Hybrid soft materials where one component exhibit well-controlled anisotropy are ideal for engineering fine material microstructures with an impact in its macroscopic properties. Among these systems, liquid crystalline polymer networks are distinct given their imprinted liquid crystalline order in an elastic rubbery network. A wide variety of out-of-plane actuation behavior can be encoded in these materials thru implementing complex microstructures in the nematic director field. While most imprinted designs are based on spatial variations of the nematic director, very few theoretical studies have been made on dual-phase elastomers: samples that combine well-defined regions with nematic order and isotropic regions. Depending on patterning design, these materials exhibit a variety of actuation behavior, going from helical twisting to chiral bending and accordion folding. By implementing finite element elastodynamics simulations at the continuum level, we demonstrate this actuation variety based on several key design factors: director orientation, pattern orientation, as well as domain and sample size*.
Towards alternative methods for engineering microstructures in hybrid materials, we examine the process of structural templating on particle suspensions by melt solidification. In this process, nucleation and growth of a phase transition can re-arrange particle disorder, imprinting the structure and morphology of the growing solid. Via numerical experiments on a simple coarse-grain model for particle kinetics at a melt/crystal interface, we investigate tunable structural templating given by crystallization speed. We evaluate the threshold crystallization velocity for structural templating on systems with finite and infinite crystal thickness and show its dependence on particle size, solvent size, melt viscosity and system-intrinsic interaction strength^.
Overall, these simulations studies show an exceptional agreement with experimental observations, providing light for further development of advanced hybrid soft materials with complex microstructures.
* Work supported by the International Young Scientist Fellowship, IOP-CAS and the President International Fellowship Initiative, CAS.
^ Work supported by NSF DMR-1408323