For poly(e-caprolactone) (PCL)-based materials, the crystalline skeleton and its structural integrity determine the strength and toughness of the materials. Meanwhile, the amorphous regions actually serve as the nano/microscale compartments that can host functional ingredients (e.g., drugs, inorganic additives, etc) excluded from the PCL crystallites. Thus, the distribution and the size of these amorphous compartments play a key role in the materials’ performance. The goal of our study is to directly visualize the internal architectures (i.e., spatial distribution of amorphous and crystalline phases) of PCL-based materials (e.g., nanofibers, microfibers, and composite fibers). By using PCL thin films as model systems, we first demonstrated that, when the Candida antarctica lipase B (CALB) enzyme is used at very low concentrations (e.g., approximately 0.01-0.075 mg×mL-1), it preferentially breaks down amorphous chains prior to crystalline chains, suggesting its high degradation selectivity. Top-down dissection using the CALB enzyme was then performed on other PCL-based systems including nano/microfibers, nanofibers, and composite fibers. Hierarchically assembled crystalline domains (e.g., in the case of thin films) or hierarchically nanostructured crystalline skeletons (e.g., in the case of fibers) were clearly revealed using scanning electron microscopy (SEM). This finding allows top-down direct visualization of nanoscale lamellae using high resolution SEM, providing an easily-accessible route to study the internal structures of semicrystalline PCL and the hierarchical self-assembly of nanoscale lamellae. By using low concentrations of CALB enzyme, the structural differences in the crystalline skeletons of PCL nanofibers and microfibers were clearly captured, which allowed mapping out the spatial distribution of amorphous compartments that can potentially host functional ingredients.

Visualizing the inner architecture of poly(e-caprolactone)–based biomaterials and its impact on performance optimization

2019 Fall National Meeting

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