Excluded volume effects of sulphobetaine polymers

The intrinsic viscosity, [η], radius of gyration, 〈S2〉1/2, and hydrodynamic radius, Rh were measured for the sulphobetaine type polyampholyte, poly(N‐3‐sulphopropyl)‐N‐methacrylooxyethyl‐N,N‐dimethyl ammonium betaine), in aqueous solution at various added‐salt concentration, Cs. The electrostatic expansion factors for polyampholyte effect, αe, were estimated for the sulphobetaine polymers over the wide range of molecular weights and Cs. It is concluded that the third‐power type equation for expansion parameters of both non‐ionic and the electrostatic excluded volume effect (attractive polyampholyte effect) can favorably explain the Cs dependence for the change of molecular dimensions in solution at intermediate ionic strength.