The Polymerisation of Acrylonitrile With Ferric Chloride as Photoinitiator

Ross, Ian C (1963) The Polymerisation of Acrylonitrile With Ferric Chloride as Photoinitiator. PhD thesis, University of Glasgow.

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A detailed kinetic study has been made of the photosensitized polymerization of acrylonitrile in dimethyl formamide solution with ferric chloride as both catalyst and terminating agent. It has been shown that ferric chloride readily forms complexes with solvents containing atoms which act as electron donors, and that a complex exists between ferric chloride and dimethyl formamide which probably involves co-ordination via carbonyl oxygen atoms. There is evidence also that two species of ferric chloride exist in dimethyl formamide, and that one of these is more readily reduced by absorption of light or reaction with free radicals than the other. Not with standing the complex nature of these solutions, it appears that the process whereby free radicals are obtained on photolysis with u.v. light primarily involves a relatively simple reaction, namely electron transfer from chlorine to iron to form chlorine atoms. These atoms, however, do not initiate polymerization directly; it is probable that the solvent is attacked to produce further radicals which react with monomer to initiate chains. The extinction coefficient of ferric chloride in dimethyl formamide at 3650A is 5 x 10e3 litre mole-1 cm-1, such that absorption of irradiation at this wave length in reaction vessels of 2 cm. diameter containing chloride concentrations greater than ca. 3 x 10 mole litre is virtually complete. It is shown that under these conditions the rate of production of ferrous iron, and consequently the rate of initiation, is independent of ferric chloride concentration. At concentration greater than ca. 2 x 10e-3 mole litre , termination occurs by reaction of growing radicals with ferric chloride. To describe this system, a simple kinetic scheme is postulated which indicates that, under stationary state conditions, rates of polymerization and initiation should be given by the expressions where kp and kt are the velocity coefficients of propagation and termination, ki is the constant relating the rate of initiation, In, to the intensity of irradiation, Io, and [M] and [FeCl3] represent the monomer and ferric chloride concentrations. In as measured by titration for ferrous iron with ceric ammonium sulphate, is 1.64 x 10e-1 mole litre sec , and by substitution of this value for in equation (1), a value of 0. 078 is obtained for kp/kt 25

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Polymer chemistry
Date of Award: 1963
Depositing User: Enlighten Team
Unique ID: glathesis:1963-79478
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 05 Mar 2020 09:06
Last Modified: 05 Mar 2020 09:06

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