Surface deacetylation of chitin nano-whiskers
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Surface deacetylation of chitin nano‑whiskers Siyu Chen1 · Dajun Chen1 Received: 30 January 2019 / Revised: 16 October 2019 / Accepted: 8 November 2019 © Springer-Verlag GmbH Germany, part of Springer Nature 2019
Abstract In this paper, chitin nano-whiskers (CNWs) were prepared through acid hydrolysis. The surface deacetylation of the prepared CNW in alkali conditions was carried out. The morphologies, crystallinity, degree of deacetylation and antibacterial property of the nano-whiskers were studied by transmission electron microscopy (TEM), Fourier transform infrared spectra, X-ray diffraction, antibacterial testing and so on. The results confirmed that the amino groups were successfully introduced onto the surface of the CNW, so that the nano-rod-like morphology of the whisker was still maintained. The degree of deacetylation of CNW increased from 4.4% up to a maximum of 55.2% with the increase in NaOH concentration and reaction temperature. Furthermore, deacetylation kinetics of CNW was also investigated. It was found that the deacetylation process followed the pseudo-first-order kinetics. The apparent rate constant of the reaction increased with the increase in NaOH concentration and reaction temperature. The apparent activation energy of the reaction was estimated as 27.71 kJ/mol. The deacetylated CNW exhibited much improved antibacterial property, and the percentage bacterial reduction of the sample reached 85%. Keywords Chitin nano-whisker · Surface deacetylation · Kinetic characteristics
Introduction Chitin nano-whisker (CNW) is a kind of rod-shaped crystal material. Due to its special nano-size and high modulus [1], CNW is now widely used as a reinforcing filler in various polymers composites, such as natural rubber [2], maize starch [3], polyvinyl alcohol [4–6], chitosan [7], PEO-LiPF6 matrix [8], and polyacrylate [9]. However, CNW tends to self-aggregate in polymer matrix, as the traditional nanoparticles do, resulting in lowering the effect of mechanical enhancement to the polymers. There are a number of N-acetyls and hydroxyls on the surface of CNW, which make * Dajun Chen [email protected] 1
State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University, Shanghai 201620, China
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possible the surface modifications of the CNW and could result in more excellent performance of CNW [10]. For example, the strength, elongation and hydrophobicity of CNW were improved by grafting PCL onto the CNW surface via ring-opening polymerization [11]. Li et al. [12] used l-lactide-grafted CNW as a reinforcing filler for PLLA matrix. And the cytocompatibility and biocompatibility of PLLA matrix were better than those of the neat PLLA. Wang et al. [13] reported the work about the acetylated CNW films which showed improved hydrophobicity, and Dutta et al. [14] introduced the N-halamine onto the surface of CNW by chlorination with acetyl for improving its antibacterial activity. Chitosan is an i
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