Nonionic Urea Surfactants:  Influence of Hydrocarbon Chain Length and Positional Isomerism on the Thermotropic and Lyotropic Phase Behavior

Abstract

The thermotropic and lyotropic phase behavior of 1- and 5-decyl urea, and 1-, 2-, 4-, and 6-dodecyl urea have been studied. This allowed the effect of positional isomerism to be examined. Intermolecular hydrogen bonding by the urea moiety is the dominant factor in determining the solid-state thermal behavior and crystal solubility boundary of these linear nonionic surfactants. The positional isomers where the urea moiety was not situated at the terminus of the hydrocarbon chain exhibited higher melting points than the 1-alkyl ureas. This has been rationalized by postulating interdigitated chains in the solid state. In the urea surfactant-water systems, three phases are observed, viz. crystalline solid, a dilute aqueous solution of the alkyl urea, and an isotropic liquid. The last two phases coexist in the low-surfactant, high-temperature region of the binary phase diagram. An overview of structure-property correlations for linear nonionic urea surfactants is presented in light of the new physicochemical data obtained for the decyl urea and dodecyl urea positional isomers.

Dimeric and monomeric surfactants derived from sulfur-containing amino acids

“…The surfactants lack antimicrobial activity, which can be due to their short hydrophobic tail of only eight carbon atoms [37][38][39], however increase of the hydrocarbon chain is likely to be accompanied by a decrease in water solubility [16][17][18][19].…”

“…The urea moiety that links the amino acid residue to the hydrophobic portion of the surfactants may alter the properties of these compounds by means of intra-and inter-molecular hydrogen bonding and offers the additional advantage of potential antifungal/antiviral activities [13][14][15], while the amino acid residue renders them water-soluble, as most of nonionic surface active ureas reported in the literature suffer from low water solubility [13][14][15][16][17][18][19]. The compounds thus obtained can be considered as N-carbamoylamino acids, a class of amino acid-based surfactants that is seldom described in the literature.…”

Lamellar crystalline self-assembly behaviour and solid lipid nanoparticles of a palmityl prodrug analogue of Capecitabine—A chemotherapy agent

“…At low temperatures, the crystals and solution coexist. As the temperature is increased above the crystal solubility temperature (CST), the crystal changes to an isotropic liquid phase that coexists with the solution [39].…”

A Family of Hydrogels Based on Ureido‐Linked Aminopolyol‐Derived Amphiphiles and Bolaamphiphiles: Synthesis, Gelation under Thermal and Sonochemical Stimuli, and Mesomorphic Characterization

“…[27] This behavior has been previously studied in a series of linear nonionic urea surfactants derived from decyl and dodecyl ureas, the intermolecular hydrogen-bonding by the urea moiety being the dominant factor in determining the solid-state thermal behavior and crystal solubility boundary. [28] In this study, the surfactant properties of the amphiphilic molecules could be further assessed by means of surface-pressure-molecular-area isotherms and estimations of the critical micelle concentrations, as shown in the Supporting Information.…”