Solution polymerization is a method of industrial

polymerization In polymer chemistry, polymerization (American English), or polymerisation (British English), is a process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks. There are many fo ...

. In this procedure, a

monomer A monomer ( ; ''mono-'', "one" + '' -mer'', "part") is a molecule that can react together with other monomer molecules to form a larger polymer chain or two- or three-dimensional network in a process called polymerization. Classification Chemis ...

is dissolved in a non-reactive

solvent A solvent (from the Latin language, Latin ''wikt:solvo#Latin, solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a Solution (chemistry), solution. A solvent is usually a liquid but can also be a solid, a gas ...

that contains a

catalyst Catalysis () is the increase in rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quick ...

or initiator. The reaction results in a polymer which is also soluble in the chosen solvent.

Heat In thermodynamics, heat is energy in transfer between a thermodynamic system and its surroundings by such mechanisms as thermal conduction, electromagnetic radiation, and friction, which are microscopic in nature, involving sub-atomic, ato ...

released by the reaction is absorbed by the solvent, reducing the

reaction rate The reaction rate or rate of reaction is the speed at which a chemical reaction takes place, defined as proportional to the increase in the concentration of a product per unit time and to the decrease in the concentration of a reactant per u ...

. Moreover, the

viscosity Viscosity is a measure of a fluid's rate-dependent drag (physics), resistance to a change in shape or to movement of its neighboring portions relative to one another. For liquids, it corresponds to the informal concept of ''thickness''; for e ...

of the reaction mixture is reduced, preventing

autoacceleration In polymer chemistry, autoacceleration (gel effect) is a dangerous reaction behavior that can occur in free-radical polymerization systems. It is due to the localized increases in viscosity of the polymerizing system that slow termination rea ...

at high monomer

concentration In chemistry, concentration is the abundance of a constituent divided by the total volume of a mixture. Several types of mathematical description can be distinguished: '' mass concentration'', '' molar concentration'', '' number concentration'', ...

s. A decrease in viscosity of the reaction mixture by dilution also aids heat transfer, one of the major issues connected with polymer production, since most polymerizations are exothermic reactions. Once the desired conversion is reached, excess solvent must be removed to obtain the pure polymer. Accordingly, solution polymerization is primarily used in applications where the presence of a solvent is desired anyway, as is the case for

varnish Varnish is a clear Transparency (optics), transparent hard protective coating or film. It is not to be confused with wood stain. It usually has a yellowish shade due to the manufacturing process and materials used, but it may also be pigmente ...

and

adhesives 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 advantage ...

. Another application of polymer solutions includes the manufacture of

fiber Fiber (spelled fibre in British English; from ) 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 inco ...

s by wet or dry spinning or

plastic film Plastic film is a thin continuous polymeric material. Thicker plastic material is often called a "sheet". These thin plastic membranes are used to separate areas or volumes, to hold items, to act as barriers, or as printable surfaces. Plast ...

s. Disadvantages of solution polymerization are decrease of monomer and initiator concentration leading to reduction of reaction rate, lower volume utilization of reactor, additional cost of the process related to solvent recycling, toxicity and other environmental impacts of most of organic solvents. One of the major disadvantages of the solution polymerization technique is that however inert the selected solvent may be, chain transfer to the solvent cannot be completely ruled out and, hence, it is difficult to get very high molecular weight product. From common solvents, especially chlorinated hydrocarbons are susceptible to chain transfer in radical polymerization. Intensity of chain transfer for different compounds may be quantified by use of

chain transfer In polymer chemistry, chain transfer is a polymerization reaction by which the activity of a growing polymer chain is transferred to another molecule: \ce^\bullet + \ce^\bullet where • is the active center, P is the initial polymer chain, X i ...

constants and the decrease of

degree of polymerization The degree of polymerization, or DP, is the number of structural unit, monomeric units in a macromolecule or polymer or oligomer molecule. For a homopolymer, there is only one type of monomeric unit and the ''number-average'' degree of polymeriza ...

may be calculated using Mayo equation.

