Colloidal stabilization of graphene sheets by ionizable amphiphilic block copolymers in various media

TL;DR

This study demonstrates effective stabilization of graphene sheets using ionizable amphiphilic block copolymers, enabling high-quality dispersions and enhanced mechanical properties in polymer composites.

Contribution

It introduces a novel two-step exfoliation and stabilization method using star-shaped copolymers for producing high-quality graphene dispersions.

Findings

High concentration stable graphene suspensions achieved

Graphene/polymer composites show 145% increase in storage modulus

Star-shaped copolymers effectively stabilize monolayer graphene

Abstract

In this work, linear polystyrene-poly(2-vinylpyridine) (PS-b-P2VP) and heteroarm star PS_22P2VP_22 ionizable block copolymers were used as dispersing agents for the liquid-phase exfoliation of pristine graphene. Various strategies such as direct exfoliation, film hydration and phase transfer have been employed and compared. The best strategy involved a two-step process, namely, pre-exfoliation of graphite in polymer/CHCl3 solutions followed by phase transfer to acidified water. High concentrations of stable aqueous suspensions of graphene flakes, highly enriched in monolayer structures, were then obtained by using the star-shaped copolymers as stabilizers. The as-prepared graphene/copolymer hybrids were used as a filler material in order to prepare functional polymer composites for mechanical reinforcement. Such copolymer-modified graphene sheets have proven to be efficient reinforcing agents of PVA, as a significant increase of storage modulus (145% higher than that of neat PVA) was achieved even at a low graphene weight fraction of 0.1 wt%.