University of Connecticut |
Polymer Program SeminarNovel Nanostructures in the Self-Assembly of Chiral Block Copolymers Friday, September 1, 2006 11:00 am , IMS Room 20 Chirality driven microphase-separated morphology with helical sense such as PLLA nanohelices hexagonally packed in PS matrix was obtained from chiral diblock copolymers, poly(styrene)-b-poly(L-lactide). This is perhaps for the first time; superstructures with helical sense in self-assembly of chiral block copolymers were generated in the bulk and self-assemble to a two-dimensionally packed lattice. Now, the analyses of block copolymer thermodynamics should be complicated by the chiral entities of constituted components. Orderly packed nanohelical channels can be obtained after hydrolysis, and this provides new opportunities for block copolymer applications in the fields of nano-sciences. Also, the nanohelical structure appears as spring-like behavior in response to the applied stimulations. The self-assembled nanohelices can be transformed into crystallization- and shear-induced cylinders. The stress-induced cylinders were found thermally reversible and able to revert to original nanohelices upon annealing through undulation. This unique phase behavior thus creates a possible way for manipulating switchable nanohelical structures in practical applications.
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