Experimental and Theoretical Approach to Nonequivalent Adsorption of Novel Dicephalic Ammonium Surfactants at the Air/Solution Interface
The interfacial behavior of novel dicephalic cationic surfactants, N,N-bis[3,3'-(trimethylammonio)propyl]alkylamide dibromides and N,N-bis[3,3'-(trimethylammonio)propyl]alkylamide dimethylsulfates, was analyzed both experimentally and theoretically in comparison to their linear standards, 3-[(trimethylammonio)propyl]dodecanamide bromide and 3-[(trimethylammonio)propyl]dodecanamide methylsulfate. Adsorption of the studied double head-single tail surfactants depends strongly upon their structure, making them less surface active in comparison to the single head-single tail structures having the same alkyl chain length. Surface tension isotherms of aqueous solutions of the studied dicephalic derivatives were measured using the pendant drop shape analysis method and interpreted with the so-called surface quasi-two-dimensional electrolyte (STDE) model of ionic surfactant adsorption. The model is based on the assumption that the surfactant ions and counterions (bromide and methylsulfate ions in the studied case) undergo nonequivalent adsorption within the Stern layer, and it allows for accounting for the formation of surfactant ion-counterion associates in the case of multivalent surfactant headgroup ions. As a result, good agreement between theory and experiment was obtained. Additionally, the presence of surfactant-counterion complexes was successfully confirmed by both measurements of the concentration of free bromide ions in solution and molecular modeling simulations. The results of the present study may prove useful in the potential application of the investigated dicephalic cationic surfactants.
Available from: Michał Sowa
- "The work reported here extends our recent studies on new drug delivery nanocarriers, their fabrication and imaging , drug encapsulation, release profiles and biological impact     and has been mainly focused on determination and comparing of three different preparation techniques, i.e., solventdiffusion (SD), hot homogenization-ultrasonification (HHU) and microemulsification (ME) of biocompatible phosphatidylcholine (PC)-SLNs, containing Polawax NF in the internal lipid phase. All these experiments were attempted to describe the physical state and stability, as well as enhanced availability in aqueous SLN dispersions of newly prepared flavonoid cocrystals, i.e., baicalein–nicotinamide (1:1) (BaiNam), myricetin–piracetam (1:1) (MyrPac) and myricetin–caffeine (1:1) (MyrCaf) cocrystals in relation to the starting flavonoids (for structures and abbreviations see Scheme 1). "
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ABSTRACT: The present study has been focused on determination and evaluation of three different preparation techniques i.e., solvent-diffusion, hot homogenization-ultrasonification and microemulsification, applied in fabrication of biocompatible phosphatidylcholine solid lipid nanoparticles ((PC)-SLNs), containing Polawax National Formulary (NF) in the internal lipid phase. The fabricated lipid nanoparticles were loaded with the newly synthesized flavonoid cocrystals i.e., baicalein-nicotinamide (1:1) (BaiNam), myricetin-piracetam (1:1) (MyrPac) and myricetin-caffeine (1:1) (MyrCaf) cocrystals in relation to the starting flavonoids, differing in solubility and physical state. The assessment of all studied drugs entrapment and availability in aqueous SLN dispersions has been carried out; the size along with size distribution of lipid nanoparticles loaded with the studied flavonoids cocrystals and flavonoids was determined by the DLS technique, while the structural changes–by FT-IR spectroscopy and X-Ray powder diffraction (XRPD) of the lipid nanomatrices. XRPD and FT-IR analyses confirmed that parent flavonoids as well as their cocrystals are present in the nanoparticles fabricated with solvent-diffusion method as physical mixtures with the lipid and their crystalline structures at least partially conserved. Summarizing, we designed and fabricated the biocompatible SLN-type nanocarriers of enhanced physical stability and availability for the flavonoids delivery - a vast group of naturally occurring polyphenolic compounds, considered as active pharmaceutical ingredients.
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ABSTRACT: Novel dicephalic surfactants containing a quaternary ammonium and a guanidine group were synthesized, and the effect of the alkyl chain length on micellization and antimicrobial activity were investigated. Surface tension and conductivity were applied to study the self-aggregation of the amphiphilic molecule in aqueous solution. The results indicated that these compounds reduce the surface tension to a level of 30–36 mN/m at the air/water interface and that there is a characteristic chain length dependence of the micellization process of surfactants. The antimicrobial activity was evaluated against Gram-negative, Gram-positive bacteria and fungi, indicating strong antibacterial activity against tested strains.
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ABSTRACT: In the present work new sorbic acid amphiphilic derivatives are characterized. One single-chain quaternary ammonium bromide bearing sorbic group, sorbyloylundecyltrimethyl ammonium bromide, and three analogical double-chain, so-called gemini, surfactants with propylene, butylene and hexylene spacers were obtained. Chemical data, interfacial activity (CMC values: 2.3–12.3 mM) and micellar properties were investigated for both single-chain and gemini compounds.Cationic surfactants include a positively charged nitrogen atom, which is able to conduct charges, and thus quaternary salts are known for their anti-electrostatic properties. It is very important, especially in a low hygroscopic atmosphere with a high dust level, to easily conduct any charge from the surface of protective garments, i.e. glasses, clothing and other objects. Synthesized compounds revealed very good or excellent capacities to neutralize charges appearing on polyethylene and polypropylene surfaces. The values of surface resistance Rs (0.001–9 × 1011 Ω), charge half-decay times τ1/2 (0.20–8.70 s) and induced potentials Uind (46–850 V) of these polymers impregnated with surfmers are presented. However, these were only the results appearing before the first wash. Compounds presented in the work were designed to be able to polymerize. The presence of a polymerizable sorbic group at the hydrophobic terminal allowed us to prepare a layer on the surface of polymers, by impregnating foil and fabric with surfmer solutions and direct UV irradiation polymerization processes. Unpolymerized layers can be washed off the polymeric surfaces, but after irradiation conductive properties are still acceptable even after washing, especially on polypropylene.
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