Crystallization of Syndiotactic Polystyrene in β-Form. 3. Energetic Analysis of the Incorporation Mechanism of Stacking Faults into the Crystal

Crystallization-temperature ( T c ) dependence of the probability of the presence of stacking faults, p, in the solution-grown β-form single crystal of syndiotactic polystyrene (s-PS) was analyzed on the basis of the growth theory of the polymer crystal. By comparing the experimentally obtained T c dependence of p with the theoretical one, it is deduced that the relative energy difference, Δ E /Δ h f, between the regular and the faulted structures of s-PS decreases linearly with increasing T c: Here, (Δ h f − Δ E ) and Δ h f mean the heat of fusion for the faulted structures and that for the regular one, respectively. This result leads to an expectation that the faulted structure will be dominant when T c is above a certain critical temperature. Such a fault-rich crystal is to give the hk 0-diffraction pattern, in which the reflections with h + k = odd are absent. This feature has been really found in the X-ray diffraction pattern from the β‘-form crystal by De Rosa et al . ( Polymer 1993, 33, 1423).