High performance controlled reactors from micellar assemblies of aromatic amino acid amphiphiles for nanoparticle synthesis

Microscopic properties and stabilization mechanism of a supercritical carbon dioxide microemulsion with extremely high water content

HYPOTHESIS

Developing the supercritical carbon dioxide microemulsion with a broad water content (W₀) window can provide more possibility for designing highly efficient chemical processes, which is challenging due to the lack of comprehension about its formation mechanism. Molecular dynamics simulation method is expected to reveal the microscopic stabilization mechanism of high-W₀ microemulsions.

SIMULATIONS

All-atom molecular dynamics simulations of the ternary systems with varied W₀ stabilized by 4FG(EO)₂ surfactant were designed according to phase behavior experiments. A systematic investigation was performed concerning the self-assembling, equilibrium morphology and detailed microstructure of the microemulsion droplet. An in-depth comparative study about the distribution of both H₂O and CO₂, the interfacial behaviors of 4FG(EO)₂, as well as the microscopic interactions was conducted.

FINDINGS

For the first time, direct evidence was provided for the formation of water-in-carbon dioxide microemulsion with extremely high W₀ (80) under the effect of 4FG(EO)₂. Furthermore, a unique interfacial phenomenon, i. e. CO₂ accumulating at the interface, was revealed to be responsible for the formation and enhanced stability of the nanosized droplet with high W₀. This should set a new guiding star for synthesizing and selecting effective interfacial modifiers to create high-W₀ microemulsions.

Nanocarriers of solid lipid from micelles of amino acids surfactants coated with polymer nanoparticles

Polymer nanoparticle coated micelle assemblies of lauryl ester of tyrosine (LET) act as potential nanocarriers for the model solid lipid stearyl alcohol. The coating is afforded by a simple methodology of heterophase polymerization reaction of styrene or the mixture of styrene and butyl acrylate at a mole ratio of 0.8:0.2 in the presence of 200 mM LET in water. On the contrary, the polymer nanoparticles produced under similar conditions in the presence of a structurally similar surfactant, lauryl ester of phenyl alanine (LEP), failed to act as nanocarrier. The micelle templates of LET and LEP favored polymerization under controlled conditions as observed from the near monodisperse distribution of molecular weight and size of the polymers. The particle size distribution of poly(styrene) (PS) and poly(styrene-co-butyl acryalte) (PS-co-PBA) nanoparticles from LET was smaller at 24 and 20 nm in comparison to those from LEP. The encapsulation efficiency of polymer nanoparticles from LET surfactant is explained on the basis of difference in the coating of micelle assemblies, which we believe must be arising due to difference in the solubilization site of the monomers in the surfactant micelles before polymerization reaction. The solubilization of the model monomer, benzene at different regions, varying between shell and core of LET and LEP micelles is established from (1)H nuclear magnetic resonance spectra. The evidence for the coating of micelle assemblies from surface tension measurements and the encapsulation of stearyl alcohol in the polymer nanoparticle dispersions from LET drawn from transmission electron microscopy, differential scanning calorimetry, and thermogravimetric analysis is discussed.