Signature of multiple glassy states in micellar nanoparticle-polymer composites

TL;DR

This study investigates how varying polymer grafting density in micellar nanoparticle-polymer composites leads to different glassy states, revealing complex temperature-dependent dynamical transitions.

Contribution

It demonstrates the existence of multiple glassy states in nanoparticle-polymer composites and links these states to grafting density and temperature effects.

Findings

Lower grafting density leads to attractive glass at low temperatures.

Higher grafting density results in gel-like behavior at low temperatures.

Transitions between glassy states are driven by temperature and grafting density.

Abstract

We present results of temperature dependent measurements of dynamics of micellar nanoparticle - polymer composites of fixed volume fraction and variable polymer chain grafting density. For nanoparticles with lower grafting density we observe dynamically arrested state at low temperatures corresponding to an attractive glass while at high temperature the same system shows relaxation typical of a repulsive glass. For higher grafting density, the low temperature dynamics resembles more of a gel which crosses over to a repulsive glass at high temperature. Possible reasons for such fascinating dynamical transitions is delineated.