NOVEL CELLULOSE DERIVATIVES .4. PREPARATION AND THERMAL-ANALYSIS OF WAXY ESTERS OF CELLULOSE

Cellulose esters with linear aliphatic acyl substituents ranging in si ze from C-12 (lauric acid) to C-20 (eicosanoic acid) were prepared in homogeneous solution (DMAc/LiCl) using a novel synthetic method based on the use of a mixed p-toluenesulfonic/carboxylic acid anhydride. The resulting waxy cellulose esters had a high degree of substitution (DS ), between 2.8 and 2.9, and showed little degradation. Thermal analysi s of these cellulose derivatives by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) revealed a series of transitions that represented motion by both ester substituents and cellulosic main chain. Broad crystallization and melting transitions attributed to side-chain crystallinity were observed in the range betw een -19 and +55 degrees C; these side-chain T-m and T-c transition tem peratures increased by 10 degrees C per carbon atom of the ester subst ituent. The T,of these derivatives increased linearly with increasing substituent size from 94 degrees C for C-12 (cellulose laurate) to 134 degrees C for C-20 (cellulose eicosanoate). Evidence of ''main-chain' ' crystallization was not observed for these samples, except in the ca se of peracetylated C-12 and C-14 eaters, which had T-m values of 96 d egrees C and 107 degrees C, respectively. (C) 1996 John Wiley & Sons, Inc.