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The synthesis and incorporation of diaryliodonium salts into polymeric materials and the thermal decomposition of diaryliodonium salts
Abstract
Diaryliodonium salts have received much attention as photoactivated curing agents for many applications. Irradiation of a film containing a diaryliodonium salt leads to the formation of a strong Bronsted acid, which initiates secondary reactions within the film. Examples of such secondary reactions include; acid catalyzed polymerization, depolymerization, and crosslinking. Thus, irradiation of a diaryliodonium salt in the presence of a polymer containing epoxy groups in the main chain would yield an insoluble, crosslinked material. Diaryliodonium salts have also been incorporated into the main chain of polymeric materials. Such materials have been shown to make effective photosensitive films. We have studied the incorporation of diaryliodonium salts into polyamides. Bis (4-(2-aminoethyl)phenyl) iodonium bromide was caused to react with sebacoyl chloride to yield a polyamide, which was insoluble in most solvents making the preparation of films difficult. Our attention then turned to the preparation of diaryliodonium salts which contained polymerizable functional groups. Such salts were thought to be potential photohardening agents in polymeric materials. Irradiation of a film containing Bis (3((2-methacroyloxyethoxycarbonyl))phenyl) iodonium bromide and polyvinyl alcohol gave a material which was resistant to a solvent wash. GPC and DSC results suggested the presence of high molecular weight species which may have contributed to the films' solvent resistance. We also undertook a mechanistic reinvestigation of the thermal decomposition of diphenyliodonium salts and found products not previously reported in the literature. Diphenyliodonium tetrafluoroborate, when heated, gives fluorobenzene, iodobenzene, biphenyl, three iodobiphenyl isomers, terphenyl, other polyaromatics and Bronsted acids. A mechanism involving free radicals and radical cations is proposed to account for the formation of these products. For example, homolytic cleavage of the C-I bond gives a phenyl radical/iodobenzene radical cation geminate pair. Recombination of this pair leads to the formation of the iodobiphenyl isomers. A secondary reaction of an iodobiphenyl isomer with a phenyl radical leads to an iodoterphenyl isomer. The formation of the other polyaromatic compounds is proposed to follow similar coupling reactions.
Subject Area
Organic chemistry
Recommended Citation
Demassa, John Matthew, "The synthesis and incorporation of diaryliodonium salts into polymeric materials and the thermal decomposition of diaryliodonium salts" (1991). Doctoral Dissertations Available from Proquest. AAI9132840.
https://scholarworks.umass.edu/dissertations/AAI9132840