The plastic revolution is coming out - exploring the new limits of polymers
The plastic revolution is coming out - exploring the new limits of polymers
Hermann staudinger was a pacifist, but he had to win. In 1920, the German chemist put polymer (including rubber and fiber, widely compounds) by a similar small smaller chains form, these small molecules connected by strong chemical bonds. But the vast majority of them think that there is no justification for this view, and that the polymer is a loose collection of small molecules. Staudinger refused to back down, sparking a decade-long dispute.
In the end, lab data proved he was right, giving him the Nobel Prize in chemistry in 1953. Synthetic polymers are now ubiquitous: last year, the world produced about 300 million tons of synthetic polymers. Now, from clothing, paint and packaging to medicine, 3D printing and self-healing materials, staudinges hypothesized that molecular chains have entered every aspect of modern life. Polymer based composites even make up half of Boeing's new 787 dreamliner.
So where does the polymer go next? Recently, the national science foundation has organized a 10-yearly event to try to find out what new areas are emerging, or to make some answers to the question.
"The general trend is that the applications of polymers will continue to expand into areas that have traditionally not worked." "Said Tim Lodge, a molecular chemist at the university of Minnesota in Minneapolis and editor of the journal big molecules. This expansion has been driven by the development of polymer science in all fields. "Now, almost every department of chemistry has staff of polymer research." He says research in the field of polymer frontiers is increasingly interdisciplinary.
Researchers to master the production of chemical structure of polymer chain technology more and more, but they often can't predict whether the production of polymer with membrane or dosing system need special characteristics. Overcoming these challenges will require a deeper understanding of how polymer chemical structures affect physical characteristics at various levels, ranging from nano-meters to meters.
Forever polymer
Polymers exist everywhere, and that's the problem. "Most of the polymers we use in our daily lives come from petroleum products. They are durable, but they are also durable." Marc Hillmyer, director of the center for sustainable polymers (CSP) at the university of Minnesota. Eighty-six percent of all plastic packaging has been discarded after a single use, causing a large amount of plastic waste to be accumulated in waterways and landfills, releasing pollutants that endanger wildlife.
This is the reason for the explosion of renewable resources and biodegradable polymers in the past decade. Currently, the market has been able to see a polymer based on natural starch, and it also includes a synthetic polyester (PLA), which is made from a propyl ester or lactic acid process, which can be seen in tea bags and medical implants.
But sustainable polymers have less than 10 percent of the overall plastic market, says Hillmyer. One of the barriers is that they are too expensive; Another problem is that the monomolecular building blocks of natural starch contain more oxygen than petroleum-based hydrocarbons. This will affect the characteristics of the polymer, such as making the material hard, and it is difficult to directly replace cheap, flexible plastics such as polystyrene and polyethylene.
One option is to strengthen environmentally sustainable polymers such as the PLA by mixing them with traditional polymers. But there are obvious drawbacks to this approach, such as making some plastics less transparent. The CSP researchers overcame this problem by adding 5 per cent of a cheap oil polymer (containing some soluble in water). These added materials form a spherical structure that can significantly enhance the durability of the PLA without reducing its transparency.
Hillmyer's team has also produced a partially recyclable polyurethane foam that can be used for a wide range of products such as insulators, cushions and gaskets. The composition of this polyurethane plastic includes a low-cost polymer called polyester (PMVL), which is based on the edited bacterial monomers.
This kind of foam plastic heated to 200 ℃, can make polyurethane decomposition, extract of monomer molecules can be reused. However, it remains to be seen whether these sustainable polymers can be commercialized. "A lot of times, the biggest challenge is mass production, which requires an economic advantage." Hillmyer said.
Interest in the membrane
In a world of mixtures, polymers can restore order. Polymer membranes have been used as molecular "sieves" to separate gases, seawater desalination and to keep molecules in the fuel cells isolated. They will have a bigger impact in the future, Lodge said. "There are many problems that can be solved through better membranes."
The use of membrane separation mixture is much lower than that of distillation. It can also save more space by using a scrubber, which traps pollutants by chemical reactions. The membranes made of polymers can not only achieve large-scale, inexpensive production, but also cover large areas and have no structural defects that make the wrong molecules pass.
The membrane of separable gases has been used in industry to separate hydrogen and carbon dioxide from natural gas. Improved membranes can cope with more difficult tasks, such as resolving similar hydrocarbon propane and propylene. Chemically more powerful membranes can operate at higher temperatures to remove carbon dioxide from the flue gas.
Chemist at the university of Texas at Austin membrane Benny Freeman hope to improve gas fracturing wastewater treatment method of the project, the project of water through the pressure to drink within the rock crack, thereby releasing the gas. After use, the water will become very dirty, standard membranes is block can be blocked, so the water must be under great pressure to pass, and the film also must use chemical cleaning, it will shorten the life.
But Freeman found a way to avoid the problem: by mimicking the waterproof glue that binds a clam to a rock, adding a thin layer of bionic dopamine-like coating on the membrane. The team has used the membranes for some of the building blocks of the U.S. navy to purify it before dumping oily water at the bottom of the cabin.
Polymer front
Widely used polymers such as polystyrene and polyethylene are extremely monotonous in one respect: they repeat the same monomer structure. This monotony is particularly tedious compared to the "quad-vocal symphony" of DNA, which is encoded by four monomers; It is more monotonous than the complex masterpieces of proteins, a complex 3D structure formed by 23 amino acids.
One of the most challenging frontiers of polymers is the ability to cut synthetic polymers with the same precision so that chemists can adjust the electronics and physical characteristics of their products. "Over the past five years, it has become very fashionable." Jean-francois Lutz, a university of Strasbourg university in France, said. A sequence controlled polymer can contain monomers in a predetermined sequence to form a specific length of fiber.
Compared with traditional semiconductor technology, the polymer that controls the sequence can store data in a more compact and inexpensive way, each of which represents one bit of information. In early August, Lutz showed a series of different polymer fibers that could encode 32 bits of information.
Polymer information storage is growing. In April, the intelligence advanced research programme (IARPA), the agency that funded the study of high-risk research in the scientific community, gathered experts from biotechnology, semiconductors and software to attend the seminar. "The field is vibrant and the researchers are growing." David Markowitz, technical adviser to IARPA, who helped organize the workshop.
But this approach still faces huge technological challenges, and the current synthesis technology is still too slow and expensive. The key to solving many other problems in data storage and polymer frontier areas is to study better ways to predict polymer properties and adjust production. This will require multiple forces. "We need to work with physicists, materials scientists and theoretical chemists." "We need to start a new field," Lutz said.
