Preparation and adsorption of refined polyelectrolyte complex nanoparticles

Area of Science:

• Materials Science
• Colloid and Surface Chemistry

Background:

• Polyelectrolyte complexes (PECs) are formed by mixing oppositely charged polymers.
• Nonstoichiometric PECs can exhibit complex phase behavior upon mixing and processing.

Purpose of the Study:

• To characterize the bulk and surface properties of centrifuged nonstoichiometric PEC dispersions.
• To investigate the adsorption behavior of PEC coacervate particles onto surfaces.

Main Methods:

• Preparation of PECs using poly(diallyldimethylammonium chloride) (PDADMAC) and sodium poly(maleic acid-co-alpha-methylstyrene) (PMA-MS).
• Centrifugation to separate PEC dispersions into supernatant (SUP), coacervate (COAC), and precipitate phases.
• Characterization using mass, turbidity, particle hydrodynamic radii (R(h)), titratable charge, attenuated total-reflection-Fourier transform infrared (ATR-FTIR) spectroscopy, scanning electron microscopy (SEM), and atomic force microscopy (AFM).

Main Results:

• Centrifugation separated PEC dispersions into SUP, COAC, and precipitate.
• The COAC phase consisted of 200-nm nanoparticles, containing 60% of the polymer mass and 20% of the titratable charge.
• The SUP phase contained excess polycations and 80% of the titratable charge.
• Linear relationships were observed between turbidity, R(h), and COAC concentration.
• Adsorption of COAC particles onto polyelectrolyte multilayer (PEM) surfaces followed Langmuir model kinetics.
• Adsorbed COAC particles were hemispherically shaped, with coverages >= 25%.

Conclusions:

• Centrifugation effectively separates nonstoichiometric PEC dispersions into distinct phases with differing compositions and properties.
• The coacervate phase comprises nanoparticles with significant polymer content.
• The adsorption behavior of PEC coacervate particles on surfaces is predictable and comparable to synthetic latices.