Aggregation behavior of surfactants with cationic and anionic dendronic head groups

• Published in: Journal of colloid and interface science 2019-01, Vol.534, p.430-439
• Main Authors: Chiappisi, Leonardo, Keiderling, Uwe, Gutierrez-Ulloa, Carlos E., Gómez, Rafael, Valiente, Mercedes, Gradzielski, Michael
• Format: Article
• Language: English
• Subjects: Dendrimeric surfactants; Self-assembly; Small-angle neutron scattering
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/j.jcis.2018.09.005

[Display omitted] Ionic dendronic head groups possess very different structural features than simple surfactant head groups. Accordingly, their self-assembly behavior is expected to differ from that of conventional surfactants. The number of generations of the headgroup should play a particularly relevant role. A novel type of surfactants with different dendronic head groups (cationic and anionic) was studied in this work. A systematic variation of the number of generations of the head group (n = 1, 2, and 3), of the head group charge (cationic and anionic), and of the length of the hydrophobic chain (hexanoyl and hexadecanoyl chains) was performed and the self-assembly behavior probed by means of small-angle neutron scattering (SANS) in order to obtain detailed structural insights. The analysis of the scattering data shows that the general packing parameter concept applies also to dendrimeric surfactants and a larger head group results in smaller aggregates. However, in contrast to conventional surfactants, increasing the head group size results in a stronger tendency to self-aggregate, as a consequence of the head group’s partly hydrophobic character. Another peculiarity of the self-assembled aggregates, is the low aggregation numbers and the high water content within the micelle, as a result of the highly branched head group.