STUDY OF THE POLARITY AND HYDROGEN-BOND ABILITY OF DODECYLTRIMETHYLAMMONIUM BROMIDE MICELLES BY THE KAMLET-TAFT-SOLVATOCHROMIC-COMPARISON-METHOD

We have studied the dipolarity/polarizability (pi), hydrogen-bond don or acidity (alpha), and hydrogen-bond acceptor basicity (beta) of dode cyltrimethylammonium bromide (DTAB) micelles using the Kamlet-Taft sol vatochromic comparison method. DTAB micelles were found to be quite po lar (pi = 1.02), to have relatively strong hydrogen-bond donating abi lity (alpha = 0.700), and to have moderate hydrogen bond accepting abi lity (beta = 0.486). These values are compared to the pi-, alpha-, an d beta-values of sodium dodecyl sulfate (SDS) micelles obtained in a p revious solvatochromic study and are found to be qualitatively consist ent with linear solvation energy relationship studies of both SDS and DTAB micellar systems. The chemical interpretation of these parameters and the nature of DTAB micelles which they reflect are discussed. By comparison to the solvatochromic parameters of representative pure sol vents such as DMSO (pi = 1.00), 2-propanol (alpha = 0.69), and ethylbe nzoate (beta = 0.43), it is evident that the micellar environments obs erved by the various indicators are quite dipolar. very strong hydroge n bond donors, and moderately strong hydrogen bond accepters.