Temperature-Responsive Zwitterionic Polymers That Undergo UCST-Type Liquid-Liquid Phase Separation under...

Area of Science:

• Polymer Chemistry
• Materials Science
• Biophysics

Background:

• Liquid-liquid phase separation (LLPS) is crucial for cellular organization and function.
• Temperature-responsive polymers exhibit phase transitions with temperature changes.
• Achieving UCST-type LLPS in polymers under physiological ionic strength remains challenging.

Purpose of the Study:

• To synthesize novel temperature-responsive zwitterionic polymers.
• To investigate their UCST-type LLPS behavior in aqueous media with physiological ionic strength.
• To explore the influence of copolymer composition and ionic strength on phase separation.

Main Methods:

• Copolymerization of sulfabetaine (SaB) and sulfobetaine (SB) monomers.
• Characterization of cloud point (CP) transitions with temperature.
• Microscopic observation of coacervate droplet formation and dissolution.

Main Results:

• Synthesized P(SaB-co-SB) copolymers exhibiting UCST-type LLPS at physiological ionic strength.
• Observed that CP increases with higher SaB content.
• Demonstrated coacervate droplet formation below CP and dissolution above CP, unlike typical UCST polymers.

Conclusions:

• Zwitterionic copolymers P(SaB-co-SB) enable UCST-type LLPS under physiological conditions.
• Dipole-dipole interactions between SaB units are key to this phenomenon.
• These polymers show potential for applications requiring tunable phase separation in biological environments.