Impact of Nanoscale Confinement on Crystal Orientation of Poly(ethylene oxide).

Using a layer-multiplying coextrusion process to fabricate films with thousands of alternating polymer nanolayers, we report here a new crystalline morphology in confined polymer nanolayers and an abrupt transition in the crystallization habit. At higher temperatures, poly(ethylene oxide) crystallizes as large, in-plane lamellae. A 5 °C change in the crystallization temperature produces an on-edge lamellar orientation. The results point to a transition from heterogeneous nucleation to substrate-assisted nucleation. This may be a general phenomenon that accounts for previously unexplained differences in the preferred chain alignment of confined polymer crystals.