Precise control of cyclodextrin-based pseudo-polyrotaxane lamellar structure via axis polymer composition

Area of Science:

• Supramolecular Chemistry
• Polymer Science
• Materials Science

Background:

• Self-assembly of cyclodextrin (CD) with guest polymers is recognized for biocompatibility and accessibility.
• Triblock copolymers like poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) (PEO-PPO-PEO) are key components in such assemblies.

Purpose of the Study:

• To investigate the impact of PEO-PPO-PEO triblock copolymer composition on self-assembled structures formed with beta-cyclodextrin (β-CD).
• To understand the mechanism of lamellar or plate formation based on β-CD complexation with specific polymer segments.

Main Methods:

• Synthesis and characterization of PEO-PPO-PEO triblock copolymers with varying PEO lengths.
• Complexation studies with β-CD to induce self-assembly.
• Morphological analysis of the resulting self-assembled structures (lamellar and plate).

Main Results:

• PEO-PPO-PEO copolymers with longer PEO chains (e.g., EO5PO29EO5, EO14PO29EO14, EO75PO29EO75) formed lamellar structures with pseudo-polyrotaxane nanosheets.
• β-CD selectively complexed with the PPO core, leading to microphase separation and controlled layer thickness.
• Shorter PEO chains (EO2PO29EO2) resulted in plate structures due to β-CD complexation with both PPO and PEO segments.
• The length of the central PPO block was crucial for lamellar structure formation.

Conclusions:

• Precise control over lamellar structure thickness (both crystalline β-CD/PPO and amorphous PEO layers) is achievable by tuning copolymer composition.
• The findings offer fundamental insights into CD-based self-assembly, expanding potential applications.
• This work highlights the importance of polymer segment length and selective complexation in directing self-assembly morphology.