TheInfoList

In
polymer chemistry Polymer chemistry is a sub-discipline of chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavior ...
, a copolymer is a
polymer A polymer (; Greek ''poly- Poly, from the Greek :wikt:πολύς, πολύς meaning "many" or "much", may refer to: Businesses * China Poly Group Corporation, a Chinese business group, and its subsidiaries: ** Poly Property, a Hong Kong inc ...

derived from more than one species of
monomer In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavior and the changes they undergo during a ...

. The
polymerization In polymer chemistry, polymerization (American English), or polymerisation (British English), is a process of reacting monomer, monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks.Clayden, J ...
of monomers into copolymers is called copolymerization. Copolymers obtained by copolymerization of two monomer species are sometimes called ''bipolymers''. Those obtained from three and four monomers are called ''terpolymers'' and ''quaterpolymers'', respectively. Commercial copolymers include
acrylonitrile butadiene styrene Acrylonitrile butadiene styrene (ABS) (chemical formula A chemical formula is a way of presenting information about the chemical proportions of s that constitute a particular or molecule, using symbols, numbers, and sometimes also oth ...
nitrile rubber Nitrile rubber, also known as nitrile butadiene rubber, NBR, Buna-N, and acrylonitrile butadiene rubber, is a synthetic rubber A synthetic rubber is any artificial elastomer. They are polymers synthesized from petroleum byproducts. About 32-million ...
,
styrene-acrylonitrileStyrene acrylonitrile resin is a copolymer plastic Plastics are a wide range of synthetic polymers, synthetic or semi-synthetic materials that use polymers as a main ingredient. Their Plasticity (physics), plasticity makes it possible for plastics ...

, styrene-isoprene-styrene (SIS) and ethylene-vinyl acetate, all formed by
chain-growth polymerizationChain-growth polymerization (American spelling) or chain-growth polymerisation (British spelling) is a polymerization technique where Unsaturated compound, unsaturated monomer molecules add onto the active site on a growing polymer chain one at a tim ...
. Another production mechanism is
step-growth polymerization Step-growth polymerization refers to a type of polymerization In polymer chemistry, polymerization (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set ...

, used to produce the nylon-12/6/66 copolymer of
nylon 12 Nylon 12 is a nylon polymer with the formula CH2)11C(O)NH. It is made from ω-aminolauric acid or laurolactam monomers that each have 12 carbons, hence the name ‘Nylon 12’. It is one of several nylon polymers. Synthesis Nylon 12 can be pr ...
,
nylon 6 molecule used to synthesize Nylon 6 by ring opening polymerization Nylon 6 or polycaprolactam is a polymer developed by Paul Schlack at IG Farben to reproduce the properties of Nylon 6-6, nylon 6,6 without violating the patent on its production. ...

and
nylon 66 Nylon 66 (loosely written nylon 6-6, nylon 6/6, nylon 6,6, or nylon 6:6) is a type of polyamideA polyamide is a polymer with repeating units linked by amide bonds. Polyamides occur both naturally and artificially. Examples of naturally occurrin ...

, as well as the
copolyesterCopolyester forms when modifications are made to polyesters, which are combinations of diacids and diols. For example, by introducing other diacids, such as isophthalic acid (IPA), or other diols, such as cyclohexane dimethanol (CHDM) to the polyest ...
family. Since a copolymer consists of at least two types of constituent units (also
structural unitIn polymer chemistry, a structural unit is a building block of a polymer A polymer (; Greek '' poly-'', "many" + '' -mer'', "part") is a substance or material consisting of very large molecule File:Pentacene on Ni(111) STM.jpg, A scanning ...
s), copolymers can be classified based on how these units are arranged along the
chain A chain is a wikt:series#Noun, serial assembly of connected pieces, called links, typically made of metal, with an overall character similar to that of a rope in that it is flexible and curved in compression (physics), compression but line (g ...
. ''Linear copolymers'' consist of a single
main chain A ridge or a mountain ridge is a geographical feature consisting of a chain of mountains or hills that form a continuous elevated crest for some distance. The sides of the ridge slope away from narrow top on either side. The lines along the ...
, and include alternating copolymers, statistical copolymers and block copolymers. '' Branched copolymers'' consist of a single main chain with one or more polymeric
side chain In organic chemistry Organic chemistry is a branch of chemistry that studies the structure, properties and reactions of organic compounds, which contain carbon in covalent bonding.Clayden, J.; Greeves, N. and Warren, S. (2012) ''Organic Chemis ...
s, and can be
grafted Grafting or graftage is a horticulture, horticultural technique whereby tissue (biology), tissues of plants are joined so as to continue their growth together. The upper part of the combined plant is called the scion () while the lower part is c ...
, star shaped or have other architectures.

