Viscoelastic properties of hyaluronic aqueous solutions

Viscoelastic properties of hyaluronic acid (KA) aqueous solutions were studied in the range of C-p (polymer concentration)= 1.0 similar to 0.25 wt% and T/s (period)= 180 similar to 23040 at 36.0 degrees C by a magnetic rheometer, which was newly constructed in our laboratory. The behavior was tried to express with a simple mechanical model, and by adopting the value of (a) C-p/wt% =1.0, much less than J(1.0)much greater than/Pa-1=68.0 (mean value of T/s=2880 similar to 23040), (b) C-p/wt%=0.75, much less than J(0.75)much greater than/Pa-1=67.9 (mean value of T/s=1440 similar to 11520), (c) C-p/wt%=0.5, much less than J(0.5)much greater than/Pa-1=68.7 (mean value of T/s = 360 similar to 11520), and (d) C-p/wt%=0.25, much less than J(0,25)much greater than/Pa-1=80.5 (mean value of T/s=360 similar to 11520), dispersion curves for Na-type HA aqueous solutions could be well, expressed by a Voigt model in the above range of the concentrations and periods. The Cole-Cole plot of f(1) = [<J(1) r>/(1 + omega(2)lambda(2))] against f(2) = [<J(t), (T)>.omega lambda/(1 + omega(2)lambda(2))] was also tried with the values of (a) much less than J(1.0)much greater than/Pa-1=68.0 (C-p/wt%=1.0), beta=0.725, and (b) much less than J(0.5)much greater than Pa-1= 68.7(C-p/wt%=0.5), beta=0.725, and the observed values fitted with these calculated curves. Na+ ion in Na-type HA was replaced by Mi alkaline ion (Li+, K+, or Cs') by passing through ion exchange resins. In the case of K-type HA solutions, viscosities decreased by two orders from those of Na-type HA solutions, but rigidities did not change so much. Viscosities of the solutions decreased in the order of Na+, Li+, K+, and Cs+, differing from the order of alkaline-ion series. Activation energies of viscous Bow were found as = 30 kJ mol(-1) for each solution, which is nearly equal to that of hydrogen bond energy.