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Ishii, Haruyuki, et al. Microporous and Mesoporous Materials 241 (2017): 366-371.
Dihexadecyldimethylammonium bromide (DHAB), a double-chain quaternary ammonium surfactant, plays a critical structure-directing role in the preparation of mesoporous silica materials with expanded pore sizes. Compared to its shorter-chain analogue, didodecyldimethylammonium bromide (DDAB), DHAB exhibits stronger hydrophobic interactions and enhanced micelle packing, enabling the formation of larger surfactant aggregates. When incorporated during the hydrolysis and condensation of tetraethyl orthosilicate around monodisperse silica cores (<100 nm), DHAB effectively templates a uniformly coated silica shell with significantly enlarged mesopores.
Following calcination at 500 °C, complete surfactant removal yields monodisperse SiO₂@mSiO₂ particles possessing high BET surface area (≈1250 m²/g), large pore volume (≈1.77 cm³/g), and an expanded mesopore diameter centered at ~4.7 nm. The pore-enlargement effect arises directly from the long C16-C16 alkyl chains of DHAB, confirming the critical dependence of mesostructure architecture on surfactant chain length.
In addition to porosity control, the resulting silica shells exhibit intrinsic luminescence originating from uniformly distributed organic residues retained during template removal. The enhanced emission intensity correlates with increased mesoporous shell volume, emphasizing the dual function of DHAB-templated shells in both structural and optical modulation.
Overall, DHAB serves as a powerful mesostructure-directing agent for fabricating large-pore, luminescent mesoporous silica nanomaterials, providing a versatile route for nanoplatforms in sensing, imaging, and drug delivery research.
Guha, Pritam, et al. Colloids and Surfaces A: Physicochemical and Engineering Aspects 546 (2018): 334-345.
Dihexadecyldimethylammonium bromide (DHDAB), a bi-tail quaternary ammonium surfactant, plays a pivotal structural and functional role in the design of hybrid cationic vesicles (HCVs) for advanced drug delivery applications. In the reported system, DHDAB was incorporated into soylecithin/ion-pair amphiphile (SLC/IPA) assemblies to enhance vesicle stability, modulate membrane packing, and facilitate drug encapsulation. Surface pressure-area analyses revealed strong hydrophobic interactions between DHDAB and the SLC/IPA matrix, supporting its efficient intercalation within the bilayer and contributing to robust vesicle formation.
When loaded with piroxicam (Px), the DHDAB-containing vesicles exhibited monodispersity, positive zeta potential, and prolonged colloidal stability for up to two months. The amphiphilic architecture of DHDAB enabled favorable membrane fluidization, as confirmed by AFM, while DSC and FTIR studies indicated that Px resides within the membrane palisade region, enhancing hydration through increased hydrogen bonding. Structural characterization using SANS and SAXS demonstrated that DHDAB contributes to controlled bilayer thickness and lamellar spacing, both critical parameters for drug hosting efficiency.
Importantly, Px-encapsulated DHDAB-modified vesicles exhibited minimal hemolysis (<2%) and significantly enhanced anticancer activity against human neuroblastoma (SH-SY5Y) cells, while maintaining biocompatibility toward normal lymphocytes. These findings highlight DHDAB as an essential structural additive for engineering stable, biocompatible, and therapeutically potent nanocarriers for hydrophobic drug delivery.
Kashiyani, J., et al. Industrial & Engineering Chemistry Research 64.42 (2025): 20122-20136.
Dihexadecyldimethylammonium bromide (DHDAB), a long-chain double-tailed quaternary ammonium surfactant, exhibits exceptional capability in directing cooperative self-assembly within mixed surfactant systems. In aqueous environments, DHDAB forms strongly synergistic assemblies with biologically relevant bile salts such as sodium cholate (NaC) and sodium deoxycholate (NaDC), enabling the construction of robust and tunable nanostructures for biomedical applications.
Thermodynamic analyses derived from surface tension, conductivity, and mixed micelle modeling (Clint, Rubingh, Rosen) demonstrate significantly reduced critical micelle concentrations and negative interaction parameters, confirming strong attractive forces between DHDAB and bile salts. These interactions arise from electrostatic complementarity, hydrophobic chain mismatch, and favorable intermolecular hydrocarbon packing, resulting in spontaneous and entropy-driven micellization.
Structural characterization via DLS, SANS, and TEM confirmed that DHDAB-containing mixtures form vesicular micelles rather than simple spherical aggregates. The observed morphologies correlate with packing parameter predictions, reflecting the influence of DHDAB's dual C16 hydrocarbon chains on curvature and bilayer stabilization.
The resulting mixed vesicles display enhanced stability, tunability, and favorable physicochemical characteristics ideal for nanocarrier design, controlled drug release, and the development of sustainable soft-material platforms. These findings underscore the value of DHDAB as a key structural surfactant for engineering advanced self-assembled nanostructures and highlight its potential in future targeted delivery and functionalized biomedical applications.
