Dissolution inhibitory effect of a urea additive on a carboxyl polymer through a supramolecular structure

The effect of the addition of carbonyl compounds such as amide, imide, urea , and ester derivatives on the dissolution rate of carboxyl-group-containin g polymers in an alkaline solution was investigated. Urea derivatives lower ed the dissolution rate of the polymer film more than the ether carbonyl co mpounds did, and 1,3-diphenylurea inhibited the dissolution of the polymer film much more efficiently than other urea derivatives. Structural studies of the dissolution inhibition led to the proposal of a supramolecular struc ture, in which the urea functionality hydrogen bonded to two carboxyl group s of the polymer to form a hydrophilic domain surrounded by the hydrophobic substituents of the urea derivatives. The existence of this supramolecular structure is supported by the infrared spectra of the urea additives in th e polymer films.