EFFECT OF THE NET CHARGE-DISTRIBUTION ON THE AQUEOUS-SOLUTION PROPERTIES OF POLYAMPHOLYTES

The zwitterion nature of ampholytic polymers provides features that ar e useful in environmental and industrial applications, e.g. ion-exchan ge membrane, as flocculants in sewage treatment and in oil recovery pr ocesses. In the latter case, the increase in viscosity which is observ ed in the presence of brine (anti-polyelectrolyte behavior) make them ideal candidates for high salinity media. The aqueous solution propert ies of a series of ampholytic terpolymers based on sodium-2-acrylamido -2-methylpropanesulfonate (NaAMPS), methacryloyloxyethyltrimethylammon ium chloride (MADQUAT) and acrylamide (AM), prepared in inverse microe mulsions have been investigated by viscometry and light scattering exp eriments. The distribution of the net charge among the chains was vari ed by adjusting the initial monomer composition and the degree of conv ersion. The effect of this distribution on the solubility of the sampl es and on the chain conformation was studied. It was found that sample s with a narrow distribution of net charges were soluble in water even ii the average net charge is small. Addition of salt produces a trans ition from an extended conformation to a more compact one in qualitati ve agreement with theoretical predictions. A practically alternated Na AMPS-MADQUAT copolymer prepared in homogeneous solution and with a sma ll average net charge shows a behaviour quite similar to that of the t erpolymers.