Session B44: Physics of Copolymers I

11:15 AM–2:15 PM, Monday, March 21, 2011
Room: A309

Sponsoring Unit: DPOLY
Chair: Darrin Pochan, University of Delaware

Abstract ID: BAPS.2011.MAR.B44.2

Abstract: B44.00002 : Microphase Separation in Block-Random Copolymers of Styrene and Hydrogenated Isoprene

11:51 AM–12:03 PM

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  Bryan S. Beckingham
    (Princeton Univesity)

  Richard A. Register
    (Princeton University)

The capacity to synthesize block-random copolymers, which are block copolymers with one or more random copolymer blocks, allows for continuous tuning of the interblock segregation strength, $\chi $, through the composition of the random copolymer. The ability to tune $\chi $ effectively decouples the block copolymer molecular weight from its order-disorder transition temperature. By lithium-initiated anionic polymerization with added triethylamine, we synthesize near-monodisperse and near-symmetric block-random copolymers of styrene and isoprene: PI-PSrI (50{\%} wt. styrene). In comparison to PS-PI diblock copolymers, the number of unfavorable segmental contacts in the disordered state is decreased and hence the effective interblock $\chi $ is reduced. Isoprene-hydrogenated derivatives of these block-random copolymers exhibit microphase separation into well-ordered lamellae and display sharp thermally-induced order-disorder transitions via small-angle x-ray scattering. The observed reduction in $\chi $, as gauged by the molecular weight required to achieve a desired T$_{ODT}$, matches well with the mean field prediction.

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