Cited by 257Polymer crystallization and propertiesbiodegradable polymer synthesis and propertiesX-ray Diffraction in Crystallography

Crystal Structure Analysis of Poly(l-lactic Acid) α Form On the basis of the 2-Dimensional Wide-Angle Synchrotron X-ray and Neutron Diffraction Measurements

Wasanasuk, Kaewkan, Tashiro, Kohji, Hanesaka, Makoto, Ohhara, Tokashi, Kurihara, Kazuo, Kuroki, Ryota, Tamada, Taro, Ozeki, Tomoji +1 more·2011·Macromolecules

Abstract

The crystal structure of poly( l -lactic acid) (PLLA) α form has been analyzed in detail by utilizing the 2-dimensional wide-angle 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 Å at SPring-8, Japan and the WAND data were measured using a neutron beam of wavelength 1.510 Å with a cylindrical imaging-plate camera of BIX-3 system at Japan Atomic Energy Agency. The initial crystal structure model was extracted successfully by a direct method under the assumption of the space group P 2 1 2 1 2 1 using about 700 X-ray reflections observed at −150 °C, the number of which was overwhelmingly large compared with the data reported by the previous other researchers and allowed us to perform more precise structural analysis. 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 ( R ) became minimal: R was 18.2% at −150 °C and 23.2% at 25 °C. The thus-obtained chain conformation took the distorted (10/3) helical form with 2 1 helical symmetry along the chain axis. However, the symmetrically forbidden reflections 003, 007, 009 etc. were detected in a series of the 00 L reflections, requiring us to erase the 2 1 screw symmetry along the molecular chain. By assuming the space group symmetry P 12 1 1, the structural refinement was made furthermore and the finally obtained R factor was 19.3% at −150 °C and 19.4% at 25 °C. Although the structural deviation from the 2 1 screw symmetry was only slightly, this refined model was found to reproduce the observed reflection profiles well for all the layer lines. The thus X-ray-analyzed crystal structure was transferred to the WAND data analysis to determine the hydrogen atomic positions. The R factor was 23.0% for the 92 observed reflections at 25 °C. The agreement between the observed and calculated layer line profiles was good. In this way the crystal structure of PLLA α form has been established on the basis of both the X-ray and neutron diffraction analyses.

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Crossref · 10.1021/ma2006624

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Authors
Wasanasuk, K., Tashiro, K., Hanesaka, M., Ohhara, T., Kurihara, K., Kuroki, R., Tamada, T., Ozeki, T., & Kanamoto, T.
Affiliations
  • Toyota Technological Institute (JP)
  • Japan Atomic Energy Agency (JP)
  • Tokyo Institute of Technology (JP)
  • Tokyo University of Science (JP)
Corresponding author
Tashiro, Kohji
Venue
Macromolecules
Published
2011-07-20
Volume
44
Issue
16
Pages
6441-6452
ISSN
  • 0024-9297 (ISSN-L)
  • 1520-5835
OpenAlex
W2321290696
Cited by
257
References
36
Citations by year
2026: 14 · 2025: 26 · 2024: 19 · 2023: 24 · 2022: 25 · 2021: 18 · 2020: 23 · 2019: 15 · 2018: 21 · 2017: 11 · 2016: 17 · 2015: 10 · 2014: 10 · 2013: 12 · 2012: 10
FWCI
9.27
Type
journal article
Language
en
Open access
closed
Locations
Macromolecules (publishedVersion)
Funders
Japan Society for the Promotion of Science (22550056)
Topics
  • Physical Sciences › Materials Science › Polymers and Plastics › Polymer crystallization and properties
  • Physical Sciences › Materials Science › Biomaterials › biodegradable polymer synthesis and properties
  • Physical Sciences › Materials Science › Materials Chemistry › X-ray Diffraction in Crystallography
Keywords
poly(L-lactic acid), crystal structure, helical chain conformation, hydrogen atom positions, neutron diffraction, wide-angle X-ray diffraction, layer lines, polymer crystallization, stereocomplex polymers, biodegradable polymers, chain conformation

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