Monitoring the Transition from Spherical to Polymer‐like Surfactant Micelles Using Small‐Angle X‐Ray Scattering

Abstract

Despite over a century of modern surfactant science, the kinetic pathways of morphological transitions in micellar systems are still not well understood. This is mainly as a result of the lack of sufficiently fast methods that can capture the structural changes of such transitions. Herein, a simple surfactant system consisting of sodium dodecyl sulfate (SDS) in aqueous NaCl solutions is investigated. Combining synchrotron radiation small-angle X-ray scattering (SAXS) with fast stopped-flow mixing schemes allows monitoring the process where polymer-like micelles are formed from globular micelles when the salt concentration is suddenly increased. The results show that "worm-like" micelles are formed by fusion of globular micelles and short cylinders in a fashion that bears similarities to a step-like polymerization process.

Synthesis and Design of Aggregation‐Induced Emission Surfactants: Direct Observation of Micelle Transitions and Microemulsion Droplets

“…[2] Kinetic monitoring of transition processes of micelles from spherical to wormlike micelles by in situ small-angle X-ray scattering (SAXS) has led to an impressive amount of data. [3] Thed evelopment of av isualization technology would open new opportunities for the interrogation of the world of micelles.H owever,t he direct visualization of micelle transitions by ah igh-contrast fluorescence imaging method has not yet been described.…”

Molecular Programming of Biodegradable Nanoworms via Ionically Induced Morphology Switch toward Asymmetric Therapeutic Carriers

“…Particle stability was confirmed when no changes in the correlation data were observed during incubation under physiological conditions. Indeed, sodium dodecyl sulfate (SDS) micelles only undergo spontaneous morphological transitions when [NaCl] reached 1 m , which is well above physiological conditions . The critical aggregation concentration (CAC) was determined using a 1‐anilino‐8‐naphthalenesulfonate (ANS) assay.…”

“…Indeed, sodium dodecyl sulfate (SDS) micelles only undergo spontaneous morphological transitions when [NaCl] reached 1m, which is well above physiological conditions. [25] The critical aggregation concentration (CAC) was determined using a 1-anilino-8-naphthalenesulfonate (ANS) assay. CAC values of SMs were measured at ≈0.030 mg mL −1 (2.7 × 10 −6 m), with NWs displaying a slightly lower CAC at ≈0.022 mg mL −1 (2.0 × 10 −6 m) ( Figure S33, Supporting Information).…”

A matéria mole e a luz síncrotron

“…O trabalho revelou que o processo deve ocorrer a partir de sucessivos processos de fusão dos agregados globulares, formando agregados cada vez mais alongados, em uma escala de tempo de até dezenas de nanosegundos (8). …”