Associating and rheological behaviors of fluorinated cationic guar gum in aqueous solutions

The fluorinated cationic guar gum (FCGG) was prepared with cationic guar gum (CGG) and fluorinated reactive monomer (FAM). FAM was synthesized from isophorone diisocyanate and 2,2,3,4,4,4-hexafluoro-1-butanol. The molecular structure, associating and rheological behaviors of FCGG were studied by the FT-IR, (19)F NMR, X-ray diffraction, dynamic rheometer and fluorescence spectroscopy, respectively. The results show that FAM is successfully incorporated into CGG. With the increased degree of substitution (DS), the crystallinity is reduced from 3.01 to 0.67% and the characteristic relaxation time is changed significantly from 0.10 to 3.3s. At low shear rates (<20s(-1)), the viscosity of FCGG solution increases with the increase of shear rates. The bigger the DS, the higher the apparent viscosity. The viscosity retention factor of FCGG can reach 126.97% at 30°C and 51.33% at 60°C, respectively. The data indicate that FCGG has much better heat resistance.