Polymorphism of syndiotactic poly(p-methylstyrene) unoriented samples

The complex polymorphic behavior of syndiotactic poly(p-methylstyrene) (s-PPMS) is discussed. It has three crystalline forms, a mesomorphic form, and several clathrate structures. Two crystalline forms and several different clathrate structures have been obtained by solution crystallization. The third crystalline form and the mesomorphic form have been obtained by annealing protocols using unoriented samples. Other possible interconversions between different forms of s-PPMS by annealing procedures are also described