Direct visualization of cationic surfactant aggregates at a cellulose-water interface

Area of Science:

• Surface science
• Colloid and interface science
• Materials chemistry

Background:

• Surfactant adsorption on surfaces is crucial for various applications.
• Understanding aggregate structure at interfaces informs material properties.
• Cellulose interfaces present unique challenges for surfactant assembly.

Purpose of the Study:

• To determine the structure of adsorbed cetyltrimethylammonium bromide (C(16)TAB) aggregates at the cellulose-water interface.
• To elucidate the mechanism of C(16)TAB adsorption and admicelle formation on cellulose.
• To compare C(16)TAB aggregation on cellulose with other hydrophilic surfaces.

Main Methods:

• Soft-contact atomic force microscopy (AFM) imaging was employed.
• C(16)TAB was adsorbed from a solution above its critical micelle concentration.
• Neutron reflectivity data was considered for mechanistic comparison.

Main Results:

• Predominantly spherical micellar structures (admicelles) were observed at the cellulose-water interface.
• Some areas exhibited short rod-like aggregates.
• The findings suggest a similar adsorption mechanism to that on silica surfaces.

Conclusions:

• The buildup of the surfactant layer occurs through direct micelle adsorption.
• Polar interactions between the C(16)TAB headgroup and the cellulose surface drive admicelle formation.
• The observed admicelle structures are consistent with previous studies on similar hydrophilic substrates.