ether coatings differential scanning photocalorimetry dsp is known to be useful for directly monitoring the rate and extent of the cationic photoinitiated polymerizations of epoxide monomers this method was employed to determine the general order of propenyl ether reactivity with respect to vinyl ethers and epoxides of similar structure using identical amounts of the same photoinitiator the photopolymerizations of propenyl ethers were found to be extremely rapid a comparison of the three curves showed that the propenyl ether monomers were very much more reactive than epoxides as well as considerably more reactive than analogous vinyl ethers propenyl ether monomers are the most rapidly polymerizing monomers yet examined in photoinitiated cationic polymerization as a result dsp is not sufficiently sensitive to allow it to be used for distinguishing among the reactivities within a series of related propenyl ethers real time infrared spectroscopy rtir has been shown to be an excellent method for determining both the rate and extent of free radical and cationic photopolymerizations it is particularly advantageous for following the rates of extremely rapid photopolymerizations the application of this technique involves simultaneous uv irradiation of a monomer while monitoring the decrease of the characteristic band at 1660 1680 cm 1 due to the carbon carbon double bond of the propenyl ether group a thin 25 u03bcm layer of the liquid monomer containing the photoinitiator was placed between two.