Water Soluble Polymers. 76. Electrolyte Responsive Cyclocopolymers with Sulfobetaine Units Exhibiting Polyelectrolyte or Polyampholyte Behavior in Aqueous Media

Abstract

Copolymers of N,N -diallyl- N,N -dimethylammonium chloride (DADMAC) and the zwitterionic monomer 3-( N,N -diallyl- N -methylammonio)propanesulfonate (DAMAPS) have been prepared in a 0.5 M NaCl aqueous solution using 2-hydroxy-1-[4-(hydroxyethoxy)phenyl]-2-methyl-1-propanone (Irgacure 2959) as the free-radical photoinitiator. The feed ratio of DADMAC:DAMAPS was varied from 100:0 to 0:100 mol % with the total monomer concentration held constant at 2.5 M. 13 C NMR data indicate that the resulting polymers maintain the five-membered ring structure in the cis conformation common to diallylammonium salts. Reactivity ratio studies indicate that the sulfobetaine monomer is incorporated randomly along the polymer backbone. Laser light scattering provided molecular weights and second virial coefficients, which varied from 5.16 × 10 4 to 8.42 × 10 4 and 5.54 × 10 -4 to 1.89 × 10 -4 mL mol g -2, respectively. Solution behavior is dependent upon ionic strength as determined by low shear viscosity and dynamic light scattering experiments. For cyclocopolymers containing <40 mol % sulfobetaine, classical polyelectrolyte behavior is shown by viscosity decreases with increasing ionic strength. However, for polymers containing ≥ 40 mol % sulfobetaine, chain expansion occurs as the ionic strength is increased above that required for the Donnan equilibrium.