Chitosan/biological benzoxazine composites: Effect of benzoxazine structure on the properties of composites

In this study, two bio-based benzoxazines, PH-f and SA-f, were synthesized and used to prepare benzoxazine/ chitosan (CS) composites of PH-f/CS and SA-f/CS and their corresponding curing products poly(PH-f)/CS and poly(SA-f)/CS. Differential scanning calorimeter (DSC) and Fourier-transform infrared spectroscopy (FTIR) spectra show that, compared with poly(PH-f)/CS, the formation of imine-linkages (C=N) between SA-f and CS accelerates the benzoxazine ring-opening reaction and lowers the curing temperature of SA-f/CS. Although poly (PH-f)/CS and poly(SA-f)/CS have lower thermal stability than corresponding pure polybenzoxazine, it is still high and their LOI values are >35, indicative of good flame retardancy. Due to the formation of C--N bonds between SA-f and CS, the poly(SA-f)/CS composite has more regular surfaces and a more uniform pore distribution than poly(PH-f)/CS, with a specific area of 1.135 m2/g and porosity of 97.5%. The unique pore structure of the poly(SA-f)/CS composite gives it high adsorption capacity (reaching 95% for rhodamine B within 48 h), suggesting that it is a promising adsorption material.