Water soluble polymers. 76. Electrolyte responsive cyclocopolymers with sulfobetaine units exhibiting polyelectrolyte or polyampholyte behavior in aqueous media

Copolymers of N,N-diallyl-N,N-dimethylammonium chloride (DADMAC) and the zw itterionic 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-radi cal photoinitiator. The feed ratio of DADMAC:DAMAPS was varied from 100:0 t o 0:100 mol % with the total monomer concentration held constant at 2.5 M. C-13 NMR data indicate that the resulting polymers maintain the five-member ed ring structure in the cia conformation common to diallylammonium salts. Reactivity ratio studies indicate that the sulfobetaine monomer is incorpor ated randomly along the polymer backbone; Laser light scattering provided m olecular weights and second virial coefficients, which varied from 5.16 x 1 0(4) to 8.42 x 10(4) and 5.54 x 10(-4) to 1.89 x 10(-4) mt mol g(-2), respe ctively. Solution behavior is dependent upon ionic strength as determined b y low shear viscosity and dynamic light scattering experiments. For cycloco polymers containing <40 mol % sulfobetaine, classical polyelectrolyte behav ior is shown by viscosity decreases with increasing ionic strength. However , for polymers containing greater than or equal to 40 mol % sulfobetaine, c hain expansion occurs as the ionic strength is increased above that require d for the Donnan equilibrium.