Mark David Dadmun - US grants

- - ~ 9702313 Dadmun In this CAREER award the effect of varying the amount of hydrogen bonding present in a polymer blend containing a liquid crystalline polymer and an amorphous polymer on its phase behavior and engineering properties will be explored. The amorphous polymer will be a copolymer where one monomer (vinyl phenol) can participate in hydrogen bonding while the other monomer can not (styrene). The amount of hydrogen bonding present between the two polymers will be systematically varied by altering the composition of the amorphous copolymer. The effect of this variation on the phase `ehavior and, consequently the engineering properties (i.e. storage and loss modulus, tensile strength, viscosity) of the blend will be determined. It is expected that the change in the amount of hydrogen bonding present will produce systems which exhibit wide range miscibility, primarily immiscibility, and systems where the miscible/immiscible window is accessible. This last system will be utilized to examine the influence of the polymer chain anisotropy of the liquid crystalline polymer on the phase decomposition kinetics. The results will provide a fundamental understanding of the physical chemistry of blends containing a liquid crystalline polymer which can be utilized in the development of novel materials with tunable properties. The preparation of undergraduate and graduate students for careers demands different emphases from an instructor/advisor. Faculty primarily interact with undergraduate students via the classroom while the maturation of graduate students involve learning in both the classroom and the laboratory. Therefore, a description of a teaching philosophy which is followed is presented. A summary of the proposed teaching philosophy is to utilize effective teacher-student interaction to insure that students learn and understand the desired curriculum; to make chemistry accessible through more everyday examples; to inspire students to think a nalytically by detailing complex relationships in lecture and in workshops; and to prepare students for a vocation by introducing them to the methods by which chemical concepts are utilized in industry via industrial visitors and trips to local chemical plants, by attacking and solving problems as groups, and by introducing them to common engineering principles. %%% The proposed research program will examine how manipulation of the microscopic structure of high performance, liquid crystalline polymers can be utilized to create new materials with target properties. It is hoped that the results will provide fundamental information which can be used to guide product development such that the desirable characteristics of liquid crystalline polymers can be efficiently exploited commercially. ***

This award from the Major Research Instrumentation program supports the acquisition of a Small Angle X-ray Scattering (SAXS) Facility at the University of Tennessee. The instrument will be used to characterize the structure of materials on a length scale of 1-100 nm.
Current and future research that will benefit from the SAXS facility ranges from studies of the structure of 'soft materials' such as polymers to the more traditional 'hard materials.' The studies of soft materials include investigation of the morphology of (a) polymer blends and copolymers, (b) polymer crystallization, (c) polymer electrolytes, (d) polymer composites and (e) processed polymers (fibers, films, moldings, etc.). Studies of 'hard materials' include investigations of (a) the nanostructure of new metal oxide based materials, (b) the nanometer-size dispersions of metals and compounds in sapphire, (d) development of nanoparticles through pulsed laser ablation techniques, and (e) void formation in carbon fibers. An interesting overlap involves the use of microphase separated diblock and triblock copolymers as templates to synthesize new nanostructures, well ordered carbon nanotubes, and nanoscale magnetic wires. In addition, studies of X-ray scattering of materials will provide background for neutron scattering studies at Oak Ridge National Laboratory with the HFIR reactor upgrade and, in the longer term, the completion of the Spallation Neutron Source (SNS).
This acquisition will (1) foster the development of new areas of research in nanoscience and new collaborations among UT faculty in science and engineering, especially in the soft materials area, (2) develop new collaborations among UTK faculty and students with scientists and engineers at Oak Ridge National Laboratory, and with and other internationally prominent researchers, (3) provide opportunities for SAXS measurements to investigators from neighboring institutions, especially those that have traditionally served underrepresented minorities.

