POLY(AMMONIO ALKOXYDICYANOETHENOLATE)S AS NEW HYDROPHOBIC AND HIGHLY DIPOLAR POLYZWITTERIONS .3. SOLUBILITY PROPERTIES

The solubility properties of amorphous ryloyloxy)ethyldimethylammonio) ethoxy]-ethenolate] (zwitterionic lateral group of mu = 25.9 D) invest igated in 43 solvents of widely differing polarity may be interpreted in terms of solvent molar refractivity (dispersion interactions), dipo le moment (dipolar interactions), basicity (donor-acceptor interaction s with the ammonium site) and hydrogen-bond-donating power (hydrogen b onding to the anionic site). In dimethylformamide, representative of s trongly dipolar aprotic media, the phase diagram is characterized by a lower critical solution temperature corresponding to a lower theta te mperature of about 65.8 +/- 1-degrees-C. Coil expansion at 25-degrees- C, as derived from intrinsic viscosity measurements, is an increasing function of the concentration of added lithium salts (less-than-or-equ al-to 1.5 mol l- 1), and the order of anion efficiency is Cl- > Br - > I- > ClO4-. In trifluoroethanol, representative of weakly associated and strongly protic solvents, the addition of tetramethylammonium salt s (less-than-or-equal-to 1 mol l-1) results in coil expansion only in the case of the more polarizable ClO4- and I- anions, while Cl- and Br - promote chain collapse. The hydrophobic polyzwitterion becomes water soluble at 25-degrees-C only in the presence of high salt concentrati ons, such as NaSCN > 2.5 mol l-1, ZnCl2 > 5 mol l-1, C2H5NH3+NO3- > 6 mol l-1, and the phase diagram is characterized by an upper critical s olution temperature strongly dependent on salt concentration (dT/d[NaS CN] = -70-degrees-C 1 mol-1). In strongly acidic media, such as concen trated H2SO4, HClO4 aqueous solution (40-60 wt%) or methanesulfonic ac id, partial protonation of the anionic sites transforms the polyzwitte rion into a water soluble cationic polyelectrolyte.