Boron-Rich Soft Hydrogels Based on the Coassembly of Cationic A‑B‑A Triblock Copolymers with Closo-Dodecaborate

TL;DR

This paper introduces a new type of hydrogel made from boron clusters and cationic polymers, showing unique structural and mechanical properties.

Contribution

The study presents a novel electrostatic hydrogel based on anionic boron clusters and cationic triblock copolymers.

Findings

The coassembly forms 10–15 nm domains that evolve into macroscopic gels with increasing concentration.

Rheology shows that longer PGEA blocks produce stronger, more gel-like systems with shear-thinning behavior.

The gels exhibit self-healing properties with structural reorganization.

Abstract

We present an unusual
type of electrostatic hydrogel based on anionic
boron cluster compounds, which remain almost unexplored in the literature.
Cationic PGEA–PEO–PGEA triblock copolymers coassembled
with dianionic closo-dodecaborate clusters to nanostructures
with the PGEA/closo-dodecaborate domains with a diameter
of around 10–15 nm. Flower-like micelles were observed only
at high dilutions, and the dynamic character of the domains was expressed
by the formation of bigger particles consisting of multiple domains
connected by the PEO bridges. The size of the nanogel particles gradually
increased with the sample concentration, leading to macroscopic gelation
of the solutions. The SAXS analysis revealed that the shape of the
domains is also changing with sample concentration, and isolated short
cylinders merge into a continuous phase in the gel-like samples. The
rheology measurements showed that the length of the PGEA domain-forming
blocks has a significant impact on the mechanical properties of the
gels, and the increasing block length leads to stronger and more gel-like
systems. All of the gels exhibit marked shear-thinning behavior, which
extends over more than five decades of shear rates. Furthermore, the
samples are largely self-healing but indicate certain structural reorganization
of the network.

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