Chemical modification of chitosan: Synthesis and characterization of chitosan‐crown ethers

Abstract

AbstractFour novel Schiff‐type chitosan (CTS)‐crown ethers were synthesized through a reaction between NH2 in CTS or crosslinked chitosan (CCTS) and CHO in 4′‐formylbenzo‐crown ethers, and four secondary‐amino‐type CTS‐crown ethers were prepared through the reduced reaction of NaBH4, respectively. Their structures were characterized by elemental analysis, Fourier transform infrared (FTIR) spectra analysis, solid‐state 13C‐NMR analysis, and X‐ray diffraction (XRD) analysis. The elemental analysis results showed that the percentage of nitrogen in all CTS‐crown ethers were lower than that of CTS or CCTS. From the FTIR data of CTS, CCTS, and CTS‐crown ethers I–VIII, we saw that the characteristic peaks of CN, NH, and Ar appeared and that the characteristic peaks of pyranoside in the chain of CTS or CCTS were not destroyed. The XRD spectra demonstrated that CTS‐crown ethers I–VIII gave lower crystallinities than CTS or CCTS, which indicated that these compounds were considerably more amorphous than CTS or CCTS. In the solid‐state 13C‐NMR spectra, all of these CTS‐crown ethers had a particular peak of aromatic at 128 or 129 ppm, and the greatest difference between Schiff‐type CTS‐crown ethers and secondary‐amino‐type CTS‐crown ethers was that the Schiff‐type CTS‐crown ethers had the particular peak of CN, which disappeared in secondary‐type CTS‐crown ethers. All these facts confirmed that the structures of CTS‐crown ethers I–VIII were as expected. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2221–2225, 2003