Tuning the Properties of High Molecular Weight Chitosans to Develop Full Water Solubility Within a Wide pH Range

17 February 2020, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


The preparation of chitosans soluble in physiological conditions has been sought for years, but so far solubility in non-acidic aqueous media has only been achieved at the expense of lowering chitosan molecular weight. In this work, we applied the multistep ultrasound-assisted deacetylation process (USAD process) to β-chitin and obtained extensively deacetylated chitosans with high molecular weights (Mw ≥ 1,000,000 g mol-1). The homogeneous N-acetylation of a chitosan sample resulting from three consecutive USAD procedures allowed us to produce chitosans with a high weight average degree of polymerization (DPw ≈ 6,000) and tunable degrees of acetylation (DA from 5 to 80%). N-acetylation was carried out under mild conditions to minimize depolymerization, while preserving a predominantly random distribution of 2-amino-2-deoxy-D-glucopyanose (GlcN) and 2-acetamido-2-deoxy-D-glucopyanose (GlcNAc) units. This close to random distribution, inferred with deconvolution of nuclear magnetic resonance (1H NMR) spectra, is considered as responsible for the solubility within a wide pH range. Two of the highly N-acetylated chitosans (DA ≈ 60 % and ≈ 70 %) exhibited full water solubility even at neutral pH, which can expand the biomedical applications of chitosans.


controlled acetylation
high molecular weight
water solubility


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