Micellar Properties of Nicotinamide-Based Surfactants K. KALYANASUNDARAM,* T. COLASSIS,* R. HUMPHRY-BAKER,* P. SAVARINO,'~ E. BARNI,'~ E. PELIZZETTI,~ AND M. GRATZEL* * lnstitut de Chimie Physique, Ecole Polytechnique Fdddrale de Lausanne, CH-IOI5 Lausanne, Switzerland; 5i Istituto di Chimica Fisica Applicata, Universitd di Parma, 1-43100 Parma, Italy; and "~ Istituto di Chimica Organica Industriale della Universitd di Torino, 1-10125 Torino, Italy Received September 13, 1988;acceptedJanuary 27, 1989 Data on the critical micellar concentration (CMC) and critical micellar temperature (CMT) are reported for various 1-alkyl-3-carbamoylpyridinium halide surfactants (N-alkylnicotinamides) R-NA+X- (R = C4, C8, Cm, C~2, C14, and C16, X = C1, Br, and I) in aqueous solution. Nicotinamide-based surfactants have critical micelle concentrations similar to that of corresponding alkylpyridinium halide surfactants though the critical micellar temperatures of the former are significantly higher (15-25°C). © 1989 Academic Press, Inc. INTRODUCTION Nicotinamide adenine dinucleotide (NAD + ) is an important cofactor taking part in nu- merous cellular processes, particularly in the intermediary metabolism and in energy con- version reactions (e.g., electron transport and oxidative phosphorylation) ( 1, 2). Also there is growing interest among bioorganic chemists to use NADH in enzyme-mediated asymmet- ric synthesis. Hence various aspects of its chemistry and biochemical mode of action have been subject to detailed scrutiny. It has been firmly established that the nicotinamide moiety is the portion that undergoes the re- versible redox reactions during the numerous processes involving NAD + or NADP +: NAD + + H + + 2e- ~ NADH E~ = -0.320 V vs NHE [1] In connection with our attempts to make a systematic investigation on some of the above cited basic chemistry associated with the nic- otinamide chromophore, we have synthesized and characterized a series of nicotinamide- based surfactants, nicotinamide derivatives in which the pyridinium N is quaternized with long chain alkyl halides, RNA+X - ( 1-alkyl- 3-carbamoylpyridinium halides), as model compounds. Though the synthesis of N-alkyl- nicotinamide has been known for quite some time (3), except for some scattered studies, to our knowledge, there has not been any sys- tematic study on this important class of model compounds. In this paper, we report on our observations on the critical mieellar temper- ature (CMT) and critical micelle concentra- tion (CMC) in aqueous solutions. EXPERIMENTAL Materials. 1-Alkyl-3-carbamoylpyridinium surfactants were synthesized by the reaction ofnicotinamide with a series of 1-haloalkanes in solvents such as xylene or DMF (heating under reflux for 4-8 h) as described in the literature (3-13 ). The product is often insol- uble and precipitated during the reflux. The solution is cooled, precipitate filtered, and washed three times with acetone (only the reactants are soluble in acetone). The product is finally recrystallized from ethanol. Ca, C8, and C10 derivatives were obtained in the form of shiny white powder. C12, C14, and C16 products appeared slightly brownish and were recrystallized from water to obtain shiny white powders. The mp data (°C) for the N-alkyl- 469 Journal of Colloid and Interface Science, Vol. 132,No. 2, October15, 1989 0021-9797/89 $3.00 Copyright© 1989by AcademicPress,Inc. All rightsof reproductionin any formreserved.