title: Surface modification of bacterial cellulose nanofibers for property enhancement of optically transparent composites: dependence on acetyl-group DS.
abstract: 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 x 10(-6) to below 1 x 10(-6) 1/K.
authors: Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Japan. sifuku@rish.kyoto-u.ac.jp
authors: Shinsuke
authors: S
authors: Ifuku
authors: Masaya
authors: M
authors: Nogi
authors: Kentaro
authors: K
authors: Abe
authors: Keishin
authors: K
authors: Handa
authors: Fumiaki
authors: F
authors: Nakatsubo
authors: Hiroyuki
authors: H
authors: Yano
mesh_terms: D000107:Acetylation; D000180:Acrylic Resins / Q000737:chemistry; D001426:Bacterial Proteins / Q000737:chemistry*; D002482:Cellulose / Q000737:chemistry*; D006358:Hot Temperature; D008027:Light; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D053758:Nanoparticles / Q000737:chemistry*; D055095:Optics and Photonics; D013055:Spectrophotometry, Infrared; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties; D013696:Temperature; D014961:X-Ray Diffraction
chemical_list: D000180:Acrylic Resins; D001426:Bacterial Proteins; D002482:Cellulose