No abstract

The free radical polymerization of a phosphonated styrene, dimethyl vinylbenzylphosphonate (VBP), in the presence of stable nitroxide 2,2,6,6-tetramethyl-1-piperidinyloxyl radical (TEMPO), initiated by dicumyl peroxide (DCP) at 125 °C, has been studied. The apparent rate of polymerization K p[M•] is eight times higher than that of styrene, but the “living” character of the polymerization could not be verified by SEC. So, a macromolecular initiator PS−TEMPO was used in order to follow the evolution of average number molecular weights by 1H NMR. Under these conditions, the “living” character of the polymerization could be checked and various block copolymers (11000/7500; 11000/11000) were prepared. As for vinylbenzyl chloride and other monomers bearing electroattractive groups, the polymerization was shown to be much faster than that of styrene.

No abstract

The telomerization of acrylic acid with thioglycolic acid (mercaptoacetic acid) in aqueous medium, with various initiators (H,O,, Na,S,O,, K2S20,, thermal initiation and 2,2'-azobis(2-amidiniopropane) dihydrochloride) has been achieved. Thus, we were able to point out the limitation of the chain length due to the transfer agent, which is characteristic of a telomerization reaction. Mono-, di-and tri-adducts were isolated and characterized after esterification of the reaction medium with ethanol, then hydrolized. These various adducts were used as standards for size-exclusion chromatography, and the influence of the reaction parameters (initiator, temperature, quality of solvent, amount of telogen was investigated. We also determined the transfer constant of thioglycolic acid (C, = 0,47). It is worth to note that knowing this value, it is possible to control precisely the number-average degree of polymerization of this type of reaction. This allowed us to prepare telomers with a 50% final weight concentration in the dry extract, as it was recommended for their use in paper industry.