Molecules delivering drugs as they walk

Molecules delivering drugs as they walk

An octopus-like polymer can "walk" along the wall of a narrow channel as it is pushed through by a solvent. Now research in The Journal of Chemical Physics, which is published by the American Institute of Physics, provides a theoretical model that compares the transport characteristics of straight- and branched-chain polymers in smooth channels as well as in channels whose walls interact with the polymer -- work that could aid in the development of carrier molecules for delivering drugs at a controlled rate in the body.

"The deformability of particles makes them very different from atoms or hard colloids," says author Arash Nikoubashman of Heinrich Heine University of Dusseldorf, Germany. "Equilibrium studies show a huge impact on the self-organization of these molecules and we wanted to know how this aspect expresses itself when the molecules are pushed around by a flowing solvent."

The researchers compared the flow of linear polymers to that of dendrimers, or regularly branched polymers. Results indicate that flow through a narrow channel is independent of the number of monomers in the polymer chain. In a smooth channel, flow is also independent of shape: the linear polymer and the dendrimer both travel in the rapid solvent flow toward the center of the channel. When patches that attract the polymer are placed on the wall, however, the dendrimer "walks" along the wall from patch to patch, while the linear polymer tends to remain close to the wall, moving very slowly, if at all, through the channel.

Possible applications of this research include an understanding to the movement of biological molecules through pores, and the development of dendritic carriers to deliver molecules at a controlled rate. Blood vessels resemble the model channel with patches of differing chemical affinities.

"At the moment we are investigating the cargo transport capabilities of dendrimers," says Nikoubashman. "Place a guest molecule, such as a drug within a dendrimer that has affinity to specific patches on the vessel wall and let it flow with the solvent." As the dendrimer docks on the patches, it may be possible to deliver the cargo to the dock while the carrier washes away with the flow.

New photosensitive film converts light into kinetic energy, bends when irradiated

New photosensitive film converts light into kinetic energy, bends when irradiated

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Left: Molecular formulae of a polymer brush. Center: Schematic illustration of the polymer brush. Right: Photograph of a bottle-cleaning brush for comparison.

(PhysOrg.com) -- Japanese researchers at RIKEN have successfully developed a revolutionary new polymer film that changes shape upon irradiation with UV and visible light. Described in Science, the film is the largest-ever example of a material whose molecular elements are ordered in three dimensions on a macroscopic length scale, marking a breakthrough in techniques for molecular design and processing.

Living organisms depend crucially for their growth and development on their ability to assemble molecules into large, ordered three-dimensional structures. The same assembly processes offer an attractive means for designing materials and devices with novel functions, yet scientists have thus far found such processes impossible to reproduce at a macroscopic scale.

To overcome this impasse, the research group used a structure known as a “polymer brush” made up of a polymethacrylate backbone with outstretched side-chains, which together form a cylindrical shape. Azobenzene molecules, known for their propensity to deform when irradiated, were inserted into the side chains, and a free-standing cast film, created from a solution of the polymer brushes, was then tested for photomechanical response.

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Top: Photomechanical bending motion of hot-pressed polymer brush film. Bottom: Structural deformation of azobenzene molecule upon exposure to UV and visible light.

When no such response was initially detected, the researchers adopted a different approach, sandwiching the polymer brushes between Teflon sheets to first melt them at 130 °C, then “hot-press” them at 115 °C. The hot-pressing process, they discovered, aligned the main chains of the brushes perpendicular to the film plane, while the side chains oriented themselves horizontally along the stretching direction of the Teflon sheets. The resulting 3D molecular ordering enables the film to literally bend and stretch upon alternating irradiation by UV and visible light.

In converting light energy directly into a mechanical force, this remarkable photoresponsive bending motion breaks new ground in the study of functional materials, suggesting applications in the design of muscle-like biomorphic devices. As a technique, the combination of polymer brushes and hot-pressing vastly expands the scale at which such materials can be manufactured, promising to bring advances from the world of molecular processing to the macroscopic level of our daily lives.

Plastics used to fix teeth could help prevent spread of disease

Plastics used to fix teeth could help prevent spread of disease

(PhysOrg.com) -- Researchers at Cranfield University have designed tiny particles that stop bacteria from communicating with each other in a bid to prevent spread of infection and disease.

Using similar plastics that dentists use to correct misaligned teeth, the Cranfield Health team has developed polymers that absorb the bacteria?s signal to attack so they are fooled into ?thinking? their numbers are low and don?t switch to a more dangerous state. By removing the signal molecules the bacteria isn?t killed but instead it makes it much more difficult for them to develop a resistance to drugs and therapies.

The ability to disrupt bacterial communication, therefore preventing the bacteria from releasing toxins or forming sticky, drug-resistant layers (biofilms), is an important target for new medical treatments. It is generally accepted that biofilms are responsible for 70% of all human infections so new preventative measures are urgently needed.

