Closed-loop phase behaviour in block copolymers

Du Yeol Ryu, Unyong Jeong, Jin Kon Kim, Thomas P. Russell

Research output: Contribution to journalArticle

100 Citations (Scopus)


Closed-loop phase diagrams are known in systems with specific intermolecular interactions. In weakly interacting systems, however, such behaviour has never been observed. Here, diblock copolymers formed from polystyrene covalently linked to poly (n-pentylmethacrylate), P(S-b-nPMA), which have only weak segmental interactions, are shown to exhibit a closed-loop phase behaviour over a narrow range of molecular weight. The endothermic transitions from the disordered to ordered and back to the disordered state, as a function of increasing temperature, are dominantly entropie morigin.The morphology and rheological properties of P(S-b-nPMA) undergo characteristic changes at the transitions. Whereas the disorder-to-order transition temperature increases with decreasing molecular weight, the order-to-disorder transition temperature decreases. At a limiting molecular weight, the closed-loop vanishes and no ordering occurs. These findings provide quantitative insight into an elusive transitionin weakly interacting multi component systems.

Original languageEnglish
Pages (from-to)114-117
Number of pages4
JournalNature materials
Issue number2
Publication statusPublished - 2002 Oct

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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