Influence de l'Initiateur de Polymérisation et de la Masse Moléculaire du Produit Formé, sur l'Absorption des Ultrasons par les Solutions de Polyméthacrylate de Méthyle

The variation of the characteristic frequency N* (i.e., the frequency at which the rapid decrease of the ultrasonic absorption occurs) has been studied as a function of molecular weight Mw for different poly(methyl methacrylate) samples dissolved in benzene. Two categories of these products show up according to the initiator of polymerization. For the first one N* increases with Mw; for the second one N* does not depend on Mw. It appears that the variations of N*, either as a function of the initiator for the same molecular weight, or as a function of the molecular weight for a series of fractions, are not determined only by the global degree of NMR tacticity. The molecular weight does not seem to have a direct influence on the value of N*.