Polymers with bound positive or negative charges are referred to as polyelectrolytes, macroions, or polyions. These polymers may be synthetic, natural or modified. the synthetic polyelectrolytes include polymers that can be made by several methods, the major one being chain growth polymerization. The distinctive behavior of polyelectrolytes in aqueous solutions is what separates this class of polymers from non-ionic polymers. In aqueous solution, the polymer coils are greatly expanded by the presence of charged groups. If the solution is free of added electrolytes the polymer coil expands as the polymer concentration decreases. This is known as the "polyelectrolyte effect". In the presence of added electrolytes, the polyelectrolytes behave like non-ionic polymers and chain expansion is not observed.
Polyelectrolytes which contain both acidic (cationic) and basic (anionic) functional groups are known as polyampholytes. Often, these polymers undergo aqueous dissolution only in the presence of salt and coil dimensions increase as the ionic strength of the solution increases. This is primarily due to the screening of attractive electrostatic interactions within the polymer coils. As one might guess, this behavior may be advantageous to applications where a viscosifying agent in saline environments is necessary.
As one might imagine there are various practical applications for both polyelectrolytes and polyampholytes. The various practical applications of polyelectrolytes hinge upon the fact that these materials are: (a) water soluble polymers capable of promoting major changes in the fluid properties of aqueous suspensions and slurries; (b) substances which may be absorbed by neutral particles, thus imparting a surface charge to the particles; (c) substances whose ionized groups interact very strongly with ions and colloidal aggregates of opposite charge; and (d) substances which can be tailored to be sensitive or insensitive to chemical and biological degradation. Polyelectrolytes find applications as thickeners, dispersants, water conditioners, waste treatment agents, soap and detergent additives, soil conditioners, ion-exchange resins, and enhanced oil recovery agents. Polyampholytes have been utilized in petroleum recovery, various drilling fluids, cements, flocculants and in the field of drag reduction.
Continuing research within our laboratories include the synthesis of hydrophobically modified carboxybetaine and sulfoxybetaine monomers and their incorporation into acrylamide-based polymers. Their solution behavior is characterized by viscosity, light scattering (classical and dynamic) and fluorescence measurements.