Crystallization-Modulated Nanoporous Polymeric Materials with Hierarchical Patterned Surfaces and 3D Interpenetrated Internal Channels

Poly(oxymethylene)/poly(L-lactic acid) (POM/PLLA) blends are typical melt-miscible binary systems. During isothermal crystallization at various temperatures, in the presence of amorphous PLLA chains, POM crystallizes into banded spherulites with different band spaces, which forms a continuous crystalline phase and serves as a sturdy frame in the final porous materials. On the other hand, the amorphous PLLA chains are simultaneously expelled out from POM crystal lamellae to generate the other continuous phase during the crystallization of POM. Consequently, the interpenetration of the POM lamellae and the amorphous PLLA phase construct a cocontinuous phase structure. All the PLLA constituents are fully included in the interlamellar or interfibrillar of POM crystals. Thus, nanoporous POM materials with hierarchical patterned surface and 3D interpenetrated internal channels have been successfully obtained by extracting the amorphous PLLA phase. It is further found that the POM crystal morphologies in the blends are much dependent on the crystallization conditions. Therefore, the hierarchical patterned structure and the size of internal channels (pore size) can be modulated by adjusting the crystallization conditions.