Preparation, characterization and novel photoregulated rheological properties of azobenzene functionalized cellulose derivatives and their α-CD complexes

Novel azobenzene functionalized hydroxypropyl methylcellulose (AZO-HPMC) polymers and their α-CD (α-Cyclodextrin) complexes have been prepared. FT-IR, 1H NMR and FT-Raman spectroscopy confirm the existence of azobenzene chromophores in AZO-HPMC polymers. α-CD can improve the water solubility of AZO-HPMC by formation of inclusion complexes with azobenzene side groups. Rheological studies substantiate that both AZO-HPMC and its α-CD complex undergo thermoreversible sol–gel transitions in aqueous solutions. Viscometric measurements suggest that the association between azobenzene side groups can be eliminated by α-CD. The effect of photoirradiation on the rheological behavior shows that the gelation temperature of AZO-HPMC increases after UV irradiation, while the gelation temperature of AZO-HPMC/α-CD complex decreases after UV irradiation. [Copyright &y& Elsevier]