MATERIALS SCIENCE: Pushing Polymers Around

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Science  27 Oct 2006:
Vol. 314, Issue 5799, pp. 566c
DOI: 10.1126/science.314.5799.566c

Block copolymers self-assemble into intricately patterned structures because of the tendency for the chemically distinct blocks to segregate. Patterns can be tuned by changing the lengths and interactive properties of the two polymer segments or by adding another component to the mix.

Laiho et al. explore the effects of adding fullerene (C60) molecules to a diblock copolymer of polystyrene (PS) and poly(4-vinylpyridine) (P4VP) dissolved in xylene. At the chosen block lengths, the polymer alone formed a PS matrix containing hexagonally ordered P4VP cylinders. Initially, added C60 was sequestered in the PS domain, as observed in solution by optical spectroscopy. This localization was mirrored in the morphology of cast films as a reduced abundance of cylinders, indicating that the PS had been swollen by dissolution of C60. However, when the solutions were aged, they underwent the same purple-to-brown color change observed in aging pyridine solutions of C60, consistent with the formation of charge transfer complexes between C60 and the electron-donating pyridyl fragments of the P4VP domains. In films cast from these solutions, the P4VP morphology shifted from cylindrical to spherical. The authors suggest that charge transfer complexation is thus a potentially useful tool in designing self-assembled morphologies. — MSL

Macromolecules 39, 10.1021/ma061165g (2006).

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