A new approach to polymer crystallization used in an analysis of data of syndiotactic polypropylene

Under the conditions of “normal growth” on rough surfaces, crystallization rates follow from the balance between the attachment and detachment of the chain sequences building up the layer-like crystallites. In the proposed model, detachment rates are related to the change in the mean-field potentials experienced in the crystal and the melt; attachment rates are associated with the population number of straight sequences in the melt. Both rates show an exponential dependence on the sequence length. Combination of this picture with the basic kinetic criterion that the crystallite thickness found at a chosen crystallization temperature maximizes the growth rate yields equations that agree with the general observations. A detailed check of the model predictions is carried out in a discussion of data recently obtained for syndiotactic polypropylene. Attachment rates calculated using an RIS treatment are in fair agreement with those derived from the experimental data on the basis of the model.