Activated Carbon Fibers
J. Economy,* C. Mangun, K. Benak, L. Dominguez, Z. Yue
National Science Foundation, DMR 92-08545

Fundamental studies aimed at understanding the mechanism of adsorption and desorption of contaminants in activated carbons are being pursued. These include determining factors that control pore diameter, pore diameter distribution, and surface character (acidity vs. basicity). With this kind of basic knowledge it is anticipated that one can design greatly improved adsorption systems to control a wide range of atmospheric pollutants, including CO2, freons, SOx, and indoor air contaminants. Use of such fibers as substrates for a wide range of catalytic processes is actively being explored. Design of new kinds of fibers such as high surface area SiC fiber and ion exchange fibers is being pursued. Under a DARPA grant, DABT-63-98-C-0053, fabrication of specially tailored activated carbon fiber assemblies is underway with the goal of removing highly toxic materials from drinking water.

Anisotropic Polymer Fluids
K. S. Schweizer,* G. T. Pickett
U.S. Department of Energy, DE-FG02-96ER45439 (In cooperation with the Materials Research Laboratory)

Novel liquid state integral equation theories of fluids composed of polymers with spatially anisotropic conformations are being developed. A new mechanism for nematic and dissotic liquid crystal formation in flexible and semiflexible polymer fluids has been discovered. Generalizations to treat the influence of attractive cohesive forces and rigid rod polymers are underway. Predicting the anisotropic structure of confined polymer thin films is also possible with the new approach.

Collagen Fibril Characterization
P. H. Geil,* A. Pederson
Industrial Technology Research Institute, Taiwan

The morphology, molecular packing, and orientation of collagen fibrils in samples of potential use in and as artificial skins has been characterized by transmission electron microscopy and WAXS and SAXS.

Dielectric Studies of Confined Polymers
S. Granick,* Y.-K. Cho, S. Jeon
Petroleum Research Fund, American Chemical Society

This research focuses upon dielectric relaxation of high polymer chains confined to molecularly thin spacings. In situ dielectric measurements of normal-mode relaxation are made for homopolymer melts and diblock copolymer adsorbed brushes. The significance is to provide, by measurements of a kind that have not been made previously, a valuable perspective from which to understand the motions and relaxations of confined polymers.

High-Temperature Adhesives and Matrices
J. Economy,* A. Hall, K. Xu, A. Lopez
Defense Advanced Research Projects Agency/Allied Signal

A new family of thermosetting resins based on aromatic copolyesters has been developed. These materials provide for the first time thermosets that retain 100% of their properties at 200?C, are stable in air at 350?C, and pick up minimal moisture. It has been shown that these polymers can be processed as adhesives, matrices for composites, and rigid foams with very low dielectric constants. The cured resins can also form strong adhesive bonds by solid-state interchain transesterification reactions at temperatures of 200? to 300?C. It has been shown that composites can be fabricated by solid-state processing techniques, greatly simplifying current processes for preparing composites. A new approach to a low-cost, high-module polyester fiber has been devised. The oligomers can also be processed into compound coating by vapor depositions under vacuum.

Improved Ceramic Composites
J. Economy,* S. Seghi
U.S. Air Force Office of Scientific Research (SBIR)

A broadly based program to develop improved matrices for advanced ceramic composites based on boron nitride is being pursued. The borazine oligomer used to form the boron nitride is also being examined as a precursor to BN in the form of a thin-film dielectric insulator as well as adhesion for high-temperature ceramics. The composite of carbon fibers in a BN matrix shows major advantages over carbon fiber/carbon matrix composites for use as aircraft brakes.

Liquids of Branched Marcomolecules
K. S. Schweizer,* T. M. Chang
U.S. Department of Energy, DE-FG02-96ER45439; Oak Ridge National Laboratory (In cooperation with the Materials Research Laboratory)

The structure and thermodynamic properties of many arm star, 'core-shell' soft colloids and other highly branched macromolecular fluids are being studied with microscopic statistical mechanical theory. Such systems display unusual equilibrium and dynamic behavior because of the intermediate degree of interpenetration of different macromolecules. Understanding the phase behavior of alloys of such highly branched macromolecules with linear chains is also under study in order to provide molecular-level guidelines for controlling miscibility.

Macromolecule-induced Interactions between Spherical Particles
K. S. Schweizer,* Y.-L. Chen
U.S. Department of Energy, DE-FG02-96ER45439; Oak Ridge National Laboratory (In cooperation with the Materials Research Laboratory)

Microscopic statistical mechanical theories of the structure and thermodynamics, dilute suspensions of spherical particles in polymers solutions are being developed. The particles may be nanometer-sized proteins or micelles, larger objects such as dendrimers, or micron-sized colloids. The complex influences of particle size, polymer concentration and molecular weight, and steric and specific attractive forces on equilibrium properties are under study. Specific applications to protein-water soluble polymer suspensions and rigid rod polymer solutions are of particular present interest.

