Phase transition properties of polyethylene glycol-cellulose blends and their miscibility in mixed solvents

The phase transition properties of blends of polyethylene glycol (PEG) with cellulose (CELL) prepared from solution in N,N-dimethylacetamide/lithium chloride (DMAC/LiCl) and those from solution in dimethylsulfoxide/paraformaldehyde (DMSO/PF) were found to be completely different. The differences of the phase transition properties were probably related to the different miscibilities of these two polymers in the two solvent systems. Ln DMAC/LiCl, the miscibility of CELL and PEG was limited; the composite obtained exhibited a solid-liquid phase transition and had a small phase transition enthalpy. However, in DMSO/PF, these two polymers had a high level of miscibility; the composite obtained exhibited a solid-solid phase transition and had a large phase enthalpy. It is suggested that the differences of miscibility and the phase transition properties were caused by the different dissolving mechanisms of CELL and the differ ent interactions in these two solutions.