***
This award from the Major Research Instrumentation program supports the acquisition of a Small Angle X-ray Scattering (SAXS) Facility at the University of Tennessee. The instrument will be used to characterize the structure of materials on a length scale of 1-100 nm.
The SAXS system will serve faculty, postdoctoral research fellows, and students in a wide range of sub-disciplines of Materials Science, including polymer science and engineering, ceramics, metallurgy, and solid state physics. Examples of areas of study include investigation of the structure of (a) polymer blends and copolymers, (b) polymer crystallization, (c) polymer electrolytes, (d) polymer composites (e) processed polymers (fibers, films, moldings, etc.), (f) new metal oxide based materials, (g) the nanometer-size dispersions of metals and compounds in sapphire, (h) development of nanoparticles through pulsed laser ablation techniques, and (i) void formation in carbon fibers.
This acquisition will (1) foster the development of new areas of research in nanoscience and new collaborations among UT faculty in science and engineering, especially in the soft materials area, (2) develop new collaborations among UTK faculty and students with scientists and engineers at Oak Ridge National Laboratory, and with and other internationally prominent researchers, (3) provide opportunities for SAXS measurements to investigators from neighboring institutions, especially those that have traditionally served underrepresented minorities.

This award from the Instrumentation for Materials Research program will allow the University of Tennessee to purchase instrumentation for chromatographic separation and molecular characterization of polymers and copolymers that are synthesized and/or studied at the University of Tennessee (UT). More specifically, two chromatographs - one capable of operation at elevated temperatures and the other operating at ambient or near ambient temperatures - will be purchased. To optimize the utility of these systems for characterizing complex polymers, such as branched polymers, block and graft copolymers, and polymers with reactive end-groups, the instrument will include a variety of detectors including light scattering, differential viscometer, ultraviolet, and differential refractometer units. To further expand the usefulness of the room temperature chromatograph, columns will be purchased for operating this unit as either a size exclusion chromatograph (SEC) or as a temperature gradient interaction chromatograph (TGIC), as necessary. The acquisition of these instruments will provide UT polymer scientists and engineers with a state-of-the-art facility for measurement of polymer molecular weights, polydispersities, conformational characteristics, and branching. Improved polymer characterization capabilities will favorably impact the research of more than 60 researchers in the UT Chemistry, Materials Science, and Chemical Engineering Departments, including projects such as the correlation of molecular weight distribution to complex rheology, crystallization studies of polymers and copolymers, optimization of interfacial adhesion in polymer blends and composites, effect of biopolymer structure on food chemistry, and new branched polymers as novel elastomers and for testing polymer dilute solution theory. In addition, these instruments will allow us to develop new laboratories for Introduction to Polymer Chemistry, Polymer Physical Chemistry, and Polymeric Materials courses, thus exposing approximately 100 undergraduate and graduate students annually to the use of multi-detector SEC and TGIC for polymer characterization.

The acquisition of instrumentation for chromatographic separation and molecular characterization of polymers and copolymers that are synthesized and/or studied at the University of Tennessee. This will provide polymer scientists and engineers with a state-of-the-art facility for measurement of molecular weights, polydispersities, conformational characteristics, and branching of polymers and copolymers. Improved polymer characterization capabilities will favorably impact the research of more than 60 researchers in the UT Chemistry, Materials Science, and Chemical Engineering Departments. In addition, these instruments will allow the PI's to develop new laboratories for Introduction to Polymer Chemistry, Polymer Physical Chemistry, and Polymeric Materials courses, thus exposing approximately 100 undergraduate and graduate students annually to the use of multi-detector Size exclusion chromatography and temperature gradient interaction chromatography for polymer characterization.

Linda Magid of the University of Tennessee Knoxville is supported by the Experimental Physical Chemistry Program for research that focuses on how changes in counterion structure change the three-dimensional structure (shape and conformation) of surfactant aggregates, and how these changes affect the macroscopic properties (such as viscosity, detergency, and wetting) of their solutions. Surfactants self-assemble in aqueous solution to form aggregates with a variety of molecular shapes, including spheres, extended wormlike structures, branched networks of worms and vesicles, and bilayer structures. Ionic surfactant aggregates carry a net electrical charge and have a variety of similarities to conventional polyelectrolytes. At the core of this research is a technique for tuning the aggregates' structures by changing the chemical structure of the surfactant ions. Special emphasis is placed on understanding which structural features lead to aggregate branching, and which lead to shrinking of wormlike structures back to spheres. Scattering methods (light, x-rays, and neutrons), microscopy, and nuclear magnetic resonance spectroscopy will be used to investigate both the microstructure and dynamics of aggregates. Deuterated surfactants and polyelectrolytes will be synthesized for neutron scattering experiments. Teaching and training will be promoted through two curricular development activities benefiting high school students and undergraduates.

