Sol–gel matrix dispersed liquid crystal composite: Influence of methyltriethoxysilane precursor and solvent concentration

Influence of methyltriethoxysilane (Me-TES) concentration on operating voltage and optical transmittance of ormosil dispersed liquid crystal (ODLC) electro-optical films is investigated. The films are prepared using tetraethoxysilane (TEOS) and Me-TES in molar ratios ranging from 1:5 to 5:1, respectively. Possibility to obtain ODLCs without using solvents in the synthesis is demonstrated for the first time. Although some alcohol (approximately 3–4 moles per 1 mole of alkoxide) is created by chemical reactions during ODLC formation, it is shown that generally avoiding solvents in the process results in wider LC droplet size distribution, increased thickness of films, and larger variation of the transmittance. It is also shown that lower operating voltages can be achieved than reported earlier while also using significantly lower concentrations of Me-TES. In addition, a novel approach to avoid cracking of the ODLC films by using polyvinylpyrrolidone (PVP) is introduced.