Surface Modification of Bacterial Cellulose Nanofibers for Property Enhancement of Optically Transparent Composites:  Dependence on Acetyl-Group DS

• Published in: Biomacromolecules 2007-06, Vol.8 (6), p.1973-1978
• Main Authors: Ifuku, Shinsuke, Nogi, Masaya, Abe, Kentaro, Handa, Keishin, Nakatsubo, Fumiaki, Yano, Hiroyuki
• Format: Article
• Language: English
• Subjects: Acetylation; Acrylic Resins - chemistry; Applied sciences; Bacteria; Bacterial Proteins - chemistry; Cellulose - chemistry; Cellulose and derivatives; Composites; Exact sciences and technology; Fibers and threads; Forms of application and semi-finished materials; Hot Temperature; Light; Materials Testing; Microscopy, Electron, Scanning; Nanoparticles - chemistry; Natural polymers; Optics and Photonics; Physicochemistry of polymers; Polymer industry, paints, wood; Spectrophotometry, Infrared; Spectroscopy, Fourier Transform Infrared; Surface Properties; Technology of polymers; Temperature; X-Ray Diffraction
• ISSN: 1525-7797; 1526-4602
• DOI: 10.1021/bm070113b

Bacterial cellulose (BC) nanofibers were acetylated to enhance the properties of optically transparent composites of acrylic resin reinforced with the nanofibers. A series of BC nanofibers acetylated from degree-of-substitution (DS) 0 to 1.76 were obtained. X-ray diffraction profiles indicated that acetylation proceeded from the surface to the core of BC nanofibers, and scanning electron microscopy images showed that the volume of nanofibers increases by the bulky acetyl group. Since acetylation decreased the refractive index of cellulose, regular transmittance of composites comprised of 63% BC nanofiber was improved, and deterioration at 580 nm because of fiber reinforcement was suppressed to only 3.4%. Acetylation of nanofibers changed their surface properties and reduced the moisture content of the composite to about one-third that of untreated composite, although excessive acetylation increased hygroscopicity. Furthermore, acetylation was found to reduce the coefficient of thermal expansion of a BC sheet from 3 × 10-6 to below 1 × 10-6 1/K.