Smart viscoelastic and self-healing characteristics of graphene nano-gels

TL;DR

This study presents the synthesis and detailed rheological analysis of graphene-polyethylene glycol gels that exhibit self-healing, shear-thinning, and enhanced elastic properties due to their microstructure, with potential smart material applications.

Contribution

It introduces a simple refluxing synthesis method for stable graphene-polymer gels and provides comprehensive viscoelastic characterization revealing their self-healing and smart behavior.

Findings

Gels show shear thinning and yield stress behavior.

Presence of graphene nanoflakes enhances structural stability and self-healing.

Gels exhibit resonance-induced elastic disruption and recovery.

Abstract

Readily synthesizable nano-graphene and poly ethylene glycol based stable gels have been synthesized employing an easy refluxing method and exhaustive rheological and viscoelastic characterizations have been performed to understand the nature of such complex gel systems. The gels exhibit shear thinning response with pronounced yield stress values which is indicative of a microstructure where the graphene nanoflakes intercalate with the polymer chains and form a pseudo spring damper network. Experimentations on the thixotropic behavior of the gels indicate that the presence of the G nanoflakes leads to immensely augmented structural stability capable of withstanding severe impact shears. Further information about the localized interactions of the G nanoflakes with the polymer chains is revealed from the amplitude and frequency sweep analyses in both linear and nonlinear viscoelastic regimes. Massively enhanced cross over amplitude values are recorded and several smart effects such as enhanced elastic behavior at increasing forcing frequencies are registered. Structural resonance induced disruption of the elastic behavior is observed for the gels for a given range of frequency and the proposition of resonance has been justified mathematically. It is observed that post this resonance bandwidth, the gels are able to self-heal and regain their original elastic behavior back without any external intervention. More detailed information on the viscoelastic nature of the gels has been obtained from creep and recovery compliance tests and justifications for the spring damper microstructure has been obtained. Smart features such as enhanced stress relaxation behavior with increasing strain have been observed and the same explained based on the proposed microstructure.