Peculiarities in atom transfer radical copolymerization.

In recent literature it is quite common to treat living radical copolymn. completely analogous to its free radical counterpart. When doing so it is often obsd. that small deviations in the copolymn. behavior occur. In this work the obsd. deviations can be interpreted on the basis of reactions specific for living radical polymn., such as the activation - deactivation equil. in atom transfer radical polymn. Reactivity ratios obtained from atom transfer radical copolymn. data, interpreted according to the conventional terminal model deviate from the true reactivity ratios of the propagating radicals. Furthermore, the copolymn. of monomers that strongly deviate in equil. const. between active and dormant species may exhibit for low molar mass copolymers a significant correlation between molar mass distribution and chem. compn. distribution. The rationale behind this correlation is that the chains that happen to add a relatively large fraction of the more dormant monomer lag behind in their growth. The more dormant monomer refers to the monomer creating a chain end with the lower equil. const. in the activation - deactivation process. This monomer will be preferentially present in the low molar mass fraction of the distribution, whereas the other monomer will be present to a larger extent in the high molar mass fraction.