Based on a type of ?smart? plastic, unlike expensive antibodies, which can be made to do the same job, these polymers can be synthesised in bulk using cheap raw materials. It is possible to foresee that these polymers when prepared in powder format could be easily integrated into traditional wound dressing materials or, when the particles are packed into capsules, they could be delivered directly to the gut in order to treat bacterial infections.

Dr Elena Piletska, who has pioneered this work, said: ?The polymers which we described are not expensive and could be prepared in large quantities. It is difficult to say when these materials will be commercialised and in general use. I hope that one day they will be a part of common practice for the treatment of gut and wound infections, or become an important ingredient for mouthwash or even chewing gum in oral care. We have already obtained a ?proof of concept? for this technology but further development would require the investment and support to fulfil this potential highly innovative technology. The interest and commitment of the pharmaceutical industry could make all the difference.?

Pull-chain 'polymer' solves puzzle of complex molecular packing

Pull-chain 'polymer' solves puzzle of complex molecular packing

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Partial three-dimensional reconstruction, from X-ray tomographic data, of the packing of 2.1-mm ball chains, projected onto a plane. When tightly packed, the chains form nearly circular rigid loops, like the one in the lower right of the image. This behavior may form the basis of a model for better predictions of the rigidity of polymers. (Image: Ling-Nan Zou and Mark L. Rivers)

(PhysOrg.com) -- Sometimes the simplest things hold the key to understanding complex effects. It turns out that a humble metal pull-chain -- just like those used on ceiling fans -- can be a pretty good model for complex properties of polymer materials.

A group of University of Chicago researchers used X-ray microtomography to study what happens when beaded metal chains are packed more and more tightly into a container. The results look similar to those obtained when a polymer becomes rigid, the difference between molten and hard plastic.

Both naturally occurring and synthetic, polymers are large, chain-like molecules found in plastics, rubber and a variety of other substances. With this pull-chain model, the behavior of individual ?molecules? can be studied in a way that is impossible with real polymers.

?We were looking for new ways to study how particles pack into stable structures,? said Ling-Nan Zou, PhD?09, lead author of a paper that appeared in the Oct. 16, 2009 issue of Science. ?The most dense and stable arrangement is like a pile of oranges at the grocery store, but sometimes less dense arrangements can still be stable, and we don?t really understand why.? These lower-density yet rigid structures are said to be ?jammed.?

The researchers chose an elegantly simple physical analog to a polymer: a flexible ball-chain. Each metal sphere is a ?monomer,? or polymeric component; the linking rods are ?bonds.? When twisted into a loop, there?s a point when the chain stops being flexible: The loop won?t get any smaller. That is, the ?bonds? have a maximum angle beyond which they can?t flex. It turns out that this property explains a lot.

To do the experiment, the team cut metal chain into segments of a certain length, poured the segments into a tube, and shook the tube in a defined way to compact the chains. They varied the lengths of the segments and the amount of shaking and then measured the height of the packed chain in the tube, from which they derived the density of the packing.

They also imaged the packed container with x-ray microtomography at beamline 13-BM-D at the U.S. Department of Energy?s Advanced Photon Source at Argonne National Laboratory. The beamline is operated by GeoSoilEnviroCARS, part of the University of Chicago Center for Advanced Radiation Sources.

?We needed the resolution available at this beamline because regular tomography doesn?t work for objects this small,? explained Zou, now a postdoctoral fellow at Harvard University. The spheres in the chains were only 2.4 millimeters in diameter (about the diameter of a grain of rice).

While standard tomography can image sub-millimeter, to accurately trace bonds and bond-angles, the team needed micrometer resolution. ?With the data from GSECARS, we can accurately locate every monomer and trace every bond,? Zou said.

They found that even though the density decreased for longer chains, the packings were still stable. The tomography images provided the explanation: The long chains form stiff partial loops (see illustration) that reduce the density but provide stability.

Although the pull-chain or ?granular? polymers are clearly different from real polymers in significant respects, there is at least one remarkable similarity. The relation of chain length to density in the granular polymer is nearly identical to the relation of chain length to the liquid-to-glass transition temperature in real polymers.

A mathematical model is being developed based on the new results for granular polymers. ?With this kind of model, we may find new behaviors to study experimentally and new ways to explain why polymers have the properties they do,? Zou said. In particular, polymers can behave in a very complex and hard-to-measure fashion under sideways forces, or shear. Now, with the knowledge gained from the experiments on granular polymers, researchers can try to recreate such behavior and then look at the ?molecular? level for detailed explanations that could guide the design of new polymer-based materials.

Making light work of artificial muscles

Making light work of artificial muscles

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The light-responsive film is made up of polymer brushes (right) that have self-assembled into a two-layer, three-dimensional array (left). Credit: Reproduced, with permission, from Ref. 1 2011 American Association for the Advancement of Science

A new form of self-assembling polymer film that bends and stretches when hit by light is pointing the way to a new family of functional materials. This flexing film is the first material to have been made by coaxing complex molecules to form large-scale, highly ordered three dimensional arrays -- a discovery that could change the way that many active material are made, from artificial muscles to solar cells.

