Emerging strategies for assembling inorganic nanoparticles into ensembles with multiscale organization are establishing a new paradigm for the synthesis of devices and functional materials with applications ranging from drug delivery to photonics. In this work, the solution self-assembly of amphiphilic ionic block copolymers into morphologically tunable aggregates provides the inspiration and design strategy for nanoparticle building blocks with the essential chemical and conformational features of ionic block copolymer chains in aqueous media. We produce inorganic nanoparticles with surface-tethered mixed brushes of hydrophobic and chargeable hydrophilic chains which self-assemble in polar solvent mixtures into unprecedented hierarchical superstructures analogous to known ionic block copolymer aggregates but with complex organizations of nanoparticles in three dimensions. Electrostatic repulsion between hydrophilic chains forces nonequilibrium pathways to variable kinetic structures with internal lamellar organization of nanoparticles; however, decreasing electrostatic interactions through salt or acid addition allows tunable equilibrium assemblies, including supermicelles and bilayer vesicles of nanoparticles, to be formed. The application of ionic block copolymer assembly principles and mechanisms opens a new chemical toolbox for the organization of nanoparticles into functional assemblies.

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The interaction of emeraldine base polyaniline (EB) with Cu(II), Fe(III), and Zn(II) in 1-methyl-2-pyrrolidinone (NMP) solution was monitored using electronic UV−vis−NIR, resonance Raman, and electron paramagnetic resonance (EPR) spectroscopies. The films prepared from these solutions were also spectroscopically characterized. It was demonstrated that the nature of the products (semiquinone and quinone segments) formed from the interaction of EB and metal ions is strongly dependent on the nature of the cation, the metal/EB molar ratio, and the concentration of the components. The presence of semiquinone segments (radical cation) in EB solutions with Cu(II) and Fe(III) was undoubtedly confirmed by the observation of an electronic absorption band at ca. 900 nm, a characteristic Raman band at ca. 1330 cm-1 (νC - N •+ ), and also an EPR signal at g = 2.006. The influences of metal/EB molar ratio and metal ion concentration on the formed species were investigated in Cu(II) and Fe(III) solutions, and it was verified that diluted solutions favor the formation of oxidized segments (pernigraniline) instead of doped ones (emeraldine salt). No matter the nature of metal ion solutions, all the polymeric films show a spectroscopic behavior of ES (doped polymer) according to electronic and Raman spectroscopic data.

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This work emphasizes the important role of the synthetic parameters in the structure of the polymeric material obtained in the aniline polymerization. The polymers formed by the oxidative polymerization of aniline by copper(II) ions in acidic aqueous solution, acetonitrile/water medium, and also copper(II) acetate complex encapsulated into MCM-41 molecular sieve were characterized by resonance Raman spectroscopy using three exciting laser lines and other techniques such as UV−vis, FTIR, and XANES (Nitrogen K edge). Additionally the products were investigated by thermogravimetric analysis and powder X-ray diffraction. When Cu(II) ions in acidic aqueous medium are used, emeraldine salt (ES−PANI) is formed through the usual head-to-tail polymerization mechanism, while in acetonitrile/water medium a polymer is observed having mainly phenazine-like rings, quinonediimine, and/or phenylenediamine segments in the chains, suggesting that a distinct mechanism is operating. The average molecular weights of the free polymers synthesized in water and in acetronile/water were, respectively, ca. 37 300 and 16 900 Da. The encapsulated polymer synthesized in Cu(II)-MCM-41 is a polymeric mixture of (i) ES−PANI and (ii) the polymer obtained when this metal cation was used as oxidant in acetonitrile/water medium. All the characterization data were compared to those ones obtained for standard free polyaniline and also for the encapsulated polymer into mesoporous MCM-41 formed by using persulfate in acidic aqueous medium as oxidant.