Copolymerisation of acrylonitrile under homogeneous and heterogeneous conditions

• Main Author: Shilton, Richard William
• Published: University of Leicester 1968
• Subjects: 540
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.737089

A study has been made of the copolymerisation behaviour of acrylonitrile with the monomers methyl acrylate and vinylidene chloride respectively. The project arose from reports by workers at Courtauld's Ltd. that the lengths of the sequences of the monomer units in certain copolymers of acrylonitrile and vinylidene chloride were longer than predicted by statistical considerations. The copolymerisation of methyl acrylate with acrylonitrile was studied to examine the possibility of a preferential swelling of polymer particles by one monomer during polymerisation. Copolymerisation was carried out in three different solvents, and unsuccessful attempts were made to measure the sequence lengths in the polymers directly using NMR spectroscopy. Only compositional analysis was possible by this means, but measurements of the thermal properties of the polymers indicated that the sequence lengths were short in all cases. It was found that the Alfrey-Lewis copolymerisation equation was obeyed when the reaction was carried out homogeneously in dimethylformamide, but it was not obeyed when it was carried out heterogeneously in hexane or butanol. The copolymerisation of acrylonitrile with vinylidene chloride was studied in several different solvents, and also in mixed solvent systems. Sequence lengths were measured by NMR spectroscopy, and were found to be short for all methods of preparation. In no case was the Alfrey-Lewis copolymer equation obeyed, even in those solvent systems for which the reaction was homogeneous. The preparation of copolymers homogeneously in dimethylformamide showed the least deviation from the simple copolymer equation; for some of the systems used the results could be fitted to the equation derived by Merz et al. in which the effect of the penultimate group in the polymer chain is considered. The problems in setting up a model for heterogeneous polymerisation have been discussed.