Effects of polydispersity on the order-disorder transition in block copolymer melts

Nathaniel A. Lynd, Marc A. Hillmyer

Research output: Contribution to journalArticlepeer-review

110 Scopus citations

Abstract

We prepared controlled-polydispersity poly(ethylene-alt-propylene)-b- poly(DL-lactide) (PL) and polystyrene-b-polyisoprene (SI) block copolymers to study the effects of the molecular weight distribution on the order-disorder transition at controlled composition and overall molecular weight. Small-angle X-ray scattering and rheological measurements were carried out to characterize the changes in the order-disorder transition in these self-assembled materials as a function of their composition and polydispersity index. We determined that in both asymmetric PL and SI systems increasing polydispersity in the minority component resulted in a decrease in the segregation strength at the order-disorder transition, whereas increasing polydispersity in the majority component results in an increase in the segregation strength at the order-disorder transition. We speculate that increasing PDI in the majority domain weakens the effective potential holding the phase-separated microdomains ordered on a lattice.

Original languageEnglish (US)
Pages (from-to)8050-8055
Number of pages6
JournalMacromolecules
Volume40
Issue number22
DOIs
StatePublished - Oct 30 2007

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