Horseradish peroxidase-catalyzed synthesis of high-quality polyaniline in Good’s buffer ionic liquid-buffered H2O/AOT/isooctane bicontinuous microemulsion

Here, a functionalized organic salt composed of [Nk,k,k,k]+ (k = 1-4) and [MES]- (2-(N-morpholino)ethanesul- fonate),i.e., Good's buffer ionic liquid with self-buffering and biocompatible properties, was chosen as elec-trolyte as well as buffer to construct a H2O/AOT/isooctane bicontinuous microemulsion for enzymatic synthesis of polyaniline (PANI). Studies on the effects of the functionalized organic salt on the phase behavior indicate that [Nk,k,k,k][MES] can tune the phase inversion temperature of AOT-stabilized oil-water microemulsion system through changing the cationic alkyl chain length, exhibiting the properties of both inorganic salt and co-alcohol. More interestingly, the stability of horseradish peroxidase (HRP) solubilized in the H2O(0.1 M [N1,1,1,1][MES], pH = 4.5)/AOT/isooctane bicontinuous microemulsion is much better than that formulated with mixed sur-factants AOT/SB-12 and inorganic salt. Studies on the HRP-catalyzed oxidative polymerization of aniline in the present bicontinuous microemulsion indicates that at low surfactant content and high oil-water ratio, the present microemulsion resulted in a PANI with better conductivity than the counterpart reported elsewhere. This work is of guiding significance for constructing a less-component and enzyme-compatible bicontinuous microemulsion for template-assisted biopolymerization.