Zhifang Yang

Synthesis of Electroactive Tetraaniline—PEO—Tetraaniline Triblock Copolymer and Its Self-Assembled Vesicle with Acidity Response

A novel ABA triblock copolymer containing electroactive tetraaniline [(ANI)(4)] and poly(ethylene oxide) (PEO600, M(n) = 600), (ANI)(4)-b-PEO600-b-(ANI)(4), was synthesized by coupling tetraaniline and PEO600 with tolylene 2,4-diisocyanate. FTIR, NMR, and UV-vis spectroscopy were combined to characterize the chemical structure of (ANI)(4)-b-PEO600-b-(ANI)(4). The electrochemical properties, self-assembly, and acidity response of copolymer in aqueous solution were investigated by cyclic voltammetry, electron microscopy, and dynamic light scattering. Different from pure tetraaniline and polyaniline, the triblock copolymer in 1.0 M sulfuric acid solution only exhibits one oxidation peak in cyclic voltammetry. In a neutral aqueous solution, the triblock copolymer self-assembled into vesicles with diameter of about 258 nm. Upon acidification with HCl, the size of the vesicles increases to 471 nm and 1.19 microm when the concentration of HCl changes to 10(-3) and 10(-1) M, respectively. With addition of aqueous 1.0 M HCl to the triblock copolymer solution in THF, hollow spheres and bowl-like aggregates were obtained. A bilayer model was proposed for the vesicle formation, and the mechanism of acidity response was discussed.

Hierarchical hybrids of carbon nanotubes in amphiphilic poly(ethylene oxide)-block-polyaniline through a facile method: from smooth to thorny.

A facile approach was developed to synthesize conjugated block copolymer (BCP) poly(ethylene oxide)-b-polyaniline (PEO-PANI). Aldehyde group-terminated PEO was prepared by an esterification reaction of p-formylbenzoic acid and PEO and then reacted with PANI from chemical oxidative polymerization. FT-IR, (1)H NMR, and GPC results indicated that BCPs with different PEO block lengths were successfully synthesized. Moreover, the BCPs were employed to noncovalently modify multiwalled carbon nanotubes (MWNTs) through either the direct or indirect method. In the former method, transmission electron microscopy images showed that a core-shell MWNT@BCP hybrid with a shell thickness of gyration diameter of PEO block (2Rg,PEO) was obtained in 1-methyl-2-pyrrolidone (NMP). These hybrids can be well dispersed in many common solvents and poly(vinyl alcohol) matrix. With the increase of PEO block length, the stability of the MWNT dispersion would be highly improved. Interestingly, in the indirect method where deionized water was added to the NMP solution of BCP/MWNT mixture, the surface of the hybrid micelles encapsulated with MWNTs changed from smooth into hierarchically thorny with the increase of BCP/MWNT weight ratio. In this case, the water contact angle had a minimum value of ~70° at the ratio of 1/8, indicating that the hierarchical thorns followed a Cassie-Baxter regime rather than a Wenzel one. A possible formation mechanism of the unique structure was also proposed.

Well-structured holographic polymer dispersed liquid crystals by employing acrylamide and doping ZnS nanoparticles

High diffraction efficiency and low driving voltage are typically considered to be prerequisites for the practical applications of holographic polymer dispersed liquid crystals (HPDLCs), which are especially critical for their use in the state-of-the-art low-threshold mirrorless tunable lasers. Nevertheless, high driving voltages are usually resulted for HPDLCs upon increasing the holographic diffraction efficiency via optimizing the monomer/LC formulations. Herein, we present that doping nanoparticles into HPDLCs with controlled distribution is a facile and efficient approach to circumvent the aformentioned issues. Zinc sulfide (ZnS) nanoparticle doped HPDLCs with high diffraction efficiency (94.0 ± 2.1%), and a low threshold driving voltage of 2.5 V µm−1 that is decreased from 11.6 V µm−1 for the pristine form, are achieved by doping 8 wt% ZnS nanoparticles into the HPDLCs based on an acrylamide monomer, N,N-dimethylacrylamide, that contributes significantly to the high diffraction efficiency up to 98.2 ± 1.4%.