Multiple thin film formation from dilute mixtures of polyethyleneimine (PEI) and cetyltrimethylammonium bromide (CTAB)

Self-assembly and phase behaviour of PEI : cationic surfactant aqueous mixtures forming mesostructured films at the air/solution interface

“…It is important to note that lm formation boundary is in agreement with the previously reported hypothesis of the existence of a limiting surfactant concentration below which no lm formation is observed at the surface. 20 In that work, we reported 0.13 mmol L À1 as the surfactant concentration remaining in solution aer the formation/removal of eleven lms (initial composition: 1 mmol L À1 CTAB and 0.5% PEI). This value of limiting concentration lies in the CFFC boundary of PEI : CTAB phase diagram reported here (Fig.…”

“…This is mainly due to the screening by the polymer between micelles in the lm. 20 At higher polymer concentrations, PEI incorporation reaches saturation and since the polymer is essentially neutral it does not affect d-spacing; however, at lower concentrations the repulsion threshold is overcome and the mesostructure expands. In the dilute regime, the d-spacing remains constant upon changes in composition, which seems a consequence of the low level of micelle repulsion within the lm due to such low surfactant concentrations.…”

“…The same distance (52 Å) was previously reported as the d-spacing characteristic of mesostructured lms grown in the PEI : CTAB system. 19,20 Therefore, the cationic surfactant headgroup structure does not exert a signicant inuence on this value for lm forming mixtures within a dilute regime (i.e. #CMC and 1% of PEI).…”

“…Interestingly, multiple lm regeneration can occur as long as the surfactant concentration in the bulk solution remains greater than a lower limiting value. 20 Taking into account the potential applications that could be designed for such PEI : CTAB systems in elds ranging from encapsulation, 21 coatings, delivery, and catalysis to templating, 22,23 more fundamental studies are needed in order to understand the main processes leading to lm formation and mesostructure growth, to achieve control over structure and function. Two aspects not yet studied in these similarly charged systems are the inuence of surfactant structure on the selfassembly processes and the determination of the lowest surfactant concentration below which there is no lm formation.…”

Magnetic titania-silica composite–Polypyrrole core–shell spheres and their high sensitivity toward hydrogen peroxide as electrochemical sensor

“…S3c shows the TEM image of the aerosol particles containing mesopores instead of macropores without the addition of iron chloride. Under this condition, there is no formation of CTA + X À1 Fe 3+ large colloids template for the macropores in the solution and the mesopores are templated by CTAB micelles [34,51]. The sensor materials were prepared based on the inorganic particles with two kinds of oxides and PPy polymer.…”