Anisotropic Polymer Conformations in Aligned SWCNT/PS Nanocomposites

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• 作者：Wei-Shao Tung ; Russell J. Composto ; Nigel Clarke ; Karen I. Winey
• 刊名：ACS Macro Letters
• 出版年：2015
• 出版时间：September 15, 2015
• 年：2015
• 卷：4
• 期：9
• 页码：916-920
• 全文大小：300K
• ISSN：2161-1653

文摘

Polymer radii of gyration in isotropic single-walled carbon nanotube (SWCNT)/polymer nanocomposites were previously found to increase with increasing SWCNT concentration. Here, the SWCNTs in nanocomposites were aligned by melt fiber spinning, and the polymer chain conformations were found to be anisotropic. Using SAXS and SANS, the anisotropic SWCNT meshes were found to have smaller mesh sizes in the direction perpendicular to the alignment direction than along the alignment direction. At fixed SWCNT orientation, the radius of gyration was probed parallel and perpendicular to the alignment direction, R_g^par and R_g^per, respectively, using SANS. With increasing SWCNT concentration, R_g^per increases significantly more than R_g^par, such that the extent of anisotropy increases with SWCNT concentration. The anisotropic polymer conformation is larger in the direction perpendicular to the alignment direction, which corresponds to a smaller SWCNT mesh size. Thus, when the SWCNT concentration and alignment combine to produce a SWCNT mesh size that is smaller than the unperturbed R_g, the polymer conformation circumvents the SWCNTs by adopting a larger R_g. Changes in the polymer conformation in nanocomposites with rod-like nanoparticles has important ramifications for entanglement density, polymer dynamics, and mechanical properties.