Primary radical termination in polymerization: Evaluation of the characteristic constant
TL;DR: In this paper, the authors derived an equation which allows determination of the classical efficiency of initiation as a function of [I]/[M]2 and also allowed a correction of Rp in handling the above equation by taking into account the small amount of monomer consumed in initiation.
About: This article is published in European Polymer Journal.The article was published on 1974-08-01. It has received 89 citations till now.
Citations
More filters
TL;DR: In this article, a method is proposed for analysing the problems associated with non-ideal polymerizations reflected mainly in the variability of Rp/[I]0·5[M] where Rp is the rate of polymerization and [I] and [M] are the initiator and monomer concentrations, respectively.
74 citations
TL;DR: The dialkyldiazene or azo-compound initiators are one of the most important classes of initiators being widely used in both conventional and reversible-deactivation radical polymerization (RDRP).
66 citations
TL;DR: In this paper, a review summarizes nearly 400 references (since 1990) intended to highlight directions on the synthesis of telechelic oligomers and macromonomers by radical techniques, taking into account the recent developments in conventional radical polymerizations, such as dead-end polymerizationand also telomerization reactions.
Abstract: This review summarizes nearly 400 references (since 1990) intended to highlight directions on thesynthesis of telechelic oligomers and macromonomers by radical techniques. This review first takes intoaccount the recent developments in further conventional radical polymerizations, such as dead-end polymerizationand also telomerization reactions. Among all the conventional radical polymerizations, addition–fragmentationtransfer (AFT) polymerization realized a real breakthrough for the synthesis of telechelic oligomersand especially for macromonomers by coupling AFT with catalytic chain transfer. Then, surveys concerningtelechelic oligomers and macromonomers prepared by living radical polymerizations are mentioned. Atom transferradical polymerization, nitroxide-mediated polymerization, reversible addition–fragmentation chaintransfer polymerization and also iodine transfer polymerization allow for accurate control of chain-endfunctionality, either a functional group or a double bond. Novel reactions like radical couplingof oligomers previously obtained by living radical polymerizations are enhanced.
61 citations
TL;DR: The kinetic features of vinylidene fluoride (VDF) radical polymerization in solution, initiated by bis(4-butylcyclohexyl)peroxydicarbonate, have been investigated in three different solvents (acetone, ethyl acetate and methyl acetate) under homogeneous conditions as discussed by the authors.
59 citations
TL;DR: In this paper, the authors used benzoyl peroxide (BPO) as an initiator at 85°C ± 1°C under an inert atmosphere of nitrogen in xylene as solvent.
Abstract: Radical polymerization of limonene (limonene) using benzoyl peroxide (BPO) as an initiator at 85°C ± 1°C under an inert atmosphere of nitrogen in xylene as solvent was carried out. The system follows nonideal kinetics: Rp α [I]0.3 [M]1.4, due to both primary radical termination and degradative chain transfer reaction. The activation energy of the polymerization was estimated to be 22.97 kJ mol−1. 1H-NMR spectrum of polymer shows the presence of a triplet between 2 and 2.5 δ, which reveals that β-carbon of limonene is the active site in the polymerization of limonene. The FTIR spectrum of the polymer shows band at 1645 cm−1 due to gem disubstituted CC stretching vibrations. The glass transition temperature (Tg) of the polylimonene of the polylimonene is 116°C. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
54 citations
References
More filters
178 citations
68 citations
TL;DR: In this article, the termination reactions of macroradicals, and the dimerisation of primary radicals, which have escaped from the initial cage, are treated as diffusion-controlled rections.
Abstract: The termination reactions of macroradicals, and macroradicals by primary radicals (“primary-radical termination”) and the dimerisation of primary radicals, which have escaped from the initial cage, are treated as diffusion-controlled rections. Typical values for diffusion-controlled rate constants are assigned to the reactions of the primary radicals, and the extent of the deviations from the simple rate equations and the MAYO equations, arising from primary-radical termination, is estimated.
The predictions, in the cases of methyl methacrylate and styrene polymerisations, are consistent with the deviations from the simple laws observed experimentally. The treatment does not predict the behaviour of vinyl acetate polymerisations as, surprisingly, this monomer shows no kinetic evidence of primary-radical termination.
Die Abbruchsreaktionen von Makroradikalen, die Reaktionen der Makroradikale mit Primarradikalen, („primarradikalische Abbruchsreaktion”) und die bimolekularen Reaktionen zwischen Primarradikalen, die den Kafig verlassen haben, werden als diffusions-beschrankte Reaktionen behandelt. Den Reaktionen der Primarradikale werden charakteristische Werte der diffusionsbeschrankten Geschwindigkeitskonstanten zugeordnet und das Ausmas der Abweichungen von den einfachen Geschwindigkeitsgleichungen und den Gleichungen von MAYO, die aus dem Abbruch durch Primarradikale entstehen, wird abgeschatzt.