Understanding the properties of surfactant aggregates is of significant fundamental as well as practical interest. Surfactant aggregates are used widely in personal care products, drug delivery, and a variety of other applications. A long-term goal of this research is to establish a "chemical dictionary" that allows surfactant scientists to understand how bulk properties like viscocity can be manipulated by simple changes in counterion content. In addition, this research has important connections to understanding the impact of counterions on the flexibility of biological molecules such as DNA.

Mark D. Dadmun, Department of Chemistry, University of Tennessee, Rigoberto C. Advincula, Department of Chemistry, University of Houston, S. Michael Kilbey, Department of Chemistry, Clemson University, Jimmy W Mays, University of Tennessee and Grant D. Smith, University of Utah, are funded with an award from the Collaborative Research in Chemistry Program with funds provided by the Division of Chemistry, the Division of Materials Research and the Office of Multidisciplinary Activities. This multifaceted team will investigate a novel chemical process to modify and control interfaces; multiply bound polymer chains (MBPCs). Well-defined polymers of various architectures will be synthesized, and theory, simulation and experimental techniques utilized to investigate the kinetics of assembly, surface organization, layer structure, and properties of MBPCs made from these materials. Additionally, the use of MBPCs in a number of macroscopic applications will be examined.

This multiinstitution, multidisciplinary research will produce surfaces with bound loops that have desired structural features and/or confer useful properties on solid interfaces. Technological impacts, including the modifation of interfaces to promote or prevent adhesion, stabilization of colloid particles, improvement of multi-component polymer systems, and altered the wear characteristics of surfaces, will result from this research. This research program will also provide an interdisciplinary training ground for undergraduate and graduate students, and will use student exchanges to expose the students to socially and culturally diverse environments. Also, a number of experiments will be carried out at National Laboratories, including the National Institute of Standards and Technology, Oak Ridge National Laboratory, and Sandia National Laboratory. Students will acquire hands-on experience in a multi-user facility and develop the next-generation of neutron users. The participation of under-represented groups in polymer research will take place through the Engineering in Diversity Program, the Tennessee Louis Stokes Alliance for Minority Participation, and the Western Alliance to Expand Student Opportunities Program. Further, science teachers from public high schools and junior colleges will spend four weeks in research laboratories contributing to this project, providing exposure to polymers and polymer research. Finally, a website for polymer interfaces will be developed.

A series of experiments that provide an understanding of how to control and optimize the extent of intermolecular hydrogen bonding that occurs in a multi-component polymer system are proposed. DMR supported research has demonstrated that miscible blends containing a liquid crystalline polymer (LCP) and an amorphous polymer can be created by optimizing the extent of intermolecular hydrogen bonding between the two species. The physical, engineering, and thermodynamic parameters of miscible LCP/amorphous matrix will be determined using small angle neutron scattering, its phase decomposition process monitored by time-resolved light scattering, and its engineering properties (tensile, strength and flow properties) measured by standard techniques. The effect of LCP rigidity on the ability to form miscible blends will be examined to probe the universality of the ability to induce miscibility in LCP/amorphous polymer blends by optimizing intermolecular interactions. The impact of controlling and optimizing the extent of intermolecular interactions on the properties of polymer nanocomposites will also be studied. This will be accomplished by correlating the dispersion of single carbon nanotubes and layered silicates in a multi-component polymer mixture to the level of hydrogen bonding between the two components. The completion of this set of experiments will furnish critical information that will define the limits of the optimization of hydrogen bonding between two components in a multicomponent polymer mixture to improve its dispersion and properties and define crucial parameters that will enable the design and production of robust multicomponent polymer systems, including true molecular composites and nanocomposites.

