Thermal, Mechanical and Magneto-Mechanical Characterization of Liquid Crystalline Elastomers Loaded with Iron Oxide Nanoparticles

Abstract

Liquid crystalline elastomers (LCEs) are materials that reveal unusual mechanical, optical and thermal properties due to their molecular orientability characteristic of low molar mass liquid crystals while maintaining the mechanical elasticity distinctive of rubbers. As such, they are considered smart shape-changing responsive systems. In this work, we report on the preparation of magnetic sensitized nematic LCEs using iron oxide nanoparticles with loadings of up to 0.7 wt%. The resultant thermal and mechanical properties were characterized by differential scanning calorimetry, expansion/contraction experiments and extensional tests. The magnetic actuation ability was also evaluated for the neat elastomer and the composite with 0.5 wt% magnetic content, finding reversible contractions of up to 23% with the application of alternating magnetic fields (AMFs) of up to 48 kA/m at 300 kHz. Thus, we were able to demonstrate that the inclusion of magnetic nanoparticles yields LCEs with adjustable properties that can be tailored by changing the amount of particles embedded in the elastomeric matrix, which can be suitable for applications in actuation, sensing, or as smart substrates.

Magneto-responsive liquid crystalline elastomer nanocomposites as potential candidates for dynamic cell culture substrates

“…After synthesis, homogeneous films with no indication of phase separation were obtained. Films changed from transparent with a yellowish tinge for the neat elastomers to opaque and brownish as the concentration of nanoparticles increased as shown in Figure 1a The phase behavior of the elastomers was identified from DSC thermograms from which glass transition temperatures (T g ) and nematic-to-isotropic phase transition temperatures (T ni ) were reported previously elsewhere [30] and are summarized in Table 1. Both T g and T ni decreased with increasing nanoparticle concentration.…”