Preparation And Application Of Polybissilsesquioxane Films With Chiral Liquid Crystal Phase Structure Through A Self-Templating Approach

Bridged polysilsesquioxanes(BPS)has been valued for its simple preparation method,high tunable structure and diverse functions.The exploration of different bridged units provides more possibilities for the preparation of potential applied materials.Liquid crystal(LC)has both the order of crystal and the fluidity of liquid Fixing the orientation structure formed by LC molecules can obtain different functional materials with a good application prospect.The LC unit and inorganic component were connected by C-Si bond,and the bridged sesquisiloxanes containing LC unit could be self-assembled to prepare LC phase structure BPS after the orderly orientation was formedBased on the preparation of BPS materials through a self-templating approach of our research group,our work is shown as follows:Firstly,four bridged sesquisiloxane monomers containing different LC units and a chiral dopant centered on isosorbide have been designed and synthsized.The synthesis of target monomers can achieve through the hydrosilylation reaction of LC compound with double bond at both ends.Chiral dopant is used to induce the generation of chiral nematic phaseSecondly,sesquisiloxane monomers were tested by polarizing microscope(POM)and differential scanning calorimeter(DSC).It was found that two kinds of sesquisiloxanes(Bola-1 and Bola-2)were nematic LCThirdly,the chiral nematic phase was induced by mixing CD-iso with nematic phase LC Bola-1.After the molecules self-assemble into helical structure,the BPS film with chiral nematic structure was obtained by hydrolyzing and crosslinking of sesquisiloxane without any templates.The morphology and optical properties of the films were characterized,it was found that the material would change color when i??ersed in solvent.Therefore,it can be used as sensors for organic solvent.Finally,CD-iso was mixed with nematic phase LC Bola-2 to induce the generation of chiral nematic phase.The preliminary study showed that the system presented red,green and blue reflection colors with the decrease of temperature at a single concentration of chiral dopant.The cause of its formation and the structure of chiral self-assembly need to be further explored.