Anionic-Surfactant-Stabilized Hydrophobic Ionic-Liquid-Based Bicontinuous Microemulsion as a Medium for Enzymatic Oxidative Polymerization of Aniline

Abstract

The hydrophobic ionic liquid [C8mim]­[PF6] (1-octyl-3-methylimidazolium hexafluorophosphate)-based bicontinuous microemulsion stabilized by the anionic surfactant [C4mim]­[AOT] (1-butyl-3-methylimidazolium bis­(2-ethylhexyl) sulfosuccinate) was first tried as a medium for horseradish peroxidase (HRP)-triggered oxidative polymerization of aniline. The effects of the mass ratio of [C8mim]­[PF6]-to-water (α), the mass fraction of [C4mim]­[AOT] in the total mixture (γ), and temperature (T) on the enzymatic polymerization were investigated using UV–vis–NIR absorption, electron spin resonance, and small-angle X-ray scattering spectroscopy techniques. The bicontinuous microemulsion is demonstrated to play a template role in the biosynthesis of polyaniline (PANI). The conductivity of the resulting PANI depends on the microemulsion microstructure and the microstructure- and T-dependent catalytic properties of the solubilized HRP. With the increase in α, the conductivity of the synthesized PANI decreases due to the increase in the template curvature (decrease of the microdomain size) and the decrease in the activity and stability of HRP. Compared with α, γ has little effect on the microdomain size of the template; so, the γ-dependent change in the conductivity of PANI is mainly caused by the changes of the microstructure-dependent activity and stability of HRP. Over the range of 20–35 °C, T has little effect on the microdomain size, but it greatly changes the activity and stability of HRP. With the increase in T, the activity of HRP increases steadily, but its stability decreases significantly, which should be one of the reasons why the conductivity of PANI decreases with increasing T. In conclusion, lower values of α, γ, and T are favorable for the biosynthesis of conductive PANI. The present study not only deepens the insight into the role of the template in the process of PANI synthesis, but also opens up a green new way for the biosynthesis of the conducting polymer.

Lipase‐Catalyzed Hydrolysis of α‐Phenylethyl Esters in a Hydrophobic Ionic Liquid‐Based Bicontinuous Microemulsion Stabilized by Zwitterionic Surfactant

“…It is shown that as γ increases both the peak position and the peak intensity have small changes, and the derived d values also vary slightly. These results are quite different from these derived in classical oil‐water BME due to the relatively poor surfactant efficiency in the HIL‐based BME against the classical oil‐water BME [11a,13,17] . The fact that the yield increases with increasing γ is probably due to the increased interfacial area and therefore the enhanced lipase activity.…”

“…The smaller the microdomain size, the stronger the interfacial effect on lipase. As confirmed in Figure 5, the peak positions of the fluorescence spectra of lipase (caused by its endogenous fluorescent groups) in both BMEs are close to each other, but the fluorescence intensity in the mixed SB‐8/SB‐16 system is higher than in the single SB‐12 system, indicating stronger interaction between the interface and the solubilized lipase and therefore lower lipase activity [13,17] …”

“…As confirmed in Figure 5, the peak positions of the fluorescence spectra of lipase (caused by its endogenous fluorescent groups) in both BMEs are close to each other, but the fluorescence intensity in the mixed SB-8/SB-16 system is higher than in the single SB-12 system, indicating stronger interaction between the interface and the solubilized lipase and therefore lower lipase activity. [13,17] Figure 2. The HPLC profile of α-phenylethyl ester and its hydrolysis product (here the hydrolysis of α-phenylethyl butyrate catalyzed by lipase (A) was taken as an example).…”

Hemin-catalyzed oxidative oligomerization ofp-aminodiphenylamine (PADPA) in the presence of aqueous sodium dodecylbenzenesulfonate (SDBS) micelles

“…1). As monomers, either aniline, [1][2][3][4] the aniline dimer p-aminodiphenylamine (PADPA) 5 (Fig. 1), or mixtures of aniline and PADPA 6 were used.…”

Ionic Liquid-Based Microemulsions: Efficient Nanoreactors for Synthesis of Core–Shell Nanoparticles under Ambient Conditions

“…SAILs have a distinctive solvation environment, and the Coulombic and ionic interactions, together with weak intermolecular interactions, result in hierarchical nanosegregated domains. The benefits of IL-based MEs and their potential for improved efficacy of conventional MEs in various applications have been studied as well. − In recent past, extensive research on IL-based MEs has been documented, with an emphasis on their microstructure and physicochemical characteristics . The literature has reported instances of numerous conventional surfactants forming dry micelles in an IL medium .…”