PYRROLIDONE-BASED SURFACTANTS (A LITERATURE-REVIEW)

As the alkyl group of N-alkylated pyrrolidones is increased to C8P, surface-active properties become important. The resulting surfactant can interact synergistically with an anionic surfactant. This interaction is based on the electronegativity of the pyrrolidone carbonyl oxygen which can accept a proton to form a pseudoquaternary ammonium ion that can form an ion pair with large anions (i.e., anionic surfactants). The resulting ion pair is further stabilized by hydrophobic bonding between the two alkyl chains. In addition, pyrrolidone can electrostatically interact with aromatics, hydrogen-bond to nonionics, and, in essence, associate electrostatically/hydrophobically similarly to polyvinylpyrrolidone. This interaction of the pyrrolidone functional group can be transposed from one surfactant hydrophobe structure to another. This paper reviews the literature concerning the addition of pyrrolidone to a variety of hydrophobes of interest to both industrial and academic researchers. The chemistry of selected surface-active pyrrolidone derivatives, prepared from butyrolactone, aminoethylpyrrolidone, epoxypropylpyrrolidone, chloromethylpyrrolidone and itaconic acid, is reviewed. Pyrrolidone is a versatile substituent, capable of enhancing the performance of a variety of surfactant I structures by improving water solubility, compatibility and solvency in a compact head group that favors surfactancy. In addition, the pyrrolidone ring, when incorporated into derivatives, usually reduces toxicity.