Reactivity Ratios for Copolymerizations of Ethene with Acrylic Acid Esters

1 Reactivity Ratios for Copolymerizations of Ethene with Acrylic Acid Esters 

Reactivity ratios rj are defined by r, = ka/kij, the ratio of homopropagation, ka, to cross-propagation, rate coefficients, where fcy refers to the addition of monomer j to a free-radical chain-end terminating in species i. Under ideal polymerization conditions the mole fraction of monomer units i contained in the copolymer Fj is given by eq (4.6-14), which holds for both the terminal and the implicit penultimate unit models (see Section 4.6.4.3) [45]. 

In eq (4.6-14) / is the mole fraction of monomer i in the reacting monomer mixture. This equation is used to derive r, and rj = kjj/kji from the measured 

That the two reactivity ratios are correlated may be taken into account by calculating 95 % confidence intervals for these quantities according to the pro- 

The variation of reactivity ratios with pressure is small. The activation volume, AV (ri) = -(51n ri/9p)r/ 7, serves as a quantitative measure of this dependence. To derive reliable, accurate AV fn) values, experiments over an extended pressure range are required. Unfortunately, the pressure range of ethene-acrylate copolymerizations is not easily extended (to induce larger changes in n) as polymerization pressure is limited towards high p by the equipment and towards low p by inhomogeneity of the reaction mixture. 

---