Thiourea as a transfer agent in the radical polymerization of methyl methacrylate in aqueous solution at 42

✍ Scribed by D. Pramanick; A.K. Chatterjee

• Publisher: Elsevier Science
• Year: 1980
• Tongue: English
• Weight: 313 KB
• Volume: 16
• Category: Article
• ISSN: 0014-3057
• DOI: 10.1016/0014-3057(80)90122-6

✦ Synopsis

Chain transfer involving thiourea in radical polymerization of methyl methacrylate in acidic aqueous media has been studied by polymer endgroup analysis using the dye-partition technique. Thiourea has feeble reactivity in chain transfer, the transfer constant with respect to poly (methyl methacrylate) radicals being 1.21 x 10 -4 at 42 °. This chain transfer study led to the development of a new method for studying the tautomeric equilibrium between the thione and thiol forms of thiourea. The equilibrium is pH dependent and the equilibrium constant at 42 ° is 232. The ratios of the equilibrium concentrations of the thiol to thione forms of thiourea at various pH's have been calculated. The thiol form is responsible for the chain transfer reactivity; it predominates in strongly acidic media and is almost absent above pH 3.5. This new method may be used for studying the thione-thiol tautomerism of other thiourea derivates.