Siloxane Matrix Molecular Weight Influences the Properties of Nanocomposites Based on Metal Complexes and Dielectric Elastomer.

Alina Soroceanu,George T. Stiubianu

doi:10.3390/ma14123352

Abstract

Siloxane-based elastomers are some of the most sought-after materials for the construction of actuators and equipment for energy harvesting devices. This article focuses on changes of the mechanical (breaking stress, breaking strain, Young’s modulus) and dielectric properties for elastomers prepared with silicones, induced by the variation of molecular weight of the matrix, with three different silicone polymers having 60,000 g/mol, 150,000 g/mol, and 450,000 g/mol (from GPC measurements). Multiple siloxane elastomers were crosslinked with methyltriacetoxysilane using the sol-gel route. The dielectric permittivity values of the elastomers were also enhanced with two different complex structures containing siloxane bond and 3d transition metals as filler materials for polydimethylsiloxane polymers with various molecular weights. The dielectric spectroscopy tests demonstrated a small decrease (5%) for the values of the dielectric permittivity in relation to increased molecular weight of the siloxane polymer, both for samples prepared with pure polymer and for samples with metal complexes. The samples of nanocomposites showed a >50% increase of dielectric permittivity values relative to samples prepared of pure siloxane elastomer. The thermal tests demonstrated that the nanocomposites retained thermal stability similar with samples prepared of pure siloxane elastomer. The behavior under controlled conditions of humidity showed a trend of increased water vapor sorption with increasing molecular weight but an overall hydrophobic stable character of nanocomposites.

Highlights

Over the last three decades, there has been an increased focus on the development of materials that can work as actuators or energy harvesting devices [1,2]
We introduced as fillers for polydimethylsiloxane (PDMS) matrix (Mn = 60,000) multiple metal complexes that have in their structure both the siloxane bond and metal such as manganese, iron, and chromium [15]
Films of dielectric elastomers were prepared by room temperature condensation with siloxane polymers of different molecular weights and with metal complexes as fillers

Summary

Introduction

Over the last three decades, there has been an increased focus on the development of materials that can work as actuators or energy harvesting devices [1,2]. While demonstration installations have been built for such technologies, it is still necessary to develop methods for material optimization with a focus on specific applications [3]. Studies conducted in this area have highlighted the fact that natural muscles generate linear motion, while electric motors in industrial robots, consumers, and generators in power plants generate circular motion [4,5]. Silicone-based dielectric elastomer polymers are soft polymeric materials that bring together the properties required for actuation and energy harvesting: large energy density, fast response times, operation in air, long lifetimes, and low Young’s modulus as well as high value for breaking strain [6,7]

Methods

Results

Discussion

Conclusion