Nobuhiko Hosono, Takuzo Aida and colleagues at RIKEN Advanced Science Institute in Wako and The University of Tokyo developed the self-assembly protocol. The researchers found that brush-shaped polymers would form an orderly film when hot-pressed between two sheets of Teflon.

They made their discovery while studying a polymer in which each side chain, or bristle, of the brush structure incorporates light-responsive azobenzenes—two benzene rings separated by a pair of nitrogen atoms. When hit by UV light, the bond between the nitrogens rearranges, contracting the side chain.

The researchers used this photoisomerization behavior to confirm the remarkable long-range order of the polymer structure. Because the side chains were all aligned, when those at the surface were hit by light they curled up in concert, bending the film. A second beam of light at a different wavelength reversed the isomerization process, and the film relaxed back to its original shape.

The trick to making the material is to heat it between two sheets of Teflon that have been drawn tight in one direction, says Hosono. This tension orients the Teflon sheets’ internal structure along a single axis, which acts as a template for the molten polymer brushes sandwiched in between. The side chains of the polymer brush align with the Teflon, pulling each brush upright. As each polymer brush aligns in the same way, it forms a repeating three-dimensional array.

Hosono, Aida and colleagues expect the technique to work for other polymer brushes with similar side chains. To improve the artificial muscle-like behavior of their polymer film, Hosono says the team will try cross-linking the polymer side chains. This will prevent the molecular structure from becoming disordered as the polymer repeatedly curls and relaxes over many cycles, giving the muscle a longer lifetime.

The team is already assessing other potential applications. The wide-area three-dimensional molecular ordering of the polymer brush has great potential for building electronic devices, says Hosono. “We now have designed a new type of polymer brush for development of highly efficient thin-layer organic solar cells.”

Chemists Identify New Way to Create Photovoltaic Devices

Chemists Identify New Way to Create Photovoltaic Devices

Photovoltaic device diagram

(PhysOrg.com) -- A promising new polymer-based method for creating photovoltaic devices, which convert sunlight into electricity, has been identified by chemists at the University of Massachusetts Amherst. Their new technique should lead to more efficient power production than achievable by the current generation of semiconductors.

The work by Sankaran Thayumanavan and colleagues at UMass Amherst, with others at the University of California-Riverside, is highlighted in the current issue of the Journal of the American Chemical Society (JACS), a premier chemistry journal, for the clever way it mimics nature?s way of harnessing solar energy.

To achieve the breakthrough, Thayumanavan and co-workers took inspiration from plants and experimented with organic molecules to mimic the photosynthetic machinery of plants. Their new paper demonstrates how a photosynthesis-style photovoltaic device can be designed using large, highly branched, non-biological organic molecules called dendrimers, based on plant anatomy. Branches allow the dendrimer to absorb photons from a wide area and funnel this energy to the dendrimer?s core where it is connected to a polymer ?wire.? At the core, charge is separated and the electrons travel down the polymer ?wire? to an electrode where electricity is produced.

As Thayumanavan explains, ?Our method is inspired by an energy-harnessing process that plants use in nature, which evolved over millions of years to be efficient in terms of capturing a lot of energy and transporting it short distances without power loss. In the future, photovoltaic devices may no longer rely on slower, less efficient human-made semiconductors. Our work should lead to lighter, more efficient and sustainable photovoltaics.? Thayumanavan, known to colleagues as ?Thai,? is director of the UMass Amherst?s Fueling the Future Center for Chemical Innovation.

He adds, ?The hope is that such a bio-inspired design could approach the conversion efficiency that plants achieve naturally.?

The recent JACS article by him and colleagues titled, ?Dendritic and linear macromolecular architectures for photovoltaics: A photoinduced charge transfer investigation,? was selected by the journal editors to appear in a special section, ?Harnessing Energy for a Sustainable World.? They predict that the research will transform the way engineers design future photovoltaic devices.

The editors add, ?Innovation through scientific discovery is a necessary component of much societal advancement. To truly implement sustainable practices, energy must be harnessed more cleanly and stored for efficient distribution and use. This systems-level change sometimes referred to as the New Industrial Revolution, will require novel materials as well as savvy analysis and modeling to ensure success.?

Brilliant counterfeit protection

Brilliant counterfeit protection

June 2, 2010

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Beside counterfeit protection, the process is also suitable for an effective quality assurance: Here outlines characterize well-bonded and poorly bonded coatings on a function sheet. Such sheets are used to manufacture OLEDs. (© Armin Okulla/Harald Holeczek)

(PhysOrg.com) -- Counterfeit products create losses in the billions each year. Beside the economic damages, all too often additional risks arise from the poor materials and shoddy workmanship of "knock-off artists". Yet with the aid of fluorescing dyes, materials can be individually tagged and identified with certainty.

For quite some time now, product piracy has been affecting more than just consumer goods, like watches and designer clothing. The producer industry also has to combat bogus and qualitatively inferior materials. Specialized security features, like watermarks, bar codes, RFID tags and holograms label the products, and thus safeguard them from falsification, theft and manipulation. So when it comes to security features: the more complicated it is to imitate a brand, the more secure the system.

