Jason Jung, Grade 11, ISEC 2015 Runner-Up

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Perhaps the most strategic military resource a country could own is rubber. In fact, during the mid-20th century, the U.S. relied heavily on natural rubber imported from Southeast Asia for automobile tires, military vehicles, and footwear for soldiers. As a result, when this supply was cut off at the start of Second World War, a dilemma known as the World War II Rubber Crisis arose. The American government was forced to join forces with rubber companies, the young petrochemicals industry, and university research laboratories to somehow feed the 70,000-ton appetite of the economy and military at the time (American Chemical Society National Historic Chemical Landmarks, 1998); thus, research in polymer chemistry was established and its value and necessity was demonstrated. Today, the polymer industry has exploded and is used in countless instances. They can also be found in every corner of the Earth: the plastic keys of a keyboard, the rubber in car tires, and the polyester in many clothes are all forms of polymers. Polymers are made up of a large repetition of similar unit structures, called monomers, bonded together. Their structure and properties depend on the arrangement and type of monomer. As a result, polymers have the potential to form objects with vastly significant scientific and consumer application in perhaps boundless ways. Unlike most research fields, studies in polymers are nearly always interdisciplinary. It is in its very nature to cut across traditional boundaries of chemistry, biochemistry, medicine, physics, biology and materials science and engineering (Carraher and Tsuda, 1980). Modern polymer chemistry often bases off of preexisting biological polymers, making alterations to their form and structure.

Mother Nature was the original polymer chemist, designing starches, cellulose, and chitin with the glucose monomer and utilizing their functions in varying places. Contemporary biologists take inspiration from them and some even use parts of them in their research. The Olsen Research group at MIT, for instance, incorporates both biochemistry and polymer design to create materials that can have a plethora of beneficial applications. This particular group of researchers is precisely engineering hydrogels to reinforce, toughen, and create bioactive materials in them. These allow the gel to be optimized for tissue integration and cell delivery. To accomplish this, they use both traditional and biological approaches to polymer synthesis. The result is a biomaterial that can cease internal hemorrhaging and reinforce tissue. Specifically, in vitro tests have shown reduced blood clotting by 77 %, and a formation of stable clot-gel systems. Further, in vivo tests indicated that the nanocomposites are biocompatible and capable of promoting hemostasis in normally lethal liver lacerations (Assmann, Avery, Gaharwar, et al, 2014). Based on these effects, the applications for this new bio-polymer are significant. For example, it can improve upon conventional methods that are hard to deploy on the battlefield and cannot be used on incompressible wounds, such as fibrin glue and tissue adhesives.

Another way biology has been utilized in polymer chemistry is in the creation of hybrid materials. Specifically, when organic polymers are combined with nanoscale inorganic particles, the new polymer has extraordinary properties depending on what is combined. Further, there are many ways in which they can be joined. As a result, countless structures and polymers can be made. To get a specific material with the correct properties, it is highly important to tailor the formation process with the final product in mind (Kickelbick, 2002). Because of the wide variety of properties that organic-inorganic hybrid materials can have, they can be used in many fields. For example, one combination is conductive and can be used in superconductors and solid-state lithium-ion batteries. Lithium-ion batteries with hybrid components display greater membrane stability at high temperatures compared to those of pure organic systems, which makes the batteries more reliable and efficient (Kickelbick, 2002). In optics, light-emitting diodes, photodiodes, and solar cells benefit as well. These optic contraptions are more stable in the long-term and have improved electronic properties (Kickelbick, 2002). Because of the high potential for future application, the area of these hybrids has received considerable attention from the research community, which will only make way for even more combinations and discoveries. Bridging biology and polymers have proven to be highly successful in improving modern devices and creating new ones.

