DIELECTRIC STUDY ON MOLECULAR MOTIONS OF POLY(GLUTAMIC ACID) IN AQUEOUS-SOLUTION OVER A FREQUENCY-RANGE OF 10(5)-10(10) HZ

Dielectric relaxation measurements over an extremely wide frequency re gion from 100 kHz to 20 GHz were performed on poly(glutamic acid) in d ilute aqueous solution at 25-degrees-C. Three relaxation peaks could b e found. The high frequency peak around 10 GHz could be easily due to orientation of water molecules, and the intermediate one around 100 MH z could be assigned to a micro-Brownian motion of the main chain. The relaxation strength of the intermediate process is proportional to f(c )4.9, where f(c) is the fraction of coil. This means that linear linka ge of five repeat units in the coiled part is required for the motion. At the limit of f(c) = 1, the relaxation time for the lowest frequenc y process is 1 X 10(-8) s, which is in complete agreement with that fo r the overall rotation of a coiled polymer in solution. On the other h and it takes a value of 5 x 10(-6) s at f(c) = 0, which is reasonably in good agreement with that observed for the_ overall rotation of a ro dlike polymer with the same size in solution.