pH-sensitive surfactants find applications in many fields, including responsive drug delivery and smart material design. The rational design of the surfactant molecular structure leads to species presenting strong variations of the micellization parameter (e.g., critical micelle concentration, cmc, and aggregate dimension) in a controlled pH range. In the present work, the micellization of the branched amine oxide surfactant N,N-dimethyl-2-propylheptan-1-amine oxide (C10DAO-branched) is studied as a function of pH in dilute aqueous mixtures. Its behavior is compared with that of the linear isomer N,N-dimethyldecan-1-amine oxide (C10DAO-linear). The samples are investigated by potentiometric titrations, fluorescence spectroscopy, and Dynamic Light Scattering (DLS). With increasing pH, micellized C10DAO-branched presents a higher tendency to remain in the protonated/cationic form with respect to the linear isomer. As a consequence, the minimum cmc value, observed when the protonated and the deprotonated/zwitterionic forms of the surfactant coexist in the micelles, is shifted to higher pH values. The volume of these C10DAO-branched “mixed micelles” is more than one order of magnitude higher than that of completely protonated or deprotonated aggregates. This is a singularity of the branched surfactant, not observed for the linear isomer. Overall, the results highlight that the branched molecular architecture of the surfactant tail, favoring the formation of low-curvature aggregates, enhances H-bonding between the protonated and deprotonated headgroups, which synergistically stabilizes the flatter surface of bulkier aggregates. Taking into account the good biodegradability of surfactants with a limited number of short side chains, purposely designed branched surfactants appear as a suitable option to accurately tune supramolecular aggregation in pH-responsive formulations.

pH-responsive micellization of an amine oxide surfactant with branched hydrophobic tail / Scermino, L.; Fabozzi, A.; De Tommaso, G.; Valente, A. J. M.; Iuliano, M.; Paduano, L.; D'Errico, G.. - In: JOURNAL OF MOLECULAR LIQUIDS. - ISSN 0167-7322. - 316:(2020), p. 113799. [10.1016/j.molliq.2020.113799]

pH-responsive micellization of an amine oxide surfactant with branched hydrophobic tail

Scermino L.;Fabozzi A.;De Tommaso G.;Iuliano M.;Paduano L.;D'Errico G.
2020

Abstract

pH-sensitive surfactants find applications in many fields, including responsive drug delivery and smart material design. The rational design of the surfactant molecular structure leads to species presenting strong variations of the micellization parameter (e.g., critical micelle concentration, cmc, and aggregate dimension) in a controlled pH range. In the present work, the micellization of the branched amine oxide surfactant N,N-dimethyl-2-propylheptan-1-amine oxide (C10DAO-branched) is studied as a function of pH in dilute aqueous mixtures. Its behavior is compared with that of the linear isomer N,N-dimethyldecan-1-amine oxide (C10DAO-linear). The samples are investigated by potentiometric titrations, fluorescence spectroscopy, and Dynamic Light Scattering (DLS). With increasing pH, micellized C10DAO-branched presents a higher tendency to remain in the protonated/cationic form with respect to the linear isomer. As a consequence, the minimum cmc value, observed when the protonated and the deprotonated/zwitterionic forms of the surfactant coexist in the micelles, is shifted to higher pH values. The volume of these C10DAO-branched “mixed micelles” is more than one order of magnitude higher than that of completely protonated or deprotonated aggregates. This is a singularity of the branched surfactant, not observed for the linear isomer. Overall, the results highlight that the branched molecular architecture of the surfactant tail, favoring the formation of low-curvature aggregates, enhances H-bonding between the protonated and deprotonated headgroups, which synergistically stabilizes the flatter surface of bulkier aggregates. Taking into account the good biodegradability of surfactants with a limited number of short side chains, purposely designed branched surfactants appear as a suitable option to accurately tune supramolecular aggregation in pH-responsive formulations.
2020
pH-responsive micellization of an amine oxide surfactant with branched hydrophobic tail / Scermino, L.; Fabozzi, A.; De Tommaso, G.; Valente, A. J. M.; Iuliano, M.; Paduano, L.; D'Errico, G.. - In: JOURNAL OF MOLECULAR LIQUIDS. - ISSN 0167-7322. - 316:(2020), p. 113799. [10.1016/j.molliq.2020.113799]
File in questo prodotto:
Non ci sono file associati a questo prodotto.

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11588/847975
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 13
  • ???jsp.display-item.citation.isi??? 14
social impact