Jimmy Mays, Ph.D. - US grants

This proposal is for a three-way collaboration between U. Minnesota, Princeton, and U. of Alabama, with different but mutually enhancing expertise in synthetic chemistry and materials science, to obtain needed information on the interfacial physical chemistry of amphophilic polymer dispersants. The specific approach is to study the direct effects of systematic variations os molecular weight, chemical structure, polymer architecture, and other factors which might possibly be used for tailoring amphophilic polymer dispersants, on the interactions that determine the macroscopic properties of colloidal dispersions. Effects of systematic variation of molecular characteristics of adsorbed layers of amphophilic block copolymers on the interaction forces between two such macroscopic layers will be studied. Polymers molecules with well-defined molecular weights and architectures will be synthesized by anionic polymerization and characterized with respect to block molecular weights, compositions, and architectures. Direct measurement of forces between adsorbed layers will be made. Theoretic modelling of the measured interaction profiles using self-consistent field theory will be carried out. With the measured and qualitatively modelled interactions having been determined, the response of macroscopic dispersion properties can be related in a direct way to molecular characteristics of the dispersion agents.

9303112 Morrison A combined experimental and theoretical investigation will be carried out addressing the issue of melt fracture in the processing of polymeric materials. A set of experiments with monodispersive polybutadine and polystyrene will be conducted in various shear flows. The results will be compared to existing and new calculations on a variety of constitutive equations which predict viscoelastic instabilities. The investigators hope to establish an unambiguous constitutive explanation of melt fracture. If the investigators succeed in establishing such an interpretation of a so far ambiguous and controversial phenomenaon, it will open the door to eliminating failures from melt fracture in the processing of polymeric materials. ***

9802853 Mays This award is for the purchase of a state-of-the-art size exclusion chromatography (SEC) instrument for use in characterizing polymers that are synthesized at the University of Alabama at Birmingham. To maximize the utility of this instrument for accurately and rapidly characterizing a wide range of synthetic materials, we will equip the instrument with superior flow rate stability and with multiple detectors: refractive index, ultraviolet (photodiode array), and multi-angle laser light scattering (MALLS) detectors. The dual concentration detectors are useful in examining compositional variations in many copolymers, while the MALLS detector allows determination of absolute molecular weights without reliance on calibration curves (standards of the same type as the polymer being analyzed are often not available). SEC/MALLS also allows conformational characteristics of polymers to be determined. Use of the MALLS detector along with the differential viscometer that is already available in our laboratory will allow for rapid detection and quantification of long chain branching in polymers. The combination of these various detectors is especially useful in our work with graft copolymers, which combine copolymer character with branching. %%% This project supports equipment used in the development of advanced polymeric materials leading to better paints, improved ceramics, lighter faster electronics, and low cost biodegradable plastics from renewable resources. It will involve the integration of education and research through the participation and training of students, including students from under represented groups through participation in the NSF Alliance for Minority Participation Program. * * *

9980398
Advincula

This award supports a three year collaborative research project between Professor Rigoberto Advincula of the University of Alabama and Professor Hiroaki Usui of the Tokyo University of Agriculture and Technology in Japan. The researchers will be investigating surface initiated polymerization of amino acid derivatives by ion assisted deposition: polymer and film characterization. Ion-Assisted deposition (IAD) is a novel extension of the vacuum evaporation method. Recently there has been growing interest in polypeptide films on solid substrates. IAD offers the potential for aligning dipoles during synthesis, holding much promise for the creation of tethered polypeptide chains having controlled orientation. An important question is whether the orientation parameters affect primarily the deposition of the polymerization process. Polymers usually do not evaporate easily, so the researchers will explore the fundamental differences between polymers produced by three different methods: 1) direct evaporation of simple polymers, 2) step-growth polymerization and 3) addition polymerization.

The project brings together the efforts of two laboratories that have complementary expertise and research capabilities. The U.S researchers are experts in the mechanism of polymerization, polydispersity, microstructure and film characteristics. Their Japanese collaborator is a pioneer in the use of the vacuum evaporation method for fabrication of polymeric ultrathin films. Polymer ultrathin films have important applications in microelectronics, electro-optics and biotechnology. The project advances international human resources through the participation of a several graduate students including underrepresented groups. Through the exchange of ideas and technology, this project will broaden our base of basic knowledge and promote international understanding and cooperation. Results of the research will be published in international scientific journals and also presented at scientific meetings in the U.S. and abroad.

