Preparation and property of liquid crystalline slide-ring gels

The slide-ring gels formed by crosslinking of polyrotaxane (PR) composed of polyethylene glycol and α-cyclodextrin (α-CD) have sliding crosslinks. The gels show good properties in tensibility and strength compared to conventional chemical and physical gels. On the other hand, liquid crystalline gels are hybrid materials having both properties of gels and liquid crystals (LCs). In this study, LC-PR and their crosslinked product of LC slide-ring gels were prepared by introducing cyanobiphenyl (CNBP) groups into the α-CDs of PR. The PR substituted by CNBP through alkyl chain exhibits LC phase. The phase transition behavior of the LC-PR was observed by polarized optical microscope. Schlieren texture, typical for nematic phase, was observed at room temperature under crossed polarizers. The nematic to isotropic phase transition was observed with increasing temperature. Interestingly, the LC-PR dissolved in a low molecular weight nematic LC, 4-cyano-4′-pentylbipheny, and the solution formed a slide-ring gel by adding a crosslinking reagent.