MECHANISM, KINETICS AND POTENTIAL MORPHOLOGICAL CONSEQUENCES OF SOLID-STATE POLYMERIZATION

The likely mechanism which allows the required migration of functional groups for solid-state polymerization (SSP) of polyamides and polyest ers is shown to be interchange reactions. This ''chemical diffusion'' of functionality has exactly the same mathematical form as that of cla ssical diffusion of small molecules. The consequent model for kinetics of SSP in fine geometries is seen to fit experimental data well. It y ields an estimate of the critical distance over which the functionalit y jumps with each interchange reaction. The critical reaction distance thus obtained, similar to 5 Angstrom, is similar to those determined from diffusion-controlled reactions of small molecules. The profound c hanges that interchange reactions can produce during SSP in the topolo gy of chain segments in the intercrystalline regions of flexible and s emirigid polymers, especially in oriented structures, are revealed.