Télomérisation en milieu aqueux, 1. Télomérisation de l'acide acrylique avec l'acide thioglycolique

The telomerization of acrylic acid with thioglycolic acid (mercaptoacetic acid) in aqueous medium, with various initiators (H 2 O 2 ,Na 2 S 2 O 8 ,K 8 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 T = 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.