Formation and structure of ionomer complexes from grafted polyelectrolytes

Area of Science:

• Polymer Science
• Supramolecular Chemistry
• Materials Science

Background:

• Ionomer complexes are formed by mixing oppositely charged polymers.
• Grafted copolymers offer unique architectures for complex formation compared to linear polymers.
• Understanding the self-assembly of these complex systems is crucial for designing novel materials.

Purpose of the Study:

• To investigate the structure and formation of grafted block ionomer complexes (GBICs) and grafted ionomer complexes (GICs).
• To compare the size and formation mechanisms of GBICs and GICs with traditional complex coacervate core micelles (C3Ms).
• To explore the influence of temperature and polyelectrolyte length on the assembly of these ionomer complexes.

Main Methods:

• Light scattering measurements to determine the size of ionomer complexes.
• Synthesis and characterization of grafted block copolymers and linear polyelectrolytes.
• Self-consistent field (SCF) calculations to model micelle formation.

Main Results:

• GBICs exhibit significantly larger sizes (~70-100 nm) compared to GICs (~6-22 nm).
• The formation mechanism of GICs differs from C3Ms and GBICs, with GIC size dependent on homopolyelectrolyte length.
• Complexes show a slight size decrease with increasing temperature, with reversible behavior observed for some systems.

Conclusions:

• The experimental sizes of GBICs and GICs deviate from SCF predictions, suggesting secondary association mechanisms.
• Grafted copolymers with segregated blocks form larger structures than randomly grafted copolymers.
• Temperature and polymer architecture play critical roles in the self-assembly and properties of ionomer complexes.