The crystalline structures associated with melting and crystallization behaviors of monodisperse
linear polyethylene confined in cylindrical nanopores were investigated by X-ray diffraction and differential
scanning calorimetry. The crystalline structures, melting, and crystallization behaviors of PE under the imposed
cylindrical confinement were noticeably different from those of the bulk state. The isothermal crystallization
experiments showed that the overall crystallization of polyethylene in cylindrical nanopores was dominated by
the nucleation rather than the growth of crystallites. The c- and a-axes of orthorhombic PE crystals developed in
nanoporous alumina were preferentially oriented perpendicular to the long axis of cylindrical nanopore while the
b-axis was parallel to the pore axis. The melting temperature of polyethylene in the nanopores was substantially
depressed, and it was analyzed with the Thomson−Gibbs equation. The crystallinity of linear polyethylene in
cylindrical nanopores was less than 50%, whereas the bulk value was 71.6%.
The crystallization of monodisperse linear polyethylene confined in nanoporous alumina is investigated with the calorimetric measurements. We observe a drastic change in crystallization behavior, specifically nucleation, with a decrease in the pore diameter. Crystallization in relatively larger pores with the diameters of 62 and 110 nm occurs at lower temperatures within a very narrow range, whereas crystallization in smaller pores with diameters of 15-48 nm occurs at a higher and broad range of temperatures. Nucleation and crystallization kinetics in nanopores is discussed based on classical nucleation theory as well as the Avrami theory.
We fabricated silver nanowire (AgNW)-coated cellulose papers with a hierarchical structure by an efficient and facile dip-coating process, and investigated their microstructures, electrical conductivity and electromagnetic interference (EMI) shielding effectiveness. SEM images confirm that AgNWs are coated dominantly on the paper surfaces, although they exist partially in the inner parts of the cellulose papers, which demonstrates that the AgNW density gradually decreases in thickness direction of the AgNW/cellulose papers. This result is supported by the anisotropic apparent electrical conductivity of the AgNW/cellulose papers depending on in-plane or thickness direction. Even for a AgNW/cellulose paper obtained by a single dip-coating cycle, the apparent electrical conductivity in the in-plane direction of 0.34 S/cm is achieved, which is far higher than the neat cellulose paper with ∼10(-11) S/cm. In addition, the apparent electrical conductivity of the papers in the in-plane direction increases significantly from 0.34 to 67.51 S/cm with increasing the number of dip-coating cycle. Moreover, although the AgNW/cellulose paper with 67.51 S/cm possesses 0.53 vol % AgNW only, it exhibits high EMI shielding performance of ∼48.6 dB at 1 GHz. This indicates that the cellulose paper structure is highly effective to form a conductive AgNW network. Overall, it can be concluded that the AgNW/cellulose papers with high flexibility and low density can be used as electrically conductive components and EMI shielding elements in advanced application areas.
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