The broader impacts of this work will come from the experience of Science teachers from a public High School when they spend four weeks in a university lab contributing to this project, obtaining hands-on laboratory experience and training in polymer demonstrations. The teachers will utilize this experience in their classroom to introduce high school students to polymers and research. This research will also be disseminated to a broad range of audiences by the development a public outreach webpage called "The Fact of the Matter" to educate the public regarding the contribution of materials to technological advances. Further impact will result from the completion of neutron scattering experiments at the National Institute of Standards and Technology as well as Oak Ridge National Laboratory where the students participating in this project will acquire hands-on experience in a multi-user facility and develop the next-generation of neutron users to insure the continued health of these National facilities. Finally, Current collaborations and interactions with industrial and/or government laboratories will expedite the transfer of the guidelines and fundamental understanding garnered from this project to commercial viable technologies that will benefit society. The results of this project will provide critical guidelines that will ultimately enable the rational design of multicomponent polymer mixtures (blends and nanocomposites) that can be used to create materials with a broad range of targeted properties for an enormous range of technological applications including the next generation of extraordinary structural, flame resistant, and/or thermally stable materials.

TECHNICAL ABSTRACT
Dispersing nanoparticles, such as carbon nanotubes, in a polymer matrix offers a promising method to create new materials with novel properties. Unfortunately, most nanoparticles do not homogeneously disperse in a polymer matrix, and thus the fabricated mixtures rarely attain the targeted properties. This project will seek to overcome this limitation by developing an understanding of how intermolecular interactions between polymer and pristine nanotubes can be accomplished and optimized. This will be realized by determining the ability of various polymer-bound functional groups to form electron donor-acceptor (EDA) interactions with pristine single-walled nanotubes (SWNT) and correlating the nature and extent of this interaction to the dispersion of the SWNT in a polymer matrix and to the structural and functional properties of the ultimate nanocomposite. Additionally, the most promising functional groups that form EDA complexes with SWNT will be incorporated into copolymers as a minor component. In these nanocomposites, the extent of non-covalent interaction formation in the nanocomposite will be monitored and correlated to the dispersion of the nanofiller in the polymer matrix and to the nanocomposite properties. This copolymerization will broaden the range of polymer structures, and thus targeted functionality, that can be incorporated in well-dispersed polymer nanocomposites. The design of the experiments builds on our previous NSF-supported work that demonstrates that optimizing non-covalent interactions (hydrogen bonding) between polymer and nanoscale filler can dramatically improve the dispersion and thermal, electronic, and structural properties of the resultant nanocomposite. Thus, a series of experiments will be completed that utilizes our expertise in non-covalent polymer-nanofiller interactions to develop methods to rationally tune the interfacial interaction between a nanofiller and polymer matrix to improve the homogeneity and properties of the resultant nanocomposite, while preserving the interfacial structure required for a targeted functionality.

NON-TECHNICAL ABSTRACT
Homogeneous mixing nano-sized fillers with a polymer enables the production of new materials with a range of properties that are not accessible with polymers alone. For instance, the inclusion of clays in a polymer matrix has been shown to improve its heat deflection temperature, flame resistance, gas permeability and strength. Alternatively, the incorporation of carbon fullerenes or nanotubes in a conjugated polymer matrix improves its ability to turn sunlight into energy. Unfortunately, creating this homogeneous mixture of polymers and nanoparticles is difficult, as most nanoparticles will not effectively disperse in the polymer matrix. Improved mixing behavior has been realized by modifying the surface of the nanoparticle, however this alteration often results in a decrease in its desired properties. This project will seek to overcome this limitation by developing methods to incorporate attractive interactions between the polymer and nanoparticle, without altering the structure of the nanoparticle, with the ultimate goal of using these attractive interactions to improve the dispersion of the nanoparticles in the polymer matrix and the properties of the final nanocomposite. This project will also train local high school science teachers in polymers, educate the public regarding the contribution of materials to technological advances via a public outreach website (www.factofthematter.org), and expedite the transfer of the guidelines and fundamental understanding garnered from this project to commercially viable technologies by collaborating with industry.

