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Discovery of New Structural Change of Polymer Melt (Press Release)

Release Date
28 Feb, 2012
  • BL10XU (High Pressure Research)
- Pressure-induced nanoscale structural change

Keio University
The University of Tokyo
Kyoto University
Japan Synchrotron Radiation Research Institute (JASRI)

Through cooperative research*1, Ayano Chiba (Assistant Professor) at the Faculty of Science and Technology of Keio University, Nobumasa Funamori (Associate Professor) at the School of Science of the University of Tokyo, Mikihito Takenaka (Associate Professor) at the Graduate School of Engineering of Kyoto University, Yasuo Ohishi (Senior Scientist) of JASRI, and their colleagues discovered a new structural change of a polymer melt. Polymers are indispensable in our daily lives as materials for products ranging from plastic bottles to the Boeing 787 jet airplane. A melt obtained by melting a polymer at high temperatures is considered one type of liquid. In this cooperative research, the scientists found that the isotactic poly(4-methyl-1-pentene) melt undergoes an abrupt change in its structure at a scale of approximately 1 nm (atomic arrangement) when pressure is applied. This finding indicates the presence of two types of liquid structures for the melt, i.e., sparsely and densely packed structures, depending on the pressure. It is possible to significantly change the properties of a single polymer, such as viscosity and refractive index, by utilizing this structural change. This finding provides interesting insight for the fundamental study of polymers, liquids, and glasses and may also be applied to the development of new materials with pressure-induced functions.

The results of this study were published online in the American scientific journal Physical Review E on 27 February 2012.

"Pressure-induced structural change of intermediate-range order in poly(4-methyl-1-pentene) melt"
Physical Review E 85, 021807 (2012)
*1 The corroborative research was carried out with Kazuhiko Tsuji (Professor Emeritus) at the Faculty of Science and Technology of Keio University, Stephen M. Bennington (Professor) at Rutherford Appleton Laboratory, Sanjay Rastogi (Professor) at Loughborough University, and their colleagues.


Fig.1 Formula of poly(4-methyl-1-pentene) (P4MP1)

Fig. 1 Formula of poly(4-methyl-1-pentene) (P4MP1)

Fig.2 Pressure-dependent X-ray diffraction patterns of polymer P4MP1 melt
Fig. 2 Pressure-dependent X-ray diffraction patterns of polymer P4MP1 melt

X-ray diffraction is used for structural analysis of not only crystals but also liquids. Spikelike peaks are observed for crystals; however, round curved diffraction patterns, as shown in the figure, are observed for liquid and amorphous materials. The information on the atomic arrangement in a liquid is obtained by analyzing the position and height of the peaks.

Fig.3 Schematics of polymer P4MP1 melt structures
Fig.3 Schematics of polymer P4MP1 melt structures

The black solid and red thin lines indicate main and side chains, respectively. Refer to Fig. 1 for main and side chains. The left and right figures show the schematics of the sparsely packed structure in the low-pressure range and densely packed structure in the high-pressure range, respectively.

Fig.4 Schematics of polymer P4MP1 melt structures
Fig.4 Pressure dependence of position and height of the first sharp
diffraction peak (FSDP) in the diffraction patterns of polymer P4MP1 melt

Filled and open symbols indicate the FSDP data in the case of increasing and decreasing pressures, respectively. The position of FSDP obtained from Fig. 2 and the height of FSDP divided by the height of the second sharp diffraction peak are plotted in the left and right figures, respectively. It is found that the position and height of the FSDP significantly change, i.e., the nanoscale structure significantly changes in the liquid, with pressure. The structural change is found to be reversible because the diffraction pattern returns to the original pattern after reducing the pressure. It is considered that the P4MP1 melt has sparse and dense structures at pressures lower and higher than that where the bend in the graph is observed, respectively.

For more information‚ please contact:
 Dr. Ayano Chiba (Keio University)
 Dr. Nobumasa Funamori (University of Tokyo)
 Dr. Mikihito Takenaka (Kyoto University)
 Dr. Yasuo Ohishi (JASRI)