Philip Pincus, Ph.D. - US grants

This proposal outlines an interdisciplinary program designed and constructed to attack an important specific problem in new materials: the achievement of higly oriented semiconducting and metallic polymers through solution processing. The program includes the following components: (I) Synthesis of Soluble Conjugated Polymers and Compatible Polymer Blends, (II) Solution Processing of Semiconducting and Metallic Polymers and of Polymer Blends, (III) Theoretical Studies of Specific Problems Underlying the Solution Processing of Conducting Polymers, and (IV) Characterization of the Highly Oriented Conducting Polymers and Polymer Blends, and Characterization of the Polymer Solutions from which they are processed. This Materials Research Group brings together an interdisciplinary set of talents and expertise to form a coherent program to attack the problem of the preparation and characterization of highly oriented semiconducting and metallic polymers through solution processing.

A combined numerical and analytic investigation of the solution properties of conjugated polymers will be carried out. The focus will be on the interplay between conformational and electronic degrees of freedom. The model is based on the Huckel theory for the pi electrons with explicit dependence of the resonance integrals on bond rotation angles. It is planned to carry out exact diagonalizations of the electronic Hamiltonian, including the statistical freedom in the rotation angles, using Monte Carlo methods. Subsequent studies will include side-group interactions, elastic energies, and Coulomb correlations as well as external fields (electric and hydrodynamic). The numerical studies will be augmented by various analytic methods for limiting cases; these include high-temperature expansions, RG calculations, boson representations, etc. A goal is to confront such experimental quantities as optical absorption, frequency dependent dielectric function, neutron and light scattering structure factors, and viscoelastic properties.//

This award, part of the Materials Chemistry and Chemical Processing Initiative, will support the collaborative research of Dr. F. Wudl and Dr. P. Pincus at the Univeristy of California at Santa Barbara. The research will focus on the preparation, characterization and theoretical studies of rigid carbon-heteroatom clusters (heterospherophanes). The grant is a joint action of the Divisions of Materials Research (Solid-State Chemistry) and Chemistry (Organic Synthesis). Heterospherophanes will be hollow molecular spheres consisting of alternating benzene rings and heteroatoms such as chalcogen or nitrogen. The heteroatoms within each cluster will be located, relative to each other, in a cubic closest packed lattice. The diameter of the sphere's cavity will depend on the nature of the heteroatom. Due to the high symmetry, electronic character and structural design of these clusters, they will exhibit unusual condensed matter properties depending on whether they are neutral or charged. The neutral heterospherophanes are likely to be hard, high-melting solids. The charged heterospherophanes will be capable of encapsulating a countercation, producing an atom of macromolecular dimensions. The encapsulated counterion should also allow the formation of three dimensional organic metals.

This award is for the renewal of research previously supported under a Materials Research Group grant (DMR 8703399) at the University of California - Santa Barbara. The research of the group focuses on the design and synthesis on the supermolecular length scale of multi-functional, high performance electronic and optical polymer blends using gel processing. The morphology of these gels is being determined using x-ray diffraction, optical, scanning, and electron microscopy, mechanical, and electrical measurements, optical spectroscopy, luminescence, and photo-induced absorption. Polymers being investigated include ultra-high molecular weight polyethylene, polyvinyl alcohol, polyacrylonitrile, unblended conjugated polymer systems, and phase-segregated highly oriented polymer blends such as polyaniline/poly(p-phenylene terephthalamide). Materials are being processed into fibers, thin films, and conducting foams taking care to control the morphology, phase stability, and spinodal decomposition. The research is multi-disciplinary, combining condensed matter physics, synthetic chemistry, theory, and polymer science. This grant provides the ideal mechanism to train students to synthesize, process and characterize polymers, with the interaction of all of the scientific approaches and methods used to study polymers.

9301199 Safinya Synchrotron based small- and wide-angle x-ray scattering methods will be used to characterize the structure, phase-behavior, and interlayer (in lamellar preparations) and inter-macromolecular interactions, and the protein shape stability of (1) native and reconstituted self-assembled membrane proteins, (2) functionalized biomolecular interfaces, and (3) a new material which will be based on membrane proteins complexed with associating polymers. The project is an interdisciplinary effort involving experiment and theory. The theory will use statistical mechanics techniques to address the phase bahavior and mechanics of membranes with internal degrees of freedom, as well as to examine fundamental issues underlying self association in complex fluids. %%% X-ray techniques employing radiation from synchrotron light sources will be used to investigate the structure and dynamics of complexes involving proteins (separated from native membranes) which are associated with polymers or other molecules, or surfaces. The objective is to develop a new environment, such as a nest of polymer molecules, with which the membrane protein will associate. If such an association structure is developed, it would represent a new "biomolecular" material which could trap photoactive and other membrane molecules in a three-dimensional network. Such a structure may be useful as a memory storage element, biosensor or other system. The project is interdisciplinary and involves both a theory and an experimental component. ***

