On Biomimetics
330
micelle aqueous solution. The pH of the reaction solution was adjusted to pH=2, and the
polymerization of pyrole monomers initiated in the presence of ammonium persulfate, the
polymerization ended with the precipitation of a black nanoparticle powder. [Scheme 1]
Consequently, the chiral DHBCs were removed by solvent extraction, leaving chiral
mesoporous voids. The obtained chiral mesoporous polypyrrole had an average size of 300
nm with a pore size of 3.5 nm. The use of DHBCs for imprinting chirality onto a polymeric
support was proven to be effective for chiral discrimination by adsorption. The CMPPy
shown chiral discrimination of racemic mixtures valine and alanine enantiomers with the
same chirality imprinted on the polymeric support. The maximum value of enantiomeric
excess (e.e) observed in adsorption measurements was 54%, and a chiral selectivity factor of
5.05 was calculated for CMPPy. The authors also compared the chiral resolution power of
CMPPy before and after extraction of the chiral polymers. Before solvent extraction, CMPPy
shows a very low surface area and low chiral resolution capability.
Scheme 1. (a) Templating of chiral block copolymers (CBCs) for synthesizing the CMPPy,
and electrostatic interaction between negatively charged carboxylic groups of CBC
molecules and protonated imine nitrogens of polypyrrole (PPy), (b) after extraction of CBCs
from the mesopores.
a b