A heteropolymer or copolymer is a polymer A polymer is a large molecule composed of repeating structural units typically connected by covalent chemical bonds. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a wide variety of properties derived from two (or more) monomeric A monomer is an atom or a small molecule that may bind chemically to other monomers to form a polymer or cluster[citation needed]. The most common natural monomer is glucose, which is linked by glycosidic bonds into polymers such as cellulose and starch, and is over 76% of the weight of all plant matter species, as opposed to a homopolymer A polymer is a large molecule composed of repeating structural units typically connected by covalent chemical bonds. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a wide variety of properties where only one monomer is used.[1] Copolymerization refers to methods used to chemically synthesize a copolymer.
Commercially relevant copolymers include ABS plastic Acrylonitrile butadiene styrene (chemical formula (C8H8)x· (C4H6)y·(C3H3N)z) is a common thermoplastic used to make light, rigid, molded products such as piping (for example plastic pressure pipe systems), musical instruments (most notably recorders and plastic clarinets), golf club heads (used for its good shock absorbance), automotive body, SBR, Nitrile rubber Nitrile rubber, or Buna-N, is a synthetic rubber copolymer of acrylonitrile and butadiene. Some trade names are: Nipol, Krynac and Europrene, styrene-acrylonitrile, styrene-isoprene-styrene (SIS) and ethylene-vinyl acetate Ethylene vinyl acetate is the copolymer of ethylene and vinyl acetate. The weight percent vinyl acetate usually varies from 10 to 40%, with the remainder being ethylene.
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Types of copolymers
Since a copolymer consists of at least two types of constituent units (also structural units In polymer chemistry, a structural unit is a building block of a polymer chain, and related to the repeat unit. It is the result of a monomer which has been polymerized into a long chain. When different monomer are polymerized, a copolymer is formed. It is a routine way of developing new properties for new materials), copolymers can be classified based on how these units are arranged along the chain.[2] These include:
- Alternating copolymers with regular alternating A and B units (2)
- Periodic copolymers with A and B units arranged in a repeating sequence (e.g. (A-B-A-B-B-A-A-A-A-B-B-B)n)
- Statistical Copolymers are copolymers in which the sequence of monomer residues follows a statistical rule. If the probability of finding a given type monomer residue at a particular point in the chain is equal to the mole fraction of that monomer residue in the chain, then the polymer may be referred to as a truly random copolymer[3] (3).
- Block copolymers comprise two or more homopolymer subunits linked by covalent bonds (4). The union of the homopolymer subunits may require an intermediate non-repeating subunit, known as a junction block. Block copolymers with two or three distinct blocks are called diblock copolymers and triblock copolymers, respectively.
Copolymers may also be described in terms of the existence of or arrangement of branches in the polymer structure. Linear copolymers consist of a single main chain whereas branched copolymers consist of a single main chain with one or more polymeric side chains.
Other special types of branched copolymers include star copolymers, brush copolymers, and comb copolymers.
A terpolymer is a copolymer consisting of three distinct monomers A monomer is an atom or a small molecule that may bind chemically to other monomers to form a polymer or cluster[citation needed]. The most common natural monomer is glucose, which is linked by glycosidic bonds into polymers such as cellulose and starch, and is over 76% of the weight of all plant matter. The term is derived from ter (Latin), meaning thrice, and polymer A polymer is a large molecule composed of repeating structural units typically connected by covalent chemical bonds. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a wide variety of properties.
- Stereoblock copolymers
A special structure can be formed from one monomer where now the distinguishing feature is the tacticity Tacticity is the relative stereochemistry of adjacent chiral centers within a macromolecule . The practical significance of tacticity rests in the link between tacticity and the physical properties of the polymer. The regularity of the macromolecular structure influences the degree to which it has rigid, crystalline long range order or flexible, of each block.
Graft copolymers
Graft copolymers are a special type of branched copolymer in which the side chains are structurally distinct from the main chain. The illustration (5) depicts a special case where the main chain and side chains are composed of distinct homopolymers. However, the individual chains of a graft copolymer may be homopolymers or copolymers. Note that different copolymer sequencing is sufficient to define a structural difference, thus an A-B diblock copolymer with A-B alternating copolymer side chains is properly called a graft copolymer.