# Reactivity ratios

The ''reactivity ratio'' of a growing copolymer chain terminating in a given monomer is the ratio of the
reaction rate constantIn chemical kinetics Chemical kinetics, also known as reaction kinetics, is the branch of physical chemistry that is concerned with understanding the rates of chemical reactions. It is to be contrasted with thermodynamics, which deals with the direc ...
for addition of the same monomer and the rate constant for addition of the other monomer. That is, $r_1 = \frac$ and $r_2 = \frac$, where for example $k_$ is the rate constant for propagation of a polymer chain ending in monomer 1 (or A) by addition of monomer 2 (or B). The composition and structural type of the copolymer depend on these reactivity ratios r1 and r2 according to the
Mayo–Lewis equationThe Mayo–Lewis equation or copolymer equation in polymer chemistry describes the distribution of monomerA monomer ( ; '' mono-'', "one" + '' -mer'', "part") is a molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image ...
, also called the copolymerization equation or copolymer equation, for the relative instantaneous rates of incorporation of the two monomers. $\frac = \frac$

# Linear copolymers

## Block copolymers

Block copolymers comprise two or more
homopolymer A polymer (; Greek '' poly-'', "many" + '' -mer'', "part") is a substance Substance may refer to: * Substance (Jainism), a term in Jain ontology to denote the base or owner of attributes * Chemical substance, a material with a definite chemical ...
subunits linked by covalent bonds. The union of the homopolymer subunits may require an intermediate non-repeating subunit, known as a junction block. Diblock copolymers have two distinct blocks; triblock copolymers have three. Technically, a block is a portion of a macromolecule, comprising many units, that has at least one feature which is not present in the adjacent portions. A possible sequence of repeat units A and B in a triblock copolymer might be ~A-A-A-A-A-A-A-B-B-B-B-B-B-B-A-A-A-A-A~. Block copolymers are made up of blocks of different
polymerized In polymer chemistry, polymerization (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of varieties of the English language native to the United State ...
monomers In chemistry Chemistry is the scientific Science () is a systematic enterprise that builds and organizes knowledge Knowledge is a familiarity or awareness, of someone or something, such as facts A fact is an occurrence in th ...
. For example, polystyrene-b-poly(methyl methacrylate) or PS-b-PMMA (where b = block) is usually made by first polymerizing
styrene Styrene () is an organic compound In , organic compounds are generally any s that contain - . Due to carbon's ability to (form chains with other carbon s), millions of organic compounds are known. The study of the properties, reactions, an ...

, and then subsequently polymerizing
methyl methacrylate Methyl methacrylate (MMA) is an organic compound with the chemical formula, formula CH2=C(CH3)COOCH3. This colorless liquid, the methyl ester of methacrylic acid (MAA), is a monomer produced on a large scale for the production of poly(methyl meth ...

