Polydimethylsiloxane (PDMS) is the most widely explored and utilized polysiloxane, possessing an extremely low glass transition temperature as well as excellent thermal stability. As a liquid at room temperature, most applications require PDMS to be chemically crosslinked and / or combined with fillers to realize the requisite mechanical properties. While mechanical reinforcement of PDMS by nanofillers is well-known, the realization of consistently high levels of dispersion of nanoparticles in a PDMS matrix remains a challenge. One strategy to control nanoparticle dispersion involves grafting ionic functional groups to the nanoparticle surface (thus creating so-called nanoparticle ionic materials, or NIMs described by Giannelis and coworkers) and combining these charged nanoparticles with a polymer matrix containing functional groups with the opposite charge. This approach inspired us to design ionic PDMS-silica nanocomposites from (cationic) ammonium-functionalized PDMS and (anionic) sulfonate-functionalized silica nanoparticles, with the aim of influencing the distribution and dispersion of the nanoparticles. The impact of the PDMS molecular weight, charge density and charge location on the distribution and dispersion of ionic silica nanoparticles and on the mechanical reinforcement of the nanocomposites are described. In addition, molecular dynamics simulations are used to estimate the expected lifetimes and concentrations of temporary ionic crosslinks between nanoparticles and polymer matrix present in the nanocomposites described herein.

Ionic polydimethylsiloxane-silica nanocomposites: From synthesis and characterization to mechanical reinforcement

ACS Fall 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.