This Americas Program award will support the first U.S.-Mexico bilateral symposium on the physics of complex fluids, organized by Dr. Philip Pincus of the University of California, Santa Barbara and Dr. Magdaleno Medina-Noyola, of the Universidad Autonoma de San Luis Potosi, Mexico. The primary objectives of the symposium are the development of specific collaborations between U.S. and Mexico; the establishment of an organizational framework for nurturing continuing exchanges; and the development of a plan for fostering mutual access to special facilities and instruments in both countries. The complex fluids field, a developing multidisciplinary scientific area involving physics, chemistry and biology, has applications to a diverse range of technologies, including, among others, enhanced oil recovery, processing of high performance structural ceramics and polymers, biomolecular materials, and microreactors. Consequently, the symposium will involve representatives from academia and industrial laboratories as well.

9407741 Pincus This theoretical research will be carried out at both the University of California at Santa Barbara and the University of California at Los Angeles. Analytical and simulational investigations will be done on polymers which are soluble in aqueous solvents because of hydrogen bond formation between the solvent molecules and the moities on the chain, e.g., oxygen on the backbone of polyethylene oxide. The particular focus will be on the interplay between the chemical nature of the hydrogen bond and the hydrophobic interaction associated with the hydrocarbon backbone. These uncharged hydrosoluble polymers have important applications to technological issues associated with the use of inorganic solvents and also as models for the activity and function of a class of biopolymers. The work will be extended to copolymers where one part has hydrogen bonding character and the other part is a more typical hydrocarbon. Such copolymers are potential candidates for vesicle stabilizers in drug delivery systems. %%% This theoretical research will be carried out at both the University of California at Santa Barbara and the University of California at Los Angeles. Analytical and simulational investigations will be done on polymers which are soluble in water. ***

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Safinya

This project investigates the properties of biomolecular materials consisting of biological polymers (e.g. DNA; components of the cell cytoskeleton which consists of the filamental proteins: microtubules, intermediate filaments, and filamental-actin) condensed with oppositely charged chemical species such as multivalent counter-ions. These materials are useful models for statistical theories of polyelectrolytes. For example, the studies should shed light on the nature of the molecular forces in the condensation of DNA in vivo (i.e. the DNA packing problem). The project provides excellent training for graduate students within a diverse, interdisciplinary program enabling them to acquire skills that are currently in great demand in Industry, National Laboratories, and Universities. Advanced miniaturized materials will be produced from biological molecules self-assembled on patterned surfaces. The biological-semiconductor hybrid materials should be utilized in the next century in pharmaceutical, biomedical, and semiconductor industries emphasizing miniaturized materials (e.g. nano-conduits and nano-wires).
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This project offers excellent research and education opportunities for graduate students within a diverse, interdisciplinary program, focused on biomolecular materials, in particulal biological materials that self-assembled on patterned surfaces. Potential uses of these processed materials include chemical and biological sensors, micro-machine elements, and molecular sieves. The graduate students will acquire skills that are currently in great demand in a broad range of industries including those which combine nanometer scale fabrication systems with biomolecular materials in chemicals, pharmaceutical and biotechnology, and semiconductors. They will be trained in state-of the-art techniques which include, methods for preparing biomolecular self-assemblies, fabrication of micron and nanometer scale patterns on semiconducting surfaces, direct imaging with Atomic Force Microscopes and optical light microscopes, and structural measurements using quantitative x-ray diffraction methods at the National Synchrotron Facilities at Stanford and Argonne National Laboratories.
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This combined experiment and theory project is in the area of soft condensed matter physics. The research will explore phases, structures, and interactions, in supramolecular assemblies of filamentous cytoskeletal proteins and their associated biomolecules. The importance of the experiments lies in their potential to uncover the origin of fundamentally new attractive forces between charged biological polymers, which can lead to new states or arrangements of matter. The project should shed light on the physics of charged polymers, which constitute a group of technologically important industrial materials. The program trains graduate students in state-of-the-art techniques required to address complex multidisciplinary problems at the interface between physics, engineering, chemistry, and biology. The research includes structure characterization at National Synchrotron X-ray Laboratories and in-house imaging with laser-scanning confocal microscopy. This will provide student training in research settings where traditional discipline boundaries between physics, engineering, chemistry, and biology, have been removed, and teamwork and problem solving are emphasized. This will prepare the students to tackle and solve complex technological problems in their careers in academe, industry, or government.
This combined experiment and theory project is in the area of soft condensed matter physics. The research focuses on producing and characterizing novel materials that are obtained when biological polymers (e.g. proteins) are brought together to form new structures with dimensions between one-billionth of a meter and one-thousandths of a meter. New "composite" materials in this size range can have technological applications in areas such as molecular-based chemical sensors, molecular sieves for separations and purification technologies, and chemical and drug delivery vehicles. The project is highly interdisciplinary and exposes graduate students to a broad spectrum of techniques. These include state-of-the-art structure characterization with synchrotron x-ray diffraction at National Synchrotron X-ray Laboratories, and in-house imaging with cutting edge optical and electron microscopes. The educational significance and impact of this interdisciplinary project, at the interface between physics, engineering, chemistry, and biology, is in the training of students with a broad outlook toward problem solving. They will be valuable not only in academic settings, but also in the industrial and government job force where interdisciplinary research is required and rewarded.

