Atom transfer versus catalyst transfer: Deviations from ideal Poisson behavior in controlled polymerizations

- Molecular weight distributions in controlled polymerizations were simulated numerically.
- ATRP and catalyst transfer polymerization were analyzed.
- The possible sources of deviations from Poisson distribution were identified.

Over the past several years there has been growing interest in a new class of controlled living polymerizations jointly referred to as catalyst-transfer polycondensations (CTPs), in which monomers are coupled by a variety of metal-catalyzed metatheses, such as Grignard metathesis polymerization (GRIM). Interest in these processes is primarily driven by their applicability to the synthesis of conjugated polymers for organic electronics. In this article we use computational modeling of polymerization reactions to identify inherent factors which cause the widely observed deviation of chain length distributions in CTP products from the Poisson distribution expected for ideal living polymerizations. The primary source of these deviations is shown to be related to intermittent deactivation of metathesis pathways which transform the newly added monomer into a chain end capable of further propagation. Maximum departures from ideal behavior are observed when the rates of processes involved in metathesis are comparable with the rate of polymerization.

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