CAREER: Liquid Crystal-Templated Sequential Infiltration Synthesis of Hybrid Organic/Inorganic Materials with Multidimensional Chiral Structures

University Of North Texas, Denton TX

Investigators

Abstract

NON-TECHNICAL ABSTRACT Chirality is a geometric property of a molecule or structure that cannot be made to match its mirror image. It is widely prevalent in natural systems like DNA, proteins, and beetle shells. It is also of vital importance in diverse fields such as chiral mechanical and optical structures, bioseparation, and pharmaceuticals. Current exploration of chiral structures mostly involves molecular design and self-assembly of low mechanical strength organic materials. However, the kind of hybrid organic/inorganic materials with superior properties required for engineering applications are plagued by significant knowledge gaps in terms of synthesizing these materials. With this CAREER award, supported by the Solid State and Materials Chemistry program and the Condensed Matter Physics program, both in NSF’s Division of Materials Research, the principal investigator and her research group at the University of North Texas investigate new strategies for developing chiral hybrid materials by using abundant chiral liquid crystals (CLCs) as templates for nucleation and growth of these hybrid organic/inorganic materials. This is an integrated education-research program that centers on a fundamental understanding of the chemical reactions, physical behavior, and structural engineering involved in transforming LC morphologies into hybrid or fully inorganic materials; and revealing underlying structure-property relationships to unlock chirality-endowed multidimensional structures, as well as potentially novel optical and mechanical properties. The project promotes STEM education in soft-matter science and engineering, with a particular emphasis on engaging female and Hispanic students. By creating summer research opportunities, workshops and outreach activities, the principal investigator strives to include, inspire, and empower students from underrepresented groups, kindling their interests and participation in materials science. Activities are specifically designed to educate a new generation of scientists and engineers who better reflect the diversity of the Dallas-Fort Worth area, and to build a nationally-recognized soft-matter program in North Texas and beyond. TECHNICAL ABSTRACT Chiral nematic or cholesteric phases in liquid crystals (LCs) exhibit asymmetrical packing of molecules, and thereby result in a finite twist angle between adjacent molecules and long-range chiral ordering similar to helical superstructures in DNA. The increase in chirality leads to the formation of 3D cubic symmetry, known as blue phases (BPs), that consist of double-twisted cylinders. The chiral properties of LCs (from nano to micrometers) are widely used in display technologies, electro-optics, and sensors. However, exploiting the full potential of such beneficial chiral structures to adapt to diverse engineering conditions, e.g., temperature, stress, and chemical environments, needs to overcome the inherently mechanically weak nature of LCs. In particular, the rapidly growing market for miniaturized device technologies requires materials with integrated flexibility and optical and mechanical performance at micro/nanoscale precision, all of which put CLCs in a more unique position than conventional solid crystalline materials. In this CAREER project, supported by the Solid State and Materials Chemistry program and the Condensed Matter Physics program, both in NSF’s Division of Materials Research, the principal investigator and her research group study novel reaction mechanisms facilitated by 2D/3D chiral templates to synthesize hybrid organic/inorganic materials with chirality across disparate length scales. The functional polar groups in mesogenic monomers used for LC structure polymerization serve as reactive moieties for sequential infiltration synthesis of metal oxides. The helical hierarchical and 3D lattice structures formed by highly chiral LCs, including BPs, guide the diffusion, nucleation, and growth of organometallic precursors inside the templates. By combining advanced experimental techniques and computational modeling, the research advances the fundamental understanding of thermodynamics, transport, and site selectivity of inorganic species in CLCs. Furthermore, the principal investigator studies the interplay among molecular architecture, synergistic self-assembly, and spatially controlled nucleation and growth of organic/inorganic species within complex multidimensional CLC/BP structures. This fundamental understanding allows the rational design of chiral-structured metal oxide-reinforced LC composites and unlocks their full potential in diverse application fields that include chiral optics, chiral mechanical devices, asymmetric catalysis, chiral separation and sensors This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.