Solubility of Chitin: Solvents, Solution Behaviors and Their Related Mechanisms

By J. Roy, F. Salaün, S. Giraud, A. Ferri. 2017

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Chitin is a natural polysaccharides having a unique molecular arrangement of 2-(acetylamino)-2-deoxy- d -glucose, it possesses multifunctional properties and is suitable for various applications mainly in pharmaceutical, biomedical food, textiles and pack- aging fields. Therefore, being considered as a superior material for a sustainable future of industrial development, chitin perfectly meets up the demands with diversified func - tionalities in applications, excellent biocompatibility and biodegradability. Non-toxicity to human and environment (air, water and soil) is a great opportunity for this revolutionary, innovative and sustainable material. Moreover, antibacterial potency and low immuno genicity of chitin have broadened the aspects of research and development on structure- function relationship toward biological tissues and activities. Despite abundance, low cost and availability, many experimental data from potential studies, reproducibility problems of chitin solubility measurement still limit the development of products and access to the market in large volume. Batch-to-batch variability, non-precise characterization and ran - domly distributed acetyl groups of chitin structure eventually results in a bad reproducibility of chitin solubility. Therefore, the chapter aims to organize the information of chitin structure at molecular level and correlate solubility with chitin structure. Moreover, the dissolution mechanism and solution behaviors in different solvents will be discussed in this chapter. conjugate base of a weak acid, which can interact with the H-bonds of chitin. It destroys the hydrogen bonds and solubilizes the crystal chitin. Xie and coworkers investigated the IL, 1-butyl-3-methyl-imidazolium chloride ([Bmim]Cl) as a solvent but they achieved partial dissolution of chitin and chitosan at 110°C probably due to the moderated polarity of the IL and coworkers found that 1-allyl-3-methylimidazolium exhibited good solvent property for the dissolution of 5 wt% chitin when it was at 100°C for 48 h The obtained chitin solution was quite clear and homogeneous as confirmed by scanning electron microscopy analysis. The chitin powder recovered and regenerated by methanol treatment possessed the same crystalline structure as that of the crab shell. No degrada tion of chain or decrease of molecular weight had been occurred. Upon increasing the chitin amount to 7 wt%, a gel was obtained. Wang and coworkers studied the effect of three ILs: alkyl imidazolium chloride ([AMIM]Cl), alkyl imidazolium dimethyl phosphate ([MMIM] [Me 2 PO 4 ]) and 1-allyl-3-methyl-imidazolium acetate ([AMIM]Ac) on the solubility of a series of different DA (degree of acetylation) of chitin The dissolution of 5 wt% chitin occurs at 110°C in the [AMIM]Ac while [AMIM]Cl and [MMIM][Me 2 PO 4 ] can dissolve 0.5 wt% and 1.5 wt% chitin at 45 and 60°C, respectively. The observation showed that acetate anions are more efficient to break down the network of hydrogen bonds than the chloride and dimethyl phosphate anion. Similar findings were observed when 1-butyl-3-methylimidazolium acetate ([BMIN]Ac) and 1-butyl-3-methylimidazolium chloride ([BMIN]Cl) were used as solvent at room temperature [ 3 ]. The study showed that limited chitin solubility

Subfields: Biomaterials, Food Science, Organic Chemistry

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