Nucleation of a Lamella

More recently, Strobl [18] has stimulated a discussion by arguing that in all processes of polymer crystallization, a mesomorphic precursor phase is first formed before the crystalline phase. Blocks of this mesomorphic state then attach to the growth front, as sketched in Fig. 1.5. This model, inspired by the observation of the hexatic phase in short n-alkanes [19, 20], is actively contested by the polymer community. Whether such mesomorphic phases are stable intermediates before the formation of the crystalline phase and whether a critical chain stiffness is required for such mesomorphic phases are being discussed. Several laboratories worldwide are pursuing experiments to explore this aspect of poljmer crj talUzation. 

During the recent years, we have attempted to evaluate the imderlying assumptions and ideas of the current growth theories mentioned above im-der different conditions and to provide molecular interpretation of the various phenomenological parameters appearing in the LH theory. We have approached the various issues by a combination of tools. First, we have performed Langevin djmamics simulations of many chains in dilute solutions crystallizing into lamellae. Our simulations [29, 32] are based on the united-atom 

Thus the new model offers an opportunity to unify the diverse behaviors of kinetics of polymer crystallization observed experimentally. 

New entropic barrier model for growth with molecular congestion at the growth front 

The manifestations of chain entropy are present at all temperatures, except at T = 0. Two major conclusions that emerge from considerations of free energy by including chain entropy are the following  

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As reported in [22] and [29], Fig. 2 shows a typical sequence of images depicting nucleation of a lamella by a single chain of N = 700 beads as obtained from Langevin dynamics simulations. The chain is quenched to T = 9.0... 

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