pH-responsive behavior of selectively quaternized diblock copolymers adsorbed at the silica/aqueous solution...

Area of Science:

• Polymer Science
• Surface Chemistry
• Materials Science

Background:

• Amphiphilic block copolymers can form surface aggregates on solid substrates.
• The quaternization degree of polymer blocks influences their interfacial behavior.
• Understanding pH-responsive polymer films is crucial for smart material applications.

Purpose of the Study:

• To characterize the pH-responsive desorption and swelling of selectively quaternized PDMA-PDEA films at the silica/aqueous interface.
• To investigate the influence of quaternization degree and adsorbed layer structure on this behavior.
• To assess the reversibility of the pH-responsive phenomena.

Main Methods:

• Quartz crystal microbalance with dissipation monitoring (QCM-D)
• Zeta potential measurements
• Contact angle analysis
• In situ atomic force microscopy (AFM)

Main Results:

• Copolymer films formed micelle-like aggregates on silica at pH 9.
• Highly quaternized copolymers showed negligible desorption at pH 9 and pH 4, while weakly quaternized ones desorbed.
• Films exhibited reversible swelling and desorption over two pH cycles (9-4-9-4).
• pH-responsive behavior correlated with the degree of quaternization and adsorbed layer structure.

Conclusions:

• Selectively quaternized PDMA-PDEA films demonstrate tunable pH-responsive behavior at silica interfaces.
• Both the density of cationic sites and the film's structural organization dictate the response.
• These findings offer insights for designing advanced responsive polymer coatings.