Binding of dodecyloxyethylpyridinium bromide to polymer: the effect of molecular geometry of surfactant

Dodecyloxyethylpyridinium bromide (C12EPB) has been synthesized and compare d with the normal N-alkylpyridinium bromides, CnPB (n = 12, 13, 14) to see how the insertion of an oxyethylene group influences the binding behavior t o an oppositely charged linear polymer, sodium poly(2-acrylamide-2-methypro panesulfonate) (PAMPS). The geometry factor of surfactant in micellization and in polymer-surfactant interaction are focused on. The oxyethylene group gives a contribution by - 1.3 kT to the free energy of micellization and b y - 1.4 kT to the free energy of binding. The micelle and the cluster of su rfactant on polymer are considered to consist roughly of two regions, an ou ter region containing the ionic headgroup and the first three or four carbo ns of alkyl chain, and an interior region containing the remaining portions of hydrocarbon chains. The interpositioning of a linkage segment at a-posi tion extends the hydrophobic chain in the inner region and favors the surfa ctant self-association as well as the binding with the oppositely charged p olymer. (C) 1999 Elsevier Science B.V. All rights reserved.