Experimental and Theoretical Approach to Nonequivalent Adsorption of Novel Dicephalic Ammonium Surfactants at the Air/Solution Interface

Department of Chemistry, Wrocław University of Technology, Poland.
The Journal of Physical Chemistry B (Impact Factor: 3.3). 08/2010; 114(32):10471-80. DOI: 10.1021/jp1049809
Source: PubMed


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.

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    • "The work reported here extends our recent studies on new drug delivery nanocarriers, their fabrication and imaging , drug encapsulation, release profiles and biological impact [19] [20] [21] [22] 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: 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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