A detailed study of polysiloxane nanofiber formation by surface initiated polymerization of vapor phase organotrichlorosilane reagents is presented. Substrate composition, substrate activation, reagent quantity, reaction pressure, and reaction time are parameters shown to influence nanofiber synthesis. Stepwise variation of the parameters isolates the role of each on polysiloxane nanofiber growth, and a mechanism for fiber formation is proposed based on these findings. Tunable aqueous wettability of the fibers is also demonstrated in this report, with contact angles varying from 85 degrees to 130 degrees +/-2 degrees depending upon fiber surface density and length. Aqueous contact angles are further increased to > 150 degrees by either solution functionalization of calcined fibers or copolymerization with an organofluorosilane reagent.