Multi-arm star polyisobutylenes

Summary

The first synthesis of a multi-arm radial-star polyisobutylene (*-PIB) is described. The synthesis occurred by the addition of excess divinylbenzene (DVB) linking reagent to a living polyisobutylene (PIB^⊕) charge i.e., by the “arm first” method under specific conditions. The radial structure of the *-PIB was proven by determining the molecular weight of a sample by light scattering, then selectively destroying the aromatic polydivinylbenzene (PDVB) core, and finally determining the molecular weight of the surviving alphatic PIB arms. The synthesis strategy, kinetic observations during synthesis, and procedures leading to a representative *-PIB are described. This product whose $\overline M _{\text{w}} = 1,134,400$ g/mole with $\overline M _{\text{w}} /\overline M _{{\text{n }}} = 2.83$, contained ≈90.3 mole% (∼78 wt.%) PIB arms and ≈9.7 mole% (≈22 wt.%) aromatic core; thus the number of PIB arms emanating from the core was $\overline N _{{\text{n,arm}}}$ (number average number of arms)=56 or $\overline N _{{\text{w,arm}}}$ (weight average number of arms)=110.