null检测 | Online Monitoring of the Final, Divergent Growth Phase in the Step-Growth Polymerization of Polyamines-美国布鲁克海文仪器公司

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Using automatic, continuous online monitoring of polymerization reactions (ACOMP) the final, divergent growth phase (FDGP) of the condensation polymerization of dimethylamine, epichlorohydrin, and ethylenediamine was monitored, which produced a highly ramified, polyelectrolytic polyamine. The weight average mass, Mw, increased exponentially during the FDGP, whereas weight averaged intrinsic viscosity [è]w increased slowly, reaching a plateau. Multi-detector gel permeation chromatography (GPC) revealed that polymers of mass 20 000 to 106 are branched and self-similar, but above this mass, [è] increases less strongly with M. This appears to be due to higher order ramification, a precursor to gelation. The ACOMP trends in Mw and [è]w provide direct online evidence of this process. It is shown computationally that a mere increase in polydispersity cannot explain this behavior. GPC showed the mass distribution becomes highly asymmetric as conversion increases. A plausible kinetic model for the distribution asymmetry is introduced, and a complementary model for the effects of higher order ramification on [è]w.

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