A team of German researchers from four Fraunhofer Institutes recently engineered a brand new process that is particularly forgery-proof: "We add various fluorescing dyes to the entire material," explains Dr. Andreas Holländer of the Fraunhofer Institute for Applied Polymer Research IAP. "With the aid of the fluorescence, we can precisely ascertain specific characteristics, and thereby recognize if we are dealing with the original, and if the quality standards have been met."

Fluorescence can be found in certain organic dyes: Irradiate them within a certain wave length range, and they emit their own light with a greater wavelength. The type of luminosity - i.e., wavelength and light intensity - depends on the physical and chemical properties of the materials to which the dye was applied. Various dyes react to different properties, such as pH value or viscosity. For example, a certain dye glows in a tightly-interlaced resin more strongly than in one that is not as dense.

To make a product counterfeit-proof, the researchers therefore add multiple dyes to the material. "In this manner, an individualized marker emerges that is exceedingly difficult to imitate," says Holländer. Thanks to the slight dosing, it is virtually impossible to decode the type and quantity of the dye additives: just a few ppb (parts per billion) of dye concentrates suffice to mark the material. Another advantage: The counterfeit protection definitely cannot be removed. "Using conventional security features, the spot with the labeling can be eliminated from the material, theoretically speaking. But that approach doesn?t work with our technology, since the dye permeates the entire material, and itself is a component of the identification label," says Holländer. Beside counterfeit protection, the process is also suitable for an effective quality assurance, such as with coatings: With the aid of various dyes, manufacturers can monitor the chemical composition, degree of dryness and the thickness of the coat during the production process.

The new technology has already passed the first practice tests: Researchers marked barrier sheets for organic light-emitting diodes (OLEDs) and photovoltaics with dyes a development from the Fraunhofer Polymer Surfaces Alliance POLO. The process is basically ready to be used - however, it still must be adapted to each material. A standard solution would also be contrary to the intention of the inventor: "One reason for the high degree of security of our technology is precisely because there are only material-specific solutions," reiterates Holländer.

Multifunctional polymer neutralizes both biological and chemical weapons

Multifunctional polymer neutralizes both biological and chemical weapons

In an ongoing effort to mirror the ability of biological tissues to respond rapidly and appropriately to changing environments, scientists from the McGowan Institute for Regenerative Medicine have synthesized a single, multifunctional polymer material that can decontaminate both biological and chemical toxins. They described the findings recently in Biomaterials.

"Our lab applies biological principles to create materials that can do many things, just like our skin protects us from both rain and sun," said senior investigator Alan Russell, Ph.D., University Professor of Surgery, University of Pittsburgh School of Medicine, and director, McGowan Institute, a joint effort of the university and UPMC. "Typically, labs engineer products that are designed to serve only one narrow function."

Those conventional approaches might not provide the best responses for weapons of mass destruction, which could be biological, such as smallpox virus, or chemical, such as the nerve agent sarin, he noted. Terrorists aren't going to announce what kind of threat they unleash in an attack.

"That uncertainty calls for a single broad-spectrum decontamination material that can rapidly neutralize both kinds of threats and is easily delivered or administered, and it must not damage the environment where it is applied," Dr. Russell said. "Much work has gone into developing ways to thwart either germ or chemical weapons, and now we're combining some of them into one countermeasure."

He and his team have devised a polyurethane fiber mesh containing enzymes that lead to the production of bromine or iodine, which kill bacteria, as well as chemicals that generate compounds that detoxify organophosphate nerve agents.

"This mesh could be developed into sponges, coatings or liquid sprays, and it could be used internally or as a wound dressing that is capable of killing bacteria, viruses and spores," said lead investigator Gabi Amitai, Ph.D., of the McGowan Institute and the Israel Institute for Biological Research. "The antibacterial and antitoxin activities do not interfere with each other, and actually can work synergistically."

In their experiments, the material fended off Staph aureus and E. coli, which represent different classes of bacteria. After 24 hours, it restored 70 percent of the activity of acetylcholinesterase, an enzyme that is inhibited by nerve agents leading to fatal dysfunction of an essential neurotransmitter.

The researchers continue to develop alternate decontamination strategies to address chemical and biologic weapons.

Researchers developing bio-based polymers that heal cracks

Researchers developing bio-based polymers that heal cracks

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Michael Kessler, left, and former Iowa State doctoral student Will Goertzen use a dynamic mechanical analyzer to measure the mechanical properties of polymers. Credit: Photo from Michael Kessler

Michael Kessler has worked with polymers that repair themselves when they crack. And he's worked with polymers made from vegetable oils. Now he's working to combine the two technologies.

Kessler, an Iowa State University associate professor of materials science and engineering and an associate of the U.S. Department of Energy's Ames Laboratory, is researching and developing biorenewable polymers capable of healing themselves as they degrade and crack.

"If successful, the results of this research will provide biorenewable alternatives to petroleum-based resins," says a summary of Kessler's research project. Successfully developing the concept "should have a huge impact economically and environmentally."

