Comparative study on structure and properties of cellulose acetate synthesized by homogeneous and heterogeneous acetylation

The structure and properties of cellulose acetate (CA) prepared by homogeneous acetylation in ionic liquids (CA_Homo) and heterogeneous acetylation (CA_Hete) were investigated. The characterizations of CAs such as molecular weight, molecular weight distribution, degree of substitution (DS), distribution of acetyl groups and the partial DS at C-2, C-3 and C-6 were determined by GPC, ¹H- and ¹³C-NMR. The DS of CA_Homo and CA_Hete was about 2. 50 calculated by ¹H-NMR. The distribution of acetyl groups calculated by ¹³C-NMR was C-6 > C-3 > C-2 for CA_Homo and C-3 > C-2 > C-6 for CA_Hete, respectively. In addition, the structure of CA_Homo had better uniformity than that of CA_Hete. Subsequent property studies showed that the chemical structure differences of CAs had tiny effect on their properties, such as crystallinity, solubility and thermal properties. CA_Homo and CA_Hete were all amorphous structure, and they had better solubility in polar organic solvents. The glass transition temperature and thermal stability were similar for these CAs samples. Therefore, CA_Homo synthesized by homogeneous acetylation in ionic liquids had similar physical properties as those of CA_Hete prepared by heterogeneous acetylation, but the structure of CA_Homo had better uniformity than that of CA_Hete.