Ring-opening polymerization


Ring-opening polymerization

In polymer chemistry, ring-opening polymerization is a form of addition polymerization, in which the terminal end of a polymer acts as a reactive center, where further cyclic monomers join to form a larger polymer chain through ionic propagation. The treatment of some cyclic compounds with catalysts brings about cleavage of the ring followed by polymerization to yield high-molecular-weight polymers. Exemplary polymers produced by this method include Nylon 6 and polyethylene oxide.

When the reactive center of the propagating chain is a carbocation the polymerization is called cationic ring-opening polymerization and when the active center is a carbanion the reaction is an anionic ring-opening polymerization.

A different type of ring-opening polymerization, based on olefin metathesis, uses catalysts rather than cationic or anionic propagation.

One example of an anionic ring-opening polymerization is the living polymerization of the aziridine N-"methanesulfonyl-2-methylaziridine" with the sulfonamide "N-benzyl methanesulfonamide" (1) and potassium hexamethyldisilazide (2)(Fig. 1) ["Living Ring-Opening Polymerization of N-Sulfonylaziridines: Synthesis of High Molecular Weight Linear Polyamines" Ian C. Stewart, Cameron C. Lee, Robert G. Bergman, and F. Dean Toste J. Am. Chem. Soc.; 2005; 127(50) pp 17616 - 17617; (Communication) DOI: 10.1021/ja0554357 [http://pubs3.acs.org/acs/journals/doilookup?in_doi=10.1021/ja0554357 Abstract] [http://www.cchem.berkeley.edu/~toste/publications/ianasap.pdf Article link] ] . The disilazide actives the anionic initiator by proton exchange which reacts in chain initiation with an aziridine monomer in a ring-opening reaction (DMF, 40°C). In the chain propagation step the negatively charged end of the growing polymer chain continues to react with monomer until it is depleted. The reaction is chain terminated when methanol is added and the active chain end is destroyed. The polymerization is considered living because the polydispersity is low and no evidence is found of branching. In this particular concept the sulfonyl groups can be removed by organic reduction with naphthalene (7), lithium metal and methanol to the free polyamine 8. This procedure offers an alternative to a cationic ring-opening polymerization of oxazolines with anionic initiators and subsequent acid hydrolysis of the acyl groups.

ee also

* Ring opening metathesis polymerization

References


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • ring-opening polymerization — deciklizacinė polimerizacija statusas T sritis chemija apibrėžtis Ciklinės struktūros monomero polimerizacija atsidarant ciklui. atitikmenys: angl. ring opening polymerization rus. полимеризация с раскрытием цикла …   Chemijos terminų aiškinamasis žodynas

  • Ring opening metathesis polymerisation — Ring opening metathesis polymerization (ROMP) is a type of olefin metathesis polymerization that produces industrially important products. The driving force of the reaction is relief of ring strain in cyclic olefins (e.g. norbornene or… …   Wikipedia

  • Polymerization — An example of alkene polymerization, in which each Styrene monomer unit s double bond reforms as a single bond with another styrene monomer and forms polystyrene. In polymer chemistry, polymerization is a process of reacting monomer molecules… …   Wikipedia

  • 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 Ref|1. This can be accomplished in a variety of ways. Chain termination and chain transfer …   Wikipedia

  • Addition polymerization — nM (monomer) ightarrow ( M ) n (polymer)where n is the degree of polymerization.CharacteristicsThe main characteristics are:* polymerisation process takes place in three distinct steps: # chain initiation, usually by means of an initiator which… …   Wikipedia

  • Chain growth polymerisation — Chain growth polymerization is a polymerization technique where unsaturated monomer molecules add on to a growing polymer chain one at a time [1]. It can be represented with the chemical equation: where n is the …   Wikipedia

  • Olefin metathesis — or transalkylidenation is an organic reaction that entails redistribution of alkylene fragments by the scission of carbon carbon double bonds in olefins (alkenes).[1] Its advantages include the creation of fewer sideproducts and hazardous wastes …   Wikipedia

  • industrial polymers, major — Introduction       chemical compounds used in the manufacture of synthetic industrial materials.       In the commercial production of plastics, elastomers, man made fibres, adhesives, and surface coatings, a tremendous variety of polymers are… …   Universalium

  • Polyglycolide — Chembox new Name = Polyglycolide ImageFile = PGA.png ImageName = Polyglycolide IUPACName = 1,4 Dioxane 2,5 dione Section1 = Chembox Identifiers CASNo = 26124 68 5 SMILES = O=C(O)CO Section2 = Chembox Properties Formula = (C2H2O2)n MolarMass = N/A …   Wikipedia

  • Otto Vogl — Otto Vogl, circa 2000 Born November 6, 1927(1927 11 06 …   Wikipedia


We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.