Tuning block copolymer phase behavior with a selectively associating homopolymer additive |
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Authors: | August W Bosse Vijay R Tirumala Eric K Lin |
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Institution: | Polymers Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 |
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Abstract: | We use polymer random phase approximation (RPA) theory to calculate the microphase separation transition (MST) spinodal for an AB + C diblock copolymer–homopolymer blend where the C homopolymers are strongly attracted to the A segment of the copolymers. Our calculations indicate that one can shift the MST spinodal value of the A ? B segmental interaction parameter (χABN)S to significantly lower values i.e., (χABN)S < 10.5] upon the addition of a selectively attractive C homopolymer. For a sufficiently attractive C homopolymer, (χABN)S can be pushed to negative values, indicating microphase separation in what would appear to be a completely miscible diblock copolymer. Furthermore, we show that microphase separation can occur in diblock copolymer–homopolymer blends where the segmental interactions between all polymer constituents are attractive. By tuning the value of (χABN)S with a homopolymer additive, one is therefore able to tune the effective copolymer segregation strength and thus dramatically affect the blend phase behavior. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2083–2090, 2009 |
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Keywords: | blends block copolymers diblock copolymers modeling phase behavior phase diagrams phase separation theory |
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