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 language | English (US) |
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Pages (from-to) | 8050-8055 |
Number of pages | 6 |
Journal | Macromolecules |
Volume | 40 |
Issue number | 22 |
DOIs | |
State | Published - Oct 30 2007 |