Crystal nucleation of polymers confined to droplets: Memory effects

We study crystal nucleation within an ensemble of polyethylene droplets created through the dewetting of a thin film on an unfavorable substrate. In particular, we employ standard thermal treatment procedures to induce self-nucleation in samples to gain some insight into the nature of this enhanced crystallization. The novel sample-geometry enables the monitoring of each droplet throughout successive experiments, and hence the changes in their nucleation mechanism for various thermal treatments. We find a consistent self-nucleated crystallization temperature of similar to 101 degrees C under all conditions, suggesting uniformity in the centers which facilitate nucleation. Using correlation plots, we demonstrate that the observed melt-memory effects have a stochastic rather than deterministic nature; self-nucleation is a random process. (c) 2005 Wiley Periodicals, Inc.