Recently structure and morphology of polymers under nanoscale confinements have attracted much attention. For semicrystalline polymer materials

the degree of crystallinity and the orientation of the crystalline domains are important factors in controlling their physical properties

and many efforts have been devoted to the understanding of crystallization and orientation of polymers in nanocylindrical confinements. In this paper

polyethylene nanofibers of 200 nm diameter were prepared by infiltrating porous anodic aluminum oxide (AAO) templates with polymer melt

and the crystallinity and orientation of polyethylene crystals in the nanofibers were studied by FTIR spectroscopy

polarized light microscopy (PLM)

and Xray diffraction (XRD). FTIR results showed that the degree of crystallinity in the nanofibers was lower than that in the bulk due to the confinement of the nanopores

and the crystals formed in the nanofibers oriented preferentially with the b axis aligning parallel to the axial direction of the nanofibers

while the a axis was perpendicular to the nanofiber direction. XRD data further confirmed that the b axis of the crystals was parallel to the fiber direction. It was found that the nuclei located mainly at the interface between the nanotemplate and the polymer bulk and radially grew with the fastest crystallographic growth direction (b axis) toward the bulk and the nanofibers. The crystals formed in the bulk were typical banded spherulites

while in the nanofibers

only the crystals with the growth directions compatible with the cylindrical confinement imposed by the pore geometry can grow bigger

and other growth directions were suppressed

leading to the preferred orientation of the crystals with the b axis aligning along the nanofiber direction.