The Early Stages of Polymer Crystallization: Nucleus-Induced Nucleation and Interfacial Structuring

Fully realizing the potential of advanced polymeric materials is predicated on controlling polymer crystallization. However, a comprehensive understanding of primary polymer crystal nucleation remains elusive. Therefore, we have directly quantified the shape and interfacial properties of embryonic polymer crystals (i.e., nuclei) at the molecular level during polymer crystal nucleation in entangled polyethylene melts under non-flow conditions. Through coarse-grain molecular simulations, we find that one nucleus can enhance the formation of additional nearby, distinct nuclei in a manner consistent with the lamellar stacking of semi-crystalline polymeric materials. Furthermore, the nucleus-melt interface spans several nanometers, and there is a decoupling of polymer properties in the interfacial region such that nuclei reside in nematic droplets. Through these insights, we are able to reconcile disparate previous results concerning polymer crystallization under flow and non-flow conditions from both experimental and computational studies, building bridges between regimes that have been considered distinct historically. Our work affords a new nanoscopic perspective on polymer crystallization.