Abstract:

Glycidyl dehydroabietate grafted hydroxypropyl chitosan (GDHA-g-HPCS) was obtained through the grafting reaction between hydroxypropyl chitosan (HPCS) and glycidyl dehydroabietate (GDHA), and the GDHA-g-HPCS was cross-linked with sodium glycerophosphate as cross-linking agent. The structures of intermediates and products were characterized by FT-IR, ¹H NMR and UV. The degree of substitution (D_S) of HPCS and the grafting degree (D_G) of the GDHA-g-HPCS were determined by elemental analysis. The surface activities of GDHA-g-HPCSs were investigated by surface tension method. The emulsifying abilities of GDHA-g-HPCSs were evaluated according to the stabilization time of emulsion composed of benzene and water with GDHA-g-HPCS as emulsifier. The gel formation time of cross-linked GDHA-g-HPCS was studied by inverted bottle method. When the D_S of HPCS was 110.6% and the D_G increased from 0.72% to 10.54%, the results showed the critical micelle concentration of GDHA-g-HPCSs decreased from 761.9 mg/L to 189.4 mg/L while the minimum surface tension (γ_min) was maintained about 45 mN/m, and the emulsifying ability of GDHA-g-HPCS increased at first and then decreased with the increase of D_G. When the 2 g/L GDHA-g-HPCS with the D_G of 2.81% was utilized as emulsifier, the stabilization time of benzene-water emulsion was 18 063 s much better than that of the emulsion formed by stabilizer, such as monoglyceride, sucrose ester or AEO-9. When the 30 g/L aqueous solution of GDHA-g-HPCS cross-linked by GP, a gel could be formed in 26 minutes at 37 ℃, and could be converted into a sol again in 42 minutes at 4 ℃.

Key words: hydroxypropyl chitosan, surface activity, emulsifying property, temperature-sensitive gel