Surface-Directed Self-Epitaxial Crystallization of Poly(ε-caprolactone) from Isotropic to Highly Orientated Lamellae

We report a facile means to engineer oriented surface topology of poly(ε-caprolactone) (PCL) via homoepitaxial crystallization. It involved uniaxially stretching the PCL substrate, immersing the uniaxial substrate in the PCL nutrient solution that could dissolve a small amount of PCL solute and meanwhile ensure the integrity of the substrate, as well as evaporating the solvent. Morphology observations demonstrated that uniform edge-on lamellae were aligned parallelly on the uniaxial substrate, where the orientation of epitaxial lamellae strongly correlated with the strain of the substrate. By tracking morphology evolution in each preparation step, the formation mechanism of oriented lamellae was revealed. Immersion in the nutrient solution incubated the aligned nuclei, which inherited from the featured structure of the uniaxial substrate via inherent lattice matching. During solvent evaporation, the chains precipitated on the preformed nuclei and spontaneously assembled into edged-on lamellae, resulting in the formation of unique oriented lamellae. The current effort provides insights into surface-directed self-epitaxial crystallization, by which scalable surface topology with a tuned structure can be obtained.