Synthesis and characterization of thermoplastic chitin derivative N,O-benzyl chitosan

Chitin derivatives are difficult to be melten because of their very strong inter-molecular and intra-molecular hydrogen bonds. In this paper, N, O-benzyl chitosan was synthesized by means of phase-transfer method. The total degree of substitution for this derivative was 0.8 as determined with H-1 NMR and the degree of substitution on nitrogen was 0.3 as determined with elemental analysis. This is a thermoplastic chitin derivative. It's melting point was 470 K as measured with DSC. A viscous isotropic melt occurred at the temperatures between the melting point and the decomposition temperature(513 K) while N,O-benzyl chitosan was heated on a hot stage. DSC results agreed with the results of microscopy observation. The benzyl group can not form hydrogen bonds. It is also non-polar and has larger volume. These factors weaken the interactions between chitosan chains, and therefore decrease the melting point, which was lower than the decomposition temperature. As a result, N,O-benzyl chitosan was able to melt.