0932666
Dadmun

Intellectual Merit - Conjugated polymers (CPs) are a promising class of materials for use in the conversion of solar energy to electricity. For optimal performance in bulk heterojunction CPs, the morphology of the donor and acceptor materials must form percolating interpenetrating networks maximizing interfacial contacts w/ length scale of ~10 nm. Currently, we lack the fundamental understanding to guide the formation of bulk heterojunctions to these targeted nanoscale morphologies. In this collaborative proposal, an understanding of the fundamental driving forces that govern the nanoscale self-assembly and interfaces in conjugated block copolymer (BCP) thin films will be developed in order to enable the rational design and fabrication of the targeted bicontinuous nanoscale morphologies. This will be realized by completing an interdisciplinary research program that will detail the thermodynamic driving forces that control the formation of a bicontinuous interconnected percolated morphology in a thin film of conjugated BCP with controlled rigidity on a surface that is patterned incommensurately to the periodicity of the diblock copolymer as well as the synthesis and thin film structure of conjugated diblock polymers that exhibit traditional diblock morphologies. Therefore upon completion, we will attain an understanding of the thermodynamics that control the assembly of these systems in thin films; enabling the reproducible creation of the desired bicontinuous interconnected morphologies with this structure, providing a transformative method to rationally design, tailor and fabricate nanoscale morphologies with exquisite control of size and thickness for CP systems. The successful completion of these experiments will broaden the range of nanoscale thin film morphologies that can be targeted and rationally tuned in conjugated polymer thin films, and thus allow a systematic study of CP morphology on organic photovoltaics, a critical area in their optimization, yet a parameter that is not currently controllable experimentally.

Broader Impact - This project is an integrated collaborative effort between Chemistry, Chemical Engineering, and Materials Science research groups at the University of Tennessee. The broader impacts of the proposed program are embodied in this interdisciplinary collaboration, as well as the educational experiences to which it will lead. In the course of this project, the PIs will continue their outreach programs and use their research to provide training experiences for undergraduate and high school students and K-12 teachers, as well as provide input to their own teaching and exciting areas for discussion at K-12 visits. The execution of this collaborative project will also develop an interdisciplinary system of instruction, via classroom and laboratory, for training graduate and undergraduate students in chemistry, materials science, and mathematics who will be equipped to tackle modern science and engineering challenges. This project will also further develop the sustainable research infrastructure in Tennessee, an EPSCOR state, and will be implemented to ensure the participation of underrepresented groups in this research.

Technical summary: Transition metal-oxides are highly promising materials in modern technology because they are stable at high temperatures and in corrosive environments, and because their physical and chemical properties are highly tunable. The design of metal oxides for technological applications such as electronics, photovoltaics, and catalysis necessitates a thorough understanding of the physical complexity that lies beneath the broad functionality of these materials. This project involves the acquisition of a molecular beam epitaxy apparatus with an in-situ low-temperature scanning probe microscope for the synthesis and atomic-scale characterization of novel artificially-structured oxide materials. Molecular beam epitaxy offers unique capabilities of creating atomic arrangements with atomically precise control of thickness and composition, which will be utilized to systematically tune the properties of oxide thin films and interfaces with special emphasis on clean energy applications. This special instrument for epitaxial synthesis and characterization will be an important nucleus of the educational and training activities at the Joint Institute for Advanced Materials, which is a newly-established umbrella organization at The University of Tennessee and Oak Ridge National Laboratory, fostering interdisciplinary research, education, and partnership for the development of advanced materials in East Tennessee.