(MMA) from the reactive end of the polystyrene chains. This polymer is a "diblock copolymer" because it contains two different chemical blocks. Triblocks, tetrablocks, multiblocks, etc. can also be made. Diblock copolymers are made using
living polymerization In polymer chemistry, living polymerization is a form of chain growth polymerization where the ability of a growing polymer chain to chain termination, terminate has been removed. This can be accomplished in a variety of ways. Chain termination and ...
techniques, such as atom transfer free radical polymerization ( ATRP), reversible addition fragmentation chain transfer (
RAFT A raft is any flat structure for support or transportation over water. It is usually of basic design, characterized by the absence of a hull Hull may refer to: Structures * Chassis, of an armored fighting vehicle * Fuselage, of an aircraft * H ...
), (ROMP), and living cationic or living anionic
polymerization In polymer chemistry, polymerization (American English), or polymerisation (British English), is a process of reacting monomer, monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks.Clayden, J ...
s. An emerging technique is
chain shuttling polymerizationChain shuttling polymerization is a dual-catalyst that utilizes a low-temperature oxidation catalyst to convert carbon monoxide to less toxic carbon dioxide at room temperature. It can also remove formaldehyde from the air. Catalysis () is the p ...
. The synthesis of block copolymers requires that both reactivity ratios are much larger than unity (r1 >> 1, r2 >> 1) under the reaction conditions, so that the terminal monomer unit of a growing chain tends to add a similar unit most of the time. The "blockiness" of a copolymer is a measure of the adjacency of comonomers vs their statistical distribution. Many or even most synthetic polymers are in fact copolymers, containing about 1-20% of a minority monomer. In such cases, blockiness is undesirable. A ''block index'' has been proposed as a quantitative measure of blockiness or deviation from random monomer composition.

## Alternating copolymers

An alternating copolymer has regular alternating A and B units, and is often described by the formula: -A-B-A-B-A-B-A-B-A-B-, or -(-A-B-)n-. The molar ratio of each monomer in the polymer is normally close to one, which happens when the reactivity ratios r1 and r2 are close to zero, as can be seen from the Mayo–Lewis equation. For example, in the free-radical copolymerization of copolymer, r1 = 0.097 and r2 = 0.001, so that most chains ending in styrene add a maleic anhydride unit, and almost all chains ending in maleic anhydride add a styrene unit. This leads to a predominantly alternating structure. A step-growth copolymer -(-A-A-B-B-)n- formed by the
condensation Condensation is the change of the state of matter In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space ...
of two
bifunctionalIn organic chemistry, when a single organic molecule , CH4; is among the simplest organic compounds. In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen chemical bond, bonds. Due to carbon's ability t ...
monomers A–A and B–B is in principle a perfectly alternating copolymer of these two monomers, but is usually considered as a
homopolymer A polymer (; Greek '' poly-'', "many" + '' -mer'', "part") is a substance Substance may refer to: * Substance (Jainism), a term in Jain ontology to denote the base or owner of attributes * Chemical substance, a material with a definite chemical ...
of the dimeric repeat unit A-A-B-B. An example is
nylon 66 Nylon 66 (loosely written nylon 6-6, nylon 6/6, nylon 6,6, or nylon 6:6) is a type of polyamideA polyamide is a polymer with repeating units linked by amide bonds. Polyamides occur both naturally and artificially. Examples of naturally occurrin ...

with repeat unit -OC-( CH2)4-CO-NH-(CH2)6-NH-, formed from a
dicarboxylic acidA dicarboxylic acid is an organic compound , CH4; is among the simplest organic compounds. In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecul ...
monomer and a
diamine A diamine is an amine with exactly two amino groups. Diamines are used as monomers to prepare polyamides, polyimides, and polyureas. The term ''diamine'' refers mostly to Primary (chemistry), primary diamines, as those are the most reactive. In ter ...
monomer.

## Periodic copolymers

Periodic copolymers have units arranged in a repeating sequence. For two monomers A and B, for example, they might form the repeated pattern (A-B-A-B-B-A-A-A-A-B-B-B)n.

## Statistical copolymers

In statistical copolymers 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 copolymerPainter P. C. and Coleman M. M., ''Fundamentals of Polymer Science'', CRC Press, 1997, p 14. (structure 3). Statistical copolymers are dictated by the reaction kinetics of the two chemically distinct monomer reactants, and are commonly referred to interchangeably as “random” in the polymer literature.Chanda, M. ''Introduction to Polymer Science and Chemistry''. Second Edition. CRC Press, 2013. As with other types of copolymers, random copolymers can have interesting and commercially desirable properties that blend those of the individual homopolymers. Examples of commercially relevant random copolymers include
rubber Rubber, also called India rubber, latex, Amazonian rubber, ''caucho'', or ''caoutchouc'', as initially produced, consists of polymer A polymer (; Greek ''poly- Poly, from the Greek :wikt:πολύς, πολύς meaning "many" or "much" ...

