Metal-insulator-semiconductor structures were fabricated using a polymerizable diacetylene film on silicon substrates using the Langmuir-Blodgett technique. A mercury probe was used to measure the high frequency capacitance-voltage (C-V) characteristics of the structure. The C-V curves indicate accumulation, depletion and deep depletion of the silicon surface. The dielectric constant of the 10,12-nonacosadiynoic acid (16-8 polydiacetylene) film was calculated to be 2.13. The effective fixed charge density at the insulator-silicon interface ranged from 10¹⁰ to 10¹¹ cm⁻². Hysteresis was observed in the C-V curves and appears to be consistent with charge trapping at the silicon-insulator interface. Using the C-V technique as a criterion, the polydiacetylene was thermally stable up to 120 °C.