DIFFERENTIAL SCANNING CALORIMETRY INVESTIGATION OF PHASE-TRANSITIONS IN WATER CHITOSAN SYSTEMS

Transition temperatures of water/chitosan systems with water contents ranging from 8 to 300% (weight per cent of water per dry polymer weigh t) are measured by differential scanning calorimetry (d.s.c.). Upon he ating, three kinds of phases, which vary with the water content, are o bserved for the system: cold crystallization, melting of freezable wat er, and a birefringent to isotropic phase which occurs for samples con taining 44-190% water with a transition temperature that does not vary significantly with the water content. The glass transition temperatur e (Tg) of chitosan is observed at approximately 303 K for water conten ts ranging from 8 to 30%. From the d.s.c, data, a transition map for t he water/chitosan system is compiled.