Layman summary: Metal oxides are highly promising materials for electronic and clean energy applications, including photocatalysis, where light-activated catalysts are used, for example, to split water into pure oxygen and hydrogen; and photovoltaics, which convert solar radiation into direct electric current. Nearly all such applications involve processes that take place at the surfaces or interfaces of these oxide materials. Fundamental understanding and better control of these processes would greatly benefit from the capability of producing well-defined surfaces, interfaces, and thin film materials, as well as from the capability to systematically alter and characterize the structural and electronic properties of these materials with precision down to the atomic level. The project involves the acquisition of a molecular beam epitaxy apparatus for the synthesis of artificially-structured metal-oxide materials, with special emphasis on clean energy applications, along with a scanning probe microscope for imaging individual atoms and mapping the nanoscale properties of these materials. Molecular beam epitaxy offers researchers the extraordinary capability of constructing novel materials from atomic "Lego principles," guided by theoretical calculations or predictions. This special instrument for epitaxial synthesis and characterization will be an important nucleus of the educational and training activities at the Joint Institute for Advanced Materials, which is a newly-established umbrella organization at The University of Tennessee and Oak Ridge National Laboratory, fostering interdisciplinary research, education, and partnership for the development of advanced materials in East Tennessee.

TECHNICAL SUMMARY:

In this research program, neutron scattering will be utilized to determine the miscibility, phase diagram, phase-separated structure, interfacial characteristics, and vertical phase separation of conjugated polymer:fullerene thin film mixtures as a function of polymer and fullerene structure, thermal processing, surface structure, and solvent. Conjugated polymers (CPs) are chosen as the focus of this study as they are a promising class of materials for use in the conversion of solar energy to electricity. Most studies create the CP nanocomposite, measure its photovoltaic (PV) properties and then attempt to ascertain the relationship between the PV activity and morphology based on the observed morphological features. There exists no a priori control of the morphology. The proposed research program is designed to supply thermodynamic information that will provide methods to control the formation of resultant CP:fullerene morphologies based on known surface and/or interfacial energies, and polymer:fullerene, polymer:solvent, and fullerene:solvent interactions. This knowledge will then be used to tune the interactions in the system to fabricate active layers with targeted structures. Correlation of PV activity to the fully characterized targeted morphology represents a paradigm shift in how the nanoscale morphology and photovoltaic activity are optimized in organic photovoltaics. Neutron scattering and reflectivity will be the primary tools in this project, as the large difference in neutron scattering length density between protonated polymers and fullerenes singularly allows the efficient and thorough characterization of the assembly, interfacial structure, morphology, and composition of polymer:fullerene systems. Moreover, the experiments are designed such that the experimental techniques, analyses, and interpretations will be applicable to polymer nanocomposites regardless of polymer structure and nanoparticle size, shape or constitution. Therefore, the completion of this research program will provide methods to develop an understanding of the fundamental thermodynamics and physics that govern the formation and structure of a broad range of polymer nanocomposites.

NON-TECHNICAL SUMMARY:

The direct conversion of solar energy to electricity is a promising method to solve the grand challenges facing the energy needs of the US and the world at large, as only solar energy can deliver the required power in an environmentally clean (i.e., zero carbon emission) process. However, the conversion of solar energy is currently 5-10 times more expensive than other commonly used energy sources. Major innovations made possible through fundamental, transformative research will be required to improve the efficiency of solar energy conversion and reduce its cost. The proposed research program is designed to meet this need, as its completion will provide critical fundamental information that is needed to rationally design and produce the next generation of more efficient and cost-effective photovoltaic cells. Additionally, broader impacts of this work will come from the experience of public High School students when they spend a summer in a university research lab contributing to this project obtaining hands-on laboratory experience and exceptional preparation for college. Further impact will result from the completion of experiments at the neutron facilities at ORNL and NIST where the students participating in this project will acquire hands-on experience in a multi-user facility to insure the continued health of these National facilities. This project will also further develop the sustainable research infrastructure in Tennessee, an EPSCOR state, and will be implemented to ensure the participation of underrepresented groups in this research.

PROGRAM DIRECTOR'S RECOMMENDATION

IIP 1238288
University of Tennessee Knoxville (UTK)
Duscher

The University of Tennessee Knoxville is planning to join the Industry/University Cooperative Research Center (I/UCRC) entitled Center for Next Generation Photovoltaics which is a multi-university center comprised of the University of Texas-Austin (UTA) and the Colorado State University (CSU). The existing Center focuses on the advancement of CdTe & CIGS thin films, thermal process modeling, imaging, and nanocrystal systems.

