Aqueous phase behavior of salt-free catanionic surfactants: the influence of solubility mismatch on spontaneous curvature and balance of forces

• Tipo: Artigo em Revista Científica Internacional
• Data: 2011

Autores

Bruno F B Silva (Autor) Outra; Eduardo F Marques (Autor) FCUP; Ulf Olsson (Autor) Outra

Revista

Título: Soft Matter

Vol. 7 Nº 1

Páginas: 225-236

ISSN: 1744-683X

Editora: Royal Society of Chemistry

Indexação

ISI Web of Knowledge - 35 Citações

Scopus - 37 Citações

Classificação Científica

FOS: Ciências da engenharia e tecnologias > Engenharia dos materiais

CORDIS: Ciências Físicas > Química > Química física > Química das superfícies ; Ciências Físicas > Física > Termodinâmica > Termodinâmica aplicada

Outras Informações

ID Authenticus: P-002-ZJA

DOI: 10.1039/c0sm00477d

Abstract (EN): In this paper, we investigate the phase behavior and microstructure for a series of salt-free catanionic surfactants of the type Cm+Cn- with varied chain length mismatch (m not equal n), using light microscopy, DSC, turbidity, surface tension, SAXS and SANS. The compounds consist of alkyltrimethylammonium alkylsulfonates, denoted by TA(m)So(n). Depending on the asymmetry between both ions, three regimes can be identified: (i) weakly asymmetric; (ii) approximately symmetric; and (iii) highly asymmetric. For the TA(16)So(n) compounds, with n = 8 and 9 (weakly asymmetric), the surfactant forms a lamellar phase in water, however, with a striking miscibility gap. This miscibility gap is a consequence of the concentration dependent bilayer charge density. For n = 8, also a temperature-dependent vesicle-to-micelle transition at low surfactant concentration is observed. When the mismatch is low (n = 10) only a non-swelling lamellar phase is formed (approximately symmetric regime). For high mismatch, (n = 6 and 7) an extensive micellar phase is obtained - highly asymmetric regime. Conversely, for the TA(m)So(8) compounds, where m = 12 and 14, the unconventional lamellar miscibility gap and vesicle-micelle transition are again present. These findings are rationalized by considering the effect of film charge density-arising from the chain solubility difference-on the spontaneous curvature and balance of colloidal forces. The type of phase behavior reported here should be extensive to other families of salt-free catanionic amphiphiles, where an appropriate tuning of the solubility mismatch can allow the control of self-assembly.

Idioma: Inglês

Tipo (Avaliação Docente): Científica

Nº de páginas: 12