Copolymer


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polymer

polymer (pŏlˈəmər), chemical compound with high molecular weight consisting of a number of structural units linked together by covalent bonds (see chemical bond). The simple molecules that may become structural units are themselves called monomers; two monomers combine to form a dimer, and three monomers, a trimer. A structural unit is a group having two or more bonding sites. A bonding site may be created by the loss of an atom or group, such as H or OH, or by the breaking up of a double or triple bond, as when ethylene, H2C=CH2, is converted into a structural unit for polyethylene, –H2C–CH2–. In a linear polymer, the structural units are connected in a chain arrangement and thus need only be bifunctional, i.e., have two bonding sites. When the structural unit is trifunctional (has three bonding sites), a nonlinear, or branched, polymer results. Ethylene, styrene, and ethylene glycol are examples of bifunctional monomers, while glycerin and divinyl benzene are both polyfunctional. Polymers containing a single repeating unit, such as polyethylene, are called homopolymers. Polymers containing two or more different structural units, such as phenol-formaldehyde, are called copolymers. All polymers can be classified as either addition polymers or condensation polymers. An addition polymer is one in which the molecular formula of the repeating structural unit is identical to that of the monomer, e.g., polyethylene and polystyrene. A condensation polymer is one in which the repeating structural unit contains fewer atoms than that of the monomer or monomers because of the splitting off of water or some other substance, e.g., polyesters and polycarbonates (see illustration). Many polymers occur in nature, such as silk, cellulose, natural rubber, and proteins. In addition, a large number of polymers have been synthesized in the laboratory, leading to such commercially important products as plastics, synthetic fibers, and synthetic rubber. Polymerization, the chemical process of forming polymers from their component monomers, is often a complex process that may be initiated or sustained by heat, pressure, or the presence of one or more catalysts.

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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Copolymer

 

a polymer whose macromolecules contain several types of monomeric units. In regular copolymers, the different units are arranged in periodic fashion. The simplest examples are copolymers of styrene with maleic anhydride and copolymers of certain olefins with SO2, constructed in the order . . . ABABAB . . . , where A and B are different types of monomeric units. More complicated regular sequences, with an alternating arrangement of units, are characteristic of, for example, the various amino-acid residues in certain proteins, such as the glycine-proline-hydroxyproline sequence in collagen. In irregular copolymers, the distribution of monomeric units is random, which is characteristic for many synthetic copolymers. In nucleic acids and most proteins, the irregular sequences of units are prescribed by a corresponding code, and it is these sequences that determine the biochemical and biological specificities of the corresponding compounds.

Copolymers in which the monomeric units of each type form rather long continuous sequences (blocks) that replace one another within the macromolecule are called block copolymers. One or several chains having a chemical composition different from that of the macromolecular chain may be added to the internal (nonterminal) monomeric units of the chain. Copolymers of this type are referred to as graft copolymers.

Materials with a given set of properties can be prepared by combining chemical units of various types in a single macromolecule. Thus, the synthesis of copolymers is one of the most effective means for modifying the properties of high-molecular-weight compounds.

REFERENCE

Entsiklopediiapolimerov, vols. 1–2. Moscow, 1972–74.

V. A. KABANOV

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

copolymer

[kō′päl·i·mər]
(organic chemistry)
A mixed polymer, the product of polymerization of two or more substances at the same time.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
It is worth noting in this work, that after the addition of the copolymers, the torque of the blend containing EGMA copolymer is higher than that of the blend containing EMAGMA copolymer.
Figure 7a shows the XRD patterns of neat PET and of PET/EGMA blends containing 5-20 wt% of EGMA copolymer. PET presents a halo indicating that it has an amorphous structure [29].
With the deeper compression process, copolymer concentration at air/water interface was increased.
Park, AbstrPap Am Chem S, Thin-film behavior of polystyrene-block-poly(methyl methacrylate) diblock copolymer at the air-water interface.
Preliminary analysis of the copolymer was performed using TLC (90/10 CH[Cl.sub.3]-MeOH with 1% N[H.sub.4]OH mobile phase) to check for presence of monomer.
Sukhishvili, Layer-by-Layer Films of Stimuli-Responsive Block Copolymer Micelles, J Mater Chem, 22, 7667 (2012).
Having lower crystallinity, copolymers tend to have better dimensional stability and win out on lower friction and less wear.
Figure 3 represents the [sup.13]C-NMR spectrum of AM/AMPS copolymer (90: 10).
The initial thickness of PEO-b-PS film is controlled by varying the diblock copolymer solution concentration.
For gradient latex particles prepared by radical polymerization, each copolymer chain is instantaneously formed.
Metabolix worked with compounder AlphaGary Corp., Leominster, Mass., to validate the new PHA copolymers. Metabolix plans to produce them at a 20-million-lb/yr plant being built in Spain.