A Critical Assessment of the Kinetics and Mechanism of Initiation of Radical Polymerization with Commercially Available Dialkyldiazene Initiators. (January 2019)

• Record Type: Journal Article
• Authors: Moad, Graeme
• Is Part Of: Progress in polymer science. Volume 88(2019)
• Page Start: 130
• Page End: 188
• Publication Date: 2019-01
• Subjects: A2 symmetrical initiator -- A· initiator-derived radical -- AA acrylic acid -- AIBN azobis(isobutyronitrile) -- ACHN 1, 1'-azobis-(1-cyclohexanenitrile) -- ACPA 4, 4'-Azobis(4-cyanopentanoic acid) -- AIBMe azobis(methyl isobutyrate) -- Am acrylamide -- AN acrylonitrile -- ATRP atom-transfer radical polymerization -- BA butyl acrylate -- B Banfield radical -- Bd butadiene -- BMA butyl methacrylate -- BIRP organobismuthine-mediated radical polymerization -- BzMA benzyl methacrylate -- chn· 1-cyanocyclohexyl radical -- CIDNP chemically induced dynamic nuclear polarization -- CMRP cobalt-mediated radical polymerization -- CoTMPS cobalt tetra(3, 5-disulfonatomesityl)porphrin -- cyp· 2-cyano-2-propyl radical -- Ð molar mass dispersity -- DA dodecyl acrylate -- DMA decyl methacrylate -- DMAm N, N-dimethylacrylamide -- DMAc N, N-dimethylacetamide -- DMF N, N-dimethylformamide -- DMSO dimethyl sulfoxide -- DPPH 2, 2-diphenyl-1-picrylhydrazyl [2, 2-diphenyl-1-(2, 4, 6-trinitrophenyl)hydrazyl] -- DTP degenerate-chain-transfer polymerization -- DVB divinylbenzene -- EMA ethyl methacrylate -- f initiator efficiency -- fg initiator efficiency for radical generation -- fi initiator efficiency for initiation of polymerization -- ESCP enhanced spin capturing polymerization -- GMMA glycerol monomethacrylate [2, 3-dihydroxypropyl methacrylate] -- HTEMPO 4-hydroxy-2, 2, 6, 6-tetramethylpiperidin-N-oxyl -- HQ hydroquinone -- A∙ initiator-derived radical -- A2 symmetrical initiator -- IBN 2-methylpropanenitrile -- IBMK isobutyl methyl ketone [4-methylpentan-2-one] -- ITP iodine-transfer polymerization -- Ip isoprene -- K ketenimine formed from AIBN [2-methyl-2-((2-methylprop-1-en-1-ylidene)amino)propanenitrile] -- kd rate coefficient for initiator decomposition -- ke rate coefficient for cage escape -- ki rate coefficient for initiation (addition to monomer) -- kp rate coefficient for propagation -- kt overall rate coefficient for termination -- ktc rate coefficient for termination by combination -- ktd rate coefficient for termination by disproportionation -- λ ktd/kt, fraction of termination by disproportionation -- M monomer -- Mn number average molar mass -- MA methyl acrylate -- MAN methacrylonitrile -- MeCN acetonitrile -- MEK methyl ethyl ketone [2-butanone] -- MMA methyl methacrylate -- MS mass spectrum -- MTEMPO 4-methoxy-2, 2, 6, 6-tetramethylpiperidin-N-oxyl -- Mw weight average molar mass -- ν average kinetic chain length -- NAP N-acryloylpiperidine -- NIPAM N-isopropylacrylamide -- NMP nitroxide-mediated polymerization [aminoxyl-mediated polymerization] -- NVC N-vinylcarbazole -- NVP N-vinylpyrrolidone -- OMRP organometallic-mediated radical polymerization -- PISA polymerization-induced self-assembly -- Pn polymer of chain length n -- Pn∙ propagating radical of chain length n -- PnH polymer of chain length n with a saturated end-group -- Pn= polymer of chain length n with an unsaturated end-group -- Ri rate of initiation -- Rp rate of propagation -- Rt overall rate of termination -- Rtc rate of termination by combination -- Rtd rate of termination by disproportionation -- RAFT reversible addition-fragmentation chain transfer -- RCTP reversible catalyzed chain-transfer polymerization -- RDRP reversible-deactivation radical polymerization -- RITP reverse-iodine-transfer polymerization; -- SBRP organostibine-mediated radical polymerization -- SRMP stable-radical-mediated polymerization -- St styrene -- τ mean lifetime of a propagating radical -- tBAm N-tert-butylacrylamide -- TEMPO 2, 2, 6, 6-tetramethylpiperidin-N-oxyl -- TERP organotellurium-mediated radical polymerization -- TMIO 1, 1, 3, 3-tetramethylisoidolin-N-oxyl -- TMSN tetramethylsuccinonitrile -- UV ultraviolet -- V 1, 3, 5-triphenylverdazyl -- VAc vinyl acetate -- Xn number average degree of polymerization; Radical polymerization -- initiation -- rate coefficients -- efficiency -- reversible-deactivation radical polymerization; Polymers -- Periodicals; Polymerization -- Periodicals; Polymers -- Industrial applications -- Periodicals; Polymères -- Périodiques; Polymérisation -- Périodiques; 547.7
• DOI: 10.1016/j.progpolymsci.2018.08.003
• Languages: English
• ISSNs: 0079-6700

Abstract

Graphical abstract: The dialkyldiazenes are one of the most important classes of initiator used in both conventional and reversible deactivation radical polymerization (RDRP). This paper summarizes the current state of knowledge of mechanism of radical generation and provides a critical assessment decomposition rate constants ( k d ) and efficiencies ( f ) of commercially available initiators. Abstract: The dialkyldiazene or azo-compound initiators, which include azonitriles such as azobis(isobutyronitrile) (AIBN), are one of the most important classes of initiator being widely used in both conventional and reversible-deactivation radical polymerization (RDRP). This paper briefly reviews the mechanism of radical generation from dialkyldiazenes and provides a critical assessment and recommended values for the decomposition rate coefficients ( k d ) and efficiencies ( f ) of those that are commercially available. A critique of the methods that have been used for the determination of these kinetic parameters is also provided. In this review, a focus is placed on initiation of radical polymerization of the more reactive monomers such as methyl methacrylate (MMA) and styrene at low monomer conversions; where addition of the initiator-derived radicals to monomer is not rate determining (i.e., k i > k p ) and, thus, the efficiencies for radical generation ( f g ) and for initiation of polymerization ( f i ) are similar. However, the dependence of the kinetic parameters on such factors as monomer type, monomer conversion, reaction medium, temperature, photo-irradiation, microwave irradiation and magnetic fields is also discussed. We additionally provide comment on the use of dialkyldiazenes in heterogeneous polymerization (emulsion or dispersion polymerization) and in RDRP. Dialkyldiazenes are the most used initiators in RAFT (reversible addition-fragmentation chain-transfer) polymerization and other RDRP based on degenerative chain transfer, which include iodine transfer polymerization (ITP) and tellurium-mediated polymerization (TERP). They also find significant use in various forms of stable-radical-mediated radical polymerization (SRMP), in particular nitroxide-mediated polymerization (NMP) and cobalt-mediated radical polymerization (CMRP), and have an integral role in certain atom-transfer radical polymerization (ATRP) processes, such as reverse and ICAR (initiators for continuous activator regeneration) ATRP and variations on these procedures. In each of these RDRP methods, knowledge of the parameters that characterize the kinetics and efficiency of dialkyldiazene decomposition and the mechanism of initiation is beneficial to understanding and for optimizing control over the process.