Tacticity of Syndiotactic Polystyrene sPS

Fully sPS was discovered relatively recently, and polymers are now manufactured commercially. Only limited structural information is available [40-47]. It has font main crystalline polymorphic forms a, P, y and 8. The attractive and interesting physical characteristics of this polymer can be smnmarised as follows (1) a melting temperature of 270 C, (2) a fully trans planar zig-zag backbone (a and P forms) and (3) a solid phase transition [40,42-45]. 

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

Large differences in the IR and Raman data for atactic, isotactic and syndiotactic PS related to the different chain conformations of these isomers are observed, especially in the regions of 18.51, 10.33, 11.11, 9.34 and 8.33-7.14 pm. 

In the 8.33-7.14 pm region, several conformation-sensitive skeletal vibrations are present. It is also quite likely that these bands are sensitive to chain packing. The IR spectrum of the cast film contains spectroscopic features that disappear when sample temperature is raised. Some of the weak features (9.27, 9.21 and 9.60 pm) 

Reynolds and co-workers [48] assign the two bands at 10.60 pm and 10.7 pm to the helical conformation found for the cast sample and this is removed by annealing. 

---