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Pincus


This U.S.-Mexico award will support a Symposium on Complex Fluids to be held in conjunction with a larger conference on statistical physics in Puerto Vallarta, Mexico, August 24-29, 2003. The meeting has been organized by Dr. Phillip Pincus, of the University of California, Santa Barbara, together with Dr. Magdaleno Medina-Noyola and Dr. Jaime Ruiz Garcia, both of the Institute of Physics of the Universidad Autonoma de San Luis de Potosi.

The complex fluids field is highly interdisciplinary, relying on insights from several disciplines, such as physics, biology, chemistry, and engineering. On the international scale, it has become a major area for applications and is of increased relevance to the chemical and pharmaceutical industries, biomedical engineering, and newly emerging nano-electronics and photonics efforts that use soft matter components. Furthermore the corresponding development of instrumentation and computational algorithms is vital. Both the United States and Mexico have active program in complex fluids. This symposium will provide increased visibility for the challenges and opportunities in the field as well as enhancing specific US-Mexico cooperation. The Division of Materials Research and the Office of International Science and Engineering are contributing to the support of this activity.

ID: MPS/DMR/BMAT(7623) 1101900 PI: Safinya, Cyrus ORG: UC Santa Barbara

Title: Biomolecular Materials: Structure, Phase Behavior, and Interactions

INTELLECTUAL MERIT: The aim of this proposal is to develop a fundamental understanding of the intermolecular forces and resulting structures in assemblies of filamentous proteins (in particular, neurofilaments and microtubules) derived from the cytoskeleton of neuronal dendrites and axons (the extensions used by neurons to receive and send signals to neighboring neurons). The proposal combines state-of-the-art synchrotron x-ray-scattering, x-ray-osmotic pressure, and optical and electron microscopy techniques used by the PI, and in parallel, closely related modern modeling by the co-PI. Experiments are proposed to study forces between microtubules mediated by microtubule-associated-protein (MAP) tau, an abundant unstructured biological polymer containing anionic and cationic amino acid residues, which binds to (via electrostatic interactions) and stabilizes microtubules in axons. While the precise role of MAP-tau in modulating interactions between microtubules is unclear, it is well established that aberrant interactions between tau and microtubules (e.g., due to tau mutations or over-phosphorylation) invariably lead to collapse of the cytoskeleton and neurodegeneration. Experiments are proposed to understand the structures and inter-filamentous interactions, mediated by charged neurofilament-sidearms and MAP-tau, in systems which closely mimic the distinct local environments of axons and dendrites (i.e., with different composition of the three neurofilament-sidearms and the presence or absence of MAP-tau). The specific aims of this proposal are (1) to elucidate the role of biological and synthetic multivalent counter-ions in suppressing the repulsive barrier, which prevents MAP-tau-mediated short-range attractions between microtubules, (2) to unravel the structure-function properties of MAP-tau by discovering how domain deletions (via truncated tau constructs) alter tau-mediated microtubule assembly, (3) to study the intermolecular interactions and resulting structures between neuronal cytoskeletal filaments in co-assembling mixtures of microtubules and neurofilaments, and (4) to develop quantitative models of forces between two opposing polyampholyte brushes (mimicking the structures of neurofilaments and microtubules) to closely capture the biophysics of interactions between microtubules mediated by MAP-tau, between different neurofilament-sidearms, and between neurofilament-sidearms and MAP-tau. Aside from enhancing our knowledge of the nerve cell cytoskeleton, the proposed research will further our understanding of charged-polymeric systems, a very important field of soft and biological matter, where much remains to be understood.

