RESUMEN
This study reports the preparation and characterizations of chitosan-azomethine derivatives containing oxazine ring as new crosslinked polymers. The novel chitosan derivatives have been prepared by functionalization with reactive benzoxazine precursors. Two types of aldehyde-terminated benzoxazine precursors have been synthesized using two different polyetheramines (Jeffamines), 4-hydroxybenzaldehyde, and paraformaldehyde. The benzoxazine precursors are covalently attached to chitosan via Schiff's base formation. Benzoxazine structure is confirmed by proton nuclear magnetic resonance spectroscopy (1H-NMR) and Fourier transform infrared spectroscopy (FT-IR), whereas the imine-linkage formation is confirmed by FT-IR. The benzoxazine-f-chitosan films are crosslinked by cationic ring-opening polymerization of benzoxazine. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) are used to study the thermal behavior of the obtained films. Wettability behavior of the resulting films was studied by contact angle measurements and compared with wettability of the neat chitosan film.
RESUMEN
A novel class of polymer blends has been prepared from main-chain-type benzoxazine polymer (MCBP) and chitosan (CTS), a modified biomacromolecule. A water-soluble, main-chain-type benzoxazine polymer, MCBP(BA-tepa), was synthesized from the reaction of bisphenol A (BA), tetraethylenepentamine (TEPA) and formalin. The structure of the MCBP(BA-tepa) was confirmed by proton nuclear magnetic resonance spectroscopy ((1)H NMR) and Fourier transform infrared spectroscopy (FT-IR). The polymer blends were prepared by mixing MCBP(BA-tepa) and CTS in aqueous acetic acid solution (1%). The CTS/MCBP(BA-tepa) films are cross-linked by thermal treatment via the ring-opening polymerization of benzoxazine structures in the main chain to produce an AB-cross-linked network. Differential scanning calorimetry (DSC) and FT-IR were used to study the effects of CTS on the polymerization behavior of benzoxazine. Hydrogen bonding between polybenzoxazine and CTS structures was also observed. The mechanical and thermal properties of cross-linked CTS/MCBP(BA-tepa) films were evaluated, and the results showed unusual levels of synergism. In particular, the tensile strength and thermal stability were significantly enhanced in a nonlinear fashion.