Toward understanding and optimizing the template-guided synthesis of chiral polyaniline nanocomposites

Previously we reported synthesis and characterization of water-soluble chiral conducting polymer nanocomposites via template-guided synthesis. Experimental procedures and parameters need to be carefully controlled to achieve synthesis of water-soluble nanocomposites. Here, we describe a modified synthetic procedure with higher molecular weight poly(acrylic acid) (PAA) (MW similar to 250 000) as a template. This new system allows synthesis of chiral water-soluble nanocomposites over a more broad range of conditions making the synthesis more reproducible and easier to carry out at large scale. Another objective of this work is to further understand the underlying formation mechanism of chiral polyaniline nanocomposites. We carried out a detailed study of how temperature, template, and solvent affect the final morphology and properties of these nanocomposites. We found that the extent of interaction and stability of the template/monomer/acid adduct (nanocomposite precursor) and population density of monomer surrounding the template are crucial in determining the degree of nanocomposite chirality. Detailed characterization of the nanocomposites and their precursors was carried out by circular dichroism (CD), UV-vis, FTIR, NMR, and TEM spectroscopy. On the basis of experimental results and synthetic procedures, a simplified model for the formation mechanism of chiral polyaniline nanocomposite is proposed.