| NSF Org: |
DMR Division Of Materials Research |
| Recipient: |
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| Initial Amendment Date: | April 20, 2016 |
| Latest Amendment Date: | April 20, 2016 |
| Award Number: | 1607378 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Tomasz Durakiewicz
tdurakie@nsf.gov (703)292-4892 DMR Division Of Materials Research MPS Directorate for Mathematical and Physical Sciences |
| Start Date: | September 1, 2016 |
| End Date: | August 31, 2020 (Estimated) |
| Total Intended Award Amount: | $429,580.00 |
| Total Awarded Amount to Date: | $429,580.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
3451 WALNUT ST STE 440A PHILADELPHIA PA US 19104-6205 (215)898-7293 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
PA US 19104-6205 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | CONDENSED MATTER PHYSICS |
| Primary Program Source: |
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| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.049 |
ABSTRACT
Non-technical Abstract
The proposed experimental research will have impact in two major science and technology arenas: how to make a tougher material and how to adapt ideas of liquid crystal display technology to new water-based liquid crystal systems. Broadly, the program develops new ability to formulate and manipulate micro- and nano-particles and macromolecules in solution. Thus the research enhances the science and technology enterprise that underpins applications efforts for US industries involved with sensing/actuation, microfluidics, drug delivery, photonics, printing, coatings, cosmetics and agriculture. The program will train a new generation of scientists and engineers in soft materials, formulation, advanced optical microscopy, electro-optics, microfluidics, rheology & computation. After finishing, PhD students & post-docs enter the work force and strengthen US technological and economic infrastructure; furthermore, a diverse group of undergraduate and high school participants are typically stimulated every summer in our laboratory to pursue STEM education/career choices.
Technical Abstract
The proposed program aims to advance knowledge about complex fluids and soft materials, but many findings will also interest the hard condensed matter, chemical engineering and materials science communities. The proposed experiments are unified by their focus on micro-mechanics, broadly defined. One set will measure structural and dynamical properties of colloidal glasses and crystals with goals to identify regions within these materials that are "soft" and exhibit increased propensity to deform or rearrange. A second set will investigate lyotropic chromonic liquid crystals. These liquid crystals are unusual in that they twist very easily which leads to formation of chiral structures from achiral mesogens, they exhibit two levels of assembly hierarchy from molecules to rod-mesogens to LC phases, and they are water soluble. The consequences of these properties will be probed by diffusion experiments which track motions of particles dressed by local LC director fields, by study of the competition between elastic energy and molecular assembly hierarchy in "extreme" confined geometries, and in novel "drying" of multi-phase droplets. Collectively, the experiments use advanced optical microscopies, light scattering and rheometry for sample observation, and they require formulation of novel soft materials via controlled suspension chemistry and physics, microfluidics, etc. For example, colloidal particles with different shapes, interactions and potential for in-situ manipulation are/will-be developed.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
Homogeneous samples, or samples with monodisperse ingredients, are usually desirable for materials applications; they have the benefit of easier modelling and understanding, which further offer unified starting points for exploration of non-ideal matter. On the other hand, polydispersity or molecular heterogeneity tends to introduce disorder into materials. Although molecular heterogeneity are often avoided in synthetic systems, in the real world around us, most materials are intrinsically polydisperse. For instance, the natural polymers such as rubber, wood cellulose, and silk are composed of long-chain molecules with various lengths. The natural dispersions such as milk are also comprised of constituents with a wide distribution of sizes. Importantly, molecular heterogeneity has been demonstrated to help promote formation of diverse surface patterns and morphologies in biological matter. A few examples include pollen grains, insect cuticles, fungal spores, as well as the photonic structures in butterfly wings and bird feathers.
The findings we recently published (Wei, W.-S., Xia, Y., Ettinger, S., Yang, S. & Yodh, A. G. Molecular heterogeneity drives reconfigurable nematic liquid crystal drops. Nature 576, 433–436 (2019)) thus reported on dramatic shape transformations of liquid crystalline drops, wherein the observed polymorphic transitions are driven by the polydispersity of the molecules contained inside the drops.
Specifically, we studied drops composed of polydisperse nematic liquid crystal oligomers (NLCOs) in a solution of water and surfactants. At a high temperature, the drop is spherical because the interfacial energy is high enough to dominate the system. On cooling, the surface tension and bulk elasticity vary, and excess interface is created. Depending on detailed NLCO components and surfactant concentration, the drops evolve reversibly from spheres to roughened spheres, flowers, and branched filamentous network with controllable diameter. Observations and modelling reveal that molecular heterogeneity plays a crucial role in this process; spatial segregation of oligomer chains of varying length tips the balance between free energies, driving the morphogenic phenomena.
Finally, the resultant nematic structures can be permanently locked into liquid crystal elastomers by UV curing and harvested for potential new functional materials. We are currently carrying out new experiments along these lines. The simple rules revealed by the experiments thus offer new concepts for creation of programable spatio-temporal networks. Moreover, we hope other researchers will feel encouraged to explore the potential influences of molecular heterogeneity in both living and non-living matter.
Last Modified: 09/23/2020
Modified by: Arjun G Yodh
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