Concerning the self-association of N-vinyl pyrrolidone and its effect on the determination of equilibrium constants and the thermodynamics of mixing

Hydroxylated (co)polymers from miscible blends with a wide variety of (co)p olymers that contain proton acceptor groups, such as esters, ethers, pyridi nes, etc. The former strongly self-associate through the formation of OH/OH hydrogen bonded interactions, while the latter do not self-associate to an y measurable extent. With appropriate self- and interassociation equilibriu m constants and enthalpies of hydrogen bond formation, we have been able in the past to successfully predict the phase behavior of such hydrogen bonde d polymer blends. At first glance, the vinyl pyrrolidone group appears to b e just another proton acceptor and if the appropriate interassociation equi librium constant value is determined we should be able to predict the phase behavior of hydroxylated (co)polymer blends with (co)polymers containing t he vinyl pyrrolidone group. However, it is not that simple. Using infrared spectroscopy we demonstrate in this work that the pyrrolidone group strongl y self-associates through transition dipole coupling. Ramifications to the determination of equilibrium constants, the free energy of mixing and the p hase behavior of blends involving the vinyl pyrrolidone group are discussed .