Synthesis and characterization of hydroxyethyl chitosan grafted by carboxyl ending DOVOB dendrimer: A novel liquid crystalline polymer

A novel chitosan derivative, hydroxyethyl chitosan grafted 3,4,5-tris[p-(n-dodecyloxy)-m-methoxybenzyloxy]benzoate (HECS-g-DOVOB) was prepared via grafting dendrimer 3,4,5-tris[p-(n-dodecyloxy)-m-methoxybenzyloxy]benzoic acid (DOVOB acid) onto hydroxyethyl chitosan (HECS). The structure of HECS-g-DOVOB was investigated by means of FTIR, 1H NMR, UV and circular dichroism (CD). The degree of substitution was measured to be about 0.39 per glucose unit. The DOVOB acid was able to self-assemble into a thermotropic hexagonal columnar liquid crystalline phase showing fan-like texture, the aqueous HECS solution formed lyotropic cholesteric liquid crystal showing fingerprint texture. Whereas, HECS-g-DOVOB formed lyotropic cholesteric liquid crystal in concentrated DMSO solution with a planar texture, which was different to that of both DOVOB and HECS. The cholesteric pitch of HECS-g-DOVOB is much smaller than that of HECS. The fluorescence spectrum of HECS-g-DOVOB shows excimer fluorescence which is very similar to the dendrimer is a good indication for light-emitting polymeric material.