Methyl isopropenyl ketone styrene copolymers

The efficiency of the type I reaction usually depends on the relative stability of the radicals produced. For this reason, higher type I quantum efficiencies would be expected for methyl isopropenyl ketone (MIPK) styrene copolymers because the polymer chain radical formed is tertiary rather than secondary, i.e.,... 

The dark initiation of the photosensitized degradation of a styrene-methyl isopropenyl ketone copolymer by thermally generated 7i(3iwr ) acetone using the tetramethyl-l,2-dioxetan dissociation reaction has been studied.217 The reaction... 

The copolymerization of a,p-unsaturated ketones has been studied extensively in order to improve the poor chemical and thermal stability exhibited by the homopolymers. The vinyl ketones have been copolymerized with most of the common vinyl and diene monomers. The data are given in Ref. [326]. For initiation, the same reagents could be used as for free-radical homopolymerization. Copolymerization was carried out in bulk [371] and in emulsion systems [372]. In copolymerization with methyl methacrylate, vinyl acetate [373], and styrene [371] it was concluded that the relative reactivities of the vinyl ketones increase with the increasing electron-withdrawing nature of the vinyl ketone substituent. Polar and steric effects are not observed. Most of the work has been directed toward the preparation of oil- and solvent-resistant rubbers to replaee styrene-butadiene rubber. Emulsion eopolymerization of butadiene with methyl isopropenyl ketone yielded rubbers with good solvent resistance and low temperature flexibility, but the products tended to harden on storage and were not compatible with natural rubber [374]. The reactive earbonyl function caused sensitivity to alkine reagents. Copolymers of butylacrylate and methyl vinyl ketone, for example, can be erosslinked by treatment with hydrazine [375]. 

During the late 1940s and early 1950s interest was shown in copolymers of butadiene and methyl isopropenyl ketone, CH =C(CH3)C0CH3. The rubber was claimed to be superior to the then available butadiene-styrene rubbers in stress-strain properties, cut-growth resistance, tyre tread wear resistance and swelling in hydrocarbons. On the other hand low temperature properties and processability were said to be poorer. 

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