Kessler's research project is supported by a five-year, $400,000 grant from the National Science Foundation's Faculty Early Career Development Program.

Kessler started working with self-healing materials as a doctoral student at the University of Illinois at Urbana-Champaign. He was part of a research team that in February 2001 published an article in the journal Nature that helped launch the field.

The technology has evolved into a system that embeds catalysts and microcapsules containing a liquid healing agent within a composite. As cracks develop in the composite, they rupture the microcapsules and release the healing agent. The healing agent contacts the catalyst and reacts by forming 3-D polymer chains that fill the cracks. That increases material lifetimes and reduces maintenance.

Visit his office, and Kessler will pull out a little container half filled with what looks like fine yellow powder. Those are the hollow microcapsules that make the self-healing process work, he said. (They're also the same technology behind scratch-and-sniff perfume ads.)

When Kessler joined Iowa State and the Ames Laboratory in 2005, he started working with Richard Larock, a Distinguished Professor of Chemistry and associate of the Ames Laboratory, to develop biorenewable polymers from vegetable oils.

Larock has invented and patented a process for producing various bioplastics from inexpensive natural oils, which make up 40 percent to 80 percent of the plastics. Larock has said the plastics have excellent thermal and mechanical properties and are very good at dampening noises and vibrations. They're also very good at returning to their original shapes when they're heated.

But can they be developed into a self-healing material?

Early results show there's laboratory work to do. Kessler's research has found that a healing agent for a polymer based on tung oil works too fast. Kessler and Peter Hondred, an Iowa State graduate student in materials science and engineering, are working to slow the agent for better healing.

The researchers are also working to develop encapsulating techniques that work with biorenewable polymers. And they're working to develop bio-based healing agents.

Despite the challenges, Kessler thinks there is potential to develop self-healing, biorenewable materials. He said the big question is whether researchers can push the healing efficiency of biorenewable polymers close to the 90 percent of standard composites.

New method for simple fabrication of microperforated membranes

New method for simple fabrication of microperforated membranes

Microscopically porous polymer membranes have numerous applications in microfluidics, where they can act as filters, masks for surface patterning, and even as components in 3D devices in which the perforations in stacked membranes are aligned to form networks of channels for the flow of fluids.

In the AIP journal Biomicrofluidics, Hongkai Wu, a chemist at Hong Kong University of Science and Technology, and his colleagues describe a simple new method using just one photolithographic step to fabricate free-standing polymer membranes with neatly patterned holes as small as 10 microns in diameter.

The researchers start by designing the desired pattern on a computer and printing it on a transparency (for holes larger than 20 microns in diameter) or a chrome mask (for those smaller than 20 microns). "Then," Wu says, "we place two spacers on a flat substrate and between them add a few drops of a prepolymer" -- a molecule that can form into a polymer. The prepolymer is covered with the mask, which is pressed down onto the spacers; ultraviolet light is then used to cure the membrane. The mask is then removed to reveal the free-standing, perforated membrane.

"Because our technique can fabricate membranes of pores with accurate sizes and in arbitrary shapes and sizes, and the fabrication is very easy and fast, we expect them to have many potential applications in different fields," says Wu. "These membranes can be directly used as masks to pattern inorganic, organic, and biological materials like proteins and cells, on various surfaces," he says.

"One important application of the membrane is that it makes it very simple to fabricate 3D microfluidic structures with channels running up and down through the membrane, which are difficult to make otherwise."

Novel technique informs drug delivery research

Novel technique informs drug delivery research

University College Dublin researchers led by Conway Fellow, Professor David Brayden have shown that a candidate drug delivery polymer may have potential for oral or topical use. These findings were recently published in the Journal of Controlled Release.

The team of scientists, who are part of the Science Foundation Ireland- funded Irish Drug Delivery Network, set out to investigate if an antibacterial synthetic polymer called pDMAEMA [poly(2-(dimethylamino ethyl)methacrylate] is as damaging to normal human cells as it is to bacteria.

This sticky polymer binds membranes and previous research by the team demonstrated that it has a novel bactericidal action against a range of bacteria. This finding has led to pDMAEMA being proposed as a surface-coating for medical devices in an effort to reduce the number of hospital-acquired infections.

This study, which formed part of the doctoral research by lead author Lee-Anne Rawlinson, used high content analysis, a non-invasive imaging technique that can monitor a number of parameters over a time period using up to eight fluorescent dyes. It has an unique advantage over other techniques in that it does not interfere with cells during the analysis.

The findings showed that pDMAEMA was cytotoxic to white blood cells, but not to intestinal epithelial cells, and that it did not damage intestinal mucosae in the model used even in high concentrations. This would suggest that the polymer might have potential for oral or topical use, rather than by systemic injection.

