Polybutadiene (PB)/Allylisobutyl Polyhedral Oligomeric Silsesquioxane (A-POSS) nanocomposites have been prepared by using A-POSS and butadiene (Bd) as comonomers, n-BuLi as initiator, cyclohexane as solvent, ethyltetrahydrofurfuryl ether as structure modifier through the anionic polymerization technique. The reaction conditions, the kind and content of the modifier and POSS, etc. affecting the copolymerization process and the microstructure of the nanocomposites were also investigated. The results showed that POSS incorporation obviously decreased the rate of polymerization and the molecular weight of the copolymers, increased polydispersity index of the copolymers. The reaction conditions (the reaction time and reaction temperature) had little effect on copolymerization. However, the addition of the modifier could increase the rate of polymerization significantly. In particular, the POSS incorporation resulted in dramatically increasing the content of 1,2-units in PB. POSS and the modifier had the excellent cooperative effect modifying the microstructure of the PB. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 120: 2800-2808, 2011