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Thermally reversible surface morphology transition in thin diblock copolymer films
Xiaohua Zhang1, Kevin G Yager, Nathaniel J Fredin
1Polymers Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA. xiaohua.zhang@nist.gov
ACS Nano
|June 18, 2010
Summary
Surface transitions in block copolymer (BCP) films reveal a shift from spheres to cylinders, distinct from the interior. This discovery is crucial for nanomanufacturing applications.
Area of Science:
- Materials Science
- Polymer Science
- Surface Science
Background:
- Phase transitions in materials can differ at surfaces compared to the bulk.
- Block copolymer (BCP) films are vital for nanomanufacturing due to their self-assembly properties.
Purpose of the Study:
- To investigate surface-specific thermodynamic order-order transitions in thin BCP films.
- To understand the distinct morphologies at the film boundary versus the interior.
Main Methods:
- Utilized atomic force microscopy (AFM) on ion-etched films.
- Employed grazing-incidence small-angle X-ray scattering (GISAXS) on unetched films.
- Studied thin films of poly(styrene-block-methyl methacrylate) (PS-b-PMMA).
Main Results:
- Identified a thermally reversible interfacial transition between sphere-like structures and cylinders in PS-b-PMMA films.
- Confirmed the transition is localized to the film's outer layer, with the interior maintaining a cylinder morphology.
- Demonstrated the transition's independence from film thickness (40-170 nm).
Conclusions:
- Thin BCP films exhibit unique surface ordering phenomena.
- The surface order-order transition is a critical factor in BCP film thermodynamics and dynamics.
- Findings impact the use of BCP films as templates in advanced nanomanufacturing.
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