Stimulus-responsive block copolymer nano-objects and hydrogels via dynamic covalent chemistry

Area of Science:

• Polymer Chemistry
• Materials Science
• Supramolecular Chemistry

Background:

• Block copolymers self-assemble into various nano-objects like vesicles and worms.
• Dynamic covalent chemistry offers responsive and reversible material properties.
• Controlling nano-object morphology is crucial for advanced material applications.

Purpose of the Study:

• To investigate the use of dynamic covalent chemistry for inducing reversible morphological transitions in block copolymer nano-objects.
• To explore the pH-dependent behavior of these transitions.
• To develop novel physical hydrogels using this approach.

Main Methods:

• Synthesis of poly(glycerol monomethacrylate)-poly(2-hydroxypropyl methacrylate) (PGMA-PHPMA) diblock copolymers via polymerization-induced self-assembly.
• Addition of 4-carboxyphenylboronic acid (CPBA) to induce dynamic covalent bond formation.
• pH-controlled modulation of CPBA binding and subsequent morphological changes.

Main Results:

• PGMA-PHPMA nano-objects undergo reversible vesicle-to-worm and worm-to-sphere transitions upon CPBA addition.
• CPBA binding is pH-dependent, enabling reversible morphological control.
• High copolymer concentrations lead to pH-dependent hydrogelation (gelation and de-gelation).

Conclusions:

• Dynamic covalent chemistry provides a versatile tool for controlling block copolymer nano-object morphology.
• pH-responsive physical hydrogels can be formed from these systems.
• This approach offers an alternative to traditional covalently cross-linked hydrogels.