Polymer Solutions Newsblog

Photographers can use fish-eye lenses to capture unique images.

Scientists at the Center for Layered Polymeric Systems at Case Western University have developed a unique process called forced assembly that creates alternating nanometer-thick layers of polymers. The scientists are developing various applications for the technology, ranging from new kinds of lenses to better packaging for food, medicine, and electronics to tunable lasers, writes Marlene Cimons for the National Science Foundation (NSF).

Cimons explains that forced assembly uses “a special melting process that allows the material to be cut and stacked in thousands of extremely thin layers of film.”

NSF supports the center, which has partnerships with various U.S. research universities and facilities. Among the projects close to commercialization from the center is a new fish-eye lens that could advance telescopes and cameras. She writes that it resembles the eye of an octopus, which can focus light five times more strongly than that of a human eye. She describes the lens:

The new lens consists of hundreds of thousands of layers of plastic from two different polymers, each with a different refractive index (a measurement of the speed of light through that substance). Each film has a refractive index that differs from the next by 1 percent, resulting in a powerful new lens with the ability to focus much like the eye of the octopus.

The forced assembly technology could also be used to improve the airtight qualities of plastic packaging for food, medicine, and electronics. Oxygen and water vapor can degrade these products. Cimons describes a configuration that demonstrated a 100-fold improvement in the film’s gas barrier when made into nano-sized layers:

When the researchers produced very thin films composed of even thinner layers of commonly used polymers, they found that polyethylene oxide, a standard ingredient in the plastics industry, forms a single layer of crystals in repeating chains that line up close together in an ordered pattern.

Scientists at the center also have used the technology to make inexpensive laser sheets, which are stretchable and can produce lasers with the ability to continuously change their wavelength within certain limits, unlike traditional lasers, Cimons writes. Center director Eric Baer told Cimons that the new lasers could have widespread applications in such fields as medicine, astronomy, communication, and imaging.

Source: “New Uses for Layered Polymer Films,” National Science Foundation via U.S. News and World Report, 2/15/12
Image from Wikimedia Commons, used under Fair Use: Reporting.

Graphene (shown here) is considered a 2D polymer, but not an ordered one like the new polymer.

Most polymers are one-dimensional. They are created with linearly repeating units bonded together to form a chain, though the structures may have some branching or irregular crosslinking. Now, researchers in the U.S. and Switzerland have used organic synthesis to design an ordered, 2D polymer, according to a statement from the Swiss Federal Laboratories for Materials Science and Technology.

Graphene is a naturally occurring and well-known example of a nanoscale 2D polymer, which has planar layers of carbon with a honeycomb-like pattern, as shown in the image. However, graphene “cannot be synthesized in a controlled way,” according to the statement.

In a paper published in the journal Nature Chemistry, the researchers describe the advance:

We feel that the internal order of our two-dimensional polymers will allow for the establishment of reliable structure–property relations. In addition, the present two-dimensional structure might be tuned for particular properties (and applications). This is a key opportunity that rational synthesis offers over pyrolytic approaches.

To create the 2D polymer, the researchers first crystallized a specifically designed photoreactive monomer into a layered structure. Then they used light to polymerize the layers of the crystal. Finally, they boiled the crystal in a solvent to separate the polymerized layers, which each represent a 2D polymer structure.

The researchers confirmed the 2D structure of the polymer with transmission electron microscope studies, and are working on characterizing the material’s properties. The researchers also described in the statement how they could modify the 2D polymers to create such applications as tiny molecular sieves.

Source: “Startling results in synthetic chemistry presented in ‘Nature Chemistry’ Ordered two-dimensional polymers created for the first time,” Empa press release, 2/13/12
Source: “A two-dimensional polymer prepared by organic synthesis,” Nature Chemistry, 2/5/12
Image by CORE-Materials, used under its Creative Commons license.

Researchers at the University of California, Los Angeles, have reported a tandem solar cell with record-breaking power efficiency. The cell has a unique structure that incorporates a new infrared-absorbing polymer material to use more of the solar spectrum, according to a statement from UCLA.

