Diffusion and gelation in polyadditions. I. Vindication of the classical network theory of gelation

Abstract

AbstractIn this, the first of a series of four papers, the theory of diffusion control of the gelation in polyfunctional polyadditions is rejected. It is shown experimentally, that the termination step in a model system is unaffected by diffusion control until after gelation. It is shown theoretically that diffusion control of the crosslinking step sets in even later. Investigations by Grün, and by Vaughan, are relevant to this demonstration. Quantitative application of the Stokes‐Einstein theory of diffusion confirms the conclusions reached. In the absence of diffusion‐controlled crosslinking, alternative causes are examined for observed delays in gelation. These causes are intramolecular cyclization and chain transfer effects. There are well‐known mass law effects of dilution in polyfunctional systems. However, progressive dilution with monovinyl monomer in polyaddition does not—in contrast to the effects of inert diluent in polycondensation—favor internal cyclization. The true mass law effects of such dilution can readily be allowed for.