HYDRODYNAMIC PROPERTIES OF DILUTE AQUEOUS-SOLUTIONS OF POLY(N-ETHYLMETHACRYLAMIDE)

Dilute solution properties of five nonfractionated samples of poly(N-e thylmethacrylamide) (PEMAm; 6 less than or equal to M(w) x 10(-4) less than or equal to 200), in water at temperatures from 5 to 70 degrees C were studied by viscometry. The temperature dependence of the intrin sic viscosity was very strong, and the quotients d ln[eta]/dT were neg ative. The exponent a in the Mark-Houwink-Kuhn-Sakurada equation was h igh and almost. constant at temperatures lower than 40 degrees C where upon it abruptly decreased to a = 1/2 at 70.5 degrees C. Analysis of t he intrinsic viscosity data yields the characteristic ratio of the cha in (C-infinity = 7.2 at 70.5 degrees C), the Kuhn statistical segment length (lambda(-1) = 13.6 x 10(-8) cm), and the polymer-water interact ion parameter chi (for temperatures higher than 55 degrees C). The lat ter is resolved into its entropic and enthalpic contributions. Both of them are negative. In terms of Franks' nomenclature, the system PEMAm -water can be classified as typically ''aqueous''. It is shown that th e behavior of aqueous solutions of poly(methacrylamide) is rather a '' nonaqueous'' one.