Synthesis and characterization of novel silicon-functional polyisobutylenes and their applications: Polyisobutylene brushes on silicate substrates via living cationic polymerization

A series of novel chlorosilyl functional initiators have been prepared and applied for the first time in the living cationic polymerization of isobutylene (113). Well-defined polyisobutylenes (PIBs) carrying mono-, di-, and tri-chlorosilyl head-group, and a tert-chloro end-group were synthesized using newly designed silyl-functional initiators in conjunction with TiCl4 in Hex: MeCl (60:40, v:v) at -80degreesC. EDd-group analysis by H-1 NMR spectroscopy verified the product structure and the survival of the Si-Cl head-groups during the polymerization. The chlorosilyl functional initiators and chlorosilyl functional PIBs have been employed for the synthesis of PIB brushes on-planar silicate substrates by the grafting from and grafting to techniques. The products were characterized by x-ray photoelectron spectra (XPS), atomic force microscopic (AFM), and ellipsometry. The grafting from approach yielded surface-bound polymer brushes with more uniform surface and higher grafting density compared to the grafting to technique. The film thickness of PIB brushes formed by grafting from increased linearly with increasing molecular weight of PIB. In contrast, PIB brushes produced by grafting to gave constant thickness independent of the molecular weight of PIB.