Combined Simulation and Experimental Study of Polyampholyte Solution Properties: Effects of Charge Ratio, Hydrophobic Groups, and Polymer Concentration

WA Zhang and YC Ma and ND Posey and MJ Lueckheide and VM Prabhu and JF Douglas, MACROMOLECULES, 55, 6750-6761 (2022).

DOI: 10.1021/acs.macromol.2c00977

Polyampholytes are polymers with both cationic and anionic monomers that have many features in common with proteins. These molecules have many applications associated with their natural biocompatibility and their propensity to form viscoelastic fluids and gels due to their common tendency to form self-assembled structures in solution. Recently, advances in the synthesis capabilities have enabled the fine-tuning of the monomer structure and composition, such as the sequence and ratio of the charged and hydrophobic groups. We correspondingly investigate these molecular characteristics on the solution properties of a series of poly(carbonate)-based polyampholytes using both molecular dynamics simulations and small-angle neutron scattering measurements. Our simulations suggest the importance of hydrophobic groups for understanding the observed properties of our polyampholyte solutions, a well-known fact for protein solutions. In particular, our simulations indicate that the hydrophobic groups cause the polyampholyte chains to form compact micelle-like rather than diffuse clusters at low concentrations and greatly influence the concentration dependence of the correlation peak in the structure factor describing the correlation distance between the polyampholyte chains in solution. We also construct a polyampholyte solution association map where the polymer concentration and charge ratios lead to different propensities of association (or clustering) and determine a self-assembly boundary governing the transition between self-assembled clusters that resemble micelles and a transient polymer network that percolates the system.

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