Molar mass dependence of polyzwitterion phase separation behavior and dynamics

It is known that polyelectrolytes and polyzwitterions exhibit complex chain conformation and phase diagram behavior with and without salt. Polyzwitterions are a particular type of polyampholyte that bears a pair of charges within each monomer unit, ultimately leading to charge neutrality across the entire polymer structure. These materials exhibit a range of solution and solute-responsive behaviors due to the presence of opposite charges either in the main chain or as a pendant moiety, as in polysulfobetaine. Such dipolar interactions are temperature and ionic strength dependent in media with high dielectric constant, such as water where upper critical solution temperature (UCST) is observed. We will discuss the molar mass scaling of the UCST behavior in aqueous solutions of poly(3-(acrylamidopropyl-dimethyl-ammonium) propyl-1-sulfonate) (pAPAPS) prepared by RAFT polymerization and aggregation that occurs prior to macroscopic phase separation through cloud point, dynamic light scattering, and small-angle x-ray scattering measurements. The behavior of the collective diffusion coefficient will be discussed and the relationship of the apparent scaling dependence, and relationship to the change in solvent quality near the theta temperature [1,2].



[1] PD Pickett, Y Ma, M Lueckheide, Y Mao, and VM Prabhu, J. Chem. Phys. 156, 214904 (2022).

[2] PD Pickett, Y Ma, and VM. Prabhu, J. Chem. Phys. 159, 104902 (2023).