Chitosan cross-linking with a water-soluble, blocked diisocyanate. 1. Solid state
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Updated: Sep 28, 2026

A Freeze-Thawing Method to Prepare Chitosan-Poly(vinyl alcohol) Hydrogels Without Crosslinking Agents and Diflunisal Release Studies
Published on: January 14, 2020
Eric R Welsh1, Caroline L Schauer, Syed B Qadri
1Center for Bio/Molecular Science and Engineering, Naval Research Laboratory, Washington, D.C. 20375, USA.
Abstract:
The present investigation focuses on the synthesis and application of a cross-linking agent that is compatible with the solubility characteristics of chitosan. A water-soluble, blocked-diisocyanate was prepared as a bisulfite adduct to 1,6-hexamethylene diisocyanate, which proved to be stable for several weeks in aqueous, acidic chitosan solutions at room temperature. Thermal cross-linking of chitosan as cast, dried films was investigated by varying the NCO/NH(2) ratio from 0.0 to 1.2. Spectroscopic (IR), thermal (TGA), swelling, and structural (WAXD) studies indicated that chitosan was cross-linked in a concentration-dependent manner under mild thermal conditions: 60 degrees C for 24 h. Cross-linking inefficiency was concluded to be due to lack of mobility of the reacting species in the solid state. In a preliminary study, the enzymatic degradation with Chitinase (E. C. 3.2.1.14) from Streptomyces griseus was found to be the greatest for non-crosslinked chitosan, followed by chitin, and then by cross-linked samples.
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