8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

P3.28Fri 911:10-14:00Direct observation of interaction of nanoparticles in anematic LCMiha Skarabot 1 and Igor Musevic 11 Jozef Stefan Institute, Jamova 39, 1000, Ljubljana, SloveniaThe topological properties and interactions of nanocolloids in the nematic liquid crystal 5CBhave been studied [1]. We find that silica particles, surface-functionalized with DMOAP silane,in most cases behave as a dipolar nematic colloids even when their diameter is as small as 125nm, while in few cases they behave as a quadrupolar nematic colloids. Dipolar colloids areself-assembled into linear chains along the nematic director, what is a clear sign of a dipolarcolloid orientation. The 125 nm dipolar colloidal particle is accompanied by a clearly resolvablehyperbolic point defect and behaves hydrodynamically as a much bigger particle because of theelastic distortion around it. We have measured that the diffusion coefficient is proportional tothe inverse diameter of the colloids down to 500 nm, but below this size the diffusion coefficientis practically size independent. This has a surprising consequence that the pair-binding energyof the dipolar nanocolloids is as high as 700 kT for 125 nm colloids and is practically sizeindependentin the range from 125 nm to 500 nm. This is in contrary with previous observationsof nanoparticle interactions [2] and it is a result of the very strong surface anchoring of 5CB onDMOAP-coated silica nanocolloids. A huge colloidal binding energy provides realistic groundfor the realization of complex LC colloidal structures with dimensions from 100 nm to 10 microns.[1] M. Skarabot, and I. Musevic, Soft Matter, 6, 5476, ( 2010).[2] G. M. Koenig, J. J. de Pablo and N. L. Abbot, Langmuir, 25, 13318 (2009).28