The crystallization of the α-and β-form crystals of syndiotactic polystyrene (sPS) is determined by the crystallization temperature. Being crystallized at various temperatures from the melt

sPS forms the β form crystal at high temperatures above about 230℃

α form crystal at low temperatures below about 170℃ and a mixture of the α and β form at intermediate temperatures. The effect of different cooling rates is considered in more details. Since the β form crystallizes at high ttemperature from the melt.It will first crystallize during cooling.At low cooling rates

the crystalline phase of the βform has almost reached the maximum crystallinity of the sample by cooling to 230℃.Soeven the temperature for the a form formation is reached

there is no more crystallizable sPS portion remaining for the a form formation.That is the reason why the βform is always obtained by cooling at a slow or moderate rate.If cooling reate is high enough that the βform has almost no time to crystallize at high temperature

only the a form can crystallize at low temperature.That is the reason why only the a form crystal is obtained under quenching conditions.It clearly indicates that the crystallization temperature is the intrinsic factor controlling the formation the a- and β-form crystals.