# Polymer chemistry

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Polymer chemistry is a sub-discipline of chemistry that focuses on the structures of chemicals, chemical synthesis, and chemical and physical properties of polymers and macromolecules. The principles and methods used within polymer chemistry are also applicable through a wide range of other chemistry sub-disciplines like organic chemistry, analytical chemistry, and physical chemistry. Many materials have polymeric structures, from fully inorganic metals and ceramics to DNA and other biological molecules. However, polymer chemistry is typically related to synthetic and organic compositions. Synthetic polymers are ubiquitous in commercial materials and products in everyday use, such as plastics, and rubbers, and are major components of composite materials. Polymer chemistry can also be included in the broader fields of polymer science or even nanotechnology, both of which can be described as encompassing polymer physics and polymer engineering. [1] [2] [3] [4]

## History

The work of Henri Braconnot in 1777 and the work of Christian Schönbein in 1846 led to the discovery of nitrocellulose, which, when treated with camphor, produced celluloid. Dissolved in ether or acetone, it becomes collodion, which has been used as a wound dressing since the U.S. Civil War. Cellulose acetate was first prepared in 1865. In years 1834-1844 the properties of rubber (polyisoprene) were found to be greatly improved by heating with sulfur, thus founding the vulcanization process.

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. [5] In 1907 Leo Baekeland invented the first polymer made independent of the products of organisms, a thermosetting phenol-formaldehyde resin called Bakelite. Around the same time, Hermann Leuchs reported the synthesis of amino acid N-carboxyanhydrides and their high molecular weight products upon reaction with nucleophiles, but stopped short of referring to these as polymers, possibly due to the strong views espoused by Emil Fischer, his direct supervisor, denying the possibility of any covalent molecule exceeding 6,000 daltons. [6] Cellophane was invented in 1908 by Jocques Brandenberger who treated sheets of viscose rayon with acid. [7]

The chemist Hermann Staudinger first proposed that polymers consisted of long chains of atoms held together by covalent bonds, which he called macromolecules. His work expanded the chemical understanding of polymers and was followed by an expansion of the field of polymer chemistry during which such polymeric materials as neoprene, nylon and polyester were invented. Before Staudinger, polymers were thought to be clusters of small molecules (colloids), without definite molecular weights, held together by an unknown force. Staudinger received the Nobel Prize in Chemistry in 1953. Wallace Carothers invented the first synthetic rubber called neoprene in 1931, the first polyester, and went on to invent nylon, a true silk replacement, in 1935. Paul Flory was awarded the Nobel Prize in Chemistry in 1974 for his work on polymer random coil configurations in solution in the 1950s. Stephanie Kwolek developed an aramid, or aromatic nylon named Kevlar, patented in 1966. Karl Ziegler and Giulio Natta received a Nobel Prize for their discovery of catalysts for the polymerization of alkenes. Alan J. Heeger, Alan MacDiarmid, and Hideki Shirakawa were awarded the 2000 Nobel Prize in Chemistry for the development of polyacetylene and related conductive polymers. [8] Polyacetylene itself did not find practical applications, but organic light-emitting diodes (OLEDs) emerged as one application of conducting polymers. [9]

Teaching and research programs in polymer chemistry were introduced in the 1940s. An Institute for Macromolecular Chemistry was founded in 1940 in Freiburg, Germany under the direction of Staudinger. In America, a Polymer Research Institute (PRI) was established in 1941 by Herman Mark at the Polytechnic Institute of Brooklyn (now Polytechnic Institute of NYU).

## Polymers and their properties

Polymers are high molecular mass compounds formed by polymerization of monomers. The simple reactive molecule from which the repeating structural units of a polymer are derived is called a monomer. A polymer can be described in many ways: its degree of polymerisation, molar mass distribution, tacticity, copolymer distribution, the degree of branching, by its end-groups, crosslinks, crystallinity and thermal properties such as its glass transition temperature and melting temperature. Polymers in solution have special characteristics with respect to solubility, viscosity, and gelation. Illustrative of the quantitative aspects of polymer chemistry, particular attention is paid to the number-average and weight-average molecular weights ${\displaystyle M_{n}}$ and ${\displaystyle M_{w}}$, respectively.
${\displaystyle M_{n}={\frac {\sum M_{i}N_{i}}{\sum N_{i}}},\quad M_{w}={\frac {\sum M_{i}^{2}N_{i}}{\sum M_{i}N_{i}}},\quad }$

The formation and properties of polymers have been rationalized by many theories including Scheutjens–Fleer theory, Flory–Huggins solution theory, Cossee-Arlman mechanism, Polymer field theory, Hoffman Nucleation Theory, Flory-Stockmayer Theory, and many others.

