Synthesis and aqueous solution properties of sterically stabilized pH-responsive polyampholyte microgels

Area of Science:

• Polymer Chemistry
• Materials Science
• Nanotechnology

Background:

• Polyampholyte microgels composed of poly(methacrylic acid) (PMAA) and poly(2-(diethylamino)ethyl methacrylate) (PDEA) exhibit pH-dependent behavior.
• These microgels aggregate at intermediate pH, limiting their colloidal stability and potential applications.

Purpose of the Study:

• To develop pH-responsive microgels with enhanced colloidal stability at intermediate pH.
• To investigate the impact of grafting poly(ethylene glycol)methacrylate (PEGMA) on microgel properties.
• To explore the potential of these modified microgels for DNA and protein delivery.

Main Methods:

• Emulsion copolymerization of PMAA and PDEA to form initial microgels.
• Surface grafting of PEGMA onto pre-formed microgels.
• Dynamic light scattering (DLS) to measure hydrodynamic radius (Rh).
• Zeta potential and second virial coefficient (A2) measurements to assess colloidal stability.

Main Results:

• Unmodified PMAA/PDEA microgels showed aggregation at intermediate pH (2500 nm).
• PEGMA-grafted microgels exhibited improved colloidal stability, with Rh of approximately 100 nm at intermediate pH.
• PEGMA-grafted microgels maintained their polyampholytic properties across a pH range.
• Varying MAA/DEA composition allowed tuning of the microgel isoelectric point.

Conclusions:

• Surface modification with PEGMA effectively stabilizes polyampholyte microgels at intermediate pH.
• These stabilized microgels retain their pH-responsive characteristics.
• The tunable properties make these microgels promising candidates for advanced delivery systems, such as DNA and protein delivery.