| 초록 |
It has been suggested that elastic modulus of polymer nanofibers significantly increases with decreasing size due to the alignment of polymer chains confined in nanofiber. In this study, molecular mobility of polystyrene (PS) nanofibers with various diameter was studied by analyzing spin-lattice relaxation time, T1 and T1ρ. The morphology and diameter of PS nanofibers were observed by Field-Emission Scanning Electron Microscopy (FE-SEM). The spin-lattice relaxation time was obtained by 1H solid-state NMR. The T1 of PS nanofibers at low temperature (175 to 250 K) are similar to the T1 of bulk PS. However, T1 of PS nanofibers noticeably decrease with decreasing diameter of PS nanofibers. The apparent deviation of relaxation time indicates that molecular mobility of polymer chains in nanofibers is affected by size effect. On the contrary, T1ρ of PS nanofibers doesn’t show a size-dependency. This results reveal that the relatively slow motion of PS is not affected by decreasing size. |
