Organic gels prepared from side-chain liquid crystalline polymers without the spacer

A series of side-chain liquid crystal polymers (SCLCPs) without the spacer, named poly[-(4-n-alkyl oxybiphenyl-4-oxy)methacrylate (PMBiCm, m=1, 2, 4, 6, 8, 10, 12, 14, 16, and 18), have been synthesized. The novel polymer organogels were prepared by introducing PMBiCm into common organic solvents. Solubility and gel properties of polymer organogelators differ widely according to the nature of the solvents. In aromatic solvents, PMBiCm completely dissolved in solvent due to good compatibility between biphenyl mesogen group and aromatic solvents. Poly[-(4-n-alkyl oxybiphenyl-4-oxy)methacrylate were still insoluble in polar solvents such as acetone, ethanol, DMF, ethylene glycol, and n-butanol. This behavior resulted from mismatch of solubility parameter between PMBiCm and solvent. Considering the factors of solvent, we have systematically studied 3 organic solvents with different polarities (butyl acetate, n-butyl amine, and n-heptane). It is found that the length of the alkoxy tail chain of the SCLCPs has significant influence on gelability and gel thermal stability. In further studies discussed by UV-Vis spectroscopy, the results revealed that the - stacking interaction of the biphenyl mesogens might be the key factor for guiding the self-assembly processes and the polymer gel formation. This work is useful to comprehending physical mechanism of polymer organogels. Meanwhile, those expand SCLCPs to a wide range of applications.