A novel polymer brush consisting of poly(phenylacetylene) (PPA) main chain and poly (dimethylsiloxane) (PDMS) side chains was synthesized by the polymerization of phenylacetylene-terminated PDMS macromonomer (M-PDMS). The macromonomer was prepared by the esterfication of monohydroxy-ended PDMS (PDMS-OH, degree of polymerization (DP) = 42) with p-ethynylbenzoic acid. The polymerization of M-PDMS using [(nbd)RhCl](2)/Et3N catalyst led to polymer brush, poly(M-PDMS), with M-n up to 349 000 (DP of main chain 104). Poly(M-PDMS) with narrow molecular weight distribution (M-n = 39 900, M-w/M-n = 1.11) was obtained with a vinyl-Rh catalyst, [Rh [C(Ph)= CPh2}(nbd)[P(4-FC6H4)(3)}]/(4-FC6H4)(3)P-Poly(M-PDMS)s were brown to orange viscous liquids and soluble in organic solvents such as toluene and CHCl3. The UV-vis absorptions of poly(M-PDMS) were observed in the range of 350-525 nm, which are attributable to the PPA main chain. (c) 2007 Elsevier Ltd. All rights reserved.