Unperturbed dimensions of a zwitterionic polymethacrylate

Values of intrinsic viscosity [ζ] measured in 2,2,2‐trifluoroethanol (TFE) and in 1·0M aq. NaCl solution mean square radii of gyration s2z and weight‐average molecular masses Mw measured in TFE at 298 K for 12 well fractionated poly[N‐(3‐sulphopropyl)‐N‐methacrylooxyethyl‐N,N‐dimethylammonium betaine] (PSPE) samples have been used to derive the unperturbed dimensions ( 20/M)1/2 via different extrapolation procedures. Cloud point curves for PSPE fractions in 0‐05M aq. NaCl yielded an upper critical solution temperature (0) of 308 K, which was confirmed turbidimetrically, visco‐metrically, and by light scattering, thus enabling the unperturbed dimensions to be determined directly. The mean value of (r20/M)1/2 by all procedures was 0‐052nm g‐1/2 mol1/2 which, in conjunction with the corresponding quantity calculated on the basis of free rotation, affords a value of 2‐83 for the steric factor α. From values of [ζ] in 2·0M aq. NaCl solution over the interval 283–343 K, the value of dlnr2o/dT was derived as −8·5 × 10−4 deg−1. The values of the long range interaction parameter β and the interaction parameter χ confirm that TFE is a thermodynamically better solvent than l·0M aq. NaCl solution for PSPE.