Star-Shaped Trimeric Quaternary Ammonium Bromide Surfactants: Adsorption and Aggregation Properties

Abstract

Novel star-shaped trimeric surfactants consisting of three quaternary ammonium surfactants linked to a tris(2-aminoethyl)amine core were synthesized. Each ammonium had two methyls and a straight alkyl chain of 8, 10, 12, or 14 carbons. The adsorption and aggregation properties of these tris(N-alkyl-N,N-dimethyl-2-ammoniumethyl)amine bromides (3C(n)trisQ, in which n represents alkyl chain carbon number) were characterized by equilibrium and dynamic surface tension, rheology, small-angle neutron scattering (SANS), and cryogenic transmission electron microscopy (cryo-TEM) techniques. 3C(n)trisQ showed critical micelle concentrations (CMC) 1 order of magnitude lower than that of the corresponding gemini surfactants with an ethylene spacer and the corresponding monomeric surfactants. The logarithm of the CMC decreased linearly with increasing hydrocarbon chain length for 3C(n)trisQ. The slope of the line, which is well-known as Klevens equation, was larger than those of the monomeric and gemini surfactants; however, considering the total carbon number in the chains, the slope was shallower than the monomeric and was close to the gemini. Through the results such as surface tensions at the CMC (32-34 mN m(-1)) and the parameters of standard free energy, CMC/C(20) and pC(20), it was found that 3C(n)trisQ could adsorb densely at the air/water interface despite the strong electrostatic repulsion between multiple quaternary ammonium headgroups. Moreover, dynamic surface tension measurements showed that the kinetics of adsorption for 3C(n)trisQ to the air/water interface was slow because of their bulky structures. Furthermore, the results of rheology, SANS, and cryo-TEM determined that 3C(n)trisQ with n = 10 and 12 formed ellipsoidal micelles at low concentrations in solution and the structures transformed to threadlike micelles with very few branches for n = 12 as the concentration increased, but for n = 14 threadlike micelles formed at relatively low concentrations.

Self-assembling systems based on diquaternized derivatives of 1,4-diazabicyclo[2.2.2]octane

“…Therefore, the design of novel cationic surfactants with advanced characteristics is in the focus of modern technologies. One of the basic trends in these fields is to explore multicharged surfactants capable of cooperative interactions with bound substrate [5][6][7][8]. For this reason, much attention is devoted to gemini surfactants (m-s-m geminis) demonstrating marked advantages in micellization, adsorption and binding activity.…”

Scaffold‐Hopping of Multicationic Amphiphiles Yields Three New Classes of Antimicrobials

“…[21] Thus, alkylation with the corresponding alkyl bromide (3 equivC n H 2n + 1 Br,a cetonitrile, reflux, overnight) led strictly to trisalkylation,f urnishingt he T-n,n,n series (34-40) in 70-95 %y ield after trituration. Again, there was no subsequent reactivityo bserved for the resultant tertiary amine in the T-n,n,n series, which reflects the electronic environment of Scheme2.To p: Polyamine startingc ore structures, based on previous core 7:the P-series (8,p iperazine), the C-series (9,cyclononyl), and the T-series (10,T -shapedtetramine).…”

A C18 Quaternary Ammonium Library

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