Detection of deposition rate of plasma-polymerized films by quartz crystal microbalance

The deposition rates of plasma-polymerized (pp-) films of styrene, pentafluorostyrene, allyl alcohol, allylamine, methacrolein, acrolein, and acrylic acid were determined by the quartz crystal microbalance technique. Using the same polymerization conditions (100 W RF and 100 Pa vapor pressure) for the various monomers, it was found that the deposition rates were proportional to the polymerization time. The deposition rates of pp-styrene, pp-pentafluorostyrene, pp-allyl alcohol and pp-allylamine were independent of the position of the lower electrode in the plasma polymerization equipment. In contrast, the deposition rates of pp-methacrolein, pp-acrolein and pp-acrylic acid were scattered. The average deposition rate of pp-allyl alcohol was 0.42 μg/min. The average deposition rate of pp-styrene was higher by eight times, and that of pp-pentafluorostyrene was higher by 388 times than that of pp-allyl alcohol. The average deposition rate depended on the chemical structure of the monomer, giving rise to different mechanisms of polymerization. The deposition rates of monomers containing allylic hydrogens were slow due to radical-radical coupling. These unexpected but significant differences were assumed to have arisen from initiation-controlled free radical polymerization.