For example, suppose we perform a free-radical polymerization Radical polymerization is a type of polymerization in which the reactive center of a polymer chain consists of a radical of styrene in the presence of polybutadiene Polybutadiene is a synthetic rubber that is a polymer formed from the polymerization of the monomer 1,3-butadiene. It has a high resistance to wear and is used especially in the manufacture of tires. It has also been used to coat or encapsulate electronic assemblies, offering extremely high electrical resistivity. It exhibits a recovery of 80%, a synthetic rubber Synthetic rubber is any type of artificial elastomer, invariably a polymer. An elastomer is a material with the mechanical property that it can undergo much more elastic deformation under stress than most materials and still return to its previous size without permanent deformation. Synthetic rubber serves as a substitute for natural rubber in, which retains one reactive C=C double bond A covalent bond is a form of chemical bonding that is characterized by the sharing of pairs of electrons between atoms, and other covalent bonds. In short, the attraction-to-repulsion stability that forms between atoms when they share electrons is known as covalent bonding per residue In chemistry, residue refers to the material remaining after a distillation or an evaporation, or to a portion of a larger molecule, such as a methyl group. It may also refer to the undesired byproducts of a reaction. We get polystyrene Polystyrene (IUPAC Poly(1-phenylethane-1,2-diyl)), abbreviated following ISO Standard PS, is an aromatic polymer made from the aromatic monomer styrene, a liquid hydrocarbon that is commercially manufactured from petroleum by the chemical industry. Polystyrene is one of the most widely used kinds of plastic chains growing out in either direction from some of the places where there were double bonds, with a one-carbon rearrangement. Or to look at it the other way around, the result is a polystyrene backbone with polybutadiene chains growing out of it in both directions. This is an interesting copolymer variant in that one of the ingredients was a polymer to begin with.
As with block copolymers, the quasi-composite Composite materials, often shortened to composites, are engineered materials made from two or more constituent materials with significantly different physical or chemical properties which remain separate and distinct on a macroscopic level within the finished structure product has properties of both "components". In the example cited, the rubbery chains absorb energy when the substance is hit, so it is much less brittle than ordinary polystyrene. The product is called high-impact polystyrene, or HIPS.
Block copolymers
A special kind of copolymer is called a "block copolymer". Block copolymers are made up of blocks of different polymerized A polymer is a large molecule composed of repeating structural units typically connected by covalent chemical bonds. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a wide variety of properties, including properties typically associated with plastics monomers A monomer is an atom or a small molecule that may bind chemically to other monomers to form a polymer or cluster[citation needed]. The most common natural monomer is glucose, which is linked by glycosidic bonds into polymers such as cellulose and starch, and is over 76% of the weight of all plant matter[4]. For example, PS-b-PMMA is short for polystyrene-b-poly(methyl methacrylate Methyl methacrylate is an organic compound with the formula CH2=CCOOCH3. This colourless liquid, the methyl ester of methacrylic acid (MAA) is a monomer produced on a large scale for the production of polymethyl methacrylate (PMMA)) and is usually made by first polymerizing styrene Styrene, also known as vinyl benzene, is an organic compound with the chemical formula C6H5CH=CH2. This cyclic hydrocarbon is a colorless oily liquid that evaporates easily and has a sweet smell, although high concentrations confer a less pleasant odor. Styrene is the precursor to polystyrene and several copolymers. Approximately 15 billion lt are, and then subsequently polymerizing MMA from the reactive end of the polystyrene chains. This polymer is a "diblock copolymer" because it contains two different chemical blocks. You can also make triblocks, tetrablocks, multiblocks, etc. Diblock copolymers are made using living polymerization In polymer chemistry, living polymerization is a form of addition polymerization where the ability of a growing polymer chain to terminate has been removed . This can be accomplished in a variety of ways. Chain termination and chain transfer reactions are absent and the rate of chain initiation is also much larger than the rate of chain techniques, such as atom transfer free radical polymerization (ATRP ATRP or Atom Transfer