New Materials Design and Synthesis (Chemistry)

SASAKI Laboratory

SASAKI Laboratory
<Major Research Areas>Structure analysis of polymers and XRD system developments

X-ray analysis of
intricate polymer structures

Research activity

　　Various functional polymers are daily designed and synthesized one after another. The structural information is essential for further developments, but most of them are beyond the scope of ordinary XRD methods, owing to low crystallinity and intricate disorders. New smart XRD techniques are urgently needed for the structual evaluation.

1Structure analysis of functional polymers

　　We recently clarified a crystal structure, unsolved for more than thirty years, for the α form of poly(L-lactide), which has been utilized as biodegradable and biocompatible material. The structure involved the unique chain distortion. We are also analyzing supramolecular complex structures, for instance, the inclusion compounds of some polymers with cyclodextrins.
　　Our main target is π-conjugated polymers. Their chain backbones assume the planarity which affects the physical properties. The conformation is, however, generally distorted owing to the interatomic repulsions even by hydrogens, e.g., the phenylene rings in poly( p-phenylene) are alternately rotated by ca. 20˚ owing to the ortho-hydrogen repulsions. This fact will produce the helical twisting for poly(m-phenylene). In the analyzed crystal structure (right figure), the slowly-winding unique fivefold helices engage with each other, and are stabilized by their entanglements. Collaborations will proceed with organic chemists.

2Technical developments for XRD structure analysis

　　New techniques of rapid XRD measurements for a small amount of sample, accurate data collection, and software programs are indispensable for the analyses of intricately disordered polymers. We are constructing the PC system in order to extract the significant information from the XRD digital image data. Our original programs address the linked-atom Rietveld refinement of 3D crystal structure and the XRD simulations for nematic liquid crystals, as well as the evaluation of crystallinity and orientation.

Equipment

X-ray diffractometer, Differential scanning calorimeter, Laser scanning microscope

<Keywords>
Structure evaluation of polymers, X-ray diffraction, Molecular conformation, Crystal structure
<Contact>
Shintaro Sasaki / E-mail:s-sasaki@jaist.ac.jp TEL:+81-761-51-1600 FAX:+81-761-51-1149 URL:http://www.jaist.ac.jp/~s-sasaki/shoukai.html
VoiceWe focus on the X-ray evaluation of partly crystalline but intricately disordered polymer structures, which have been difficult to analyze by ordinary XRD techniques. The hard and soft techniques to acquire significant information efficiently are explored in view of the structure-control materials design.
The main research achievements in the past five years
  1. T. Yamamoto, M. Abe, B. Wu, B. Choi, Y. Harada, Y. Takahashi, K. Kawata, S. Sasaki, and K. Kubota, Basic Information on Nonsubstituted Polyphenylene and Polythiophene Obtained via Solubilization of Polymers, Macromolecules, 40, 5504-5512 (2007).
  2. A. Kumagai, Y. Fujiwara, H. Fukumoto, S. Sasaki, H. Koinuma, and T. Yamamoto, Molecular Alignments Studied by X-ray Diffraction Analysis and Optical Properties of Vacuum-Deposited Thin Films of Thiophene- Pyridine Oligomers, Jap. J. Appl. Phys., 45, L598-L601 (2006).
  3. T. Yamamoto, A. Mahmut, M. Abe, S. Kuroda, T. Imase, and S. Sasaki, Alternating Copolymer of Thiophene and N-(Phenylethynyl)pyrrole, J. Polym. Sci.: Part B: Polym. Phys., 43, 2219-2224 (2005).
  4. N. Kobayashi, S. Sasaki, M. Abe, S. Watanabe, H. Fukumoto, and T. Yamamoto, Chain Distortion of m-Linked Aromatic Polymers: Poly(mphenylene) and Poly(m-pyridine), Macromolecules, 37, 7986-7991 (2004).
  5. S. Sasaki and T. Asakura, Helix Distortion and Crystal Structure of the α-Form of Poly(L-lactide), Macromolecules, 36, 8335-8390 (2003).