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

This paper concerns the new results obtained on the characterization of chi tins and chitosans. Large series of samples was analyzed covering a wide ra nge of water soluble and insoluble materials. The water soluble polymers we re 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 N-15 and C-13 solid state NMR was developed to be able to determine DA even in situ on insoluble natural materials. Ai l the methods proposed give a very coherent set of results. The molecular w eight distribution was established by GPC using cationic porous supports an d 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 analyze d by NMR; it is demonstrated clearly the difference between homogeneously a cetylated samples and heterogeneous samples coming fi om different routes o f 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 u nderstanding the role of the N-acetyl group content and distribution on the stiffness of the chains.