Industrially important polymers produced by solution polymerization

Polyacrylonitrile Polyacrylonitrile (PAN) is a synthetic, semicrystalline organic polymer resin, with the linear formula (CH2CHCN)n. Almost all PAN resins are copolymers with acrylonitrile as the main monomer. PAN is used to produce large variety of products in ...

(PAN) is manufactured by radical polymerization in

dimethylformamide Dimethylformamide, DMF is an organic compound with the chemical formula . Its structure is . Commonly abbreviated as DMF (although this initialism is sometimes used for 2,5-dimethylfuran, dimethylfuran, or dimethyl fumarate), this colourless liqui ...

(DMF),

dimethyl sulfoxide Dimethyl sulfoxide (DMSO) is an organosulfur compound with the formula . This colorless liquid is the sulfoxide most widely used commercially. It is an important polar aprotic solvent that dissolves both polar and nonpolar compounds and is ...

(DMSO), organic carbonates,

sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid (English in the Commonwealth of Nations, Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen, ...

nitric acid Nitric acid is an inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but samples tend to acquire a yellow cast over time due to decomposition into nitrogen oxide, oxides of nitrogen. Most com ...

or water solutions of inorganic salts and converted to fibers.

Polyacrylic acid Poly(acrylic acid) (PAA; trade name Carbomer) is a polymer with the formula (CH2−CHCO2H)''n''. It is a derivative of acrylic acid (CH2=CHCO2H). In addition to the homopolymers, a variety of copolymers and crosslinked polymers, and partially ...

(PAA) and

polyacrylamide Polyacrylamide (abbreviated as PAM or pAAM) is a polymer with the formula (-CH2CHCONH2-). It has a linear-chain structure. PAM is highly water-absorbent, forming a soft gel when hydrated. In 2008, an estimated 750,000,000 kg were produced, ...

are obtained by radical polymerization in water solution and used as thickeners, adhesives or flocculants.

Acrylate Acrylates (IUPAC: prop-2-enoates) are the salts, esters, and conjugate bases of acrylic acid. The acrylate ion is the anion . Often, acrylate refers to esters of acrylic acid, the most common member being methyl acrylate. These acrylates contain ...

and methacrylate homo- and copolymers are made by radical polymerization in toluene-acetone for

coating A coating is a covering that is applied to the surface of an object, or substrate. The purpose of applying the coating may be decorative, functional, or both. Coatings may be applied as liquids, gases or solids e.g. powder coatings. Paints ...

applications.

Polyethylene Polyethylene or polythene (abbreviated PE; IUPAC name polyethene or poly(methylene)) is the most commonly produced plastic. It is a polymer, primarily used for packaging (plastic bags, plastic films, geomembranes and containers including bott ...

(HDPE, LLDPE) - some grades are made by coordination polymerization in high boiling hydrocarbone solvents (above PE solution temperature). The advantage of this process is very high propagation rate allowing fast changes of product grades. High ''cis'' polybutadiene (BR) is manufactured by coordination polymerization in hydrocarbons. Solution styrene-butadiene rubber (sSBR) is produced by

anionic polymerization In polymer chemistry, anionic addition polymerization is a form of chain-growth polymerization or addition polymerization that involves the polymerization of monomers initiated with anions. The type of reaction has many manifestations, but tradit ...

in hydrocarbons leading to rubber with better properties for making tires than

emulsion polymerization In polymer chemistry, emulsion polymerization is a type of radical polymerization that usually starts with an emulsion incorporating water, monomers, and surfactants. The most common type of emulsion polymerization is an oil-in-water emulsion, in ...

type. Polyvinyl acetate used further for

polyvinyl alcohol Polyvinyl alcohol (PVOH, PVA, or PVAl) is a water- soluble synthetic polymer. It has the idealized formula H2CH(OH)sub>''n''. It is used in papermaking, textile warp sizing, as a thickener and emulsion stabilizer in polyvinyl acetate (PVAc) a ...

is manufactured by radical polymerization in methanol solution. Liquid polybutadienes are made by

anionic An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

or radical polymerization in hydrocarbon solutions.