Radical Polymerization is an example of a living polymerization or a controlled/living radical polymerization . Like it’s counter part, ATRA or Atom Transfer Radical Addition, it is a means of forming carbon-carbon bond through transition metal catalyst. As the name implies, the atom transfer step is the key step in the), reversible addition fragmentation chain transfer (RAFT), ring-opening metathesis polymerization (ROMP), and living cationic or living anionic polymerizations In polymer chemistry, living polymerization is a form of addition polymerization where the ability of a growing polymer chain to terminate has been removed . This can be accomplished in a variety of ways. Chain termination and chain transfer reactions are absent and the rate of chain initiation is also much larger than the rate of chain.[5] An emerging technique is chain shuttling polymerization. The most powerful strategy to prepare block copolymers is the chemoselective stepwise coupling between polymeric precursors and heterofunctional linking agents.[6] This method enables access to peculiarly exotic structures such as tetrablock quarterpolymers ABCD.[7]
Recent research in block copolymers suggests that they may be useful in creating self-constructing fabrics with potential utility in semiconductor arrays (for example, computer memory devices) by assembling fine details atop a structured base created using conventional microlithography Lithography is a method for printing using a stone (lithographic limestone) or a metal plate with a completely smooth surface. Invented in 1796 by Bavarian author Alois Senefelder as a low-cost method of publishing theatrical works, lithography can be used to print text or artwork onto paper or another suitable material methods.[8].
Phase separation
SBS block copolymer in TEM Transmission electron microscopy is a microscopy technique whereby a beam of electrons is transmitted through an ultra thin specimen, interacting with the specimen as it passes through. An image is formed from the interaction of the electrons transmitted through the specimen; the image is magnified and focused onto an imaging device, such as aBlock copolymers are interesting because they can "microphase separate" to form periodic nanostructures, as in the styrene-butadiene-styrene block copolymer shown at right. The polymer is known as Kraton Kraton is the trade name given to a number of high performance elastomers manufactured by Kraton Polymers , and used as synthetic replacements for rubber. Kraton polymers offers many of the properties of natural rubber, such as flexibility, high traction, and sealing abilities, but with increased resistance to heat, weathering, and chemicals. It and is used for shoe soles and adhesives An adhesive, or glue, is a mixture in a liquid or semi-liquid state that adheres or bonds items together. Adhesives may come from either natural or synthetic sources. The types of materials that can be bonded are vast but they are especially useful for bonding thin materials. Adhesives cure by either evaporating a solvent or by chemical reactions. Owing to the microfine structure, the transmission electron microscope or TEM Transmission electron microscopy is a microscopy technique whereby a beam of electrons is transmitted through an ultra thin specimen, interacting with the specimen as it passes through. An image is formed from the interaction of the electrons transmitted through the specimen; the image is magnified and focused onto an imaging device, such as a was needed to examine the structure. The butadiene matrix was stained with osmium tetroxide Osmium tetroxide is the chemical compound with the formula OsO4. The compound is noteworthy for its many uses, despite the rarity of osmium. It also has a number of interesting properties, one being that the solid is volatile to provide contrast in the image. The material was made by living polymerization In polymer chemistry, living polymerization is a form of addition polymerization where the ability of a growing polymer chain to terminate has been removed . This can be accomplished in a variety of ways. Chain termination and chain transfer reactions are absent and the rate of chain initiation is also much larger than the rate of chain so that the blocks are almost monodisperse, so helping to create a very regular microstructure. The molecular weight The molecular mass of a substance is the mass of one molecule of that substance, in unified atomic mass unit(s) u (equal to 1/12 the mass of one atom of the isotope carbon-12). This is numerically equivalent to the relative molecular mass of a molecule, frequently referred to by the term molecular weight, which is the ratio of the mass of that of the polystyrene blocks in the main picture is 102,000; the inset picture has a molecular weight of 91,000, producing slightly smaller domains.
