Liquidlike morphological transformations in monolamellar polymer crystals

We performed annealing experiments on monolamellar polyethyleneoxid crystal s. Even well below the melting point, local relaxations of metastable folde d states led to pronounced liquidlike molphological changes on a micron sca le of shape and perimeter of the crystalline domains, similar to dewetting of liquids. First, a rim of less folded molecules was formed around the lam ellae, making relaxations of the interior difficult. On longer time scales, hole formation within these domains was observed. Our experiments showed t hat, due to such spatial anisotropy in relaxations, polymer crystal morphol ogy depends on the thermal pathway taken, implying that a time-temperature superposition principle does not apply.