s made from styrene-butadiene copolymers and resins from styrene-acrylic or derivatives. Copolymerization is particularly useful in tuning the
glass transition The glass–liquid transition, or glass transition, is the gradual and reversible transition in amorphous In condensed matter physics Condensed matter physics is the field of physics Physics (from grc, φυσική (ἐπιστήμη ...
temperature, which is important in the operating conditions of polymers; it is assumed that each monomer occupies the same amount of free volume whether it is in a copolymer or homopolymer, so the
glass transition The glass–liquid transition, or glass transition, is the gradual and reversible transition in amorphous In condensed matter physics Condensed matter physics is the field of physics Physics (from grc, φυσική (ἐπιστήμη ...
temperature (Tg) falls between the values for each homopolymer and is dictated by the mole or mass fraction of each component. A number of parameters are relevant in the composition of the polymer product; namely, one must consider the reactivity ratio of each component. Reactivity ratios describe whether the monomer reacts preferentially with a segment of the same type or of the other type. For example, a reactivity ratio that is less than one for component 1 indicates that this component reacts with the other type of monomer more readily. Given this information, which is available for a multitude of monomer combinations in the “Wiley Database of Polymer Properties”, the Mayo-Lewis equation can be used to predict the composition of the polymer product for all initial mole fractions of monomer. This equation is derived using the
Markov model In probability theory, a Markov model is a stochastic model used to Mathematical model, model pseudo-randomly changing systems. It is assumed that future states depend only on the current state, not on the events that occurred before it (that is, it ...
, which only considers the last segment added as affecting the kinetics of the next addition; the Penultimate Model considers the second-to-last segment as well, but is more complicated than is required for most systems. When both reactivity ratios are less than one, there is an azeotropic point in the Mayo-Lewis plot. At this point, the mole fraction of monomer equals the composition of the component in the polymer. There are several ways to synthesize random copolymers. The most common synthesis method is free radical polymerization; this is especially useful when the desired properties rely on the composition of the copolymer rather than the molecular weight, since free radical polymerization produces relatively disperse polymer chains. Free radical polymerization is less expensive than other methods, and produces high-molecular weight polymer quickly. Several methods offer better control over
dispersity In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they unde ...
.
Anionic polymerization Anionic addition polymerization is a form of chain-growth polymerization or addition polymerization that involves the polymerization In polymer chemistry, polymerization (American English American English (AmE, AE, AmEng, USEng, en-U ...
can be used to create random copolymers, but with several caveats: if
carbanionA carbanion is an anion An ion () is a particle, atom or molecule with a net electric charge, electrical charge. The charge of the electron is considered negative by convention. The negative charge of an ion is equal and opposite to charged ...
s of the two components do not have the same stability, only one of the species will add to the other. Additionally, anionic polymerization is expensive and requires very clean reaction conditions, and is therefore difficult to implement on a large scale. Less disperse random copolymers are also synthesized by ″living″
controlled radical polymerization Living free radical polymerization is a type of living polymerization where the active polymer chain end is a free radical. Several methods exist. IUPAC recommends to use the term "reversible-deactivation radical polymerization" instead of "livin ...
methods, such as atom-transfer radical-polymerization (ATRP), nitroxide mediated radical polymerization (NMP), or
Reversible addition−fragmentation chain-transfer polymerization Reversible addition−fragmentation chain-transfer or RAFT polymerization is one of several kinds of reversible-deactivation radical polymerization. It makes use of a chain transfer, chain-transfer agent in the form of a thiocarbonylthio compound ( ...
(RAFT). These methods are favored over anionic polymerization because they can be performed in conditions similar to free radical polymerization. The reactions require longer experimentation periods than free radical polymerization, but still achieve reasonable reaction rates.

## Stereoblock copolymers

In stereoblock copolymers the blocks or units differ only in the
tacticity. Tacticity (from Greek τακτικός ''taktikos'' "of or relating to arrangement or order") is the relative stereochemistry of adjacent chiral that is chiral Chirality is a property of asymmetry important in several branches of science. The ...
of the monomers.

