Anionic polymerization initiated by the lamellar compounds of LiC12: 2. Thermodynamics and the propagation mechanisms in 1,4 Cis and 1.4 Trans of isoprene, -H-n.m.r. study

The polymerization of isoprene initated by LiC₁₂ in cyclohexane yields polymers whose microstructures are quite different from those obtained in homogeneous media. These microstructures change during the reaction. For the low yields, the polymer may contain up to 96% 1,4 cis. The evolution of the microstructure with the mass of the polymer formed per g of initiator is also temperature dependent. With certain types of ‘ternary’ lamellar compounds it is possible to obtain (at high yields) polymers with a high content of 1,4 cis. A mechanism of polymerization is proposed that takes into account the influence of one (or more) graphite layer over the interactions between the lithium cation of the growing living end and the monomer.