Substitution degree and fatty chain length influence on structure and properties of fatty acid cellulose esters.

A series of fatty acid cellulose esters (FACEs) with both various degrees of substitution (from DS = 1.7 to 3) and side chain length were obtained by grafting aliphatic acid chlorides (from C10 to C16) onto cellulose backbone, in a homogeneous LiCl/DMAc medium. These materials were characterized by Fourier Transformed InfraRed (FTIR) and Nuclear Magnetic Resonance of Proton (1H NMR) spectroscopies, as well as Wide Angle X-ray Scattering (WAXS), Differential Scanning Calorimetry (DSC), mechanical analyses and chemical resistance to concentrated acid and alkali solutions. Whatever the alkyl chains length and the DS, all samples displayed a layered structure composed of a planar arrangement of parallel cellulosic backbones with fully extended flexible side chains oriented perpendicular to the planar structure without interdigitation. The alkyl chains were able to crystallize as soon as they are long enough. As the DS decreased, the plasticizing effect of the alkyl chains was less pronounced and their ability to crystallize was improved. Regarding the mechanical behavior and the chemical resistance, similar results were observed whatever the DS is.

Influence of fatty chain length and starch composition on structure and properties of fully substituted fatty acid starch esters.

A series of almost fully substituted Fatty Acid Starch Esters (FASEs) has been obtained in a homogeneous LiCl/DMAc medium by grafting octanoyl (C8), lauroyl (C12) and palmitoyl (C16) chlorides onto 3 starch species: Amylo-Maize, Potato and Waxy Maize. Structure-property relationships of FASEs are investigated as a function of both fatty acid chain length and amylose/amylopectin ratio of the starch. The structural study has revealed a layered type organization in which starch chain planes are separated by fatty chains. The latter are interpenetrated and/or tilted for FASE-C16 whatever the origin of the starch is, and fatty chains partially crystallizes into a structure with hexagonal symmetry. FASEs with C8 and C12 side chains are totally amorphous. The mechanical behavior of FASEs is shown to depend on both side chain length and amylose/amylopectin ratio, and an increase in material ductility is observed at increasing amylose content for C8 and C12 side chains.