Cable-like copper nanowires (1-10 mum in length and 15-80 nm in diameter) with an insulating poly(dimethylsiloxane) (PDMS) sheath (510 nm in thickness, see Figure) have been successfully synthesized by a solvent-free reaction between CuCl and (Me3Si)(4)Si in the presence of PDMS in sealed tubes. The wire formation mechanism is proposed to be vapor-solid reaction growth.