Morphological studies on single crystals and nanofibers of poly(heptamethylene terephthalate)
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Poly(heptamethylene terephthalate) (poly(7GT)) was synthesized, and its lamellar single-crystals were grown isothermally at 70 °C from a dilute solution in 1-octanol. Poly(7GT) nanofibers were prepared via electrospinning of its solution in 1,1,1,3,3,3-hexafluoro-2-propanol. Morphology of the single crystals and that of as-spun and annealed nanofibers were investigated by transmission electron microscopy. Selected-area electron diffraction (SAED) of the crystals gave a well-defined N-pattern consisting of spot-like hk0 reflections, and that of bundles of the annealed nanofibers indicated a highly oriented fiber pattern. From the analysis of SAED diagrams for single crystals and nanofibers, it can be assumed that poly(7GT) takes an orthorhombic crystal system and its unit cell parameters estimated are as follows: a = 1.409 nm, b = 1.480 nm, c (chain axis) = 3.392 nm, and α = β = γ = 90°.
KeywordsTransmission Electron Microscopy Observation Isothermal Crystallization HFIP Lamellar Crystal Chain Axis
This study was supported by a Grant-in-Aid for Scientific Research (C) (2), partly No. 16550174 and also supported by a Grant-in-Aid for Scientific Research (C), No. 19550207, from Japan Society for the Promotion of Science (JSPS) to which M.T. and Y.K. wish to express their gratitude.
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