Researchers at UA developing next-gen conductive polymers

Researchers at UA developing next-gen conductive polymers

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Dr. Matthew Graham, left, vice president of business development for Akron Polymer Systems in Ohio, and Dr. Stephen Z.D. Cheng, dean of the College of Polymer Science and Polymer Engineering, examine a conducting polymer film, polythiophene, which Graham developed from 2002-07 as a postdoctoral researcher for Cheng. The film is used in various optical applications and has a high refractive index of about 3.

(PhysOrg.com) -- Conductive polymers, while not quite wonder materials, have the potential for being so and University of Akron polymer scientists and polymer engineers are focused on developing the next generation of the material, says Dr. Stephen Z.D. Cheng, dean of the UA College of Polymer Science and Polymer Engineering.

Cheng says that polymers designed to conduct electricity show great promise, but have not completely matured as a technology.

“A lot of R&D is still being carried out on the topic worldwide,” says Cheng, noting that current research is directed at developing the materials for specific applications.

Medical applications to rechargeable batteries

The overall range of potential applications for conductive polymers is expansive, according to Cheng, pointing to electrostatic materials, conducting adhesives, electromagnetic shielding, artificial nerves, antistatic clothing, piezoelectrics and active electronics, which utilize conductive polymers. Likewise, electrical displays, chemical/thermal/biochemical sensors, rechargeable batteries, solid electrolytes, actuators, switches and the like use conductive polymers for their electroactivity.

“Expectations for conductive polymers have not yet been met because of their limited conductivity and stability, which do not satisfy the demanding performance and lifetimes required for many devices. At The University of Akron, we are working to change that,” Cheng says.

Cheng and fellow UA polymer researchers are concentrating much of their work on developing high-performance, stable conducting polymers for solar cell and bio-related applications.

“The conductivities of the polymers are significantly lower than their inorganic counterparts. This can be improved by reducing defects in the current carrying polymer chains. Also, conducting polymers that are intrinsically conductive do not yet exist,” Cheng explains. “New materials under development are addressing these concerns. At the same time, we are focusing on cost-efficient methods to produce.”

Newly Formed PolymerPlus Emerges from Layered Polymers Research at CWRU

Newly Formed PolymerPlus Emerges from Layered Polymers Research at CWRU

(PhysOrg.com) -- A spin-off venture with its roots in advanced polymers research at Case Western Reserve University has been established, aiming to commercialize polymer technology.

PolymerPlus, LLC, has a license from the university for some of the intellectual property that has been developed at the university’s Center for Layered Polymeric Systems (CLiPS), a National Science Foundation Science & Technology Center. It will seek to find specific applications for multilayered materials for which CLiPS is well known and carry out the research and development necessary to commercialize those applications.

There is a strong technology transfer aspect to PolymerPlus, said Jim Pae, Operations Director at Case Western Reserve’s Institute for Advanced Materials. Films made of extremely thin and varying layers can produce unique, even unexpected benefits. Applications are being explored in such areas as optics and electronics.

“PolymerPlus provides a lower risk approach to developing long-range ideas that companies might have related to multilayer polymer film products and technology,” said Charles Bush, PolymerPlus president. “Should the right opportunity present itself, we might manufacture a product, but at this point our strategy is primarily to be a research and technology company.”

PolymerPlus has obtained an exclusive license to develop CLiPS gradient refractive index (GRIN) lens technology as part of a multi-million dollar development program centered on pilot-scale GRIN lens production for strategic lightweight imaging and energy collection devices. The lead production engineer of the new PolymerPlus LLC facility is Michael Ponting, a 2010 alumnus of the CLiPS graduate research program at CaseWesternReserve.

The PolymerPlus laboratory is in CRADLE, the Sherwin-Williams Co. incubator in the Cleveland suburb Valley View. Sherwin-Williams established CRADLE (Creative Research And Development Laboratory Environment) in a 12,000 square foot facility primarily to accommodate startup companies that require laboratory space.

PolymerPlus is the second CLiPS startup. AdvancedHydro, founded in 2008, is in Austin,Texas, where it is utilizing polymer coatings to extend water filtration membrane lifetime and throughput by reducing membrane fouling.

Exotic discovery made in soft polymer

Exotic discovery made in soft polymer

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To illustrate the new phase they discovered in a block copolymer crystal, Frank Bates, of the University of Minnesota in Minneapolis, along with graduate student Sangwoo Lee, used large fluffy marshmallows to represent the hairy spheres, connecting them together with plastic coffee stirrers. "Marshmallows represent the 'squishiness' of the hairy microspheres, and they are flexible enough to allow the many different angles required to combine them in the complicated sigma-phase configuration," Bates explained. Credit: Frank Bates

Professor Frank S. Bates and his research team at the University of Minnesota in Minneapolis have discovered an unusual type of soft material that was conceived of over 50 years ago, but has never before been found in a plastic--although it has been seen in stainless steel and other metal alloys.

Bates' group, which is funded by the National Science Foundation's Division of Materials Research, specializes in creating a particular class of material, called block copolymers.

"This class of polymers has been studied intensively for nearly half a century, so discovering a new equilibrium structure in a diblock copolymer is unexpected," said Bates. "I have used the analogy that this is a bit like finding a new planet."