Photovoltaic solar cells use conductive organic polymers to absorb sunlight and convert it to electricity. These polymers can be produced in high volumes at low cost, and the resulting cells are inexpensive, lightweight, and flexible, as shown in the video. Researchers have tried various strategies, including changing the architecture and materials, in the past few years to boost the efficiency of these cells.

Now, the UCLA researchers have combined both. According to a press release:

They have significantly enhanced polymer solar cells’ performance by building a device with a new ‘tandem’ structure that combines multiple cells with different absorption bands. The device had a certified power-conversion efficiency of 8.62 percent and set a world record in July 2011.

Further, after the researchers incorporated a new infrared-absorbing polymer material provided by Sumitomo Chemical of Japan into the device, the device’s architecture proved to be widely applicable and the power-conversion efficiency jumped to 10.6 percent — a new record — as certified by the U.S. Department of Energy’s National Renewable Energy Laboratory.

Yang Yang is a professor of materials science and engineering at UCLA and principal investigator on the new work. He described the concept of the tandem cell as a double-decker bus. “The bus can carry a certain number of passengers on one deck, but if you were to add a second deck, you could hold many more people for the same amount of space. That’s what we’ve done here with the tandem polymer solar cell,” he explained in a statement.

The tandem cell is more efficient compared to single-layer devices because it minimizes other energy losses, but not just any two cells will work together. Suitable polymer materials were the stumbling block for tandem cells back until now. The researchers noted the efficiency only increases when the materials for the tandem cells are “compatible with each other for efficient light harvesting.”

“By using more than one absorption material, each capturing a different part of the solar spectrum, the tandem cell is able to maintain the current and increase the output voltage. These factors enable the increase in efficiency,” the researchers said in a statement.

A schematic shows that the cell’s architecture looks like a sandwich. Glass and a metal electrode are the “bread” slices. The “meat and cheese” of the sandwich are layers of zinc oxide, a high-band gap photoactive polymer, an interlayer, and a low-band gap photoactive polymer with complementary absorption.

Yang noted in a statement that the cell is fabricated with a very low-cost wet-coating process that is compatible with current manufacturing, and he anticipates that the technology will be commercially viable.

Source: “UCLA engineers create tandem polymer solar cells that set record for energy-conversion,” UCLA press release, 2/14/12
Source: “Polymer solar cells with higher efficiency,” YouTube

Small disposable bottles of water will no longer be sold at the Grand Canyon.

People come to see the Grand Canyon’s majestic vistas, not empty plastic bottles dotting the landscape. Therefore, to help curb the litter, sale of disposable plastic water containers under one gallon will be banned at the Grand Canyon this spring.

David Schwartz reports for Reuters:

The National Park Service has approved a plan that would eliminate the sale of bottled water within 30 days, after nearly $290,000 was spent to install 10 water stations inside the park. Visitors can use the stations to refill their own water bottles, which they can tote in from the outside.

Park concessionaires, who can still sell other bottled beverages, chipped in with another three water stations.

“Our parks should set the standard for resource protection and sustainability,” John Wessels, the park service’s intermountain region director, said in a statement to Reuters. Wessels added he expects the new policy to have “minimal” impact on visitors to the Grand Canyon.

Visitors can still bring disposable bottles into the park, according to the Associated Press.

Media outlets report that the Grand Canyon officials estimate the disposable containers comprise about 20% of the park’s overall waste stream and 30% of recyclables.

Zion and Hawaii Volcanoes national parks have similar bans, but the Grand Canyon ban became more controversial late last year, Schwartz writes, “after what the public interest group Public Employees for Environmental Responsibility charged was pressure by The Coca-Cola Company.” The company, which is a large donor to the parks, and park officials have denied the claim, he adds.

Jeff Ruch, the executive director of Public Employees for Environmental Responsibility, applauded the decision, and told media outlets, “The record clearly shows intense public scrutiny forced this abrupt U-turn.”

Source: “Grand Canyon to ban bottled water sales,” Reuters, 2/8/12
Source: “Grand Canyon banning sale of plastic water bottles within national park in next 30 days,” Associated Press via The Washington Post, 2/7/12
Source: “Arizona: Disposable Bottles to Be Banned at Park,” The New York Times, 2/7/12
Image by Nouhailler (Patrick Nouhailler), used under its Creative Commons license.

