### Abstract

Fluctuations of lamellar structure prior to a [Formula Presented] transition in a nonionic surfactant–water system has been investigated by means of small-angle x-ray scattering (SAXS) and differential scanning calorimeter measurements. For large [Formula Presented] [Formula Presented] where T is the temperature and [Formula Presented] the [Formula Presented] transition temperature) in the lamellar phase, the SAXS profiles can be described by a Caillé correlation function for undulating lamellar structure. Approaching the temperature to the [Formula Presented] an excess diffuse scattering grows at the lower Q (Q is the magnitude of scattering vector) side of the first lamellar peak. Highly oriented lamellar samples revealed that the excess diffuse scattering arises from in-plane density fluctuations. We attribute this diffuse scattering to the perforation fluctuation layer (PFL) structure and we show that the PFL is an equilibrium structure. At [Formula Presented] the PFL transformed to the gyroid phase through a transient ordered structure having a rhombohedral symmetry.

Original language | English |
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Pages (from-to) | 6865-6874 |

Number of pages | 10 |

Journal | Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics |

Volume | 62 |

Issue number | 5 |

DOIs | |

Publication status | Published - 2000 Jan 1 |

Externally published | Yes |

### ASJC Scopus subject areas

- Statistical and Nonlinear Physics
- Mathematical Physics
- Condensed Matter Physics
- Physics and Astronomy(all)

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## Cite this

*Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics*,

*62*(5), 6865-6874. https://doi.org/10.1103/PhysRevE.62.6865