Prof. Dr. Axel Müller

A new synthetic route for the synthesis of polyisobutylene (PIB) stars and PIB-poly(methacrylate) block copolymers was developed by combining living carbocationic and anionic polymerizations. Rapid and quantitative monoaddition of thiophene to living PIB chains has been observed in conjunction with TiCl₄ as Lewis acid in n-hexane/CH₂Cl₂ 60/40 v/v at -78 °C leading to the formation of 2-polyisobutylenyl-thiophene (PIB-T). PIB-T was quantitatively metalated with n-butyllithium in THF at -40 °C. ¹H NMR spectroscopic and GC studies of the corresponding model compound, 2-(1,1,3,3-tetramethylbutyl)thiophene, clearly verified quantitative metalation. The resulting stable macrocarbanion (PIB-T^-,Li⁺) was used to initiate living anionic polymerization of tert-butyl methacrylate (tBMA) yielding PIB-b-PtBMA block copolymers with high blocking efficiency. PIB stars were prepared via the coupling reaction of the stable macrocarbanion with SiCl₄ as a coupling agent. Characterization of these block copolymers and PIB stars was carried out by size exclusion chromatography (SEC), liquid adsorption chromatography at critical conditions (LACCC), and NMR spectroscopy.