Looking for the perfect Valentine’s Day present for that stressed-out special someone in your life? Just get that person a big roll of bubble wrap. (Heart-shaped sheets are optional.)

According to the first ever “pop” poll stress survey, one minute of popping the bubbles in bubble wrap provides stress relief equivalent to 33 minutes of massage.

Heather Caliendo reports for PlasticsToday:

Sealed Air Corp., the makers of bubble wrap brand cushioning, conducted this poll to gauge the current stress level of Americans and reinforce the surprise stress-relieving benefits of popping bubble wrap, the company stated.

According to William V. Hickey, president and CEO of Sealed Air, Caliendo quotes, “Bubble wrap was originally intended as a form of textured wallpaper, but has transformed into an unexpected pop culture icon, becoming most recognized for the satisfying release that comes with the popping of each bubble.” Kelton Research conducted the poll.

Caliendo acknowledges “whether bubble wrap actually does help to reduce stress or not is up for debate.” But she points to information from The Freedonia Group, Inc., an industry market research firm, which stated that “the demand for protective packaging is set to increase by about 5% per year to $5.9 billion in 2016.”

That is because manufacturing output is up as is Internet shopping. So shippers need protective packaging such as mailers, bubble wrap, and air pillows to keep goods intact on their way to consumers. The study indicated that shippers find cost-effective, lightweight bubble packaging is more appealing than alternative materials such as polyurethane foam.

Caliendo noted that the study included information about whether bubble wrap’s stress-relieving characteristics have helped increase the demand for the packaging material.

Source: “Can bubble packaging’s ‘healing powers’ influence protective packaging demand?,” PlasticsToday, 2/3/12
Composite image by SALi-design and Wikimedia Commons, used under their Creative Commons license.

Mixing nanotubes (illustration shown) and sheets of reduced graphene oxide with polyvinyl alcohol makes very strong fibers.

Spiders figured out long ago how to make webs with silk that is both strong and flexible. Chemists try to mimic it, and commonly toughen synthetic polymer fibers by mixing in an additive, such as carbon nanotubes. But researchers have found that a combination of additives creates an economical material that exceeds spider silk and Kevlar in toughness.

Steve Down reports for Chemistry World:

The toughest polymer yarn of all time has been made by mixing a polymer with sheets of reduced graphene oxide (RGOF) and carbon nanotubes (CNTs) during spinning. The yarns are much cheaper than those using CNTs as the only additive, producing fibres that can be sewn like threads and coiled into springs.

CNTs can cost up to $90,000 per kilogram, whereas industrial-grade graphene oxide costs about $450 per kilogram.

Natural spider silk is composed of two types of proteins: two-dimensional sheet type and one-dimensional strand type, and their combination is very important to the toughness of the spider silk, Seon Jeong Kim of Hanyang University in Korea explained to Down. Therefore, Kim and his colleagues mixed “sheets” of RGOF and “strands” of single-walled CNT with polyvinyl alcohol (PVA).

To make the fibers from an aqueous solution of PVA, the researchers injected a 1:1 solution of single-walled CNT and wrinkled RGOFs during spinning. The resulting fibers were treated with methanol to increase crystallinity. They confirmed the interconnected structure of the fibers with scanning electron microscopy. Down writes:

The CNT bundles also attached themselves to the edges and surfaces of the RGOF sheets. This alignment led to toughness values up to 970J/g, which are greater than those reported so far for any material.

Down noted that increased hydrogen bonding is responsible for the toughness, and Kim suggested to him that the material may be used to make bullet-proof vests.

Soon Hyung Hong from the Korea Advanced Institute of Science and Technology commented to Chemistry World that the fibers are tough, but that if they were stronger and tougher, they could be used for additional applications such as cables or high-pressure vessels.

Source: “The world’s strongest fibres,” Chemistry World, 2/1/12
Image by ghutchis (Geoff Hutchinson), used under its Creative Commons license.