# Branched copolymers

There are a variety of architectures possible for nonlinear copolymer. Beyond grafted and star polymers discussed below, other common types of branched copolymers include brush copolymers and comb copolymers.

# Graft copolymers

Graft copolymers are a special type of branched copolymer in which the side chains are structurally distinct from the main chain. Typically the main chain is formed from one type of monomer (A) and branches are formed from another monomer (B), or else the side-chains have constitutional or configurational features that differ from those in the main chain. 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,
polystyrene Polystyrene (PS) is a synthetic Aromaticity, aromatic hydrocarbon polymer made from the monomer known as styrene. Polystyrene can be solid or foamed. General-purpose polystyrene is clear, hard, and brittle. It is an inexpensive resin per un ...

chains may be grafted onto
polybutadiene Polybutadiene utadiene rubber BRis a synthetic rubber A synthetic rubber is any artificial elastomer An elastomer is a polymer A polymer (; Greek ''wikt:poly-, poly-'', "many" + ''wikt:-mer, -mer'', "part") is a Chemical substance, substa ...
, a
synthetic rubber A synthetic rubber is any artificial elastomer. They are polymers synthesized from petroleum byproducts. About 32-million metric tons of rubbers are produced annually in the United States, and of that amount two thirds are synthetic. Global revenue ...
which retains one reactive C=C
double bond In chemistry, a double bond is a covalent bond A covalent bond is a chemical bond A chemical bond is a lasting attraction between atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, ...

per
repeat unit In polymer chemistry, a repeat unit or repeating unit is a part of a polymer whose repetition would produce the complete polymer chain (except for the end-groups) by linking the repeat units together successively along the chain, like the beads of ...
. The polybutadiene is dissolved in styrene, which is then subjected to
free-radical polymerizationFree-radical polymerization (FRP) is a method of polymerization, by which a polymer A polymer (; Greek '' poly-'', "many" + '' -mer'', "part") is a substance or material consisting of very large molecule File:Pentacene on Ni(111) STM.jpg, ...
. The growing chains can add across the double bonds of rubber molecules forming polystyrene branches. The graft copolymer is formed in a mixture with ungrafted polystyrene chains and rubber molecules. As with block copolymers, the quasi-
composite Composite or compositing may refer to: Materials * Composite material, a material that is made from several different substances ** Metal matrix composite, composed of metal and other parts ** Cermet, a composite of ceramic and metallic materials * ...

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 , or HIPS.

## Star copolymers

have several polymer chains connected to a central core.

# Microphase separation

Block copolymers (but not exclusively) are interesting because they can "microphase separate" to form periodic
nanostructuresImage:DNA nanostructures.png, 250px, The DNA structure at left (schematic shown) will self-assemble into the structure visualized by Atomic force microscope, atomic force microscopy at right. Image from Strong. A nanostructure is a structure of int ...
, as in the styrene-butadiene-styrene block copolymer shown at right. The polymer is known as Kraton and is used for shoe soles and
adhesive Adhesive, also known as glue, cement, mucilage, or paste, is any non-metallic substance applied to one or both surfaces of two separate items that binds them together and resists their separation. The use of adhesives offers certain advantag ...
s. Owing to the microfine structure, the transmission electron microscope or TEM was needed to examine the structure. The butadiene matrix was stained with
osmium tetroxide Osmium tetroxide (also osmium(VIII) oxide) is the chemical compound A chemical compound is a chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is any substance that has mass ...

to provide contrast in the image. The material was made by
living polymerization In polymer chemistry, living polymerization is a form of chain growth polymerization where the ability of a growing polymer chain to chain termination, terminate has been removed. This can be accomplished in a variety of ways. Chain termination and ...
so that the blocks are almost monodisperse, so helping to create a very regular microstructure. The
molecular weight A molecule is an electrically Electricity is the set of physical phenomena associated with the presence and motion Image:Leaving Yongsan Station.jpg, 300px, Motion involves a change in position In physics, motion is the phenomenon ...
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. Microphase separation is a situation similar to that of
oil An oil is any nonpolar In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound ...

and
water Water (chemical formula H2O) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known li ...

