Elasticity effects on domain coarsening of the lamellar-gyroid transition observed in a nonionic surfactant system

The coarsening process of the gyroid phase of a nonionic surfactant system is investigated by time resolved small angle neutron scattering (SANS) and small angle neutron Laue diffraction techniques. The time evolution of SANS patterns shows anomalous coarsening of the gyroid domains. The observed La ue spot from a gyroid domain becomes elongated along the radial direction w ith the elapse of time and at a certain time the elongated spot is split in to two spots. The results can be interpreted as follows. During the coarsen ing process, mismatch of the lattice orientation at the domain boundary bri ngs strong stress to the gyroid domain, resulting in the distortion of the domain. The stored stress in the domain finally brings splitting of the gyr oid domain. The elastic and fragile nature of the gyroid domains composed o f the "soft matter'' is responsible for the anomalous coarsening. [S1063-65 1X(99)04907-7].