Metal Matrix Single-Crystal Flake Composites
J. Economy,* A. Hall
University of Illinois

Single-crystal flakes of aluminum diboride in an epoxy matrix have been shown to yield outstanding planar mechanical properties far in excess of those achievable with graphite fiber epoxy composites. The current program is directed at exploring AlB2 aluminum matrix composites to develop an understanding of the crystallization kinetics of the flakes, ability to process directly into shapes, and establishing the strength-limiting characteristics of such composites. Conditions for preparing high bondings of A1B2 flakes in aluminum at temperatures below 950?C now appear feasible.

Molecular Studies of Boundary Layer Lubrication
S. Granick,* H. Ohtani
Ford Motor Co.

The objective of this research is to probe the tribology of polymer and surfactant boundary layers on a molecular level. We have developed new methods for measuring frictional forces between surfaces that are close to one another (a few angstroms) but not actually touching. With these methods, we measure the effective viscosity and shear strength of liquids of thickness comparable to molecular dimensions.

Molecular Tribology in the Biomaterials Environment
S. Granick,* T. Dellinger
National Science Foundation (Tribology Program)

The objective of this research is, in systems of biomaterials interest, to elucidate mechanisms of boundary layer friction at the molecular level, primarily through employment of the nanoscopic friction apparatus developed in this laboratory. We will probe the friction of aqueous boundary layers of tailored biologically relevant chemical composition that are positioned at well-defined separations comparable to molecular dimensions and displaced over lateral distances of microscopic extent.

Molecular Tribology of Confined Hydrocarbons and Lubrication Additives
S. Granick,* M. Drake, M. Ruths
Exxon Research and Engineering Corp.

This collaborative research between Exxon and the University of Illinois involves work in both laboratories. The conceptual objectives are to establish specific science connections beween microscopic observables and tribological properties of fluids at interfaces in chemically reactive environments. Specifically, we will integrate spectroscopic probes and rheological measurements in model asperity contacts.

Molecular Tribology of Perfluoropolyether Films
S. Granick,* T. Dellinger
U.S. Air Force Office of Scientific Research, F49620-97-1-0432

The project revolves around the tribology of perfluoroether fluids under extreme but nonetheless well-defined conditions of shear rate and confinement. This will allow one to understand the surface chemical and rheological components of perfluoroether friction, as distinct from the classical ones that are rooted in the solid-solid contact. Interpretation from molecular viewpoints is emphasized.

Morphology of Nascent Polytetrafluoroethylene Dispersion Particles and the Effects of Melt Time and Temperature
P. H. Geil,* J. Yang
W. L. Gore and Associates, Inc.

The morphology of PTFE dispersion particles, prepared by different polymerization schemes, has been characterized by bright and dark field transmission electron microscopy. Examination of the effects of melt time and temperature on the development of folded chain single crystals from dispersed dispersion particles on glass and mica substrates indicates an intermediate step of the formation of 'large' angular crystals. Significant molecular motion on the substrate occurs in the melt state.

Nanoporous Polymers
P. V. Braun,* Y.-J. Lee
U.S. Department of Energy, DE-FG02-96ER45439 (In cooperation with the Materials Research Laboratory)

This work is focused on the synthesis and characterization of polymeric materials which contain a regular distribution of nanometer sized pores. The polymers are synthesized in a lyotropic liquid crystalline media. Under the appropriate conditions, the characteristic dimensionality and structure of the lyotropic liquid crystal is imparted to the polymer during the synthesis. We are exploring routes to both bulk and thin-film materials. At this point we are primarily synthesizing conducting polymers via oxidative processes; however, other polymerization routes may also be applicable.

Nanorheology in Fine Powder Flow
S. Granick,* S. Sukhishvili
International Fine Particle Research Institute

Systematic studies are underway of particle-particle nanorheology based on the concurrent measurement of static and dynamic forces in both the shear and normal directions. This is relevant to an enormous range of fine powder applications based on rheological properties in an environment that is not dry (among them fluidization and rapid shear flow in riser reactors, segregation processes, and mixing and pneumatic conveying).

Nanotechnology with Emphasis on Tribology
S. Granick,* Y. Zhu, M. Ruths
National Science Foundation, subgrant R9915-.01.01 from University of Tennessee

This multidisciplinary, multi-institutional collaboration (University of Illinois, University of Tennessee, Sandia National Laboratory) has several goals. The first is to achieve overlap in shear rate between experiments and simulations with the same systems. The second is to expend experimental and computational study to surfaces with chemical and topographical heterogeneity.