Multicolored beaded strings

Polymers are gigantic chain-like molecules which contain hundreds or thousands of repeating units ("poly" means "many;" "mer" in chemistry means a "repeat unit").

To visualize a polymer, think of a very long string of beads, where each bead represents a basic chemical building block, or mer. Different colors stand for different repeat units. Block copolymers are created by connecting two or more of these long sequences.

For example, a diblock copolymer might contain a string of a thousand red beads followed by a sequence containing a thousand blue beads ("di" means "two"). In principle, two, three or any number of bead strings can be linked together, limited only by the strategies cooked up by synthetic chemists, Bates said.

These block copolymers can be created with a number of molecular architectures--linear sequences, branched designs or even star patterns. Different arrangements give each new material different physical characteristics.

Block copolymers exhibit a consistency somewhere between stiff solids and free-flowing liquids--similar to children's play putty--which gives them the descriptive name "melts."

"Block copolymer melts are used in many practical applications such as pressure-sensitive adhesives, tough clear plastics, elastomers in sneaker soles, asphalt additives, drug-eluting stents for clogged coronary arteries and much more," Bates said.

A happy accident

Bates and his team stumbled upon the completely new material quite by accident.

"My students were exploring the mechanical properties of polymers made from poly(lactide)--a derivative of corn--and poly(isoprene)--a synthetic form of natural rubber," Bates said. "They discovered a new and unexplainable x-ray scattering pattern."

The unusual pattern turned out to be associated with a long-predicted crystal structure, now known as the Frank-Kasper sigma phase.

"This phase was named for Sir F.C. Frank, a famous British physicist known for important theoretical contributions to the field of materials physics," Bates explained. "In the 1950s, Frank and General Electric Corporation Researcher J.S. Kasper wrote several creative papers discussing how spherical objects such as atoms might arrange into complex crystal structures."

Bates and his team reported their discovery of a Frank-Kasper sigma phase found in two different block copolymers in a recent issue of the journal Science.

Assembling themselves together

The interesting thing about block copolymers is that they can spontaneously self-assemble into tiny nanoscale structures, including spheres, when cooled. The spheres form because the different blocks, though chemically connected, repel each other like oil and vinegar.

To overcome this self-revulsion, the material organizes itself so that a core of one type of block circles in on itself, leaving a "halo" of the second type of block hanging out like a hairy fringe.

These hairy microscopic spheres are called microphases, or sometimes nanophases, and the act of forming the material into the spheres is called microphase separation.

"Imagine that dozens of block copolymers segregate to form spheres, each composed of a red spherical core surrounded by and a fuzzy blue halo," Bates said. "In a block copolymer melt this occurs everywhere, leading to a relatively dense ensemble of such hairy spheres."

Packing frustrations

Airline passengers aren't the only ones who experience "packing frustrations." As polymers cool from a liquid state to an ordered state, they, too experience the frustration of trying to cram into a small amount of space.

"In order to optimize the packing of the hairy spheres together into a solid crystalline material, they find the most efficient way to fill space," Bates explained. "Different arrangements lead to different levels of stretching and compression of the hairy halo."

To illustrate the Frank-Kasper sigma phase in the new block copolymer crystal, Bates along with graduate student Sangwoo Lee, used large fluffy marshmallows to represent the hairy spheres, connecting them together with plastic coffee stirrers

"Marshmallows represent the "squishiness" of the hairy microspheres," Bates explained, "and they are flexible enough to allow the many different angles required to combine them in the complicated sigma-phase configuration."

Crystal construction

In any crystal, a unit cell is the smallest three-dimensional pattern of atoms or molecules that is repeated in any direction as the crystal grows. Most sphere forming block copolymers, and certain atomic crystals such as iron at room temperature, exhibit a cubic structure, known as the body-centered cubic or "bcc arrangement," according to Bates.

A typical bcc crystal formed from iron has only two atoms per unit cell while a diamond, which forms a face centered cubic or fcc structure, has eight atoms per unit cell. In contrast, the Frank-Kasper sigma phase involves a complex combination of triangular and square groups of 30 block copolymer microspheres fitted together in a single unit cell.

"In this gigantic structure, each microsphere has about 200 diblock copolymers and each diblock copolymer has about 650 atoms, so there are nearly 4 million atoms in each unit cell!" Bates explained.

"The sigma-phase is a true three-dimensional crystal, albeit one that has a gigantic unit cell," said Bates. "This new arrangement indicates that there are packing forces at play related to those that produce quasicrystals, because a simple misplacement of sigma elements during phase formation could lead to a quasicrystal."

The almost crystal

Quasicrystals are materials with irregularly repeating, or aperiodic, patterns of atoms or molecules that do not contain unit cells that repeat or translate as do true crystals. "There is a close relationship between aperiodic order and periodic crystals with large unit cells," Bates said. "The Frank-Kasper sigma-phase represents the "periodic approximant" to certain dodecagonal (12-sided polygon) quasicrystals."

