The role of an initiator (perfluorooctane sulfonyl fluoride, PFOSF) in the polymerization of 1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane (V3D3) by hot-filament chemical vapor deposition has been demonstrated. Use of the initiator allows rapid deposition of films at significantly lower filament temperatures. Polymerization is initiated when radical species produced by the pyrolysis of PFOSF react with V3D3. Chain propagation occurs along the vinyl bonds of V3D3, resulting in chains with hydrocarbon backbones and siloxane rings as pendant groups. Chains are terminated by fluorocarbon radicals, sulfonyl fluoride radicals, or other propagating chains.