A comparison between Shirakawa polyacetylene or S-(CH)(x), Naarmann polyacetylene or N-(CH)(x), and Tsukamoto polyacetylene or nu-(CH)(x) during iodine vapor phase doping has been made. Thin films of each type of polyacetylene were polymerized directly onto quartz crystal substrates. The quartz crystal microbalance (QCM) is used to measure the mass change during doping (oxidation) of polyacetylene with iodine in the vapor phase. For the same mass of dopant, the highest conductivity is observed for nu-(CH)(x). The most dense polyacetylene, nu-(CH)(x), has the smallest diffusion coefficient on the order of 10(-14) cm(2)/s. The diffusion coefficient for short times (<3000 s) is similar for all three types of polyacetylene (10(-12) cm(2)/s); however, at longer times (10 000-70 000 s), the diffusion coefficients correlate with the densities of the undoped materials.