Mixing oppositely charged polyelectrolytes in solution results in stoichiometric precipitates. These products of polyelectrolyte complexation are usually porous, brittle, and challenging to put into use, but can be processed further to obtain a wide range of materials. By adding salt, a full spectrum of partly associated complexes can be accessed from rubbery solids to coacervates. Coacervates are phase-separated solution mixtures made of a gel-like phase and a liquid phase. Using complexes made from a well-known polyelectrolyte pair, poly(diallyldimethylammonium) (PDADMA) and poly(styrenesulfonate) (PSS), chain conformation was probed in a wide spectrum of assemblies, ranging from solids to decreasingly viscous gels. Neutron scattering was employed to investigate the coil dimensions of deuterated PSS inserted in specific quantities in the PDADMA/PSS complex prepared with KBr. Through contrast matching, the PSS chain is isolated from, but observed in, its complex environment. The polyanion was found to maintain a constant radius of gyration and an ideal Gaussian conformation in the solid material. However, as more KBr was added, the chain size started to shrink. A comparison was made with the same polyanion in the presence of salt alone using light scattering, excluding the effect of the polycation. The analysis reveals details about the internal structure of these complexes and a better understanding of polymer dynamics in polyelectrolyte assemblies.

Chain conformation in polyelectrolyte complexes, from solids to gels

255th National Meeting (2018)

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