Absence of the nematic phase in symmetric diblock copolymers

David C. Morse, Scott T. Milner

Research output: Contribution to journalArticlepeer-review

18 Scopus citations


We examine the possibility of nematic order in systems described by the Brazovskii model [Sov. Phys. JETP 41, 85 (1975)] of the isotropic-lamellar phase transition, including symmetric diblock copolymer melts and bilayer-forming surfactant systems. We introduce a nematic order parameter and look for states that break rotational symmetry that is, which have a well-defined direction for interfacial normals, but no phase coherence between interfaces. We find an isotropic-nematic phase transition, but it is always precluded by an isotropic-lamellar phase transition occurring at higher temperature. We show that the lamellar phase is stable to dislocation-mediated melting to a nematic phase in the limit of long copolymer chains, even though the isotropic-lamellar phase transition becomes second order in this limit.

Original languageEnglish (US)
Pages (from-to)1119-1125
Number of pages7
JournalPhysical Review E
Issue number2
StatePublished - 1993


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