Controlled Switching from the Growth of Monolamellar Polymer Crystals to the Formation of Stacks of Uniquely Oriented Lamellae

Abstract

We have used a rationally designed two-step crystallization approach to induce the formation of stacks of superposed and uniquely oriented flat-on polymer lamellae exclusively and controllably at the periphery of monolamellar polymer crystals. The probability of initiating such stacks of lamellar crystals via self-induced nucleation was controlled by the crystallization temperature, which in turn, determined the width of crystalline branches through the Mullins-Sekerka instability. We employed this approach for the formation of a "fence" of stacks of lamellar crystals at the periphery of monolamellar stereocomplex single crystals of poly(L-lactide) and poly(D-lactide). The resulting morphology resembled a "pseudo hollow crystal" with an almost empty interior of a size controllable by crystallization time. We believe that such an approach can be applied also for other crystallizable polymers.