Y. Mawatari, Asahi Motoshige, Yoshiaki Yoshida
May 13, 2014
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0
Influential Citations
30
Citations
Journal
Polymer
Abstract
Abstract The Rh-catalyzed polymerization of 2 - ethynylnaphthalene ( 2EN ) using ethanol or toluene solvents afforded helical poly(2 - ethynylnaphthalene)s (P2EN)s, i.e., yellow-colored P2EN( Y ) and red-colored P2EN( R ) in good yields, respectively. The diffuse reflective UV–vis (DRUV–vis) spectra of P2EN( Y ) and P2EN( R ) in the solid phase showed broad absorption peaks at 445 nm and 510 nm, respectively. These helical and its crystal structures were investigated using wide angle X-ray scattering (WAXS), resonance laser Raman, and molecular mechanics calculation using MMFF94 force field. Based on these analyses, we found that P2EN( Y ) was composed of stretched cis-transoid helices and P2EN( R ) was composed of contracted cis-cisoid helices in which form intramolecular π -stacking by ca. 3.4 A in distance between neighboring naphthyl rings. Furthermore, the contracted helix was energetically more stable than the stretched helix. The P2EN( Y ) changed to a red-colored polymer, P2EN( Y-R ), by immersion in toluene. This P2EN( Y-R ) completely coincides with the P2EN( R ) in its crystal structure and DRUV–vis spectrum.