Edge dislocations of colloidal chains suspended in a nematic liquid crystal

We report on the formation of edge dislocations in two-dimensional crystals of colloidal chains of particles suspended in a nematic solvent. The syste ms are obtained from a phase separation of a binary mixture composed of a p olymer and a liquid crystal. The colloidal structures are governed by elast ic interactions mediated by the nematic matrix. Since the latter one breaks the rotational invariance symmetry, distortions around dislocations cannot be appropriately described by existing theories. We develop a simple elast ic model which accounts for this symmetry breaking to gain information on f actors governing the chains interaction. We find that rotation and compress ion/dilatation moduli of the chains are of the same order of magnitude. We also calculate the energies of single and pairs of dislocations. The result s should be relevant for other layered systems such as smectics, cholesteri cs and surfactant lamellar phases in the presence of an external field.