Grafting onto cellulosic macromolecules through chain transfer to mercaptoethyl side chains. II. Mechanism of the process

The data that were presented in Part I are compared with theory. It is found that the weight increase of a mercaptoethylated cellulose acetate film during polymerization of styrene in the presence of this film is proportional to the initial monomer content and to 1 − exp {−bt} where t is the time and b a constant proportional to (catalyst concentration)1/2 times (initiation efficiency)1/2. This equation is in accordance with the theory of grafting developed by Fox and co‐workers, when the monomer conversion is low, but it is found experimentally that its validity extends well beyond values of the monomer conversion for which the equation should no longer represent a good approximation. (1) The composition of the film and therefore the monomer concentration and the rate constants change during grafting. (2) When grafting is high it becomes impossible quantitatively to remove the homopolymer by extraction of the film. (3) Chain transfer takes place not only to SH groups but also to nonmercaptoethylated parts of the cellulose acetate, It is believed that three causes are responsible for this result.