The Flow Properties of γ-Polyglutamic Acid Solutions in Capillary

Abstract Dependence of the viscosity of the solution of γ-polyglutamic acid in eater at various pH’s on the bore-size of the capillary viscometer has been studied at 25°C at various concentrations (0.01–0.05 g/100 ml). Measurements were carried out with a Maron-Belner type low shear capillary viscometer with various capillary radii (1.9×10−2–7.6×10−2cm) within the shear stress range 0.2–20 dyn/cm2 at the capillary wall. The polymer solutions showed a non-Newtonian flow behavior and a capillary bore-size dependence and both of these properties were diminished with the decreasing of pH. This capillary bore-size dependence may be attributed to the geometric hindrance of the capillary wall to the thermal motion of the polymer molecules near the wall. The dissolved state of the polymer molecules in solutions of various pH’s has been studied by means of optical rotatory dispersions, flow birefringence and intrinsic viscosity. The dissolved state of the polymer solution as well as the capillary bore-size dependence were sensitive to pH. The polymer molecule in neutral and alkaline media may be in the form of a highly expanded chain and in acid medium in a contracted form having a some ordered chain conformation.