7-Octenyldimethylphenylsilane was copolymerized with ethylene via Et(Ind)(2)ZrCl2 methylaluminoxane catalyst system without loss of catalyst activity or decrease in molar mass. The comonomer contents in the polymer samples were at a level of 0.15-1.0 mol % and the reactive phenylsilane groups were posttreated to different alcoxy- and halosilane groups, for example, Si-F, Si-Cl, Si-OCH3, and Si-OCH2CH3. The posttreatment reactions had no major effect on the molar masses or on the thermal properties (measured with differential scanning calorimetry) of the copolymers. The reaction pathways were nearly independent of the comonomer contents and the reactions reached 70-100% conversions. (C) 2004 Wiley Periodicals, Inc.