Preparation of Poly(acrylate)/Poly(diallyldimethylammonium) Coacervates without Small Counterions and Their Phase Behavior upon Salt Addition towards Poly-Ions Segregation.

Marcos Vinícius Aquino Queirós,Watson Loh

doi:10.3390/polym13142259

Abstract

In this work, we report the phase behavior of polyelectrolyte complex coacervates (PECs) of poly(acrylate) (PA−) and poly(diallyldimethylammonium) (PDADMA+) in the presence of inorganic salts. Titrations of the polyelectrolytes in their acidic and alkaline forms were performed to obtain the coacervates in the absence of their small counterions. This approach was previously applied to the preparation of polymer–surfactant complexes, and we demonstrate that it also succeeded in producing complexes free of small counterions with a low extent of Hofmann elimination. For phase behavior studies, two different molar masses of poly(acrylate) and two different salts were employed over a wide concentration range. It was possible to define the regions at which associative and segregative phase separation take place. The latter one was exploited in more details because the segregation phenomenon in mixtures of oppositely charged polyelectrolytes is scarcely reported. Phase composition analyses showed that there is a strong segregation for both PA− and PDADMA+, who are accompanied by their small counterions. These results demonstrate that the occurrence of poly-ion segregation in these mixtures depends on the anion involved: in this case, it was observed with NaCl, but not with Na2SO4.

Highlights

Electrostatic complexes are formed through the associative phase separation between oppositely charged macro-ions, for example, natural or synthetic polyelectrolytes, surfactant aggregates, or inorganic nanoparticles
Polyelectrolyte complexes (PECs) is the term given to the colloidal aggregates, dense liquid phase and solid phase that result from the association between oppositely charged polyelectrolytes
This work describes the preparation of polyelectrolyte complexes free of small counterions

Summary

Introduction

Electrostatic complexes are formed through the associative phase separation between oppositely charged macro-ions, for example, natural or synthetic polyelectrolytes, surfactant aggregates, or inorganic nanoparticles. This association gives rise to a phase that is enriched in the charged species. Polyelectrolyte complexes (PECs) is the term given to the colloidal aggregates, dense liquid phase and solid phase that result from the association between oppositely charged polyelectrolytes. When this phase contains high amounts of water, it behaves like a liquid and it is commonly named as coacervate [1,2]. Several studies exploit variations in pH [9], temperature [10], molar mass [2] and the chemical nature of the polyelectrolytes [11] as well as the salt addition in order to understand what implications they have on the properties of the PECs

Methods

Results

Conclusion