Degree of Orientation in Liquid Crystalline Elastomers Defines the Magnitude and Rate of Actuation

Abstract

The anisotropy of liquid crystalline elastomers (LCEs) is derived from the interaction-facilitated orientation of the molecular constituents. Here, we correlate the thermomechanical response of a series of LCEs subjected to mechanical alignment to measurements of the Hermans orientation parameter. The LCEs were systematically prepared with varying concentrations of liquid crystalline mesogens, which affects the relative degree of achievable order. These compositions were subject to varying degrees of mechanical alignment to prepare LCEs with orientations that span a wide range of orientation parameters. The stimuli-response of the LCEs indicates that the liquid crystalline content defines the temperature of actuation, whereas the orientation parameter of the LCE is intricately correlated to both the total actuation strain of the LCE as well as the rate of thermomechanical response.

Free-Form Liquid Crystal Elastomers via Embedded 4D Printing

“…Figure a shows the thermomechanical response of LCE printed under ambient conditions onto a glass slide. These results match literature values for printed LCE in ambient conditions where print speed and corresponding mesogen alignment show a direct correlation with mechanical actuation strain . When printed horizontally in the gel, the LCE exhibited a similar dependence on the print speed, as shown in Figure b.…”

“…These results match literature values for printed LCE in ambient conditions where print speed and corresponding mesogen alignment show a direct correlation with mechanical actuation strain. 54 When printed horizontally in the gel, the LCE exhibited a similar dependence on the print speed, as shown in Figure 3b. This indicates that embedded printing into a gel matrix has limited influence on LCE mesogen alignment.…”

Liquid Crystalline Elastomers with Tailorable Actuation Performance Based on Orthogonal Click Chemistries

“…On the other hand, the thiol-ene-dominated VE-LCE-2 achieved a reversible actuation of approximately 100% between 30 and 150 °C (Figure 5d and Figure S26b Information). We postulate that the difference in actuation performance was primarily attributed to the distinct degree of orientation: 52 The VE-LCE-2 (S = 0.74) exhibited a higher degree of orientation than EV-LCE-2 (S = 0.52), as evident from the 2D WAXS patterns (Figure 5a,b), which led to a larger actuation strain and higher work capacity (Figure S27). These findings indicate the enhanced design flexibility provided by our two-stage method compared to the conventional LCE chemistries.…”

Toward Fully Printed Soft Actuators: UV‐Assisted Printing of Liquid Crystal Elastomers and Biphasic Liquid Metal Conductors

“…[29,[25][26][27]34] LCE actuation relies on the transition between two crystalline phases: ordered alignment of mesogens along a single axis (nematic state) and a disordered (isotropic) phase. [35] This transition can be induced by heat, and results in macroscopic contraction of the transducer along the axis of nematic alignment. LCEs are promising materials for "4D printing" [30,31,36] as they can be patterned through extrusionbased printing techniques commonly used in 3D printing and direct ink writing of structures that can undergo reversible shape change.…”