Butyl rubber Butyl rubber, sometimes just called butyl, is a synthetic rubber, a copolymer of isobutylene with isoprene. The abbreviation IIR stands for isobutylene isoprene rubber. Polyisobutylene, also known as "PIB" or polyisobutene, (C4H8)n, is the homop ...

(IIR) by low temperature cationic copolymerization of

isobutylene Isobutylene (or 2-methylpropene) is a hydrocarbon with the chemical formula . It is a four-carbon branched alkene (olefin), one of the four isomers of butylene. It is a colorless flammable gas, and is of considerable industrial value. Product ...

with isoprene in ethylene or methylchloride solution. Aromatic polyamides (e.g.

Kevlar Kevlar (para-aramid) is a strong, heat-resistant synthetic fiber, related to other aramids such as Nomex and Technora. Developed by Stephanie Kwolek at DuPont in 1965, the high-strength material was first used commercially in the early 1970s as ...

and Nomex) are made by

polycondensation In polymer chemistry, condensation polymers are any kind of polymers whose process of polymerization involves a condensation reaction (i.e. a small molecule, such as water or methanol, is produced as a byproduct). Natural proteins as well as s ...

in ''N''-methyl-pyrrolidone and calcium chloride solution. This process is one of two used in the production of sodium polyacrylate, a

superabsorbent polymer A superabsorbent polymer (SAP) (also called slush powder) is a water-absorbing hydrophilic homopolymers or copolymers that can absorb and retain extremely large amounts of a liquid relative to its own mass. Water-absorbing polymers, which are cl ...

used in disposable

diapers A diaper (, North American English) or a nappy (British English, Australian English, Hiberno-English) is a type of underwear that allows the wearer to urinate or defecate without using a toilet, by absorbing or containing waste products to ...

References

{{Reflist , refs= {{Cite book , url=http://doi.wiley.com/10.1002/9780470692134 , title=Polymer Reaction Engineering, date=2007-01-01 , publisher=Blackwell Publishing Ltd , isbn=978-0-470-69213-4, editor-last=Asua , editor-first=Jos M., location=Oxford, UK , language=en , doi=10.1002/9780470692134 {{Cite book , last=Elias , first=Hans-Georg , url=https://www.worldcat.org/oclc/62131443, title=Macromolecules , date=2005–2009 , publisher=Wiley-VCH, isbn=978-3-527-31172-9 , location=Weinheim, oclc=62131443 {{Cite journal, last=Mayo, first=Frank R., date=December 1943 , title=Chain Transfer in the Polymerization of Styrene: The Reaction of Solvents with Free Radicals 1 , url=https://pubs.acs.org/doi/abs/10.1021/ja01252a021 , journal=Journal of the American Chemical Society , language=en , volume=65 , issue=12 , pages=2324–2329 , doi=10.1021/ja01252a021, issn=0002-7863, url-access=subscription {{Cite book , url=https://onlinelibrary.wiley.com/doi/book/10.1002/0471440264, title=Encyclopedia of Polymer Science and Technology, date=2002-07-15 , publisher=Wiley , isbn=978-1-118-63389-2 , editor-last=John Wiley & Sons, Inc. , edition=1, language=en, doi=10.1002/0471440264 {{Cite book , url=https://www.worldcat.org/oclc/44934461, title=Industrial polymers handbook : products, processes, applications , date=2001 , publisher=Wiley-VCH , others=Wilks, Edward S. , isbn=3-527-30260-3 , location=Weinheim , oclc=44934461 * ''Foundations of Materials Science and Engineering'', fourth edition, William F. Smith & Javad Hashem * ''Encyclopedia of Polymer Science and Technology'', J.Wiley Sons, Interscience, Publ., New York, 4th edition, 1999-2012 Polymerization reactions fr:Procédé de polymérisation#Polymérisation en solution

Industrially important polymers produced by solution polymerization

See also

References