Thermal expansion behavior of hydrate paramylon in the low-temperature region

• Published in: Carbohydrate polymers 2013-01, Vol.91 (2), p.543-548
• Main Authors: Kobayashi, Kayoko, Kimura, Satoshi, Togawa, Eiji, Wada, Masahisa
• Format: Article
• Language: English
• Subjects: (1→3)-β-d-Glucan; Applied sciences; Cold Temperature; cooling; Exact sciences and technology; Glucans - chemistry; Natural polymers; Nuclear Magnetic Resonance, Biomolecular; Paramylon; Phase Transition; Physicochemistry of polymers; Solid-state 13C NMR; Starch and polysaccharides; Synchrotron X-ray powder diffraction; Thermal expansion; X-Ray Diffraction
• ISSN: 0144-8617; 1879-1344
• DOI: 10.1016/j.carbpol.2012.08.067

► We have investigated the thermal expansion behavior of hydrate paramylon. ► There is a new hydrate paramylon phase in the low-temperature region. ► The phase transition occurred reversibly around 270K. ► The unit cell parameters and molecular conformation changed with the transition. ► We report the thermal expansion coefficients of the new hydrate paramylon phase. The thermal expansion behavior of hydrate paramylon between 100 and 300K has been investigated using synchrotron X-ray powder diffraction. The X-ray diffraction profile at 300K showed a typical pattern of the hydrate triple helical (1→3)-β-d-glucan with a hexagonal unit cell (a=15.782Å and c=18.580Å). On cooling, the hydrate paramylon had converted to a “low-temperature phase” around 270K. On passing through the phase transition, the a-axis and c-axis values decreased and increased, respectively, and the low-temperature phase at 100K exhibited a hexagonal unit cell (a=15.586Å and c=18.619Å). The phase transition took place reversibly. Below the transition point, both the a-axis and c-axis values decreased linearly. The thermal expansion coefficients are: αa=1.50×10−5K−1, αc=0.33×10−5K−1, and β=3.08×10−5K−1.