Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Mayonnaise as Model for Solid Plastics

24.03.2003


Intriguing Structural Strategy Aims at Making Designer Plastics Affordable




The future was supposed to be "plastics," according to advice given in a 1960s movie The Graduate. Many a company thought that future meant the gradual ascendancy of "designer" or specialty plastics, but almost 40 years later the market is still dominated by plastics that can be manufactured cheaply in bulk.

Six researchers from the University of California at Santa Barbara (UCSB) and one at Helsinki University of Technology in Finland report in the March 21 issue of Science a successful example of an intriguing strategy for combining the versatile properties afforded by expensive "designer" plastics with the favorable economics of the old standby, mass-produced plastics. They have done so, quite simply, by finding a way to combine the two types of plastics in one structure.


The resultant material is made mostly of the cheap plastic polystyrene or PS (the stuff of styrofoam®), but the material itself exhibits the properties of the designer plastic--the one (polyaniline) used by the researchers conducts electricity. One of the paper’s authors is UCSB physicist Alan Heeger, who shared the 2000 Nobel Prize in Chemistry for the discovery of conducting polymers such as polyaniline.

UCSB Chemical Engineering Professor Glenn Fredrickson got the idea that led to the reported research while listening at a professional meeting to a lecture on the liquid analogue of the solid material reported in Science. He figured that what could be done for liquids (as in mayonnaise), could be done for solids. Polymer and colloid scientists call such two-phase structures "high internal phase emulsions."

To explain the two-phase structure, Fredrickson begins with the easily envisioned gas-liquid, two-phase version or "foam," as in the head that forms on a newly poured glass of beer.

"This project," said Fredrickson, "is about trying to create a unique two-phase structure in a material like the structure of closed-cell-foam atop beer. That foam has gas bubbles of carbon dioxide entrained by a liquid. The spherical bubbles are close together, and there is a liquid film between them. And the spherical bubbles deform to a polyhedral shape, which enables denser packing than with rigid spheres.

"Imagine," he said, "freezing the beer foam and cutting through it. The honeycomb-like structure you would see is like the solid plastic structure we have produced."

In a standard high internal phase emulsion, the enveloping and the enveloped components are in the same state--liquid. For instance, the vast majority of mayonnaise consists of water (analogous structurally to the carbon dioxide bubble-contents of beer foam). The rest is oil plus surfactants or surface-active agents that stabilize the interfaces of the enclosed water droplets so that mayonnaise, left long in jars, doesn’t flatten.

The researchers are the first to create a two-phase structure in which both components are solids; they therefore add the word "polymeric" to the standard nomenclature. As they state in the abstract of their paper, "The resulting cellular morphology can be viewed as a high internal phase polymeric emulsion."

What they have done is to adapt to solid plastics a morphology widely known in liquid form in the food industry.

The paper’s first author, Raffaele Mezzenga, who now works in that industry at the Nestlé Research Center in Lausanne, Switzerland, conceptualized and conducted the experiments as a postdoctoral fellow shared by Fredrickson and his UCSB collaborator Edward Kramer, a materials professor. Fredrickson’s initial idea evolved in conversations with Kramer. Funding for Mezzenga came from a start-up company PolyE Inc. Heeger and his colleague Daniel Moses provided guidance about and samples of the conducting polyaniline. Another of Fredrickson and Kramer’s postdocs, Janne Ruokolainen, and his thesis advisor at Helsinki, Professor Olli Ikkala, are also authors.

Fredrickson and Kramer are particularly interested in the morphology of two-phase structures. "Phase" in polymer science is a geometric term which pertains to the regions one polymer occupies with respect to another. If, for instance, little balls of one polymer dot the expanse of another (or are embedded), then the balled-up polymer is referred to as "discrete" because the aggregates are distinct from one another. And the polymer of the expanse is referred to as "continuous" because one point on it can be connected to any other point on it by tracing a route around the embedded aggregates.

"The notion of enhancing polymer properties by embedding one in another is standard practice of polymer engineering," said Kramer. "It is to polymers what alloys are to metals. As with alloys, polymer blends usually exhibit properties that differ from the properties of each of the constituents."

With the semiconducting polymer blend reported in the Science paper ("Templating Organic Semiconductors Through Self-Assembly of Polymeric Colloidal Systems"), the key desired transport property is a function only of the expensive designer polymer polyaniline, whose disposition in the polymer blend must be continuous in order to conduct electricity, but continuous in such a way (like the liquid film around the CO2 beer foam) that only a little of this expensive material is used.

In addition to transport (of electrons, molecules, and ions), this honeycomb morphology can also be adapted to perform the opposite function of providing a barrier, required for instance in packaging fresh food products, which decay with exposure to oxygen. The kind of plastic available today to provide that barrier would cost almost as much as or more than most of the package’s contents. The Science technique would enable use of a little of that expensive plastic in combination with a cheaper plastic. The resultant material would cost a little more than the cheaper plastic alone, but would provide value by blocking spoilage that would be worth the cost.

