Preparation And Study On The Controlled Gel Formation Of Cholesterol-Bridge-Organogels

First: A cholesterol-bridge-naphthopyran dyad, denoted as NP-MCB, wasdesigned and synthesized. NP-MCB can readily self-assemble into gels underultrasound-induced in several organic solvents，also the formed gels transfer tosolution by heat easily. This reversible process can be repeated many times underalternate ultrasound-induced and heat. Scanning Electron Microscopy results showedthe morphologies of all formed xerogels in different solvents were fibrillarmicrostructure. The gels formation was due to energy and pressure afforded by theultrasonic process, resulting in formation of molecular hydrogen bonding andmolecular aggregation. NP-MCB displayed the normal photochromism both insolution and gel states. The kinetic results confirm that the colored merocyanine ingels show a slower fading speed than which in solution due to the compactaggregation of NP-MCB molecules in gels. The xerogel film formed in polar gellingsolvent had large surface wettability than that in nonpolar gelling solvent. Before andafter UV irradiation there were no obvious changes of CAs obtained whichdemonstrated the open-forms of NP-MCB in xerogels were ketene structures.Second：A cholesterol-bridge-benzimidazole dyad (PBI-MCB) was designedand synthesized. PBI-MCB can readily self-assemble into gels under cooling orultrasound-radiation in several organic solvents and the formed gels easily transfer tosolution by heat. This reversible process can be repeated many times. ScanningElectron Microscopy results showed that the morphologies of all formed xerogels indifferent solvents have fibrillar microstructure. The xerogel film formed in polargelling solvent had large surface wettability than that in nonpolar gelling solvent.