Quantifying Hydrophilicity in Polyelectrolytes and Polyzwitterions

John Akintola, Nagham Abou Hamad, Joseph B. Schlenoff

Florida State University

Many proposed applications of polymers and especially charged polymers like polyelectrolytes and polyzwitterions involves aqueous environment where water is a key component. Affinity of water for polymers were determined using different methods over the years. For example, using computational and thermal method. In the present work, the hydrophilicity of a selection of polyelectrolytes and zwitterions were determined using calorimetric measurement. In addition to that, size exclusion chromatography was used to find the scaling factor using the Flory relationship  in order to determine the quality of the solvent used and which is 0.3M NaNO3and also to find the second virial coefficient that tell about the quality of the solvent .
Calorimetric measurement showed that polyzwitterions exhibit a more exothermic enthalpy of solution in comparison to polyelectrolytes.  Further comparison of pairs of polyzwitterions and polyelectrolytes leads to an insight regarding the addition of the methyl in the polymer backbone. Calorimetric measurement proved that the addition of a polymer in the backbone make it more hydrophilic.
SEC showed that Polyelectrolytes adopt a more expanded coil conformation than polyzwitterions in the used mobile phase, which means that solvent used represent a theta solvent conditions for polyzwitterions and good solvent conditions for polyelectrolytes without giving further information about the increasing order of hydrophilicity to be compared with the calorimetric measurement. Second virial coefficient of different polymers will be compared and used to find the increasing order of hydrophilicity that can be compared to calorimetric measurement.