In this Letter, we report the controlled selective excitation of vibrational modes in the electronic ground state of polymers of diacetylene. The technique applied for exciting and probing is femtosecond time-resolved four-wave mixing spectroscopy with broad-band detection. We use a coherent anti-Stokes Raman scheme, where the difference of pump and Stokes laser wavelengths is chosen to achieve resonance with several chain modes of the polydiacetylenes. By varying the timing and the phases of the femtosecond laser pulses, the timing and intensity of these modes can be strongly influenced.