Tuning Crystal Structure, Orientation, and Morphology in Nylon-11 Aerogels via Freezing Rate Modulation during Unidirectional Freezing

Aerogels with aligned pore structures exhibit superior physicochemical and mechanical properties, making them well-suited for a wide range of advanced applications. Directional solidification of polymer solutions is a proven strategy for fabricating anisotropic aerogels with an oriented porosity. A thorough understanding of the parameters governing this process is crucial as they directly influence pore morphology and orientation, key factors that determine material performance. In this study, we systematically examined how the directional freezing temperature influences the structural and morphological characteristics of nylon-11 aerogels and further evaluated their piezoelectric energy-harvesting performance. Nylon-11 solutions were directionally frozen at various temperatures and subsequently freeze-dried to obtain aerogel samples. Samples frozen within the range of −186 to −60 °C exhibited well-aligned porous channels and oriented nylon-11 crystallites. In contrast, samples frozen between −60 and 0 °C showed no evidence of pore alignment or crystal orientation. Compared with isotropic aerogels with randomly distributed pores, the anisotropic samples exhibited markedly enhanced piezoelectric performance and improved mechanical properties. These findings highlight the critical role of freezing temperature in tailoring pore architecture and crystallite orientation in polymer-based aerogels, offering valuable guidance for the design of materials for high-performance applications.