One other subject that is significantly important in the study of polymer chemistry is, unsurprisingly, chemistry itself. It is necessary to study the structure of the polymers that are being created and to be able to make them better. One frequent application of it in this field is in the creation of tissue scaffolds. Scaffolds act as templates for regenerating tissue to guide their growth. The prerequisite for a scaffold is the ability to be dissolved afterwards and compatibility with the host’s cells; polymer scaffolds exceed these requirements. With further development of processing techniques, especially by using computer-aided technology, particles and scaffolds with extremely complex architectures can far better mimic their biological counterparts than traditional scaffolds can (Laurencin, Nair, and Ulery, 2011). Unlike most current scaffolds, which are uniformly crosshatched, these new polymer scaffolds will be uniquely tailored to complement the real cell structures, which will interact more favorably with the host cells.

Polyurethane, when used in biological environments, degrades quickly. This causes potentially dangerous blood clots to form, a process called platelet adhesion. To solve this issue, researchers have designed a polyurethane that can minimize this adhesion by selecting the length that the side chain of the polymer extends from the main chain. In one experiment, polyurethanes introduced with an alkyl side chain onto the hard segments reduced platelet adhesion after sustaining load cycles (Jun, Li, Liu, et al, 2005). In addition, this new polyurethane polymer can be used in pacemakers and artificial hearts without degrading as quickly as the generic polyurethane. Apart from benefits to biology, another valuable property of this polyurethane is its solubility in common solvents, which, according to the researchers, could be used to make car tires that can be recycled or repaired instead of being scrapped.

Chemistry can also be used to create nanofibers from polymers. As an electrically charged jet of polymer solution becomes very long and solidifies, it is collected in the form of a fiber. The capillary instability that produces beads, and the development of branches, occur under specific conditions (Renekera and Yarin, 2008). These fibers can preserve proteins, DNA, cell organelles, and chemical reagents inside them. Another application is the growing use of nanofibers in medicine, energy conversion, and agriculture. As stated before, polymers have countless combinations and forms; by creating different nanofibers by jetting different polymer solutions, the properties of those nanofibers will also be unlimited.

Unfortunately, the approaches each of these disciplines takes to polymer chemistry are not without flaw. Polymer research from a biology perspective, while it can offer insight from nature, is often limited to the proteins or natural polymers that can be studied. This creates a boundary to the extent in which polymer chemistry can be further advanced by biology. Had polymer research been solely biology-based, people would not be able to create the elastomers, polystyrenes, and adhesives that are available today. With little real-world application possible, polymer chemistry would be essentially pointless. On the other side of the spectrum, a chemistry-exclusive perspective on polymer chemistry would not only be futile, but also detrimental. Synthetic polymers are inherently poor in biodegradability. After less than a century of its use, plastic, one of the most common synthetic polymers, accounts for 80% of the seven million tons of marine debris that reaches all oceans and regional seas each year (Valavanidis and Vlachogianni, 2012). The buildup of these unusable materials over the years will cause economic, environmental, human health, and aesthetic problems.

There is therefore a clear advantage to an interdisciplinary approach to polymer chemistry: it is not possible without being so. Many advancements in polymer chemistry require an interdisciplinary view. In a study on polymer scaffolds, the abstract states: “[Creating polymer scaffolds] is a highly interdisciplinary field that encompasses polymer synthesis and modification, cell culturing, gene therapy, stem cell research, therapeutic cloning and tissue engineering” (Chiellini, 2011). This advantage is not limited to those researching polymer chemistry. A world without polymers would make modern-day living unfeasible. In 2003, the world produced 205 million tons of plastic alone, and this number continues to rise (Chiellini, Chiellinia, Dasha, et al, 2007). This statistic depicts the growing dependence on polymers in everyday life. The quality of being interdisciplinary is an advantage because it is necessary for the existence of both polymer chemistry and the modern man.

From the very beginnings of polymer chemistry during World War II, polymers have shown to be indispensable to support mankind. To this day, it still retains that position and goes further to become commonplace all over the globe. There are a number of fields that are necessary for the research in polymer chemistry, such as biology and chemistry. Research in it from those perspectives has applications in biomedicine, optics, agriculture, and much more. Polymer chemistry is a highly interdisciplinary study; to research it through a single discipline would be disadvantageous, and to research it through multiple is an essential advantage. Polymer chemistry is the result of the combining and mingling of many science fields, and cannot exist independently – it is a secondary study, the offspring of hundreds of years of research.

 

References

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