Colloidal complexes from poly(vinyl amine) and carboxymethyl cellulose mixtures

Area of Science:

• Polymer Science
• Physical Chemistry
• Materials Science

Background:

• Polyelectrolyte complexes (PECs) are formed by the electrostatic interaction between oppositely charged polymers.
• Understanding the phase behavior of PECs is crucial for their application in various fields.
• Poly(vinyl amine) (PVAm) and carboxymethyl cellulose (CMC) are common polyelectrolytes with distinct charge characteristics.

Purpose of the Study:

• To investigate the phase behaviors of PVAm-CMC polyelectrolyte complexes.
• To determine the influence of composition, pH, and salt concentration on complex formation and stability.
• To develop and validate a model for predicting the formation of PVAm-CMC complexes.

Main Methods:

• Preparation of polyelectrolyte complexes from dilute solutions of PVAm and CMC.
• Determination of phase diagrams as a function of composition and pH.
• Analysis of colloidal complex stability and particle size distribution.
• Modeling of polymer mixing ratios and degree of ionization.

Main Results:

• Phase diagrams revealed regions of soluble complexes, colloidal complexes, and precipitates.
• Colloidal complexes were stabilized by excess polymer, providing electrosteric stabilization.
• A model successfully predicted mixing ratios for complexes at pH 7, but failed at extreme pH.
• Complex formation was sensitive to NaCl concentration, with no complexation above 2 M.

Conclusions:

• The phase behavior of PVAm-CMC complexes is complex and dependent on multiple factors.
• Electrosteric stabilization plays a key role in the formation of stable colloidal complexes.
• The interaction between PVAm and CMC at pH 7 is endothermic, suggesting an entropy-driven process.
• PVAm-CMC complex size is sensitive to electrolyte concentration, highlighting the importance of ionic strength.