pH Behavior of Polymer Complexes between Poly(carboxylic acids) and Poly(acrylamide derivatives) Using a Fluorescence...

Area of Science:

• Polymer Chemistry
• Supramolecular Chemistry
• Materials Science

Background:

• Interpolymer complex formation is crucial for developing advanced materials.
• Understanding the local micro-environment during complexation is key to controlling material properties.
• Poly(carboxylic acids) and poly(acrylamide derivatives) are widely used polymers with potential for complexation.

Purpose of the Study:

• To clarify the local micro-environment during interpolymer complex formation.
• To investigate the influence of polymer structure and pH on complexation.
• To understand the role of hydrogen bonding and hydrophobicity in complex stability.

Main Methods:

• Utilized a fluorescence label technique with 3-(2-propenyl)-9-(4-N,N-dimethylaminophenyl) phenanthrene (VDP) as an intramolecular fluorescence probe.
• Synthesized polymers via free radical polymerization.
• Monitored interpolymer complexation through charge transfer emission from the VDP unit.

Main Results:

• Both poly(methacrylic acid) (polyMAAc) and poly(acrylic acid) (polyAAc) formed interpolymer complexes with poly(N,N-dimethylacrylamide) (polyDMAM).
• The micro-environments in polyMAAc/polyDMAM systems were more hydrophobic than in polyAAc/polyDMAM systems due to the alpha-methyl group, especially at acidic pH.
• Hydrogen bond formation and subsequent changes in micro-environmental hydrophobicity drive interpolymer complex formation.

Conclusions:

• The alpha-methyl group in polyMAAc significantly increases hydrophobicity during complexation with polyDMAM.
• Solution pH reduction facilitates hydrogen bond formation, altering micro-environmental hydrophobicity and promoting complexation.
• The electron-donating ability of the carbonyl group in poly(acrylamide derivatives) influences their complexation with poly(carboxylic acids).