Evidence of Ni(0) Complex Diffusion during Grignard Metathesis Polymerization of 2,5-Dibromo-3-hexylthiophene

It has been previously reported that the Grignard Metathesis polymerization of 3-alkyl thiophenes proceeds by a quasi-"living" chain growth or "catalyst transfer polycondensation" mechanism. Several publications present data in support of the transition metal species acting as an initiator and specifically maintaining Ni(0) association with a single growing polymer chain. However, our study of 2,5-dibromo-3-hexylthiophene polymerization via GPC, MALDI-TOF, and GC-MS verifies independently and in conjunction with one another that the transition metal is involved in transfer/diffusion from chain to chain during polymerization and presents the possibility of additional mechanistic controlling factors. Kinetic monitoring and characterization studies support transfer of the transition metal through diffusion from chain to chain during polymerization.