Applications in areas such as drug delivery, biomedical engineering, photovoltaics, and production of structural materials have each benefited from developments in ROMP methods.
Transport Phenomena Research Interests Polymeric materials containing multiple components can self-assemble into supramolecular structures on length scales ranging from nanometers to microns, useful in products as diverse as encapsulant gels and laptop displays.
Our research focuses on the synthesis, processing, structure, properties, and applications of such complex polymers. An active in-house program in each of these aspects facilitates cross-fertilization and rapid materials development, while research group members gain a broad background in materials science and technology.
Block copolymers comprise two or more different monomer units, strung together in long sequences rather than randomly distributed e.
Repulsions between unlike blocks yield self-assembled mesophases having intricate nanometer-scale structure, with topology and dimensions tunable through composition and molecular weight. We synthesize well-defined block copolymers of diverse chemistry through "living" polymerization techniques anionic, ring-opening metathesis, controlled free-radical.
These materials possess rich phase behavior, since the mesophase can be altered through changes in pressure or temperature, or through the addition of other molecular or macromolecular Methathesis polymerization such as solvents, nanoscale particles, other polymers or block copolymers.
The structure and properties of block copolymers can be enriched by incorporating a second self-assembling mechanism, such as block crystallization. We have effectively confined crystals inside nanoscale block copolymer microdomains, templating the crystals' size and orientation, as shown in the figure below.
Each cylinder black contains a single ribbon-like crystal white running down the cylinder axis. Remarkably, crystal confinement can be achieved even when the polymer forming the confining matrix is fluid, provided the interblock segregation strength is sufficiently large.
Recently, we have developed synthetic routes to block copolymers containing high-crystallinity blocks both linear polyethylene and hydrogenated polynorborneneusing ring-opening methathesis polymerization and catalytic hydrogenation, as well as novel diblocks from a combination of metathesis and anionic polymerizations.
In such materials, we have demonstrated that crystal thickness and melting point can be controlled through the block architecture, and we are continuing to explore the structure and properties of these high-crystallinity materials. This process can yield entire wafers covered with regular arrays of compound semiconductor GaAs, InGaAs "quantum dots" or metal Ni, Au nanoparticles dots per cm2 or patterns of parallel metal nanowiresper cm.
To obtain the long-range order necessary for an addressable array, we are studying the defect annihilation and microdomain orientation processes in these films, as well as developing novel techniques to guide the orientation of these nanoscale domains over centimeter distances.
Examples are shown in the figure below. Structures produced through block copolymer nanolithography. Ionomers contain a small amount of bound ionic functionality, such as carboxylic or sulfonic acid groups neutralized with a metal cation, whose aggregation produces dramatic material property changes.
We combine rheology and x-ray microanalysis to study chain and ion motion, the small- and large-scale components of the "sticky reptation" process by which ionomers relax, and have synthesized model ionomers by anionic polymerization to achieve rigorous control of molecular architecture and chain length.
The incorporation of polymer crystallization alongside ionic aggregation, as in polyethylene-based ionomers, further diversifies material properties. We are particularly interested in how crystal morphology and crystallization kinetics, and ultimately material properties, can be manipulated through these ionic associations.
Electroluminescent polymers, which emit light when passing current, could form the basis for bright, large-area flat-panel displays. With Professors Jim Sturm Electrical Engineering and Mark Thompson USCwe have developed a range of materials with brightnesses approaching that of a fluorescent lamp, using dye-doping to cover the full red-green-blue color spectrum.
These systems exhibit rich photophysics, with exciplexes and electroplexes controlling energy transfer to the dyes.Issue in Honor of Prof. Siegfried Blechert ARKIVOC (iv) Page 54 ©ARKAT-USA, Inc.
Formation of Pd-nanoparticles within the pores of ring opening metathesis polymerization-derived polymeric monoliths for use in.
Ring-opening metathesis polymerization (ROMP) is a type of olefin metathesis chain-growth polymerization. The driving force of the reaction is relief of ring strain in cyclic olefins (e.g.
norbornene or cyclopentene). A variety of heterogeneous and homogeneous catalysts have been developed. polymers Article Synthesis, Characterization and Thermal Properties of Poly(ethylene oxide), PEO, Polymacromonomers via Anionic and Ring Opening Metathesis Polymerization. Olefin Metathesis: Catalysts and Catalysis Matthew Cohan and Dr.
Marcetta Darensbourg. Outline • Introduction –What is metathesis? –Why is it important? • Metathesis in the general sense is the formation of a product that has exchanged bonds between starting materials. Olefin metathesis is an organic reaction that entails the redistribution of fragments of alkenes (olefins) by the scission and regeneration of carbon-carbon double bonds.
  Because of the relative simplicity of olefin metathesis, it often creates fewer undesired by-products and hazardous wastes than alternative organic timberdesignmag.com ontology ID: RXNO Acyclic Diene Metathesis (ADMET) Polymerization A second approach to olefin metathesis polymerization via acyclic diene metathesis (ADMET) chemistry was conceived many years ago but was not realized until An ADMET polymerization involves an olefin exchange reaction (Figure ) where the monomer is a diene (Figure ).