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Indexed by:期刊论文

Date of Publication:2017-10-11

Journal:ACS APPLIED MATERIALS & INTERFACES

Included Journals:Scopus、SCIE、EI

Volume:9

Issue:40

Page Number:35349-35359

ISSN No.:1944-8244

Key Words:confinement effects; hydrophobicity; hydrophilicity; jump percolation

Abstract:We report a first-order like sharp surface wettability transition with varying film thickness dependent morphology in cast films of an amphiphilic triblock copolymer. Films composed of poly(2-(N-ethylperfluorooctanesulfonamido) ethyl methyl acrylate), poly(FOSM), and poly(N,N'-dirnethyl acrylamide), poly(DMA), with thickness (h) in the transition-range, 200 < h < 300 nm, exhibited an abrupt hydrophobic to hydrophilic dynamic water contact angle transition. After an induction time, t(i) approximate to 40 to 180 s, water contact angle varied as theta(c) approximate to 116 degrees to 40 degrees with an ultrafast contact angle decay time constant, d theta(c)/dt approximate to -18 degrees/s. This behavior is a result of competing heterogeneous and antagonistic effects of bumpy poly(DMA) wetting domains against a nonwetting planar poly(FOSM) background, with a "jump percolation" wetting transition when the poly(DMA) domain density reaches unity. Outside of this film thickness range, relatively shallow decreasing water contact angle gradients were observed with a monotonically increasing poly(DMA) domain area coverage with increasing film thickness in the overall range of 40 nm (hydrophobic, theta(c) approximate to 118 degrees) < h < 500 nm (hydrophilic, theta(c) approximate to 8 degrees). The optical diffuse reflectance properties of these rough surfaces exhibit an onset of diffuse reflectance maxima correlated to the transition morphology film thickness.