期刊
ACS NANO
卷 15, 期 6, 页码 9577-9587出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsnano.0c09907
关键词
block copolymer; interfaces; soft X-rays; reflectivity; adsorption
类别
资金
- Center for Hierachical Materials Design (CHiMaD)
- Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy [DE-AC02-05CH11231]
The study investigates how interactions between the substrate and block copolymers (BCPs) with varying substrate affinity affect the interfacial width between polymer components. The results show that strong adsorption of P2VP to the substrate significantly expands the interface width, while the PMMA block appears to be more mobile.
Interactions between polymers and surfaces can be used to influence properties including mechanical performance in nanocomposites, the glass transition temperature, and the orientation of thin film block copolymers (BCPs). In this work we investigate how specific interactions between the substrate and BCPs with varying substrate affinity impact the interfacial width between polymer components. The interface width is generally assumed to be a function of the BCP properties and independent of the surface affinity or substrate proximity. Using resonant soft X-ray reflectivity the optical constants of the film can be controlled by changing the incident energy, thereby varying the depth sensitivity of the measurement. Resonant soft X-ray reflectivity measurements were conducted on films of polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) and PS-b-poly(methyl methacrylate) (PS-b-PMMA), where the thickness of the film was varied from half the periodicity (L-0) of the BCP to 5.5 L-0. The results of this measurement on the PS-b-P2VP films show a significant expansion of the interface width immediately adjacent to the surface. This is likely caused by the strong adsorption of P2VP to the substrate, which constrains the mobility of the junction points, preventing them from reaching their equilibrium distribution and expanding the observed interface width. The interface width decays toward equilibrium moving away from the substrate, with the decay rate being a function of film thickness below a critical limit. The PMMA block appears to be more mobile, and the BCP interfaces near the substrate match their equilibrium value.
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