Order–disorder transition in thin films of horizontally-oriented cylinder-forming block copolymers: thermal fluctuations vs. preferential wetting. Issue 27 (23rd June 2016)

• Record Type: Journal Article
• Authors: Kim, Sangwon; Li, Wei; Fredrickson, Glenn H.; Hawker, Craig J.; Kramer, Edward J.
• Is Part Of: Soft matter. Volume 12:Issue 27(2016)
• Page Start: 5915
• Page End: 5925
• Publication Date: 2016-06-23
• Subjects: Soft condensed matter -- Periodicals; 530.413
• DOI: 10.1039/c6sm00739b
• Languages: English
• ISSNs: 1744-683X

Abstract

Abstract : We present experimental and theoretical investigations of the order–disorder transition (ODT) in thin films of cylinder-forming diblock copolymers with asymmetric wetting conditions. Abstract : We present experimental and theoretical investigations of the order–disorder transition (ODT) in thin films of cylinder-forming diblock copolymers with asymmetric wetting conditions. Grazing incidence small-angle X-ray scattering (GISAXS) was implemented to determine the ODT temperatures ( T ODT ) for poly(styrene- b -2-vinyl pyridine) (PS-P2VP) block copolymer thin films on a P2VP-preferential silicon substrate. Specifically, films consisting of multilayers of horizontally-oriented cylindrical structures (from 1- to 9-layers) were tested. We find that films with more than 2 cylindrical layers have a T ODT comparable to the bulk case. However, T ODT decreases as the film becomes thinner and the monolayer system has an ODT 30 °C below the bulk. Using self-consistent field theory (SCFT), we studied the ordering in corresponding thin films with asymmetric (top and bottom surface) wetting conditions. Surprisingly, SCFT is found to predict an opposite trend in T ODT with film thickness than observed experimentally. Field-theoretic simulations with complex Langevin sampling were employed to resolve this discrepancy and demonstrate that thermal fluctuations in the PS-P2VP thin-film system dominate its ordering behavior in monolayer and bilayer films.