A new method for the determination of the rate of initiation in radical polymerizations

Bevington, J. C.; Bradbury, J. H.; Burnett, G. M.

doi:10.1002/pol.1954.120120138

Cited by 35 publications

(19 citation statements)

References 8 publications

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“…6, ( 1.05 ⋅ 10 −7 M −1 s −1 , 20% error), [18], the cage value resulted equal to 0.62 ± 0.12. This value was consistent with those previously reported [32][33][34].…”

Section: Rate Of Free Radical Initiationsupporting

confidence: 94%

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Calorimetric adaptation of the inhibited autoxidation method to determine the activity of individual antioxidants and natural extracts

Mosibo

Scampicchio

Ferrentino

2022

J Therm Anal Calorim

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This work aims to determine the antioxidants activity of individual antioxidants and natural extracts by isothermal calorimetry. The proposed method is an adaptation of the “inhibited autoxidation method”. It consists of the monitoring of the heat-flow signal evolved during the autoxidation of styrene, in the presence of 2,2′-azobis(isobutyronitrile) as radical initiator, with individual antioxidants or plant extracts as inhibitors, and under isothermal conditions (303 K). The resulting calorimetric traces were transformed in conversion fractions over time. The antioxidant activity was expressed with the initial slope of the inhibited period of styrene autoxidation. Also, the induction period observed at the onset of the uninhibited styrene autoxidation leaded the stoichiometry number of the reaction between antioxidants and free radicals. The approach was very simple, and it allowed to rank individual antioxidants (α-tocopherol > > gallic acid = quercetin > syringic acid > > synaptic acid > 4-hydroxybenzoic acid) and plant extracts (Olea europea > Melissa officinalis > Fraxinus excelsior > > Papaver rhoeas), based on their ability to decrease the conversion rate of styrene autoxidation. The results on plant extracts were critically compared with those from the DPPH assay. Differently to the many antioxidant assays widely used nowadays, the proposed approach has the merit to test the activity of micromolar quantities of antioxidants to inhibit the autoxidation of a large excess of an oxidizable substrate, whose oxidation is induced by a constant rate of free radicals formation under well controlled and reproducible experimental conditions.

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“…6, ( 1.05 ⋅ 10 −7 M −1 s −1 , 20% error), [18], the cage value resulted equal to 0.62 ± 0.12. This value was consistent with those previously reported [32][33][34].…”

Section: Rate Of Free Radical Initiationsupporting

confidence: 94%

“…Accordingly, when the recorded heat flow was endothermic, the conversion fraction was considered equal to zero. Overall, because of the lack of a radical chain process, the results achievable from the induction period method were used uniquely to determine R i , as suggested also by many Authors [32,33].…”

Section: Rate Of Free Radical Initiationmentioning

confidence: 99%

Calorimetric adaptation of the inhibited autoxidation method to determine the activity of individual antioxidants and natural extracts

Mosibo

Scampicchio

Ferrentino

2022

J Therm Anal Calorim

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“…Use of CI4-labeled initiators permits evaluation of Ri from the experimental values of R, and the evaluation of Y from the C14-content of the polymer. [13][14][15] Since Ri = 2fkd [I] (10) the initiator efficiency, f, can be calculated from Ri, the initiator concentration [I], and the first-order rate constant, kd, for spontaneous thermal decomposition of initiator, provided the latter is k n~w n . '~-'~ The validity of the method is subject to the conditions specified above.…”

Section: °C Now Described Conditionsmentioning

confidence: 99%

Radiochemical studies of free‐radical vinyl polymerizations. Part I. The nature of the initiation and termination processes in methyl methacrylate and styrene polymerizations using C¹⁴‐labeled initiators

Ayrey

Moore

1959

J. Polym. Sci.

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C14‐Labeled initiators, viz., di‐(ar‐C14)‐benzoyl peroxide, di‐(carboxyl‐C14)‐benzoyl peroxide, and C14‐azobisisobutyronitrile (AZBN), have been used to initiate the polymerization of methyl methaerylate at 60°C. in benzene. Determination of the rates of polymerization, and the molecular weights (M̄n) and C14‐contents of the resultant polymers permits the following conclusions to be made. (1) Rates of initiation by benzoyl peroxide and AZBN are given by the equations, Ri = 5.15 × 10−6 [Bz2O2] mole l.−1 sec.−1 and Ri = 1.17 × 10−5[AZBN] mole l.−1 sec.−1, respectively. (2) The initiator efficiency, f, for AZBN is 0.50; f for benzoyl peroxide cannot be evaluated in the absence of a reliable kd value for this compound in the present system. (3) Initiation is solely by addition of initiator radicals, R·, to the monomer; in the case of benzoyl peroxide, 43% of the radicals R· are phenyl and 57% are benzoyloxy under the reaction conditions used. (4) The average number of C14‐initiator fragments per polymer molecule, n, is 1.27, indicating that bimolecular termination of polymethyl methacrylate radicals is 57.5% by disproportionation and 42.5% by combination.

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“…This has been made possible by the use of labelled azobisisobutyronitrile. 329 In this way the complications due to solvent cage effects, intramolecular rearrangements, inefficient radical capture and diradical cyclisstion are avoided. The main precaution is to ensure that no low polymer is lost in the reprecipitation processes which are necessary to remove the unchanged or wasted catalyst.…”

Section: Radical Initiators and Rates Of Initiation Measurements Have...mentioning

confidence: 99%

General and physical chemistry

Davies¹,

Thomas²,

Skinner³

et al. 1954

Annu. Rep. Prog. Chem.

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A new method for the determination of the rate of initiation in radical polymerizations

Abstract: DiscussionProfessor H. Mark (Brooklyn): Could you tell what the range of molecular weighta was over which these experiments were carried out?

Cited by 35 publications

References 8 publications

Calorimetric adaptation of the inhibited autoxidation method to determine the activity of individual antioxidants and natural extracts

Calorimetric adaptation of the inhibited autoxidation method to determine the activity of individual antioxidants and natural extracts

Radiochemical studies of free‐radical vinyl polymerizations. Part I. The nature of the initiation and termination processes in methyl methacrylate and styrene polymerizations using C¹⁴‐labeled initiators

General and physical chemistry

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A new method for the determination of the rate of initiation in radical polymerizations

Abstract: DiscussionProfessor H. Mark (Brooklyn): Could you tell what the range of molecular weighta was over which these experiments were carried out?

Cited by 35 publications

References 8 publications

Calorimetric adaptation of the inhibited autoxidation method to determine the activity of individual antioxidants and natural extracts

Calorimetric adaptation of the inhibited autoxidation method to determine the activity of individual antioxidants and natural extracts

Radiochemical studies of free‐radical vinyl polymerizations. Part I. The nature of the initiation and termination processes in methyl methacrylate and styrene polymerizations using C14‐labeled initiators

General and physical chemistry

Contact Info

Product

Resources

About

Radiochemical studies of free‐radical vinyl polymerizations. Part I. The nature of the initiation and termination processes in methyl methacrylate and styrene polymerizations using C¹⁴‐labeled initiators