A microlayer component having improved oxygen and water vapor barrier properties (i.e., decreased permeabilities) comprises a barrier microlayer of a semi-crystalline barrier polymer in direct contact with a confining microlayer to promote in-plane crystalline lamellae formation. A microlayer component having a significant amount of in-plane crystalline lamellae may be characterized by at least 1.5× oxygen permeability improvement and at least 1.5× water vapor permeability improvement. A microlayer component having at least 1.5× improvement in oxygen and water vapor permeability may be coextruded and subjected to post extrusion stretching or heat treating.