Mapping Structure and Rheology of pH-Responsive Resins for Low-VOC Coatings

Area of Science:

• Polymer science and materials chemistry
• Sustainable coatings technology
• Rheology and particle engineering

Background:

• The paint and coatings industry is moving away from volatile organic compounds (VOCs) for environmental reasons.
• Stimuli-responsive polymer latex particles offer a way to reduce VOCs while maintaining performance.
• Understanding particle microstructure is key to controlling macroscopic properties.

Purpose of the Study:

• To investigate the relationship between particle microstructure and rheological properties of stimuli-responsive polymer latex particles.
• To evaluate the impact of pH and organic solvents on suspension rheology.
• To compare the responsiveness of this novel resin architecture to existing pH-responsive latex particles.

Main Methods:

• Small-angle neutron scattering (SANS) to determine particle microstructure.
• Dynamic light scattering (DLS) to analyze particle size and behavior.
• Rheological measurements to assess viscosity changes under varying conditions.

Main Results:

• Particles feature a cross-linked core with extended polymer tails containing carboxylic acid groups.
• Increasing pH leads to deprotonation and polymer chain extension, increasing hydrodynamic drag and viscosity.
• pH adjustment had a more significant impact on viscosity than organic solvent addition.
• The studied resin architecture demonstrated higher responsiveness per mole of pH-responsive group.

Conclusions:

• The engineered particle architecture effectively controls rheology through pH-induced changes.
• This approach offers a more sustainable and responsive alternative to traditional VOC-heavy formulations.
• The findings provide valuable insights for designing advanced, environmentally friendly coatings.