THERMAL-PROPERTIES OF SYNDIOTACTIC POLYSTYRENE

Syndiotactic polystyrene was unknown until about 1986 when it was first synthesized. As with isotactic polystyrene, syndiotactic polystrene is a semicrystalline polymer with a melting point of between 264 and 272-degrees-C. The heat of fusion for 100% crystalline syndiotactic polystyrene is 53.2 J g-1 with typical syndiotactic polystyrene samples being about 50% crystalline. The heat capacity for syndiotactic polystyrene is the same as that of atactic and isotactic polystyrene. The crystal form of syndiotactic polystyrene changes from orthorhombic to monoclinic when material which has been precipitated from solution is heated. Upon crystallizing from the melt, only the monoclinic form is obtained. The crystallization kinetics have also been studied. Syndiotactic polystyrene crystallizes much more rapidly than isotactic polystyrene. It appears to initially crystallize very rapidly after which a melt recrystallization process occurs.