Acetylation of Cellulose Nanowhiskers with Vinyl Acetate under Moderate Conditions

Abstract

A novel and straightforward method for the surface acetylation of cellulose nanowhiskers by transesterification of vinyl acetate is proposed. The reaction of vinyl acetate with the hydroxyl groups of cellulose nanowhiskers obtained from cotton linters was examined with potassium carbonate as catalyst. Results indicate that during the first stage of the reaction, only the surface of the nanowhiskers was modified, while their dimensions and crystallinity remained unchanged. With increasing reaction time, diffusion mechanisms controlled the rate, leading to nanowhiskers with higher levels of acetylation, smaller dimensions, and lower crystallinity. In THF, a solvent of low polarity, the suspensions from modified nanowhiskers showed improved stability with increased acetylation.

Nanocellulosic fillers for waterborne wood coatings: reinforcement effect on free-standing coating films

“…2 indicate significant changes in the chemistry of CNF after acetylation. Three characteristic bands are related to acetyl groups and therefore acetylated cellulose: the C=O stretching of carbonyl groups in the ester bonds around 1745-1740 cm -1 , the vibration peaks at 1240-1235 cm -1 due to stretching of C-O bonds and the methyl in-plane bending of C-CH 3 around 1375 cm -1 (Ashori et al 2014;Cetin et al 2009;Higgins et al 1961;Jonoobi et al 2010). All of them could be easily identified in the spectrum obtained for the modified CNF.…”

Homogenous esterification of cellulose pulp in [DBNH][OAc]

“…Both acetone and acetaldehyde are easy to remove from the reaction mixture and are relatively non-toxic, but flammable. In prior literature, the reactions made with VinAc were either catalyzed with a base; K 2 CO 3 , Na 2 CO 3 (Ç etin et al 2009;Jebrane and Sebe 2007;Jebrane et al 2011), or cellulose was activated with NaOH (Chen et al 2016).…”

“…The same group have just recently published an article, where [Emim][OAc] and other imidazolium based ionic liquids were used in DMSO mixtures for assessment of the mechanistic effects of ILs (Kakuchi et al 2017). Vinyl esters can also be used in cellulose esterification reactions, as an acylation reagent, but have been used in ''traditional'' solvents with catalysts or activators (Chen et al 2016;Ç etin et al 2009;Heinze et al 2003;Jebrane et al 2011;Jebrane and Sebe 2007).…”

1D and 2D NMR of nanocellulose in aqueous colloidal suspensions

“…Nanocellulose has been commonly derived by chemical or mechanical means, including acid hydrolysis (Beck-Candanedo, Roman, & Gray, 2005;Jiang, Esker, & Roman, 2010), 2,2,6,6-tetramethylpyperidine-1-oxyl (TEMPO) mediated oxidation (Saito & Isogai, 2004), biochemical enzymatic hydrolysis (Paakko et al, 2007), mechanical defibrillation (Uetani & Yano, 2011) or a combination of the above, in the form of aqueous suspensions. Structural characterization of nanocellulose, however, has been mainly carried out on their solids by welldeveloped solid state techniques such as Fourier transform infrared spectroscopy (FTIR) (Araki, Wada, & Kuga, 2001), X-ray photoelectron spectroscopy (XPS) (Jiang et al, 2010;Yuan, Nishiyama, Wada, & Kuga, 2006), energy-dispersive X-ray spectroscopy (EDX) (Lu & Hsieh, 2011) and solid-state 13 C nuclear magnetic resonance (NMR) (Berlioz, Molina-Boisseau, Nishiyama, & Heux, 2009;Cetin et al, 2009). Nanocellulose is widely known to agglomerate during drying, therefore solid-state characterization may reflect certain structural changes from drying and not necessarily the precise nature of the individual nanocellulose.…”