This proposal was received in response to NSE, NSF 00-119. This Nanoscale Exploratory Research award is part of the National Nanotechnology Initiative (NNI). It will exploit self-assembly of block copolymers of styrene and 1,3-cyclohexadiene into a core-shell cylinder-in-cylinder morphology, followed by crosslinking of poly(cyclohexadiene) (PCHD) and removal of the polystyrene (PS) segments, as a means for producing novel functionalized PCHD nanotubes. PCHD may be aromatized to poly(phenylene) (PP), a strong, crystalline, and thermally stable engineering polymer. As an alternative, PCHD can be carbonized by pyrolysis. These materials will be thoroughly characterized in terms of their sized, shapes, surface chemistry and mechanical properties. To conduct this work, an interdisciplinary collaboration between the polymer chemistry group of Dr. Jimmy Mays (University of Alabama at Birmingham, UAB) and the polymer physics/morphology group of Professor Sam Gido (University of Massachusetts, UMass) is proposed.
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Composites incorporating such nanotubes could lead to a new class of robust, lightweight, high strength materials. By controlling molecular weight and processing conditions, we should be able to create nanotubes of varying radius, wall thickness, and aspect ration. By varying the composition of the block copolymer, other shapes besides tubes (cylinders, plates) can also be made. Reactive hydroxyl groups present on the surface of these molecular objects can be used to manipulate their processing characteristics and to provide strong bonding to matrix materials. The PP nanotubes may be insulating or they may be made conducting by doping. Such materials could be used as component in a smart composite designed to transmit an electronic signal, for example, if impacted. Opto-electronic, nanoprobe, and medical applications are also envisioned for these materials.

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.

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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.

Abstract
CTS-0129613
Kilbey, S. Michael
Clemson University

In this exploratory project the PI and Co-PI will focus on creating a series of branched amphiphilic block copolymers and investigating how their assembly, organization and structure are different than brushes formed form linear polymers.

In order to maximize the productivity during this one-year exploratory project, the synthesis efforts will focus three types of architectures. The PI and Co-PI will synthesize comb-block, star-block copolymers and make proof-of-concept syntheses of A2A'B and A3A'B copolymers. The A2A'B and A3A'B copolymers are novel materials.

In terms of characterization, the PI and Co-PI will focus on two key techniques: They will use the surface forces apparatus (SFA) to investigate the structure of brushes made from the aforementioned materials; they will also investigate the surface morphology and organization using atomic force microscopy (AFM). The former technique will focus on the layers as they are assembled from a selective solvent, and the latter technique will examine dried layers after the assembly process. The focus here is to explore how the connectivity and size of the new, branched polymers affects the organization and structure of the brush layer.

This is an Exploratory/GOALI grant in which the PI and Co-PI will collaborate with Dr. Victor P. Thalacker, Senior Laboratory Manager at 3M Corporate Process Technology Center in St. Paul, Minnesota.

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.

Sparse long chain branching, LCB(side chains attached to the main polymer backbone), i.e., branching levels typically less than one branch per 1000 backbone carbon atoms, and arm molecular weights, Ma, significantly greater than the critical molecular weight (MW) for entanglements, Me, have been reported to have remarkable effects on the rheology and processing behavior of polyolefins. For example, what is believed to be one branch in every three chains on average can have similar effects on the rheology of a polyethylene(PE) as having multiple branches of various types(long and short), high molecular weight, and a broad molecular weight distribution. The goal of this research is to develop a quantitative theory for the rheological response and associated processing performance of a melt of known polymerization kinetics. In other words, it is desired to predict polymerization conditions and catalyst structure which will lead to the molecular architecture needed to produce the desired rheology, processing performance, and properties. Furthermore, it is desired to evaluate the use of LCB to render ultra-high MW resins melt processable opening the door for producing high performance materials with many applications(e.g. prosthetics, ballistics protection, coatings, etc.).

In order to theoretically design the molecular architecture of polymer chains for generating the desired processing performance, a highly interdisciplinary effort will be required which incorporates experts in experimental and theoretical rheology, polymer processing, polymerization kinetics and catalysts, and polymer synthesis and characterization (this expertise cannot be found in any one location). Scientists from two U.S. universities (Virginia Tech and the University of Tennessee) with expertise in extensional and non-linear rheology, flow birefringence, polymer processing and polymer synthesis and characterization will join forces with scientists from English(7), Dutch(1) and Greek(1) universities. The research effort will capitalize on the Leeds-based Microscale Polymer Processing (MuPP) consortium with contributions from Leeds (molecular rheology, reaction kinetics), Durham and Imperial College-London (chemistry), Sheffield (chemistry and crystallization), Cambridge and Bradford (small-scale processing), and Oxford and Eindhoven (solid state). The group at Imperial College, London is joining this co-operative program with expertise in polymerization catalyst development for tailored molecular structure. Scientists at Leeds are the world leaders in the development of molecular theories for branched polymers. The general approach is to use model systems to establish a rheological standard by which to identify the structures present in commercially produced PEs (standard analytical techniques cannot provide the required information) and then develop correlations between polymerization kinetics, molecular architecture and processing performance.

The basis for designing the branching topology of polyolefins and other resins for processing performance and establishing polymerization conditions for generating this range of topologies will be established which has not been done before for branched polymers. In addition, this program will feed into the developing fundamental research program on the dynamics of branched polymers. Improvements in the molecular theory for the melt rheology of branched polymers will also be an outcome of this cooperative research effort.

