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Low-Birefringent and Highly Tough Nanocellulose-Reinforced Cellulose Triacetate

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journal contribution
posted on 27.05.2015, 00:00 by Hiroto Soeta, Shuji Fujisawa, Tsuguyuki Saito, Lars Berglund, Akira Isogai
Improvement of the mechanical and thermal properties of cellulose triacetate (CTA) films is required without sacrificing their optical properties. Here, poly­(ethylene glycol) (PEG)-grafted cellulose nanofibril/CTA nanocomposite films were fabricated by casting and drying methods. The cellulose nanofibrils were prepared by 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation, and amine-terminated PEG chains were grafted onto the surfaces of the TEMPO-oxidized cellulose nanofibrils (TOCNs) by ionic bonds. Because of the nanosize effect of TOCNs with a uniform width of ∼3 nm, the PEG–TOCN/CTA nanocomposite films had high transparency and low birefringence. The grafted PEG chains enhanced the filler–matrix interactions and crystallization of matrix CTA molecules, resulting in the Young’s modulus and toughness of CTA film being significantly improved by PEG-grafted TOCN addition. The coefficient of thermal expansion of the original CTA film was mostly preserved even with the addition of PEG-grafted TOCNs. These results suggest that PEG–TOCNs are applicable to the reinforcement for transparent optical films.