Interactions between brushlike polyacrylic acid side chains on a polyacrylate backbone in dioxane-water

Area of Science:

• Polymer Chemistry
• Supramolecular Chemistry

Background:

• Densely grafted polymers offer unique architectures for exploring intermolecular interactions.
• Polyacrylic acid (PAA) is a versatile polyelectrolyte with tunable properties.

Purpose of the Study:

• To synthesize and characterize densely grafted polyacrylic acids (d-PAAs).
• To investigate the influence of intermolecular and intramolecular hydrogen bonding on d-PAA behavior in solution.
• To understand the aggregation behavior of d-PAAs.

Main Methods:

• Synthesis of poly(tert-butyl acrylate) macromonomers via atom-transfer radical polymerization (ATRP).
• Homopolymerization to create densely grafted poly(tert-butyl acrylate)s.
• Hydrolysis to obtain d-PAAs.
• Proton nuclear magnetic resonance (1H NMR) spectroscopy to study hydrogen bonding.
• Dynamic light scattering (DLS) to analyze aggregation.

Main Results:

• D-PAAs exhibit both intermolecular and intramolecular hydrogen bonding between carboxylic acid groups.
• Intermolecular hydrogen bonding is sensitive to polymer concentration, temperature, and water content.
• Intramolecular association leads to a contraction of hydrodynamic volume.
• Intermolecular hydrogen bonding results in the formation of aggregates (clusters).
• These clusters shrink with decreasing water concentration.

Conclusions:

• Hydrogen bonding plays a critical role in the solution behavior and aggregation of d-PAAs.
• The observed changes in hydrodynamic volume and aggregation are directly linked to the strength and type of hydrogen bonding.
• The findings provide insights into the self-assembly mechanisms of densely grafted polyelectrolytes.