AUTHOR=Hirano Takayuki , Mitsuzawa Kana , Ishioka Shun , Daicho Kazuho , Soeta Hiroto , Zhao Mengchen , Takeda Masaaki , Takai Yoshihiro , Fujisawa Shuji , Saito Tsuguyuki TITLE=Anisotropic Thermal Expansion of Transparent Cellulose Nanopapers JOURNAL=Frontiers in Chemistry VOLUME=8 YEAR=2020 URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2020.00068 DOI=10.3389/fchem.2020.00068 ISSN=2296-2646 ABSTRACT=

We report the anisotropic thermal expansion of a transparent nanopaper structure comprising cellulose nanofibers (CNFs). The coefficient of thermal expansion (CTE) of the nanopaper in the out-of-plane direction was 44.6 ppm/°C in the temperature range of 25–100°C, which is approximately five times larger than its CTE in the in-plane direction in the same temperature range (8.3 ppm/°C). Such a strong anisotropy in thermal expansion is mainly attributable to the anisotropic CTE values of single CNFs in the fiber axis and cross-sectional directions. We observed anisotropic thermal expansion even in a bioplastic composite containing only 2.5% w/w CNFs.