Memory of silica aggregates dispersed in smectic liquid crystals: Effect of the interface properties

Previous studies on nematic liquid crystals containing silica particles ind icated memory effects that might be due to hydrogen bonds between the indiv idual silica particles. We made smectic liquid crystal dispersions containi ng silica particles with various surface properties. Using a neutron scatte ring technique we studied the interfacial surface effects on the structure of the silica aggregates, and on the smectic layer alignment. Our observati ons indicate that the stability of the memory correlates to the number of O H groups on the silica surfaces. The observations imply that. with fine-tun ing of the OH content of the silica surfaces, various types of memory devic es can be designed. We considered three different effects that can memorise the alignment of the liquid crystal. Measurements on tilted SmC phases ind icate that surface effects become important only after repeated heating-coo ling cycles, as the average size of the aggregates decrease.