A Small-Angle Neutron Scattering Study of the Equilibrium Conformation of Polyelectrolytes in Stoichiometric Saloplastic Polyelectrolyte Complexes

Abstract

Stoichiometric polyelectrolyte complexes, PECs, from fully sulfonated poly(styrenesulfonate), PSS, as polyanion and poly(diallyldimethylammonium chloride), PDADMA, as polycation, were prepared by mixing them at optimized polyelectrolyte and NaCl concentrations. The complexes were compacted by ultracentrifugtion and then annealed in NaCl solutions at elevated temperatures to allow the polymers to fully intermix and relax. Small-angle neutron scattering, SANS, with contrast matching, was used to study single polyelectrolyte chain dimensions in PECs made from a mixture of deuterated and protonated PSS chains. Two PSS molecular weights in PECs were investigated at various ionic strengths. SANS curves, form factor fits, and corresponding Kratky plots indicate the Gaussian nature of the polyelectrolyte chains in the complexes regardless of molecular weight. PSS coils were slightly larger than the unperturbed dimension, more so for the higher molecular weight material, which was attributed to an effective stiffening of the chain due to ladderlike interactions between polyelectrolytes.

Compact Saloplastic Poly(Acrylic Acid)/Poly(Allylamine) Complexes: Kinetic Control Over Composition, Microstructure, and Mechanical Properties

“…The remaining water is assumed to be hydration water of the matrix, giving a water content of the matrix around 15 to 20%, which is in good agreement with the hydration measured for PAA/PAH multilayers 5, 20. While the matrix itself shrunk, and the pores grew with decreasing ionic strength, the complex swelled on a macroscopic scale due to the increased osmotic pressure probably exerted by domains of non‐stoichiometric complex located on the walls of the pores 40. Together with the voids and inhomogeneities remaining after ultracentrifugation shrinking of the matrix at low salt concentration leads to the observed porosity and pore size distributions.…”

Recent progress in the science of complex coacervation

“…55,56 The structure and dynamics of bulk coacervates have been characterized using rheology 37,47,53,[57][58][59][60][61][62][63][64][65] along with X-ray and neutron scattering. 62,66,67 Finally, the thermodynamics of bulk coacervation has been characterized using isothermal titration calorimetry (ITC). 43,50,51,[68][69][70][71][72] Despite the wealth of reports describing and/or using coacervation over the decades, only recently has the coacervate phase diagram been mapped in a systematic way.…”

Saloplastics: Processing Compact Polyelectrolyte Complexes

“…Polyelectrolyte complexes are amorphous. Neutron scattering of deuterated PSS within PDADMA/PSS complexes showed the polyelectrolyte chains to be rather compact Gaussian coils . Unlike most mixtures of neutral polymers, ion‐pairing interactions between polyelectrolyte chains maintain complete mixing at the molecular level .…”