Change in molecular weight distribution during formation and degradation of star polymers

A general model has been derived to describe the formation of star polymers via various polymerization mechanisms. The model gives the bivariate distributions of molecular weight and number of branches of the star polymers. Key parameters determining the distributions include the distribution of primary polymers and the branching density. Analytical distribution functions are obtained for the systems having branches of uniform, random, or Schulz-Zimm distributions. The distribution polydispersity of the star polymers approaches unity for sufficiently high branching densities regardless of the distribution of primary chains. The model has also been extended to give the change in the average molecular weights when star polymers undergo degradation. The scheme of disconnecting branches from star cores is considered. Polydispersity of polymer mixture shows a maximum value at an intermediate degree of degradation.