Time and energy-efficient homogeneous transesterification of cellulose under mild reaction conditions

In this research, cellulose aliphatic esters (CEs) were synthesized efficiently in an N, N-dimethylacetamide/lithium chloride system (DMAc/LiCl) with vinyl esters (VEs, number of carbon atoms ranging from 4 to 12) as acylation reagent and 1,8-diazabicyclo[5,4,0]undec-7-ene (DBU) as catalyst. The structures and properties of the products have been characterized by various analytical techniques. The key concept in this cellulose modification was the achievement the degree of substitution (DS) >2.75 at much milder temperature and shorter reaction time (under 30 degrees C within 15 min-30 min), other than previous research. Generally, the DS of obtained CEs showed a reverse trend with the length of the aliphatic chain increasing. The priority of reactions in three positions of the CEs followed the same order of C6 > C2 > C3 for a homogeneous conversion. There was no decrease of molecule weight under this mild reaction. This research provides a novel homogeneous technology to synthesize various CEs efficiently. (C) 2016 Elsevier Ltd. All rights reserved.