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Journal Articles

Structure analysis and derivation of deformed electron density distribution of polydiacetylene giant single crystal by the combination of X-ray and neutron diffraction data

Tashiro, Koji*; Kusaka, Katsuhiro*; Hosoya, Takaaki*; Ohara, Takashi; Hanesaka, Makoto*; Yoshizawa, Yoshinori*; Yamamoto, Hiroko*; Niimura, Nobuo*; Tanaka, Ichiro*; Kurihara, Kazuo*; et al.

Macromolecules, 51(11), p.3911 - 3922, 2018/06

 Times Cited Count:4 Percentile:14.91(Polymer Science)

Journal Articles

Accurate structure analyses of polymer crystals on the basis of wide-angle X-ray and neutron diffractions

Tashiro, Koji*; Hanesaka, Makoto*; Yamamoto, Hiroko*; Wasanasuk, K.*; Jayaratri, P.*; Yoshizawa, Yoshinori*; Tanaka, Ichiro*; Niimura, Nobuo*; Kusaka, Katsuhiro*; Hosoya, Takaaki*; et al.

Kobunshi Rombunshu, 71(11), p.508 - 526, 2014/11

 Times Cited Count:6 Percentile:22.87(Polymer Science)

The crystal structure analysis of various polymer substances has been reviewed on the basis of wide-angle high-energy X-ray and neutron diffraction data. The progress in structural analytical techniques of polymer crystals have been reviewed at first. The structural models proposed so far were reinvestigated and new models have been proposed for various kinds of polymer crystals including polyethylene, poly(vinyl alcohol), poly(lactic acid) and its stereocomplex etc. The hydrogen atomic positions were also clarified by the quantitative analysis of wide-angle neutron diffraction data, from which the physical properties of polymer crystals have been evaluated theoretically. The bonded electron density distribution has been estimated for a polydiacetylene single crystal on the basis of the so-called X-N method or by the combination of structural information derived from X-ray and neutron diffraction data analysis. Some comments have been added about future developments in the field of structure-property relationship determination.

Journal Articles

Crystal structure analysis of poly(L-lactic acid) $$alpha$$ form on the basis of the 2-dimensional wide-angle synchrotron X-ray and neutron diffraction measurements

Wasanasuk, K.*; Tashiro, Koji*; Hanesaka, Makoto*; Ohara, Takashi*; Kurihara, Kazuo; Kuroki, Ryota; Tamada, Taro; Ozeki, Tomoji*; Kanamoto, Tetsuo*

Macromolecules, 44(16), p.6441 - 6452, 2011/07

 Times Cited Count:174 Percentile:98.54(Polymer Science)

The crystal structure of poly(L-lactic acid) (PLLA) $${alpha}$$ form has been analyzed in detail by utilizing the 2-dimensional wideangle X-ray (WAXD) and neutron diffraction (WAND) data measured for the ultradrawn sample. The WAXD data were collected using a synchrotron-sourced high-energy X-ray beam of wavelength 0.328${AA}$ at SPring-8 and the WAND data were measured using a neutron beam of wavelength 1.510${AA}$ with a BIX-3 detector at JRR-3, JAEA. The initial crystal structure model was extracted successfully by a direct method under the assumption of the space group ${it P}$2$$_{1}$$2$$_{1}$$2$$_{1}$$ using about 700 X-ray reflections observed at -150$$^{circ}$$C. The crystal structure model obtained by the direct method was refined so that the best agreement between the observed and calculated integrated intensities was obtained or the reliability factor (${it R}$) became minimal: ${it R}$ was 18.2% at -150$$^{circ}$$C and 23.2% at 25$$^{circ}$$C. The obtained chain conformation took the distorted (10/3) helical form with 2$$_{1}$$ helical symmetry along the chain axis. However, the symmetrically forbidden reflections were detected in a series of the 00l reflections, requiring us to erase the 2$$_{1}$$ screw symmetry along the molecular chain. By assuming the space group symmetry ${it P}$2$$_{1}$$, the structural refinement was made furthermore and the finally obtained R factor was 19.3% at -150$$^{circ}$$C and 19.4% at 25$$^{circ}$$C. This refined model was found to reproduce the observed reflection profiles well for all the layer lines. The X-ray-analyzed crystal structure was transferred to the WAND data analysis to determine the hydrogen atomic positions. The ${it R}$ factor was 23.0% for the 92 observed reflections at 25$$^{circ}$$C. The agreement between the observed and calculated layer line profiles was good.

Journal Articles

Structural refinement and extraction of hydrogen atomic positions in polyoxymethylene crystal based on the first successful measurements of 2-dimensional high-energy synchrotron X-ray diffraction and wide-angle neutron diffraction patterns of hydrogenated and deuterated species

Tashiro, Koji*; Hanesaka, Makoto*; Ohara, Takashi; Ozeki, Tomoji*; Kitano, Toshiaki*; Nishu, Takashi*; Kurihara, Kazuo; Tamada, Taro; Kuroki, Ryota; Fujiwara, Satoru; et al.

Polymer Journal, 39(12), p.1253 - 1273, 2007/12

 Times Cited Count:18 Percentile:50.01(Polymer Science)

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