PH and ionic strength dependences of the intrinsic viscosity of betaine-type polyampholyte

The intrinsic viscosity, [η], was measured:for the betaine-type polyampholyte, poly(2-(methacryloyloxy)ethyl 2-(trimethylammonio)ethyl phosphate), in aqueous solution at various pH and ionic strengths, I. The linear relationship between 1/√I and[η] for ordinary polyelectrolytes was also observed for the polyampholyte at low I near isoionic pH and over a wide range of I at other pH. By comparing I dependence of the electrostatic expansion factor of the polyampholyte with that of poly(sodium acrylate), it is suggested that there is a pronounced intramoleoular attraction between the segments due to the oppositely-charged groups even when pH deviates from the isoionic pH