SBS block copolymer schematic microstructureMicrophase separation is a situation similar to that of oil An oil is any substance that is liquid at ambient temperatures and is hydrophobic but soluble in organic solvents. Oils have a high carbon and hydrogen content and are nonpolar substances. The general definition above includes compound classes with, and uses, including vegetable oils, petrochemical oils, and volatile essential oils. All oils can and water Water is a chemical substance with the chemical formula H2O. Its molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state, water vapor or steam. Oil and water are immiscible - they phase separate. Due to incompatibility between the blocks, block copolymers undergo a similar phase separation. Because the blocks are covalently bonded to each other, they cannot demix macroscopically as water and oil. In "microphase separation" the blocks form nanometer A nanometre (Greek: νάνος, nanos, "dwarf"; μέτρον, metrοn, "unit of measurement") is a unit of length in the metric system, equal to one billionth of a metre-sized structures. Depending on the relative lengths of each block, several morphologies can be obtained. In diblock copolymers, sufficiently different block lengths lead to nanometer-sized spheres of one block in a matrix of the second (for example PMMA Chemically, it is the synthetic polymer of methyl methacrylate. It is sold under many trade names, including Policril, Plexiglas, Gavrieli, Vitroflex, Limacryl, R-Cast, PerClax, Perspex, Plazcryl, Acrylex, Acrylite, Acrylplast, Altuglas, Polycast, Oroglass, Optix and Lucite and is commonly called acrylic glass, simply acrylic, perspex or plexiglas in polystyrene). Using less different block lengths, a "hexagonally packed cylinder" geometry can be obtained. Blocks of similar length form layers (often called lamellae in the technical literature). Between the cylindrical and lamellar phase is the gyroid phase. The nanoscale structures created from block copolymers could potentially be used for creating devices for use in computer memory In psychology, memory is an organism's ability to store, retain, and recall information. Traditional studies of memory began in the fields of philosophy, including techniques of artificially enhancing the memory. The late nineteenth and early twentieth century put memory within the paradigms of cognitive psychology. In recent decades, it has, nanoscale-templating and nanoscale separations.
Polymer scientists use thermodynamics In science, thermodynamics is the study of energy conversion between heat and mechanical work, and subsequently the macroscopic variables such as temperature, volume and pressure. The first to give a concise definition of the subject was Scottish physicist William Thomson who in 1854 stated that: to describe how the different blocks interact. The product of the degree of polymerization, n, and the Flory-Huggins interaction parameter, χ, gives an indication of how incompatible the two blocks are and whether or not they will microphase separate. For example, a diblock copolymer of symmetric composition will microphase separate if the product χN is greater than 10.5. If χN is less than 10.5, the blocks will mix and microphase separation is not observed.
Copolymer equation
An alternating copolymer has the formula: -A-B-A-B-A-B-A-B-A-B-, or -(-A-B-)n-. The molar ratios of the monomer in the polymer is close to one, which happens when the reactivity ratios r1 & r2 are close to zero, as given by the Mayo-Lewis equation also called the copolymerization equation:[9]
where r1 = k11/k12 & r2 = k22/k21
Copolymer engineering
Copolymerization is used to modify the properties of man-made plastics to specific needs, for example to reduce crystallinity, modify glass transition temperature Glass transition or vitrification refers to the transformation of a glass-forming liquid into a glass, which usually occurs upon rapid cooling. It is a dynamic phenomenon occurring between two distinct states of matter , each with different physical properties. Upon cooling through the temperature range of glass transition (a "glass or to improve solubility. It is a way of improving mechanical properties, in a technique known as rubber toughening Many thermoplastics such as polystyrene and PMMA are brittle when stressed, a property which limits applications. A good way of strengthening such polymers is to copolymerise elastomeric chains during manufacture. The elastomer chains form separate phases in the solid, typically 10-20 micrometres in diameter, so that when the material is strained,. Elastomeric phases within a rigid matrix act as crack arrestors, and so increase the energy absorption when the material is impacted for example. Acrylonitrile butadiene styrene Acrylonitrile butadiene styrene (chemical formula (C8H8)x· (C4H6)y·(C3H3N)z) is a common thermoplastic used to make light, rigid, molded products such as piping (for example plastic pressure pipe systems), musical instruments (most notably recorders and plastic clarinets), golf club heads (used for its good shock absorbance), automotive body is a common example.
