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Title: Synthesis of new polymers by chemical modification of polydienes
Author: Chishti, S. A. A.
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 1978
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The work reported in this thesis concerns the chemical modification of polydienes mainly cis-1,4-polybutadiene. Two different types of modifying reagents - benzenesulphenyl chloride and difluorocarbene :CF₂ - were successfully used to bring about structural changes in polybutadiene. The polymers had quite different properties from those of starting material as evidenced by changes in physical properties. The structures of these adducts were studied by IR and NMR (both proton and ¹³C) spectroscopy. Electron micrographs of the partially modified adducts of polybutadiene with benzenesulphenyl chloride showed the presence of two phases - domains of modified polymer in a continuouss polydiene matrix. This morphology is characteristic of block copolymers and indicates that the addition of sulphenyl chloride to polybutadiene does not take place in a totally random fashion. There is a degree of regioselectivity, the most obvious mechanism for which is that the S atom on a reacted monomer unit activates the double bond of an adjacent unreacted unit. Such anchimeric assistance is hindered in the presence of a nitro-group ortho to the sulphenyl chloride and hence electron micrographs of the adducts of polybutadiene with -nitro- and 2,4-dinitrobenzenesulphenyl chlorides were found to have a homogeneous morphology. Evidence for blocky structures in these polymers was also sought from ¹³C NMR spectroscopy. These studies suggest that probably the partially saturated adducts comprise a mixture of random and block structures. The theory that a neighbouring group activation mechanism operates during addition of benzene- and toluenesulphenyl chloride to polybutadienes (both cis- and trans-l,4-isomers) was evaluated by kinetic and model compound studies. The sulphide links of the fully saturated adducts of polybutadiene and benzenesulphenyl chloride and polybutadiene and toluenesulphenyl chloride yielded more thermostable polymer on oxidation to sulphone with m-chloroperbenzoic acid. Novel fluoropolymers were prepared by reaction of polybutadiene with difluorocarbene. The limited amount of data on the physical properties of polymers suggested that they could be useful elastomers, with thermal stability and other properties comparable to those of some speciality fluoroelastomers.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available