Tacticity of Syndiotactic Polystyrene

Fully syndiotactic polystyrene is a relatively recent discovery and polymers are now manufactured commercially. Only limited structural information is available [40-47]. It has four main crystalline polymorphic forms a, P, y and 8. The attractive and interesting physical characteristics of this polymer can be summarised as follows (1) 

Because of its inherent backbone stiffness and strong intermolecular interactions, the macroscopic properties such as modulus and strength are expected to exceed those of most polymers, even those of some liquid-crystalline polymers. 

Reynolds and co-workers [48] assign the two bands at 10.60 and 10.79 pm to the helical conformation found for the cast sample and this is removed by annealing. 

In the 500 cm region, bands are observed at 17.51, 18.25, and 18.69 pm. After annealing at 200 °C, only a single band at 18.55 pm remains. In iPS a single band at 17.64 pm is observed and is assigned to the skeletal out-of-plane mode of the aromatic ring [50,51]. The sPS spectra in this region are consistent with studies of PS 

The drawing process would also transform the helical form present in the cast film to the more extended all-planar zigzag form, and this is observed. Bandwidths are broader for this oriented sample than for the annealed film, indicating that the thermal treatment produced greater structural regularity than extruding the sample to a draw ratio of four. 

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