A series of novel solid-solid phase transition heat storage polyurethanes with various molecular weight PEG based soft segments and MDI-BDO based hard segments were synthesized by two-step solution polymerization.DSC

WAXD were used to study the crystallization of the soft and hard segments

microphase separation

phase transition reversibility and thermal cycling stability of the polyurethanes.The results indicated the crystallizability of soft segment was depressed by the introduction of hard segments in the polyurethane

and the soft segments were not able to crystallize until its average molecular weight was above 2000

and the hard segments were not able to form sufficient domains until its content reaching a certain value

those are the two essential conditions for the polyurethanes having good solid-solid phase transition heat storage properties.In addition

the effects of soft segment content and soft segment molecular weight on heat storage properties of the polyurethanes were also studied.The materials also show great phase transition reversibility and reasonably good stability throughout the cycling process and can be considered as promising phase change materials.