Molecular Weight Dispersity as Design Parameter to Enable Brush Particle Hybrid Materials with Enhanced Fracture Toughness and Inorganic Content

Polymer-tethered (or 'brush') particles (BPs) have been pursued as building blocks for one-component electronic and optical hybrid materials. However retention of application capability involves high inorganic fraction, along with mutually exclusive properties such as high modulus and toughness.

This contribution will present brush chain dispersity as a viable ‘design parameter’ that enables the mutual enhancement of Young’s modulus and fracture toughness, while also facilitating increased inorganic loading. Photo-SI-ATRP was used to provide a library of BP materials with controlled grafting density and dispersity in the range D = 1.05-3.1. Using this material library, a detailed analysis of the role of brush chain dispersity on structure formation as well as small- and large-strain deformation behavior of BP materials for molecular weight dispersity will be presented. Results of dynamical mechanical analysis demonstrate that Young's modulus is independent of brush dispersity while toughness strongly increases with chain dispersity. Interestingly, the degree of order in self-assembled BP films (measured in terms of the distribution of Voronoi cell area in monolayer films) is found to be robust with respect to dispersity.