The goal of this proposal is to seek NSF funding to for a planning meeting to allow the University of Tennessee Knoxville to recruit industry support to allow it to join an existing I/UCRC Center focused on Next-Generation Photovoltaics (NGP). Participation by UTK will expand the scope of the existing I/UCRC to include research on organic materials, thin-film silicon materials and artificial photosynthesis.

Low-cost, reliable photovoltaics would lead to widespread adoption of solar energy as a renewable energy source. Solar energy utilization is critically important to the future of the planet. It is also an excellent training arena for future scientists and engineers because it is highly interdisciplinary, necessitating communication and interaction across disciplines. The I/UCRC efforts will also be interfaced with key educational programs at UTK, CSU, and UTA, as well as leveraging capabilities at the Oak Ridge National Laboratory. The industrial partnerships in the I/UCRC will be vital to the success of this program. The Center will have a team of faculty and students that is diverse in gender, race and ethnicity.

NON-TECHNICAL SUMMARY

Stimuli-responsive materials alter their structure or properties according to changes in their environment. This research program will examine novel stimuli-responsive polymers whose function and properties can be controlled by exposure to light. This is promising because light can be applied remotely without physical contact, its intensity can be tuned with great fidelity, and it can be used to pattern the materials for specific uses. Unfortunately, there are only a few compounds that can be introduced into polymers that are light responsive. This research program will provide the foundation to develop a broad range of new light-responsive materials based on polymer moleculaes that can be electrically active. This increase in available light-sensitive and -patternable polymers will offer the opportunity for new applications using controlled illumination and significantly extend the practicality of light-responsive materials.

Workforce development and training of the next generation of scientists and engineers prepared to tackle the grand challenges in materials research will be realized through this integrated research-and-education program and also by engaging public high-school students in hands-on research over summer periods, providing exceptional preparation for college. Further impact will result from the completion of experiments at the neutron facilities at national laboratories (ORNL and NIST) where the students participating in this project will acquire hands-on experience in a multi-user facility. This project will also further develop the sustainable research infrastructure in Tennessee and will be implemented to enhance the participation of underrepresented groups in research.



TECHNICAL SUMMARY

The overarching goal of this research program is to develop a fundamental understanding of the mechanism by which photon absorption by conjugated polymers (CP) alters their macroscopic physical properties in order to provide guidelines by which this phenomenon can be controlled and exploited to realize new stimuli-responsive materials with targeted properties. The completion of this research program will provide a comprehensive understanding of how photon absorption by a conjugated polymer alters its configuration, morphology, dynamics and thermodynamics in blends and solutions. Correlation of local electronic and structural changes to the macroscopic dynamic response of the blends in the presence and absence of light will probe the fundamental processes that hierarchically guide the change in macroscopic behavior of conjugated polymer blends as a result of photon absorption. Examination of both CP solutions and blends will provide guidelines to control this functional response on a molecular level and offer a fundamental understanding of the structural and electro-optical processes that control this phenomenon. The experimental protocol, analysis, and interpretation are also designed to be applicable to a broad range of conjugated polymers and CP/non-CP blends. Neutron scattering will be used as a primary tool to determine the structure, depth profile, and phase behavior of the CP blends and solutions of interest. The use of neutrons simplifies the variation in experimental conditions from the presence to the absence of light, as the illumination of the sample with a floodlit beam of light will not impact the detection of the scattered neutrons, unlike a similar light scattering experiment.

This suite of experimental results will then be interpreted to elucidate guidelines to enable the rational design and control of novel light-responsive materials with targeted properties. This research program will therefore provide a fundamental understanding of the mechanism by which local photon absorption translates over multiple length scales to a variation in macroscopic physical properties with the goal of providing strategies by which this unexpected phenomenon can be manipulated and directed to produce new light-responsive materials.