. 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 file:EM Spectrum Properties edit.svg, 330px, Different lengths as in respect to the Electromagnetic spectrum, measured by the Metre and its derived scales. The nanometre is often used to express dimensions on an atomic scale and mostly in the Mo ...
-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 in polystyrene). Using less different block lengths, a "hexagonally packed cylinder" geometry can be obtained. Blocks of similar length form layers (often called
lamellae Lamella (plural lamellae) means a small plate or flake in Latin, and in English may refer to: Biology * Lamella (mycology) "False" gills of '' Craterellus tubaeformis'' A lamella, or gill, is a papery hymenophoreA hymenophore refers to the hy ...
in the technical literature). Between the cylindrical and lamellar phase is the
gyroid A gyroid minimal surface, coloured to show the Gaussian curvature at each point A gyroid is an infinitely connected Triply periodic minimal surface, triply periodic minimal surface discovered by Alan Schoen in 1970. History and properties The ...
phase. The nanoscale structures created from block copolymers could potentially be used for creating devices for use in computer
memory Memory is the faculty of the brain A brain is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exis ...

, nanoscale-templating and nanoscale separations. Block copolymers are sometimes used as a replacement for phospholipids in
model lipid bilayers A model lipid bilayer is any bilayer :''For bilayers in biology, see lipid bilayer The lipid bilayer (or phospholipid bilayer) is a thin polar membrane made of two layers of lipid molecules. These membranes are flat sheets that form a continuous ...
and
liposomes s in an aqueous An aqueous solution is a solution Image:SaltInWaterSolutionLiquid.jpg, Making a saline water solution by dissolving Salt, table salt (sodium chloride, NaCl) in water. The salt is the solute and the water the solvent. In chem ...

for their superior stability and tunability. Polymer scientists use
thermodynamics Thermodynamics is a branch of physics Physics is the that studies , its , its and behavior through , and the related entities of and . "Physical science is that department of knowledge which relates to the order of nature, or, in ot ...

to describe how the different blocks interact. The product of the degree of polymerization, ''n'', and the Flory-Huggins interaction parameter, $\chi$, 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 $\chi N$ is greater than 10.5. If $\chi N$ is less than 10.5, the blocks will mix and microphase separation is not observed. The incompatibility between the blocks also affects the solution behavior of these copolymers and their adsorption behavior on various surfaces. Block are able to self-assemble in selective solvents, to form micelles among other structures. In thin films, block are of great interest as masks in the lithographic patterning of semiconductor materials for applications in high density data storage. A key challenge is to minimise the feature size and much research is in progress on this

# Copolymer engineering

Copolymerization is used to modify the properties of manufactured plastics to meet specific needs, for example to reduce crystallinity, modify
glass transition temperature The glass–liquid transition, or glass transition, is the gradual and reversible transition in amorphous In condensed matter physics Condensed matter physics is the field of that deals with the macroscopic and microscopic physical propert ...
, control wetting properties or to improve solubility. It is a way of improving mechanical properties, in a technique known as
rubber tougheningRubber toughening is a process in which rubber nanoparticles are interspersed within a polymer A polymer (; Greek '' poly-'', "many" + '' -mer'', "part") is a substance or material consisting of very large molecule File:Pentacene on Ni(11 ...
. 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 (ABS) (chemical formula A chemical formula is a way of presenting information about the chemical proportions of s that constitute a particular or molecule, using symbols, numbers, and sometimes also oth ...
is a common example.

* Copolymers section of Polymer article *
Thermoplastic elastomer Thermoplastic elastomers (TPE), sometimes referred to as thermoplastic rubbers, are a class of copolymers or a polymer blend, physical mix of polymers (usually a plastic and a rubber) that consist of materials with both thermoplastic and elastome ...
*
Tholin Tholins (after the Greek (') "hazy" or "muddy"; from the ancient Greek Ancient Greek includes the forms of the Greek language Greek ( el, label=Modern Greek Modern Greek (, , or , ''Kiní Neoellinikí Glóssa''), generally re ...