We report on the grafting-from living cationic polymerization of isobutylene from SiO2-nanoparticles surfaces. After modification of the NP-surfaces (SiO2; 6 run) initiators (1) for the cationic polymerization of isobutylene (IB) were grafted onto the NP surface in variable densities (0.1-0.85 molecules initiator/nm(2)). With densely packed initiators (0.85 molecules initiator/nm(2)) PIB-brushes with controlled molecular weights (5000-50000 g mol(-1)) could be obtained. Various concentration-ranges of initiator-moeities in Solution as well as isobutylene were studied, revealing a controlled polymerization process only in the range between [1] = 0.4-30 mM and [IB] = similar to 0.04-3.3 M without the use of sacrificial soluble initiating systems, thus enabling a high-volume density polymerization of grafted nanoparticles without homopolymer formation. At high grafting densities (0.6-0.8 initiator molelcules/nm(2)), the polymerization proceeded with three different rate-constants, with a slower polymerization at the beginning and increasing rates of polymerization after similar to 300 and 600 s, respectively. With reduced initiators densities (below 0.4 molecules initiator/nm(2)) loss of control over the polymerization process and a significant change of the polymerization kinetics was observed.