Phase I-Phase II Compositions of Melt and Solution Polymerized Poly(p-oxybenzoate)
P. H. Geil,* Y. K. Yun, B. L. Yuan; F. Rybnikar and P. Saha (Univ. of Brno)
National Science Foundation, DMR 96-16255; Granting Agency of the Czech Republic

Polymerization of PpOBA in high-temperature solvents (300-350?C) yields morphologies varying from single-crystal whiskers (up to 50 mm length, 360?C Tk-m) to hexagonal platelet crystals (2-5 mm thickness, up to 100 mm lateral size, 320?C Tk-m). Effects of time, temperature, and concentration on the morphology and the phase I-phase II crystal structure ratio have been determined; the variation in Tk-m cannot be attributed to the phase composition. The composition of PpOBA melt polymerized in thin films is affected by the substrate; base treatment of both mica and glass result predominantly in phase II. Phase II whiskers have been grown by base initiation, with characterization in progress.

Polymer Fillers and the Role of Interfacial Rheology
S. Granick,* A. L. Demirel
National Science Foundation (International Programs)

In this collaborative effort, we study the role of polymer-solid interfacial interactions by relating measurements on model systems (at the University of Illinois) with measurements of systems of immediate practical importance (Koc University, Istanbul, Turkey). Variables of interest include polymer molecular weight, degree of crystallinity, and intensity of polymer-filler interaction.

Polymer-Peptide Interactions for Biocompatibility Applications
S. Granick,* S. Sukhishvili
Engineering Foundation

Underway are systematic studies of surface-surface interactions based on the rational design of known protein and polymer interfaces. We are interested in the effects of peptide composition, electrostatic and hydrophobic properties, and especially conformations and specific interactions with polymers.

Processing and Structural Characterization of Zein-Base Films
P. H. Geil,* G. Padua (Food Science), M.-C. N'Guyen
Illinois Council on Food and Agriculture Research

Zein, a protein from corn, plasticized with oleic acid has been shown to be suitable for the production of thin films of potential application as packaging. Optimization of the properties is being sought by variations in processing techniques (including protein unfolding, orientation, and crosslinking as well as typical plastics film production processes). Structural characterization by WAXS, SAXS, and TEM of orientation, molecular conformation, and morphology is being carried out to aid in the process improvement.

Structure and Phase Behavior of Polymer-Colloid Suspensions
K. S. Schweizer,* M. Fuchs
German National Science Foundation, DFG

Microscopic liquid state theories of mixtures of polymers and colloids are being developed. The role of macromolecular structure, colloid size, composition, and intermolecular interactions on equilibrium properties are being systematically explored. Polymer-induced crystallization of colloidal suspensions is being addressed with thermodynamic density functional methods. The influence of polymer/particle size asymmetry and solvent quality on liquid-gas type phase separation and the particle percolation transition are also under study.

Structure of Condensation Polymers
P. H. Geil,* J. Yang, A. Pederson, J.-I. Jin* (Korea Univ.); F. Rybnikar* (Univ. of Brno, Czech Rep.)
National Science Foundation, DMR 96-16255; Kosef; GACR

The morphology, crystal structure, and changes therein with temperature of a wide variety of homopolymer and both random and alternating copolymer lamellar (100A thickness) single crystals and single disclination domains have been characterized by electron microscopy and diffraction. Polymers include many rigid polyester LCPs, PET, PBT, PEN, Kevlar, Kapton, polyethers, and polyanhydrides. The high-temperature lattices for poly(p-oxybenzoate) and their relationship to the low-temperature lattices have been clarified. Crystal structures of many of the polymers have been determined by the use of electron diffraction aided by modeling. The polymers are prepared by a unique, low-temperature, confined, thin-film melt polymerization process.

Structure of Multiblock Copolymers and Ionomers
K. S. Schweizer,* K. Kolbet
U.S. Department of Energy, DE-FG02-96ER45439 (In cooperation with the Materials Research Laboratory)

Microscopic theories for the conformation and structure of self-assembling multiblock copolymers and ionomers are being developed. The influence of block length and composition on long wavelength concentration fluctuations, microdomain formation, and phase separation temperature have been systematically explored. Application to address small-angle scattering and the microphase behavior of multiblock polyurethane melts and ionomer melts have been carried out. The role of water, nonpolar solvents, and blending with homopolymers on ionomer structure physical clustering and bulk properties are of interest.

Studies of Perfluoropolyalkylether Lubrication
S. Granick,* A. Koike, M. Ruths
Hitachi Corp.

The hard disc drives used for information storage are lubricated by perfluoropolyalkylether molecules of various molecular weights and chain-end functionality. In this university-industry collaborative project, we study systematically the role of chain-end functionality, especially polarity and surface packing.