Separated Micelles Formation of pH-Responsive Random and Block Copolymers Containing Phosphorylcholine Groups

Area of Science:

• Polymer Chemistry
• Materials Science
• Supramolecular Chemistry

Background:

• pH-responsive polymers are crucial for controlled drug delivery and smart materials.
• Understanding copolymer self-assembly in aqueous media is key to designing advanced functional materials.

Purpose of the Study:

• To investigate the pH-responsive self-assembly behavior of random and block copolymers in aqueous solutions.
• To characterize the micelle formation and coexistence of distinct copolymer types.

Main Methods:

• Dynamic Light Scattering (DLS) to analyze particle size distribution and micelle formation.
• Fluorescence measurements using a pyrene probe to assess copolymer interactions and micelle structure.
• Fluorescence Resonance Energy Transfer (FRET) to confirm the separation of copolymer types.

Main Results:

• Copolymers exist as individual chains in acidic conditions (pH < ~8).
• Upon increasing pH above ~8, distinct micelles form, indicated by bimodal DLS with radii of 4.5 nm (random) and 10.4 nm (block).
• FRET efficiencies near zero demonstrate the coexistence of two separate micelle populations.

Conclusions:

• The studied copolymers exhibit pH-dependent self-assembly into distinct micellar structures.
• The formation of separate random and block copolymer micelles is confirmed, highlighting their potential for selective encapsulation and release.