BROADER IMPACTS: The proposed studies will lead to a comprehensive understanding of how nature makes use of competing intermolecular forces (e.g., attractions at short distances and repulsions at longer distances) to assemble distinct filamentous structures within the long extensions of nerve cells to impart critical functionalities such as mechanical stability and facilitated transport of materials. The understanding gleaned from the studies (e.g., about the specific chemical moieties responsible for inter-filament interactions) will enable the broader scientific community to employ a rational approach in the design of synthetic building-block mimics for constructing hierarchical structures arising from the built-in functionality at the molecular level that control intermolecular interactions. The biomimetic structures, in turn, are expected to have important technological applications, for example, as templates for miniaturized materials with applications in nano-biotechnology. The biomaterials research effort of the PIs is multidisciplinary and educates and trains undergraduate and graduate students and postdoctoral researchers in modern methodologies required to address important problems at the interface between physics, chemistry, engineering, and biology. The acquired interdisciplinary skills prepare the trainees for careers in academe, national laboratories, and industry. The principal investigators actively participate in UCSB Outreach Programs with the community colleges and with colleges and universities outside of Santa Barbara. The programs include the Internships in Nanosystems Science and Engineering Technology, California Alliance for Minority Participation, Research Internship in Science and Engineering, Cooperative International Science and Engineering Internships, and the Research Experience for Teachers. This activity allows the PIs to train a broad spectrum of students and teachers in multidisciplinary methods of science and engineering.

This award will help to support a workshop on nanoscale forces and interfacial phenomena to be held in Cancun, Mexico around January 2006. Organized by Dr. Norma Alcantar of the U. of South Florida and Dr. Phillip A Pincus of the U. of California-Santa Barbara, together with international partners Dr. Tomas Viveros of the Universidad Autonoma Metropolitana in Iztapalapa, Mexico, Dr. Suzanne Giasson, of the University of Montreal, and Dr. Roger Horn of the University of South Australia, the workshop will involve representatives from approximately 42 universities worldwide and international student participation.

The meeting will bring together scientists that are international leaders in measuring and analyzing surface forces and interfacial phenomena to provide a substantive training experience for students, postdoctoral researchers and investigators who are at early stages in their career. It will feature a discussion of critical issues facing colloid and interface science. Students and postdoctoral researchers will present their work in poster sessions. Ultimately, the workshop aims to foster collaborations at multiple levels (interdisciplinary and internationally) to attack complex problems that connect the nanoscale world to the macroscopic world. The Office of International Science and Engineering and the Directorates of Engineering and Mathematical and Physical Sciences are sharing in the funding of this activity.

This comprehensive program between the University of California at Santa Barbara and the Universitt Bayreuth in Germany aims at deepening understanding and uncovering new phenomena in systems of polyelectrolyte brushes immersed in multi-valent ionic media containing metal ions, charged surfactants, molecular ions, proteins and oppositely charged polyelectrolytes. Recent preliminary work via surface force measurement has shown new behavior, relative to that in mono-valent salt, of polyelectrolyte brushes in multi-valent media. The Surface Forces Apparatus has been used to demonstrate the extended configurations and long-range forces exerted by and between brushes immersed in good solvents. In particular, there are strong collapse transitions in some multi-valent media, observable of both flat and highly curved surfaces. New behavior signals new properties in a range of important applications of polyelectrolyte brushes. Polyelectrolyte surface properties in multi-valent ionic media, such as in physiological environments, surfaces of medical devices, rheology of water-based suspensions, flocculation or condensation of polyelectrolytes, or in the hard household water and surfactant mixtures in which many personal care products are employed, may not be straightforwardly inferred from experiments in mono-valent salt, which constitute our current knowledge base. Soft interfaces that consist of charged macromolecules, highly swollen with water, are the norm in biology, such as the cellular glycocalyx, the surfaces of lung tissue, eyelids and articular cartilage, and the interfaces between mineralized collagen fibrils in bone. Commercial products, such as those for personal care (e.g., shampoo, skin care), medical prostheses (e.g., joint replacements), materials processing (e.g., sterically stabilized dispersions of suspended particles or assemblies), anti-fogging surfaces, and gene chips, also often rely on highly hydrated, charged polymer interfaces.

The results of this work are anticipated to have applications in biology and medicine, water purification, water-based pigments, paints and coatings and the cosmetic product industry. By virtue of the collaboration between UC Santa Barbara (UCSB) and the Universitt Bayreuth (UB) that this proposed work will enable, a clear picture will emerge of how experiments on polyelectrolytes tethered to flat surfaces (at UCSB) connect with highly curved brushes (at UB), common to the surfaces of dispersed colloids. The same physics of polymers and ion confinement is at play in both systems. Many of the practical situations cited above can involve multi-valent ions for which there is much less experimental information and fewer established theoretical principles, than for media comprising mono-valent ions exclusively. Biological buffers, for example, typically contain many ionic species, including multi-valents. Multi-valent interactions, known to have strong effects on polyelectrolytes in solution, as in the condensation of DNA, have been studied very little in their effects on interfacially tethered polyelectrolytes, despite many studies in free solution and the broad biological and technological significance charged interfaces. Polymer chains in tethered assemblies (surface brushes, chains tethered to particles, and highly branched macromolecules) provide an experimental "grip" on the tethered ends of the macromolecules, which enables direct measurement of forces in a way that cannot be done with free linear polymers in solution.