Temperature-Triggered Micellization of Block Copolymers on an Ionic Liquid Surface

• Published in: Langmuir Vol. 27; no. 20; pp. 12443 - 12450
• Main Authors: Lu, Haiyun, Akgun, Bulent, Wei, Xinyu, Li, Le, Satija, Sushil K, Russell, Thomas P
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 18-10-2011
• Subjects: Chemistry; Colloidal state and disperse state; Exact sciences and technology; General and physical chemistry; Interfaces: Adsorption, Reactions, Films, Forces; Ionic Liquids - chemistry; Micelles; Micelles. Thin films; Microscopy, Electron, Scanning; Models, Molecular; Polystyrenes - chemistry; Polyvinyls - chemistry; Surface physical chemistry; Surface Properties; Temperature; Film; In situ; Micelle; Neutrons; Nanostructure; Air; Bilayer; Thin film; Ionic liquid; Thickness; Transmission electron microscopy; Morphology; Force microscopy; Styrene polymer; Homopolymer; Block copolymer; Interface; Reflectance; Micellization
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la2024988

In situ neutron reflectivity was used to study thermally induced structural changes of the lamellae-forming polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) block copolymer thin films floating on the surface of an ionic liquid (IL). The IL, 1-butyl-3-methylimidazolium trifluoromethanesulfonate, is a nonsolvent for PS and a temperature-tunable solvent for P2VP, and, as such, micellization can be induced at the air–IL interface by changing the temperature. Transmission electron microscopy and scanning force microscopy were used to investigate the resultant morphologies of the micellar films. It was found that highly ordered nanostructures consisting of spherical micelles with a PS core surrounded by a P2VP corona were produced. In addition, bilayer films of PS homopolymer on top of a PS-b-P2VP layer also underwent micellization with increasing temperature but the micellization was strongly dependent on the thickness of the PS and PS-b-P2VP layers.