A series of end-capped polyalkylene glycols (PAG) (n-butyl,n-alkyl-substituted polypropylene glycols) and polypropylene glycols (PPG) (dialkyl-, dihalo-, bis(fluoroalkyl)-substituted polypropylene glycols) were synthesized. Optimum reaction conditions were determined with regard to time, temperature, reaction ratios, and solvents for each of the PAG and PPG derivatives. An investigation was carried out to find their suitability as potentially new sonar transducer fill fluids. The density, viscosity, and speed of sound were measured as a function of temperature, and their solubilities in water were measured for several of these derivatives. The desirable properties of some of these compounds make them potentially important transducer fill fluids.