The trick that Mezzenga figured out to assemble the polymers into the desired structure entails the use of another polymer in addition to PS and polyaniline. He designed a block copolymer of PS and poly(vinyl pyridine) or PVP that would complex appropriately with the other two components. Ruokolainen and Ikkala assisted this effort.

Block co-polymers are another standard tool of polymer engineering which, in effect, splices together two polymers such that the very long molecule which results has ends with usefully different properties.

As the authors write, "A route for producing semiconducting polymer blends is demonstrated in which a doped pi-conjugated polymer [polyaniline] is forced into a three-dimensionally continuous minor phase by the self-assembly of colloidal particles and block copolymers." (The colloidal particles are PS and the block copolymers, PS-PVP.)

Because this process requires a solvent, Fredrickson points out, "it will be better suited for paints and coatings rather than for bulk materials. Many paints are currently formulated with latex colloidal particles, so the present technology provides a way to introduce new functionality, such as conductivity that could have value in antistatic coatings."

Heeger said, "The concept is simple, but elegant--and the use of block copolymers to direct the formation of the two-phase structure and the cellular morphology provides a general approach to creating ’designer’ materials. Consequently, potential applications of our initial results in the science of new materials go well beyond conducting polymers."

Jacquelyn Savani | University of California, Santa
Further information:
http://www.engineering.ucsb.edu/Announce/mayonnaise_plastics.html

More articles from Materials Sciences:

nachricht Innovate coating extends the life of materials for industrial use
28.09.2016 | Investigación y Desarrollo

nachricht Lowering the Heat Makes New Materials Possible While Saving Energy
26.09.2016 | Penn State Materials Research Institute

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: New welding process joins dissimilar sheets better

Friction stir welding is a still-young and thus often unfamiliar pressure welding process for joining flat components and semi-finished components made of light metals.
Scientists at the University of Stuttgart have now developed two new process variants that will considerably expand the areas of application for friction stir welding.
Technologie-Lizenz-Büro (TLB) GmbH supports the University of Stuttgart in patenting and marketing its innovations.

Friction stir welding is a still-young and thus often unfamiliar pressure welding process for joining flat components and semi-finished components made of...

Im Focus: First quantum photonic circuit with electrically driven light source

Optical quantum computers can revolutionize computer technology. A team of researchers led by scientists from Münster University and KIT now succeeded in putting a quantum optical experimental set-up onto a chip. In doing so, they have met one of the requirements for making it possible to use photonic circuits for optical quantum computers.

Optical quantum computers are what people are pinning their hopes on for tomorrow’s computer technology – whether for tap-proof data encryption, ultrafast...

Im Focus: OLED microdisplays in data glasses for improved human-machine interaction

The Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP has been developing various applications for OLED microdisplays based on organic semiconductors. By integrating the capabilities of an image sensor directly into the microdisplay, eye movements can be recorded by the smart glasses and utilized for guidance and control functions, as one example. The new design will be debuted at Augmented World Expo Europe (AWE) in Berlin at Booth B25, October 18th – 19th.

“Augmented-reality” and “wearables” have become terms we encounter almost daily. Both can make daily life a little simpler and provide valuable assistance for...

Im Focus: Artificial Intelligence Helps in the Discovery of New Materials

With the help of artificial intelligence, chemists from the University of Basel in Switzerland have computed the characteristics of about two million crystals made up of four chemical elements. The researchers were able to identify 90 previously unknown thermodynamically stable crystals that can be regarded as new materials. They report on their findings in the scientific journal Physical Review Letters.

Elpasolite is a glassy, transparent, shiny and soft mineral with a cubic crystal structure. First discovered in El Paso County (Colorado, USA), it can also be...

Im Focus: Complex hardmetal tools out of the 3D printer

For the first time, Fraunhofer IKTS shows additively manufactured hardmetal tools at WorldPM 2016 in Hamburg. Mechanical, chemical as well as a high heat resistance and extreme hardness are required from tools that are used in mechanical and automotive engineering or in plastics and building materials industry. Researchers at the Fraunhofer Institute for Ceramic Technologies and Systems IKTS in Dresden managed the production of complex hardmetal tools via 3D printing in a quality that are in no way inferior to conventionally produced high-performance tools.

Fraunhofer IKTS counts decades of proven expertise in the development of hardmetals. To date, reliable cutting, drilling, pressing and stamping tools made of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

European Health Forum Gastein 2016 kicks off today

28.09.2016 | Event News

Laser use for neurosurgery and biofabrication - LaserForum 2016 focuses on medical technology

27.09.2016 | Event News

Experts from industry and academia discuss the future mobile telecommunications standard 5G

23.09.2016 | Event News

 
Latest News

New imaging technique in Alzheimer’s disease - opens up possibilities for new drug development

28.09.2016 | Medical Engineering

Innovate coating extends the life of materials for industrial use

28.09.2016 | Materials Sciences

Blockchain Set to Transform the Financial Services Market

28.09.2016 | Business and Finance

VideoLinks
B2B-VideoLinks
More VideoLinks >>>