Effect of side chain length on structure and thermomechanical properties of fully substituted cellulose fatty esters

A series of cellulose esters (CEs) with high degrees of substitution has been obtained by linking aliphatic acid chlorides (from C8 to C18) onto cellulose backbone, in a homogeneous LiCl/DMAc medium. These materials have been characterized by Fourier transformed infra red (FTIR) and nuclear magnetic resonance of proton (1H NMR) spectroscopies, as well as differential scanning calorimetry (DSC), wide angle X-ray scattering (WAXS), dynamic mechanical analysis (DMA) and mechanical analyses. CEs organize in a layered type structure: cellulosic backbones are arranged in a plane, the flexible side chains being fully extended and perpendicular to the cellulosic backbone. When the fatty chain length exceeds 12 carbon atoms, a fraction of the alkyl chains crystallize into hexagonal packing. Regarding the mechanical behavior, the strain at break decreases significantly whereas no clear evolution of the yield stress is observed when the length of the lateral chain is increased.