This workshop will discuss the progress and prospects in the field of neutron scattering as a vital tool in biological research that could provide elusive and critical, unique information about complex biological systems. Special emphasis of the workshop will be on combining high-performance computation with neutron scattering. Education and broader impact activities to enable better access to neutron scattering methodologies will also be a focus of the discussion. The workshop will provide a road-map by defining the scientific, engineering and data challenges required to use neutron scattering as a tool to study biological systems.

Recent world-wide research and development activities have created an opportunity to use neutron scattering as another vital tool in biological research. This technology offers excellent potential to provide previously elusive information about complex biological systems unobtainable with other measurement tools. Neutrons are ideal for studying multi-scale phenomena intrinsic to biological processes. With no charge, they cause little radiation damage and are highly penetrating, enabling use of complex sample environments. Also, neutrons have energies similar to atomic motions, and their spin can be coupled to magnetic fields in spin echo measurements, allowing the study of dynamic processes over a wide range of timescales, from picoseconds to microseconds. Moreover, a particularly desirable property of neutrons for biology has to do with hydrogen (H), the most abundant element in biological systems. Photons and electrons interact with the atomic electric field. With just one electron, hydrogen is all but invisible to x-rays or light. Neutrons, on the other hand, interact with nuclei, and protons have a relatively strong and negative scattering length. The isotope deuterium (D) has an even stronger scattering length, which is positive. This different sensitivity of neutrons to H and D allows for enhanced visibility of specific parts of complex biological systems through isotopic substitution. These properties are the foundation by which neutron scattering can be used to obtain precise information on the location and dynamics of H at the atomic level, as well as truly unique information on large, dynamic, multi-domain complexes at longer length and time scales. The workshop will discuss neutron crystallography, small angle scattering, diffraction, reflectometry and imaging for studying soft matter structure from the atomic to micrometer length scales and, via spectroscopic measurements, self and collective motions and excitations from sub-picosecond to microsecond timescales.

This workshop is co-funded by the Molecular Biophysics Program in the Division of Molecular and Cellular Biosciences in the Biological Sciences Directorate, and by the Chemistry of Life Processes Program in the Division of Chemistry and the Physics of Living Systems Program in the Division of Physics, both in the Mathematical and Physical Sciences Directorate.

This Major Research Instrumentation award will fund the acquisition of a modern X-ray scattering instrument to support soft materials research in the Tennessee Valley and surrounding region. The instrument will be installed at the University of Tennessee in the Polymers Characterization Lab, an established user facility for academic and industrial researchers. This acquisition will enable measurements of hierarchical structure in soft materials under controlled environmental conditions, thereby informing the design of new materials for strong and lightweight composites, safe batteries, gas and water purification, oil spill remediation, drug delivery, and 3D printing. The proposed instrument is extremely flexible, easy to use, and well-suited to a large user base with a diverse and continuously evolving research portfolio. The team is highly experienced with the design, implementation, and analysis of X-ray scattering measurements, so students will receive training in advanced materials characterization, which is critical to maintaining US technological competitiveness in the global market.

This award will fund the acquisition of a multimode X-ray scattering system to support soft materials characterization in targeted or extreme environments. The system will be installed at the University of Tennessee in the Polymers Characterization Lab, an established, sustainable, and centrally-supported user facility. The proposed acquisition will enable four workhorse techniques for characterization of hierarchical structure in soft and hybrid materials: transmission small angle X-ray scattering (SAXS), transmission wide angle X-ray scattering (WAXS), grazing-incidence small angle X-ray scattering (GISAXS), and grazing-incidence wide angle X-ray scattering (GIWAXS). The instrument can accommodate samples in a variety of states, including bulk powders, liquids, and films, and is equipped with integrated environmental controls to examine material responses to temperature, humidity, gases, applied tension, and applied shear. X-ray scattering measurements will inform fundamental studies of structure-property-processing relations in soft and hybrid materials, providing immediate support to a variety of federally funded research programs in nanocomposites, energy storage, separations, renewable materials, and biomaterials. The team will leverage the acquisition of the X-ray scattering instrument for the design of new course modules and a regional immersion workshop, thereby elevating the educational experience of undergraduate and graduate students through training in advanced materials characterization.

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.