Nanoparticle-Liquid Crystalline Elastomer Composites

Abstract

Liquid crystalline elastomers (LCEs) exhibit a number of remarkable physical effects, including a uniquely high-stroke reversible mechanical actuation triggered by external stimuli. Fundamentally, all such stimuli affect the degree of liquid crystalline order in the polymer chains cross-linked into an elastic network. Heat and the resulting thermal actuation act by promoting entropic disorder, as does the addition of solvents. Photo-isomerization is another mechanism of actuation, reducing the orientational order by diminishing the fraction of active rod-like mesogenic units, mostly studied for azobenzene derivatives incorporated into the LCE composition. Embedding nanoparticles provides a new, promising strategy to add functionality to LCEs and ultimately enhance their performance as sensors and actuators. The motivation for the combination of nanoparticles with LCEs is to provide better-controlled actuation stimuli, such as electric and magnetic fields, and broad-spectrum light, by selecting and configuring the appropriate nanoparticles in the LCE matrix. Here we give an overview of recent advances in this area with a focus on preparation, physical properties and actuation performance of the resultant nanocomposites.

Nano-Objects and Ions in Liquid Crystals: Ion Trapping Effect and Related Phenomena

“…Since the well-developed surface (in other words, the high surface to volume ratio) and strong enough attractive interactions between the surface of the purifying agents and the ion are the two major factors affecting the trapping efficiency, nanoparticles known for their extremely high surface to volume ratio are promising candidates for the development of the ion capturing agents. Recent progress in the design of nanomaterials and their successful incorporation in liquid crystals [105][106][107][108][109][110][111][112][113][114][115][116][117] provides the foundation for considering nano-objects embedded in liquid crystals as ion capturing agents. We will discuss the property of nanoparticles to trap ions in the next section of this manuscript.…”

“…The intriguing properties of nanoparticles in liquid crystals are being actively studied in many laboratories around the globe, and we refer readers to review manuscripts available on this subject for more details [105][106][107][108][109][110][111][112][113][114][115][116][117]. In this section, we will analyze the existing literature from the perspective of the ion capturing phenomenon.…”

Experimental Evaluation of the Coefficient of Thermal Expansion of Chilled Aluminum Alloy-Borosilicate Glass (P) Composite

“…Composite materials are sensitive to temperature changes as the response of the matrix material to an applied load is often directly dependent on the temperature and any small changes in temperature causes the differential thermal contraction and expansion of the constituent phases that in turn results in building up of internal stresses within the material [11][12]. Thus, the study of coefficient of thermal expansion of metal matrix composites is of paramount importance.…”

Stimulus-active polymer actuators for next-generation microfluidic devices

“…In [155], recent developments in the field of LCE materials were reviewed with a focus on their use in actuator applications. Embedding nanoparticles in an LCE matrix is a promising strategy for increasing both functionality and performance of LCE-based actuators [156]. By selecting appropriate particles, the possible actuation mechanisms can be tuned for better and faster control and extended to include magnetic fields and broad-spectrum light.…”