See also
- Copolymers section of Polymer article A polymer is a large molecule composed of repeating structural units typically connected by covalent chemical bonds. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a wide variety of properties
- Tholin
References
- ^ Odian, G. (2004). "6". Principles of Polymerization. Wiley-Interscience. p. 464. ISBN The International Standard Book Number is a unique numeric commercial book identifier based upon the 9-digit Standard Book Numbering (SBN) code created by Gordon Foster, now Emeritus Professor of Statistics at Trinity College, Dublin, for the booksellers and stationers W.H. Smith and others in 1966 0-471-27400-3. http://books.google.com/?id=6cjgZbFHI4kC&pg=PA464.
- ^ Jenkins, A. D.; Kratochvíl, P.; Stepto, R. F. T.; Suter, U. W. (1996). "Glossary of Basic Terms in Polymer Science". Pure Appl. Chem. 68: 2287–2311. doi A digital object identifier is a character string used to uniquely identify an electronic document or other object. Metadata about the object is stored in association with the DOI name and this metadata may include a location, such as a URL, where the object can be found. The DOI for a document is permanent, whereas its location and other metadata:10.1351/pac199668122287.
- ^ Painter P. C. and Coleman M. M., Fundamentals of Polymer Science, CRC Press, 1997, p 14.
- ^ Polymer Research Laboratory (Princeton.edu accessed Aug 15, 2008)
- ^ Hadjichristidis N., Pispas S., Floudas G. Block copolymers: synthetic strategies, physical properties, and applications – Wiley, 2003.
- ^ Bellas, Vasilios; Rehahn, Matthias (2007). "Universal Methodology for Block Copolymer Synthesis". Macromolecular Rapid Communications 28: 1415. doi A digital object identifier is a character string used to uniquely identify an electronic document or other object. Metadata about the object is stored in association with the DOI name and this metadata may include a location, such as a URL, where the object can be found. The DOI for a document is permanent, whereas its location and other metadata:10.1002/marc.200700127. http://www3.interscience.wiley.com/cgi-bin/fulltext/114280481/PDFSTART.
- ^ Bellas, Vasilios; Rehahn, Matthias (2009). "Block Copolymer Synthesis via Chemoselective Stepwise Coupling Reactions". Macromolecular Chemistry and Physics 210: 320. doi A digital object identifier is a character string used to uniquely identify an electronic document or other object. Metadata about the object is stored in association with the DOI name and this metadata may include a location, such as a URL, where the object can be found. The DOI for a document is permanent, whereas its location and other metadata:10.1002/macp.200800463.
- ^ Self -growing material promises chip, storage advances (NetworkWorld accessed Aug 15, 2008)
- ^ Copolymerization. I. A Basis for Comparing the Behavior of Monomers in Copolymerization; The Copolymerization of Styrene and Methyl MethacrylateFrank R. Mayo and Frederick M. Lewis J. Am. Chem. Soc. The Journal of the American Chemical Society is a peer-reviewed scientific journal, published since 1879 by the American Chemical Society. The journal has absorbed two other publications in its history, the Journal of Analytical and Applied Chemistry in July 1893, and the American Chemical Journal in January 1914. A weekly publication, it; 1944; 66(9) pp 1594 - 1601; doi A digital object identifier is a character string used to uniquely identify an electronic document or other object. Metadata about the object is stored in association with the DOI name and this metadata may include a location, such as a URL, where the object can be found. The DOI for a document is permanent, whereas its location and other metadata:10.1021/ja01237a052
External links
- Introduction to Polymer Chemistry
- Block Copolymers: Institute of Physical & Theoretical Chemistry, University of Regensburg, Regensburg, Germany
- Polymer structures
- Theory and simulation of soft matter: Computational physics group (Dr. A. V. Zvelindovsky), University of Central Lancashire, Preston, United Kingdom
Categories: Polymer chemistry This category is for articles about polymers, their properties and polymer chemistry in general
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