A series of benzocyclobutene (BCB) polymers derived from a new readily available monomer, 4-(1',1'-dimethyl-1'-vinyl) silylbenzocyclobutene (4-DMVSBCB), were conveniently prepared by radical and anionic polymerization. The homo- and co-polymerization results show that the reactivity of 4-DMVSBCB in anionic polymerization is relatively higher compared with radical polymerization. The molecular weight of 4-DMVSBCB polymers and content of 4-DMVSBCB can be controlled by anionic copolymerization. The introduction of rigid and crosslinkable BCB building blocks in side chains and carbosilanes in molecule gives rise to insulating materials with good film-forming property, smooth and flat film surface, and low-dielectric constants of 2.41-2.45, as preserving good thermal stability. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 381-391, 2011