Architecture- and Composition-Controlled Self-Assembly of Block Copolymers and Binary Mixtures With Crosslinkable...

Area of Science:

• Polymer Science and Engineering
• Materials Science
• Nanotechnology

Background:

• Self-assembled block copolymer (BCP) nanoparticles (NPs) exhibit dynamic behaviors influenced by polymer chain mobility.
• Understanding chain exchange is crucial for controlling the morphology and stability of BCP nanostructures.

Purpose of the Study:

• To investigate the chain exchange behaviors in complex BCP NPs at room temperature.
• To determine the impact of copolymer architecture and crosslinking density on NP structural evolution.
• To explore methods for controlling BCP NP self-assembly and nanostructure stability.

Main Methods:

• Preparation of BCP NPs from linear and star-like polystyrene-poly(2-vinylpyridine) (PS-PVP) copolymers.
• Mixing of BCP NPs under various conditions and crosslinking densities.
• Characterization using dynamic light scattering (DLS), atomic force microscopy (AFM), and transmission electron microscopy (TEM).

Main Results:

• Observed clear structural evolution in BCP NP blends, particularly in triblock + star copolymer mixtures, driven by chain motion.
• Demonstrated that chemical crosslinking of PVP corona blocks suppresses chain exchange.
• Identified a copolymer crosslinking density (CLD) of approximately 9% as sufficient to freeze nanostructures.

Conclusions:

• Chain exchange is an inherent dynamic process in BCP NPs, enabling structural rearrangement even at room temperature.
• Tailoring copolymer architecture and crosslinking density provides a means to moderate chain motion and control self-assembled structures.
• Findings offer insights for designing novel polymer NPs for applications like drug delivery and nanoreactors.