ELECTRICAL AND HYDRODYNAMICAL PROPERTIES OF POLYPEPTIDES IN SOLUTION .I. POLY(L-GLUTAMIC ACID) IN METHANOL-WATER MIXTURES

The electric birefringence of poly(L‐glutamic acid) (PLGA) in methanol–water mixtures has been measured by the use of the rectangular pulse technique at 25°C. The permanent dipole moment, the anisotropy of electrical polarizability, and the optical anisotropy factor of PLGA in solution were obtained from the dependence of the steady‐state birefringence on the electric field strength. Further, the mean length of PLGA in solution was calculated by a parameter method developed for analyzing the decay curve of electric birefringence. The permanent dipole moment per unit length obtained from these studies was 2.96, 2.48, 2.30, 2.66 D/Å in pure methanol, 10, 30, and 50 vol‐% water, respectively. The increase of water content caused the decrease of the mean length and broadened the length distribution of PLGA. These results are discussed in relation to the viscosity and the electrical conductivity of PLGA solutions. Copyright © 1968 John Wiley & Sons, Inc.