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From Citizendium, the Citizens' Compendium
Polymer chemistry or macromolecular chemistry is a branch of chemistry that deals with the preparation and properties of polymers and macromolecules, and one of several fields that play an important role in polymer science and technology. Due to their commercial importance, most research in polymer chemistry is concerned with synthetic organic polymers, such as plastics or fibers. Many polymer chemists, however, work on problems related to medicine, biology and biochemistry, or materials science.
Basic concepts in polymer chemistry
Polymers and macromolecules
In chemistry, the terms "polymer molecule" and "macromolecule" are used interchangeably. . A polymer molecule has a high molecular mass and is comprised of many smaller, repeating subunits or monomers. Polymers may be found in nature, such as the DNA and proteins found in living cells, or created in laboratories or factories.
Polymer molecules come in many shapes and sizes. A polymer molecule may be a long chain of a single monomer repeated over and over again or a complex network containing dozens of different types of monomers. The identity, variety, and arrangement of monomers in a polymer molecule affect the chemical and physical properties of the polymer molecule.
An important area of research in polymer chemistry is finding new or better ways to prepare a polymer molecule from a stock of smaller monomers. In most cases, polymers are prepared using principles of organic chemistry. Polymer chemists are especially interested in techniques that allow them to precisely control the size and structure of the end product.
Polymer chemists are also investigating polymerization methods outside the scope of organic chemistry. One area of interest involves preparing polymers by imitating the biological processes used to create biopolymers such as proteins or cellulose. Other areas of study involve using plasma or electricity to initiate polymerization reactions.
Physical polymer chemistry
Physical polymer chemistry is the study of how a polymer molecule's structure relates to the behavior of the bulk substance. Physical polymer chemistry is closely related to the field of polymer physics and also overlaps with polymer research in materials science. Physical polymer chemists use analytical techniques such as light scattering and spectroscopy to characterize the size and structure of polymers.
Other areas of interest in physical polymer chemistry include the study of polymers in solution, the mechanical properties of polymers, and understanding phase transitions in polymer substances. There are also many researchers using principles of theoretical chemistry to better understand the structure and properties of polymer molecules.
History of polymer chemistry
Naturally occurring polymers such as amber and rubber have been used by humans for millennia. Early Mesoamericans are perhaps the true pioneers in polymer chemistry, having discovered methods for treating natural rubber that were not reproduced until thousands of years later.
The earliest work in modern polymer chemistry involved the chemical modification of naturally occurring polymers. The reaction between nitric acid and cellulose, studied by Henri Braconnot in 1832 and later by Christian Schönbein, led to the discovery of nitrocellulose and celluloid. The ensuing years saw the preparation of other cellulose derivatives, such as collodion, used as a wound dressing since the U.S. Civil War, and cellulose acetate, first prepared in 1865.
Other early work in polymer chemistry involved the modification of natural rubber to improve durability. In 1834, Friedrich Ludersdorf and Nathaniel Hayward independently discovered that adding sulfur to raw natural rubber (polyisoprene) helped prevent the material from becoming sticky. In 1844 Charles Goodyear received a U.S. patent for vulcanizing rubber with sulfur and heat. Thomas Hancock had received a patent for the same process in the U.K. the year before.
In 1884 Hilaire de Chardonnet started the first artificial fiber plant based on regenerated cellulose, or viscose rayon, as a substitute for silk, but it was very flammable. In 1907 Leo Baekeland invented the first wholly synthetic polymer, a thermosetting phenol-formaldehyde resin called Bakelite. Cellophane was invented in 1908 by Jocques Brandenberger who squirted sheets of viscose rayon into an acid bath.
The work of Wallace Carothers in the 1930s demonstrated that polymers of desired chain length and composition could be synthesized rationally from constituent monomers, laying the foundations of modern polymer chemistry and laying the framework for the now burgeoning polymer industry. Carothers is credited with the development of neoprene (1931), a synthetic rubber, the first polyester, and nylon (1935), a true silk replacement. The work of Ziegler and Natta in the 1950s laid the basis for stereospecific polymer synthesis. Stephanie Kwolek developed an aramid, or aromatic nylon named Kevlar, patented in 1966.
There are now a large number of commercial polymers, including composite materials such as carbon fiber-epoxy, polystyrene-polybutadiene (HIPS), acrylonitrile-butadiene-styrene (ABS), and other such materials that combine the best properties of their various components, including polymers designed to work at high temperatures in automobile engines.
Working in polymer chemistry
The American Chemical Society estimates that 50% of chemistry professionals will work in a polymer-related field for some portion of their career. Though polymer chemists typically earn an advanced degree in synthetic organic chemistry, some institutions offer specialized degree programs in materials science and polymer science to meet the evolving needs of the polymer industry. Given the current commercial importance of synthetic polymers, most jobs in polymer chemistry are industrial jobs.
Current areas of active interest in polymer chemistry include the following:
- Fundamental research into controlled syntheses and novel polymerization reactions
- Development of new molecular architectures, such as supramolecular polymer complexes
- Development of molecular architectures suited for molecular sensor technology
- Syntheses of polymers with energy and charge transport properties
- Biomedical applications, such as novel protein design and synthesis and targeted drug delivery
There is also emerging interest in green polymer chemistry. Most artificial hydrocarbon-based polymers are formed from petroleum products. Substantial research efforts are devoted to improved recycling methods, renewable sources of raw materials, and biodegradable polymer materials.
Nobel Prizes in polymer chemistry
2000 Alan G. MacDiarmid, Alan J. Heeger, and Hideki Shirakawa for work on electroactive polymers contributing to the advent of molecular electronics
1974 Paul J. Flory for contributions to theoretical polymer chemistry.
1963 Giulio Natta and Karl Ziegler for contributions in polymer synthesis. (Ziegler-Natta catalysis).
1953 Hermann Staudinger for contributions to the understanding of macromolecular chemistry.
The 1991 Nobel Prize in physics was awarded to Pierre-Gilles de Gennes for developing a generalized theory of phase transitions which has been particularly important for polymer chemistry.