The study of polymer thermodynamics helps improve the material properties of various polymer-based materials such as polystyrene (styrofoam) and polycarbonate. Common improvements include toughening, improving impact resistance, improving biodegradability, and altering a material’s solubility. [10]

### Viscosity

As polymers get longer and their molecular weight increases, their viscosity tend to increase. Thus, the measured viscosity of polymers can provide valuable information about the average length of the polymer, the progress of reactions, and in what ways the polymer branches. [11]

## Classification

Polymers can be classified in many ways. Polymers, strictly speaking, comprise most solid matter: minerals (i.e. most of the earth's crust) are largely polymers, metals are 3-d polymers, organisms, living and dead, are composed largely of polymers and water. Often polymers are classified according to their origin:

Biopolymers are the structural and functional materials that comprise most of the organic matter in organisms. One major class of biopolymers are proteins, which are derived from amino acids. Polysaccharides, such as cellulose, chitin, and starch, are biopolymers derived from sugars. The polynucleic acids DNA and RNA are derived from phosphorylated sugars with pendant nucleotides that carry genetic information.

Synthetic polymers are the structural materials manifested in plastics, synthetic fibers, paints, building materials, furniture, mechanical parts, and adhesives. Synthetic polymers may be divided into thermoplastic polymers and thermoset plastics. Thermoplastic polymers include polyethylene, teflon, polystyrene, polypropylene, polyester, polyurethane, Poly(methyl methacrylate), polyvinyl chloride, nylons, and rayon. Thermoset plastics include vulcanized rubber, bakelite, Kevlar, and polyepoxide. Almost all synthetic polymers are derived from petrochemicals.

## Related Research Articles

Biopolymers are natural polymers produced by the cells of living organisms. Like other polymers, biopolymers consist of monomeric units that are covalently bonded in chains to form larger molecules. There are three main classes of biopolymers, classified according to the monomers used and the structure of the biopolymer formed: polynucleotides, polypeptides, and polysaccharides. The Polynucleotides, RNA and DNA, are long polymers of nucleotides. Polypeptides include proteins and shorter polymers of amino acids; some major examples include collagen, actin, and fibrin. Polysaccharides are linear or branched chains of sugar carbohydrates; examples include starch, cellulose and alginate. Other examples of biopolymers include natural rubbers, suberin and lignin, cutin and cutan and melanin.

In polymer chemistry, condensation polymers are any kind of polymers whose process of polymerization involves a condensation reaction. Condensation polymers are formed by polycondensation, when the polymer is formed by condensation reactions between species of all degrees of polymerization, or by condensative chain polymerization, when the polymer is formed by sequential addition of monomers to an active site in a chain reaction. The main alternative forms of polymerization are chain polymerization and polyaddition, both of which give addition polymers.

Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms that contain carbon atoms. Study of structure determines their structural formula. Study of properties includes physical and chemical properties, and evaluation of chemical reactivity to understand their behavior. The study of organic reactions includes the chemical synthesis of natural products, drugs, and polymers, and study of individual organic molecules in the laboratory and via theoretical study.

A polymer is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic and natural polymers play essential and ubiquitous roles in everyday life. Polymers range from familiar synthetic plastics such as polystyrene to natural biopolymers such as DNA and proteins that are fundamental to biological structure and function. Polymers, both natural and synthetic, are created via polymerization of many small molecules, known as monomers. Their consequently large molecular mass, relative to small molecule compounds, produces unique physical properties including toughness, high elasticity, viscoelasticity, and a tendency to form amorphous and semicrystalline structures rather than crystals.

A macromolecule is a very large molecule important to biophysical processes, such as a protein or nucleic acid. It is composed of thousands of covalently bonded atoms. Many macromolecules are polymers of smaller molecules called monomers. The most common macromolecules in biochemistry are biopolymers and large non-polymeric molecules such as lipids, nanogels and macrocycles. Synthetic fibers and experimental materials such as carbon nanotubes are also examples of macromolecules.

Fiber or fibre is a natural or artificial substance that is significantly longer than it is wide. Fibers are often used in the manufacture of other materials. The strongest engineering materials often incorporate fibers, for example carbon fiber and ultra-high-molecular-weight polyethylene.

Synthetic fibers or synthetic fibres are fibers made by humans through chemical synthesis, as opposed to natural fibers that are directly derived from living organisms, such as plants or fur from animals. They are the result of extensive research by scientists to replicate naturally occurring animal and plant fibers. In general, synthetic fibers are created by extruding fiber-forming materials through spinnerets, forming a fiber. These are called synthetic or artificial fibers. The word polymer comes from a Greek prefix "poly" which means "many" and suffix "mer" which means "single units"..

In biochemistry, cellulose acetate refers to any acetate ester of cellulose, usually cellulose diacetate. It was first prepared in 1865. A bioplastic, cellulose acetate is used as a film base in photography, as a component in some coatings, and as a frame material for eyeglasses; it is also used as a synthetic fiber in the manufacture of cigarette filters and playing cards. In photographic film, cellulose acetate film replaced nitrate film in the 1950s, being far less flammable and cheaper to produce.

