Monodendrons consisting of m-linked phenyleneethynylene repeating unit with trimethylsilyl-, pentamethyldisiloxanyl- and nonamethyltetrasiloxanyl-peripheral groups were synthesized using the convergent approach. The focal point of monodendrons, terminal acetylene, was polymerized with rhodium catalyst to yield corresponding polydendrons with a high molecular weight. The polydendrons were solubile in common organic solvents, and readily formed membranes. Oxygen permselectivity was improved in the polydendrons with a space-persistent dendritic crowd. It was found that the well-defined dendritic and rod-like structure of the polydendrons was useful for pemselective membrane. Oxygen permselectivity was increased in polydendrons with a trimethylsilyl group compared to the corresponding zero generation poly(phenylacetylene) derivatives. (c) 2005 Elsevier B.V. All rights reserved.