Confined crystallization of POM in the CA-nanotubes fabricated by coaxial electrospinning

Polyoxymethylene (POM)/cellulose acetate (CA) core–sheath ultrafine fibers were fabricated by coaxial electrospinning and used to study crystallization in a confined, long cylindrical space. Scanning electron microscopy and transmission electron microscopy revealed that the core–sheath structured ultrafine morphology was presented for the fibers with the average sheath diameter from 679 to 1495 nm and core diameter from 148 to 1000 nm which increased with increasing the concentration of the POM solution. The nonisothermal crystallization study indicated that the confinements sharply reduced the crystallinity and the crystallization temperature of the POM. The Avrami index derived from isothermal crystallization was also decreased with decreasing the dimension of the confined space. However, Wide angle X-ray diffraction showed the crystal size of the POM was decreased distinctly only when the dimension of the confinement was about 150 nm and increased with increasing the dimension of the confinement. It was suggested that both the mode of the crystal growth and the crystallinity will be affected by the cylindrical confinement during POM crystallization.