Substrate effects on the confined crystallization of polycaprolactone in coextruded nanolayered films

Layer multiplying coextrusion was used to create multilayered films with hundreds or thousands of alternating layers of two polymers. This paper examines the structure-property relationships of poly(ε-caprolactone) (PCL) nanolayers confined by a variety of polymer substrates. AFM, gas transport and WAXS characterizations were utilized to demonstrate that confined PCL nanolayers crystallized as large in-plane lamellae of high aspect ratio. This phenomenon, previously observed only for poly(ethylene oxide) (PEO), may be a more general phenomenon of crystalline polymers. In-plane PCL lamellae were as effective as PEO in reducing the oxygen permeability by more than 2 orders of magnitude. Additionally, the confining polymer substrate was found to affect to orientation of the PCL nanolayers due to chemical compatibility or epitaxial induced crystallization.