Polyurethane/silica nanocomposites were prepared by solution mixing procedure

and the effect of nano-silica on the crystalline behavior in these nanocomposites was investigated by a variety of techniques.TEM results indicate that nano-silica is well dispersed in the polyurethane matrix.It is found from the DSC experiments that the crystallization of soft segments are obviously enhanced after annealing at high temperature and subsequent isothermal crystallization at 10℃

the addition of nano-silica affects the final glass transition temperature and the crystallinity of soft segments

as well as the rate of increment.Solid-state NMR analyses reveal that the mobility of soft segments is is restricted after annealing

while the mobility of hard segments obviously enhanced.The above results reveal that the interchain hydrogen bonding among hard segments is broken at high temperatures

and the increased interaction of hard segments and nano-silica results in the high mobility of hard segments

thus promoting the crystalline ability of the soft segments connected with hard segments.On the basis of the above results

a suggested model concerning the evolution of structure and dynamics in polyurethane nanocomposites under high-temperature annealing and subsequent isothermal crystallization is proposed.