Phase transition of poly(vinyl alcohol) hydrogel filled with micro-fibrillated cellulose

Aqueous solution of poly(vinyl alcohol) (PVA) forms hydrogels by freezing and thawing. In this study, micro-fibrillated cellulose (MFC) was mixed with PVA aqueous solution. Thermal properties of PVA–MFC composite hydrogels were investigated in a wide range of water content by differential scanning calorimetry (DSC). On DSC heating curves, glass transition, exothermic peak due to cold crystallization and endothermic peak attributed to melting of water were observed. Phase diagrams of PVA–MFC composite hydrogels were established based on transition temperatures. The amount of non-freezing water increased when MFC is introduced into hydrogels. Glass transition temperature of amorphous ice restrained by PVA–MFC composite hydrogel is restricted by the presence of MFC. Results obtained by DSC suggest that gelation occurs in adjacent PVA molecules due to compartmentalization in the presence of MFC molecules.