Competition between gelation and crystallization in solutions of syndiotactic polystyrene in cis-decalin

In solutions of syndiotactic polystyrene in cis-decalin there is a competition between crystallization and gelation. The molecular conformation that is adopted by the polymer chain depends on the annealing temperature. At low temperature the helix conformation is kinetically favored and a gel is formed. Between 45 and 70 °C the zigzag conformation prevails and the meso-α-phase with limited crystallinity is obtained. At higher temperature the most stable crystal phase with chains in the zigzag β-modification dominates. The competition between the different types of structure formation is most pronounced in the temperature domain that marks the transition from one regime to the other. This is clearly illustrated by the data obtained from structural analyses both in presence of the solvent by infrared spectroscopy as in the dried state by wide angle X-ray scattering. Schematic representation of the different types of structure formation and their interference in a solution of sPS in cis-decalin (w2 = 0.10).