Now that they've discovered the first block copolymer Frank-Kasper sigma phase, Bates and his team are trying to determine the range of block copolymer molecular parameters over which the sigma-phase occurs. "We are synthesizing new polymers and investigating them by x-ray scattering and electron microscopy," he said.

"Also, we will collaborate with theorists to determine whether the sigma-phase can be accounted for using current statistical mechanical tools," Bates added.

"The large unit cell suggests that we might be able to produce crystal structures with unit cell dimensions that are significantly greater than 100 nanometers (nm)," he said. "As the unit cell dimension approaches the wavelength of visible light (400 nm-700 nm), I anticipate potential uses in photonics."

Photonics is the concept of using photons, or light particles, rather than electrons, to transmit video and voice signals (fiber optics) or carry out computations (optical computing). "The potential for application of the Frank-Kasper block copolymer in photonics would be enhanced if actual quasicrystal phases are discovered," Bates said.

The next phase

"The principles associated with sigma-phase formation in the diblock copolymers might be extrapolated to other materials formed from spherical cores and "hairy" halos," said Bates. "This might be accomplished by chemically attaching polymer chains to the surface of spherical nanoparticles. A large refractive index difference between the spherical core (perhaps made from a metal) and the polymer halo would be conducive to photonics."

According to Bates, this particular research is similar to previous projects that have resulted in commercial products, including a new type of plastic and fracture resistant epoxy.

"However, in my mind, what is most significant is the connection between very disparate fields (e.g., metals, polymers, etc.) represented by this work," he said. "Nature provides certain basic ingredients upon which materials are formed. Whenever a new and unanticipated result such as this one surfaces we are forced to reconsider our presumed understanding of these scientific fields."

New material absorbs, conserves oil (w/ Video)

New material absorbs, conserves oil (w/ Video)

An ultra-lightweight sponge made of clay and a bit of high-grade plastic draws oil out of contaminated water but leaves the water behind.

And, lab tests show that oil absorbed can be squeezed back out for use.

Case Western Reserve University researchers who made the material, called an aerogel, believe it will effectively clean up spills of all kinds of oils and solvents on factory floors and roadways, rivers and oceans.

The EPA estimates that 10 to 25 million gallons of oil are spilled annually in this country alone. Spilled oil ruins drinking water, is a fire and explosion hazard, damages farmland and beaches and destroys wildlife and habitats. The harm can last decades.

The aerogel is made by mixing clay with a polymer and water in a blender, said David Schiraldi, chairman of the Macromolecular Science and Engineering department at the Case School of Engineering.

The mixture is then freeze-dried; air fills the gaps left by the loss of water. The resulting material is super light, comprised of about 96 percent air, 2 percent polymer and 2 percent clay.

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A new material made at Case Western Reserve University is designed to clean up oil spills on land and at sea. The superlight material, a clay-based aerogel, absorbs oil out of water, leaving the water behind. The oil can then be squeezed out of the aerogel, and used. Credit: Case Western Reserve University

The oil-absorbing form is just one of a growing list of clay-based aerogels being made in Schiraldi's lab. By adding different polymers, they produce materials with different properties.

"This particular one is oleophilic or oil-loving," Schiraldi said. "Chemically, it hates water, loves oil: the perfect combination."

The aeorgel can be made in granular form, in sheets or in blocks of almost any shape and is effective in fresh and saltwater or on a surface. Because absorption is a physical phenomenon, there is no chemical reaction between the material and oil. If the oil is otherwise not contaminated, it can be used.

Oil spill experts on both coasts say that the ability to squeeze out and conserve the oil is an advantage over other products currently available.

The material was first made when Schiraldi challenged his then-PhD student Matt Gawryla with idea of making kitty litter. Gawryla added the oil cleanup concept to the program.

Case Western Reserve has granted a 9-month exclusive license for this and other clay-based aerogel technologies to AeroClay, Inc. a startup company. Schiraldi will be chief scientific officer of the new company.

Self-healing polymer 'starfish' prolong lifetime of automotive oils

Self-healing polymer 'starfish' prolong lifetime of automotive oils

Researchers have created self-healing polymers that could extend the lifetime of automotive oils. These polymers are suitable to add to lubricants and could maintain the physical properties of engine oils for longer, they claim helping engine efficiency. Biological materials, such as skin, self heal following damage giving inspiration for these new materials.

Polymers are often added to automotive oils to control important physical properties such as viscosity but mechanical and thermal stress can break the polymers decreasing the efficiency and how they affect the oils properties. The research team, led by Professor David Haddleton, of the University of Warwick have now designed a self-healing, star-shaped polymer for use as a viscosity modifier.

The methacrylate polymer has vulnerable long arms which be broken off if stressed reducing performance. The research team found they could add a particular chemical combination to the polymer's backbone which, almost like a starfish, which allow broken arms to reform via a "Diels Alder cycloaddition reaction" in a self healing reaction.

The research team now plan to 'optimise the chemistry before passing it on to our industrial collaborators, Lubrizol, for development in automotive lubricant applications,' says Professor Haddleton.