Colloidal and fumed particles in nematic liquid crystals: Self-assembly, confinement and implications on rheology

Abstract The particles-in-Liquid Crystals (LCs) composites have the capability to serve as the promising candidate for enhancing the inherent characteristics of the LCs which can open new avenues for sensing, display and photochemical applications. The complexity and variety of hierarchical self-organized structures coupled with the high mechanical strength induced by the addition of the small fraction of colloidal or nanoparticles has continuously attracted the attention of the soft matter scientific community. The objective of this review is to systematically investigate the current and past literature which focusses on the implication of inclusion of particles on the behaviour of nematic LCs (NLCs) and smectic LCs in particular. Herein, we present a chronicle of the seminal work on the spherical and anisotropic particle self-assembly in NLCs, two major mechanisms of particulate network formation and its implication on the rheology of the particles-in-NLC composites. The fundamental aspects of the confinement of NLCs and smectic LCs in the pores and also in the network of fumed silica nanoparticles are discussed and the subsequent influence on the phase, structural, dynamical and rheological behaviour is explained. The article also attempts to provide a clear distinction between particles-in-NLC systems with predominantly repulsive and attractive interparticle interactions in terms of rheology and microstructure. The review also highlights the existing gaps in the literature which still lacks clarity on the chief factors governing the particle self-organization and the correlation between the confinement and rheological response. Finally, we describe the future perspectives which can potentially give rise to diverse applications of particles-in-LC composites.