Head‐to‐head polymers 27: Thermal degradation of head‐to‐head polyisobutylene

Head‐to‐head polyisobutylene degrades at a maximum rate at 320°C, a temperature about 65°C lower than head‐to‐tail polyisobutylene. Under our conditions, head‐to‐tail (the regular polyisobutylene) degrades (as do many other disubstituted vinyl monomers) to a high yield of the monomer isobutylene. Surprisingly, head‐to‐head polyisobutylene also degraded, primarily to isobutylene. Liquid, low‐molecular compounds, probably dimers, were also obtained from head‐to‐tail and head‐to‐head polyisobutylene. A mechanism of this degradation is proposed.