This research will have practical implications as it will allow industry to optimize the molecular architecture for processing performance and properties theoretically and thereby shorten time-intensive experimental programs. Graduate students will learn first hand the latest developments in molecular rheology and its use in designing molecules for processing performance. Exchanges between groups will accelerate the learning of both the theory and experimental techniques used in this program. Carefully selected undergraduates from underrepresented groups will be brought into the program to enhance their interest in polymer science and engineering.

TECHNICAL SUMMARY

Understanding remains incomplete regarding the relaxation of complex branching structures in entangled polymer melts with multiple branch points, such as H- or comb-branched polymers, or for polymers with branches of differing lengths, such as asymmetric stars and asymmetric H polymers, or for hyperbranched polymers (i.e., with branch-on-branch topology). To address these issues, which are important both scientifically and for applications to commercial polymer manufacture, we are performing a combination of the following tasks: 1. Synthesis of high-quality model branched polymers with branches of the same or different length that are carefully designed to test physical theories. 2. Careful characterization of the molecular weight and branching properties of these polymers. 3. Measurement of the linear rheological properties over a wide frequency range. 4. Comparison of the measured viscoelastic properties with predictions derived from the various alternative proposed theories. We plan to accomplish these tasks through a collaborative framework, involving a collaborator, Jimmy Mays, who will use a novel route to synthesize 1) asymmetric H polymers; 2) asymmetric star-on-star polymers, based on a core star polymer, each branch of which terminates in two unequal length branches; and 3) combs with tetrafunctional branch points. These polymers will be carefully characterized by gel permeation chromatography and TGIC, and studied through rheological measurements, including careful long-time creep rheometry with the help of instrumentations and methods available in the laboratory of Prof. John Dealy, a collaborator at McGill University. Existing computational models for predicting the measured rheology will be employed in collaboration with Chinmay Das in the McLeish group at Leeds University.

NON-TECHNICAL SUMMARY:

To form advanced plastic fibers or thin plastic sheets used for packaging, molten plastic is pulled or stretched at extremely high speeds. The performance of this process depends on how the polymer molecules in the plastic are entangled with each other, and how they escape those entanglements. Polymers that branch into multiple long strands are exceptionally useful for industry, since they serve as netting that strengthens the plastic so that it does not rip or bursting when blown into shape. Larson?s team has found that changes to as few one branch in a million branch points can significantly impact the properties of the melt relevant to its strength as a melt. The reason for this is that branched polymers entangle extremely well with other branched polymers. To escape these entanglements, they must reconfigure by reeling branches towards the branch point, like Houdini dislocating his shoulder to escape a straight jacket. Therefore, the entanglements are long-lived and make the plastic easier to shape. Larson?s team is chemically synthesizing special branched polymers that are exceptionally useful in determining how branched polymers manage to perform their ?Houdini? acts and how to optimize this for advanced performance. Their measurements of the rates at which polymers escape entanglements is providing knowledge that is of great interest to collaborators at Dow Chemical Company and other plastics manufacturing companies. The research has been highly interdisciplinary and international with collaborators at the University of Tennessee, McGill University, the University of Leeds, and Dow Chemical Company.

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.

This Partnerships for Innovation project proposes to develop multigraft copolymer-based thermoplastic elastomers by use of randomly spaced side chains, representing a more cost effective technique than the present technique which depends on difficult to produce evenly spaced side chains. Thermoplastic elastomers combine the desirable properties of crosslinked elastomers (like car tires) with low processing costs and recyclability of thermoplastics. This newly developed class of multigraft copolymer-based thermoplastic elastomers is called "superelastomers" and holds promise for improved processability and recyclability of rubbery materials used in many different products such as gloves, earbuds, condoms, nipples for baby bottles, etc. The superelastomers also have the potential to open up new applications for elastomer materials. These designer elastomers constitute a new concept where macromolecular architecture (the shape of the molecule) is used to create the desired property profile. Through partnerships and collaborations fostered by this project, the research team will progress from knowledge generated by fundamental research toward new products that will enhance U.S. competitiveness, and the partner companies will have access to new designer elastomer technology.

The broader impacts of this research are the creation of new jobs to stimulate the economy, and the reduction of the worldwide carbon footprint by developing a new class of highly tunable thermoplastic elastomers that have the potential to both be recyclable and reduce energy consumption during manufacturing.

Partners at the inception of this project are the University of Tennessee, Knoxville (Department of Chemistry, School of Business Administration, and Research Foundation), BBB Elastomers (small business, Knoxville, TN), Asius Technologies (small business, Longmont, CO), InaMei Skin Care (small business, Hadley, MA), MAPA GmbH (large business, Zeven, Germany), Fuji Film (large business, Dayton, TN), Technology 20/20 (non-profit, Oak Ridge, TN), and Venture Incite (regional venture capital firm, Oak Ridge, TN).