Hermann Staudinger was a German organic chemist who demonstrated the existence of macromolecules, which he characterized as polymers. For this work he received the 1953 Nobel Prize in Chemistry.

In chemistry and biology a cross-link is a bond or a short sequence of bonds that links one polymer chain to another. These links may take the form of covalent bonds or ionic bonds and the polymers can be either synthetic polymers or natural polymers.

Polyhydroxybutyrate (PHB) is a polyhydroxyalkanoate (PHA), a polymer belonging to the polyesters class that are of interest as bio-derived and biodegradable plastics. The poly-3-hydroxybutyrate (P3HB) form of PHB is probably the most common type of polyhydroxyalkanoate, but other polymers of this class are produced by a variety of organisms: these include poly-4-hydroxybutyrate (P4HB), polyhydroxyvalerate (PHV), polyhydroxyhexanoate (PHH), polyhydroxyoctanoate (PHO) and their copolymers.

Step-growth polymerization refers to a type of polymerization mechanism in which bi-functional or multifunctional monomers react to form first dimers, then trimers, longer oligomers and eventually long chain polymers. Many naturally occurring and some synthetic polymers are produced by step-growth polymerization, e.g. polyesters, polyamides, polyurethanes, etc. Due to the nature of the polymerization mechanism, a high extent of reaction is required to achieve high molecular weight. The easiest way to visualize the mechanism of a step-growth polymerization is a group of people reaching out to hold their hands to form a human chain—each person has two hands. There also is the possibility to have more than two reactive sites on a monomer: In this case branched polymers production take place.

Polymer science or macromolecular science is a subfield of materials science concerned with polymers, primarily synthetic polymers such as plastics and elastomers. The field of polymer science includes researchers in multiple disciplines including chemistry, physics, and engineering.

Bioplastics are plastic materials produced from renewable biomass sources, such as vegetable fats and oils, corn starch, straw, woodchips, sawdust, recycled food waste, etc. Some bioplastics are obtained by processing directly from natural biopolymers including polysaccharides and proteins, while others are chemically synthesised from sugar derivatives and lipids from either plants or animals, or biologically generated by fermentation of sugars or lipids. In contrast, common plastics, such as fossil-fuel plastics are derived from petroleum or natural gas.

Polyester is a category of polymers that contain the ester functional group in every repeat unit of their main chain. As a specific material, it most commonly refers to a type called polyethylene terephthalate (PET). Polyesters include naturally occurring chemicals, such as in plants and insects, as well as synthetics such as polybutyrate. Natural polyesters and a few synthetic ones are biodegradable, but most synthetic polyesters are not. Synthetic polyesters are used extensively in clothing.

Polymer engineering is generally an engineering field that designs, analyses, and modifies polymer materials. Polymer engineering covers aspects of the petrochemical industry, polymerization, structure and characterization of polymers, properties of polymers, compounding and processing of polymers and description of major polymers, structure property relations and applications.

Biodegradable polymers are a special class of polymer that breaks down after its intended purpose by bacterial decomposition process to result in natural byproducts such as gases (CO2, N2), water, biomass, and inorganic salts. These polymers are found both naturally and synthetically made, and largely consist of ester, amide, and ether functional groups. Their properties and breakdown mechanism are determined by their exact structure. These polymers are often synthesized by condensation reactions, ring opening polymerization, and metal catalysts. There are vast examples and applications of biodegradable polymers.

Elmer Otto Kraemer was an American chemist whose studies and published results materially aided in the transformation of colloid chemistry from a qualitative to a quantitative science. For eleven years, from 1927 to 1938, he was the leader of research chemists studying fundamental and industrial colloid chemistry problems and a peer of Wallace Hume Carothers at the Experimental Station of the E. I. du Pont de Nemours Company where both men contributed to the invention of nylon that was publicly announced on October 27, 1938. The 1953 Nobel Laureate in chemistry, Hermann Staudinger, had a high regard for the American pioneers in polymer chemistry, particularly Kraemer and Carothers

Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Their plasticity makes it possible for plastics to be moulded, extruded or pressed into solid objects of various shapes. This adaptability, plus a wide range of other properties, such as being lightweight, durable, flexible, and inexpensive to produce, has led to its widespread use. Plastics typically are made through human industrial systems. Most modern plastics are derived from fossil fuel-based chemicals like natural gas or petroleum; however, recent industrial methods use variants made from renewable materials, such as corn or cotton derivatives.

Polybutylene succinate (PBS) is a thermoplastic polymer resin of the polyester family. PBS is a biodegradable aliphatic polyester with properties that are comparable to polypropylene.

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