Structural Development during Nonlinear Free-Radical Polymerizations

Relationships have been derived which describe structural development in nonlinear free-radical polymerizations as a function of conversion. The recursive analysis is based on the assumptions of ideal network formation and those assumptions standard in the kinetic analysis of linear free-radical polymerizations. Significant is the fact that changes in average primary chain length (e.g., due to drift or Trommsdorff effect), which in linear systems give rise to large polydispersities, can be accounted for in these relationships. While it is shown that for many systems such rigor is unnecessary in the pregel regime, it is also shown that neglect of such effects in the postgel regime may lead to serious errors. For the case in which monomer depletion is the only source of a changing kinetic chain length, the gel point is observed to be delayed and the network observed to be looser in comparison with the case in which monomer depletion is neglected.