpendicular or leaned 45 degrees to the channel orientation of the mold because the orientation of the resultant force changes with the process of water diffusion which drives the surface to form the wrinkling. Additionally, they can get much smaller wrinkles than the stripe spacing of PDMS mold about one order. The wrinkle period changes with the power index of about 0.5 for various values of the multiplication product of the film thicknesses of the two layers, namely, lambda approximately (h(PS)h(PVP))(1/2).
authors.affiliation: College of Chemistry, Jilin University, 1788 Linyuan Road, Changchun 130012, People's Republic of China.
authors.forename: Weixian
authors.initials: W
authors.lastname: Qian
authors.forename: Rubo
authors.initials: R
authors.lastname: Xing
authors.forename: Xinhong
authors.initials: X
authors.lastname: Yu
authors.forename: Xinjun
authors.initials: X
authors.lastname: Quan
authors.forename: Yanchun
authors.initials: Y
authors.lastname: Han