Morphogenesis of lamellar polymer crystals

Using a previously developed simulation model we study the changes in morphology of two-dimensional chain crystals caused by annealing. A series of various intermediate crystalline states with different stability exhibiting a non-monotonous evolution of the internal energy and the degree of local order was found. This clearly shows the generic non-equilibrium character of polymer crystals. Thus, the classification scheme of equilibrium thermodynamic phases cannot be used to describe such transient states in polymer crystals. At large length scales the structural changes resemble a liquid-like behaviour while at the same time at small length scales the chains show an improvement of crystalline order. The term morphogenesis reflects this complex kinetic behaviour. In addition, simulations with constant heating rates also demonstrate the importance of relaxation processes in polymer crystals.