Phase behavior of diblock copolymer/star-shaped polymer thin film mixtures. Issue 17 (14th April 2016)

• Record Type: Journal Article
• Authors: Zhao, Junnan; Sakellariou, Georgios; Green, Peter F.
• Is Part Of: Soft matter. Volume 12:Issue 17(2016)
• Page Start: 3849
• Page End: 3853
• Publication Date: 2016-04-14
• Subjects: Soft condensed matter -- Periodicals; 530.413
• DOI: 10.1039/c6sm00627b
• Languages: English
• ISSNs: 1744-683X

Abstract

Abstract : Block copolymer chains form micelles, with poly-2-vinyl pyridine (P2VP) cores and polystyrene (PS) coronae, in the star-polystyrene (SPS) hosts. Entropic effects determine the free surface composition. Abstract : We investigated the phase behavior of thin film, thickness h ≈ 100 nm, mixtures of a polystyrene- b -poly(2-vinylpyridine) (PS- b -P2VP) diblock copolymer with star-shaped polystyrene (SPS) molecules of varying functionalities f, where 4 ≤ f ≤ 64, and molecular weights per arm M arm . The miscibility of the system and the surface composition varied appreciably with M arm and f . For large values of M arm, regardless of f, the miscibility of the system was qualitatively similar to that of linear chain PS/PS- b -P2VP mixtures – the copolymer chains aggregate to form micelles, each composed of an inner P2VP core and PS corona, which preferentially segregate to the free surface. On the other hand, for large f and small M arm, SPS molecules preferentially resided at the free surface. Moreover, blends containing SPS molecules with the highest values of f and lowest values of M arm were phase separated. These observations are rationalized in terms of competing entropic interactions and the dependence of the surface tension of the star-shaped molecules on M arm and f .