Monomer
A monomer (/ˈmɒnəmər/ MON-ə-mər; mono-, "one" + -mer, "part") is a molecule that can react together with other monomer molecules to form a larger polymer chain or three-dimensional network in a process called polymerization.[1][2][3]
Monomer molecule: A molecule which can undergo polymerization, thereby contributing constitutional units to the essential structure of a macromolecule.[4]
Classification[edit]
Chemistry classifies monomers by type, and two broad classes based on the type of polymer they form.
By type:
- natural vs synthetic, e.g. glycine vs caprolactam, respectively
- polar vs nonpolar, e.g. vinyl acetate vs ethylene, respectively
- cyclic vs linear, e.g. ethylene oxide vs ethylene glycol, respectively
By type of polymer they form:
- those that participate in condensation polymerization
- those that participate in addition polymerization
Differing stoichiometry[5] causes each class to create its respective form of polymer.
The polymerization of one kind of monomer gives a homopolymer. Many polymers are copolymers, meaning that they are derived from two different monomers. In the case of condensation polymerizations, the ratio of comonomers is usually 1:1. For example, the formation of many nylons requires equal amounts of a dicarboxylic acid and diamine. In the case of addition polymerizations, the comonomer content is often only a few percent. For example, small amounts of 1-octene monomer are copolymerized with ethylene to give specialized polyethylene.
Synthetic monomers[edit]
- Ethylene gas (H2C=CH2) is the monomer for polyethylene.
- Other modified ethylene derivatives include:
- tetrafluoroethylene (F2C=CF2) which leads to Teflon
- vinyl chloride (H2C=CHCl) which leads to PVC
- styrene (C6H5CH=CH2) which leads to polystyrene
- Epoxide monomers may be cross linked with themselves, or with the addition of a co-reactant, to form epoxy
- BPA is the monomer precursor for polycarbonate
- Terephthalic acid is a comonomer that, with ethylene glycol, forms polyethylene terephthalate.
- Dimethylsilicon dichloride is a monomer that, upon hydrolysis, gives polydimethylsiloxane.
- Ethyl methacrylate is an acrylic monomer that, when combined with an acrylic polymer, catalyzes and forms an acrylate plastic used to create artificial nail extensions
Biopolymers[edit]
The term "monomeric protein" may also be used to describe one of the proteins making up a multiprotein complex.[6]
Natural monomers[edit]
Some of the main biopolymers are listed below:
Amino acids[edit]
For proteins, the monomers are amino acids. Polymerization occurs at ribosomes. Usually about 20 types of amino acid monomers are used to produce proteins. Hence proteins are not homopolymers.
Nucleotides[edit]
For polynucleic acids (DNA/RNA), the monomers are nucleotides, each of which is made of a pentose sugar, a nitrogenous base and a phosphate group. Nucleotide monomers are found in the cell nucleus. Four types of nucleotide monomers are precursors to DNA and four different nucleotide monomers are precursors to RNA.
[edit]
For carbohydrates, the monomers are monosaccharides. The most abundant natural monomer is glucose, which is linked by glycosidic bonds into the polymers cellulose, starch, and glycogen.[7]
Isoprene[edit]
Isoprene is a natural monomer that polymerizes to form a natural rubber, most often cis-1,4-polyisoprene, but also trans-1,4-polymer. Synthetic rubbers are often based on butadiene, which is structurally related to isoprene.
See also[edit]
Notes[edit]
- ^ Young, R. J. (1987) Introduction to Polymers, Chapman & Hall ISBN 0-412-22170-5
- ^ International Union of Pure and Applied Chemistry, et al. (2000) IUPAC Gold Book, Polymerization
- ^ Clayden, Jonathan; Greeves, Nick; Warren, Stuart; Wothers, Peter (2001). Organic Chemistry (1st ed.). Oxford University Press. pp. 1450–1466. ISBN 978-0-19-850346-0.
- ^ Jenkins, A. D.; Kratochvíl, P.; Stepto, R. F. T.; Suter, U. W. (1996). "Glossary of basic terms in polymer science (IUPAC Recommendations 1996)". Pure and Applied Chemistry. 68 (12): 2287–2311. doi:10.1351/pac199668122287.
- ^ D. Margerison; G. C. East; J. E. Spice (1967). An Introduction to Polymer Chemistry. Pergamon Press. ISBN 978-0-08-011891-8.
- ^ Bruce Alberts, Alexander Johnson, Julian Lewis, Otin Raff, Keith Roberts, and Peter Walter, Molecular Biology of the Cell, 2008, Garland Science, ISBN 978-0-8153-4105-5.
- ^ Ebuengan, Kaye. "Biomolecules: Classification and structural properties of carbohydrates". Academia.edu.