Overview on structural characterization of chitosan molecules in relation with their behavior in solution.

Abstract

This paper concerns the new results obtained on the characterization of chitins and chitosans. Large series of samples was analyzed covering a wide range of water soluble and insoluble materials. The water soluble polymers were obtained by heterogeneous deacetylation and by homogeneous reacetylation. The calibration of IR spectrum was proposed and shown to be valid in all the range of DA. Application of 15 N and C solid state NMR was developed to be able to determine DA even in situ on insoluble natural materials. All the methods proposed give a very coherent set of results, The molecular weight distribution was established by GPC using cationic porous supports and the good solvent earlier proposed 0.3M AcOH/ 0.2M AcONa. The role of the distribution of acetyl groups along the chain is also discussed and analyzed by NMR ; it is demonstrated clearly the difference between homogeneously acetylated samples and heterogeneous samples coming from different routes of preparation. The dependence of Mark-Houwink parameters allowing to relate the intrinsic viscosity with the molecular weight is also briefly reported. In good concordance with experimental data, molecular modeling helps in understanding the role of the N-acetyl group content and distribution on the stiffness of the chains.