The synthesis of multifunctional cellulose graft alternating copolymers of 3,4-dihydrocoumarin and epoxides in DBU/DMSO/CO2 solvent system

Abstract

Cellulose graft copolymers having well-defined structures could incorporate the characteristics of both the cellulose skeleton and side chains, providing a new method for the preparation functionalised cellulose derivatives. Herein, a series of multifunctional cellulose grafted, alternating 3,4-dihydrocoumarin (DHC) and epoxide (EPO) copolymers (cell-g-P(DHC-alt-EPO)) were prepared in a metal-free DBU/DMSO/CO2 solvent system without adding additional catalyst. Four examples of cell-g-P(DHC-alt-EPO) with tunable thermal and optical properties were synthesized by copolymerization of DHC with styrene oxide (SO), propylene oxide (PO), cyclohexene oxide (CHO) or furfuryl glycidyl ether (FGE) onto cellulose. The nonconjugated cell-g-P(DHC-alt-EPO) showed UV absorption properties with the maximum absorption peak at 282 nm and 295 nm and photoluminescence performance. A clustering-triggered emission mechanism was confirmed and consistent with DFT theoretical calculations. In DMSO solution, the copolymer (DHCSO5) with DP of 11.64 showed ACQ behaviour as the concentration increased. In addition, DHCSO5 had good antioxidant capacity with an instantaneous radical scavenging activity of 2,2-diphenyl-1-picrylhydrazine (DPPH) up to 65 % at a concentration of 40 mg/ ml and increased to 100 % after 30 min. Thus, the multifunctional cell-g-P(DHC-alt-EPO) materials had a variety of potential applications in the fields of fluorescent printing, bio-imaging, UV- shielding and antioxidants.