In den Fallen der Polymerisationen von Methacrylsauremethylester und Styrol stimmen unsere Vorhersagen mit den beobachteten Abweichungen von den einfachen Gleichungen uberein. Die Behandlung versagt im Fall der Polymerisation von Vinylacetat, da das Vinylacetat erstaunlicherweise keinen kinetischen Beweis einer Abbruchsreaktion durch Primarradikale gibt.
23 citations
TL;DR: In this article, the rate of initiation and termination between the growing chains and primary radicals were calculated, respectively, from the equations: ==================��¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¿¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯, where VR is the rate rate of primary radical formation and k′p the rate constant of initiation.
Abstract: The reciprocal of the viscosity-average degree of polymerization (Pv−1) vs. rate of polymerization (V) relation is expressed as:
where [η] = K′Pvα, β = ktd/kt, k = rate of primary radical formation out of cages/concentration of initiator, , = rate of termination of growing chains M· by reaction with primary radicals Ri·. From this equation, several, important constants can be determined. In the polymerization of styrene at 60°C. with 2,2′-azobisisobutyronitrile, the results obtained are as follows: kp2/kt = 5.52 × 10−4 (or 5.86 × 10−4) l.-mole.−1-sec.−1. ktrM/kp = 6 × 10−5, ktrS/kp 1.1 × 10−2 (carbon tetrachloride as solvent), k = 1.57 × 10−5 (or 1.48 × 10−5) sec.−1, . These values agree well with those obtained by the other authors. The rate of initiation and the rate of termination between the growing chains and primary radicals are calculated, respectively, from the equations:
The rate of disappearance of the primary radicals through the reaction among themselves is negligible in comparison with the other termination rates in the usual conditions. The ratio of concentrations of the primary radicals R· and growing chains M· is expressed under an ordinary condition as:
where VR is the rate of primary radical formation and k′p the rate constant of initiation.
15 citations
TL;DR: In this article, the authors propose a linear representation of the variable Y as a power series of X, which is obtained from the plot of Y vs. X according to the equation.
Abstract: Die verschiedenen Auftragungen zur Ermittlung des fur den Primarradikalabbruch charakteristischen Konstantenverhaltnisses k5/kik2 wurden einer systematischen Untersuchung unterzogen. Vom Sonderfall d ≡ k3k6/k52 = 1 abgesehen, besteht dabei kein exakter linearer Zusammenhang zwischen der allgermeinen Grose und der allgemeinen Variablen . Da es aber stets moglich ist, Y als Potenzreihe von X darzustellen, ergibt sich die fur Jeden Fall gunstigste lineare Darstellungsweise, wenn n und s so gewahlt werden, das der Koeffizient des X2-Gliedes verschwindet (Bedingung n − 2 s + d = 0) und der Koeffizient des X3-Cliedes ebenfalls 0 oder zumindest moglichst nahe 0 wird. Unter diesen Bedingungen lassen sich auch noch solche Meswerte in nahezu perfekter linearer Form darstellen, bei denen die Grose als Funktion von cs um den Faktor oder mehr variiert. Wird zusatzlich noch dem Monomerverbrauch durch die Startreaktion Rechnung getragen, so ergibt sich das gesuchte Konstantenverhaltnis k5/k1k2 aus einer Auftragung von Y gegen X nach der Beziehung
Die Arbeitsweise dieser Methode wird anhand eines Beispiels demonstriert.
The various plots for estimating the ratio of rate constants characteristic for primary radical termination, k5/k1k2, have been examined systematically. Apart from the special case d ≡ k3k6/k52 = 1 there is no exact linear relationship between the general quantity and the general variable . In any case, however, Y can he expressed as a power series of X. Therefore the best way to obtain the most favourable linear representation of Y as a function of X is to choose s and n according to the condition that the coefficient of the term quadratic in X has to disappear (n − 2 s + d = 0) and the coefficient of the X3-term also equals 0 or is at least close to 0. Under these conditions even those data can be represented in an almost perfect linear form which show variations of the quantity by a factor of or more for different initiator concentrations cs. If additionally allowance is made for the consumption of monomer by the initiation process the desired ratio of rate constants, ks/k1k2, is obtained from the plot of Y vs. X according to the equation
The application of this method is illustrated using an example from literature.
8 citations