Influence of gold species (AuCl₄⁻and AuCl₂⁻) on self-assembly of PS-b-P2VP in solutions and morphology of composite thin films fabricated at the air/liquid interfaces

Abstract

Composite thin films doped with Au species were fabricated at an air/liquid interface via a series of steps, including the mass transfer of polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) across the liquid/liquid interface between a DMF/CHCl3 solution and an aqueous solution containing either AuCl4(-) or AuCl2(-), self-assembly of PS-b-P2VP in a mixed DMF-water solution, and adsorption and further self-organization of the formed aggregates at the air/liquid interface. This is a new approach for fabricating composite polymer films and can be completed within a very short time. AuCl4(-) and AuCl2(-) ions were found to significantly influence the self-assembly behavior of the block copolymer and the morphologies of the composite films, leading to the formation of nanowire arrays and a foam structure at the air/liquid interface, respectively, which originated from rod-like micelles and microcapsules that had formed in the respective solutions. The effect of the metal complex was analyzed based on the packing parameters of the amphiphilic polymer molecules in different microenvironments and the interactions between the pyridine groups and the metal chloride anions. In addition, these composite thin films exhibited stable and durable performance as heterogeneous catalysts for the hydrogenation of nitroaromatics in aqueous solutions.

New Insights into the Physicochemical and Electrochemical Characterization of Gold Phthalocyanine-Based Materials

“…C-Cl) is expected at 200-202 eV for Cl 2p 3/2 . 41 Based on existing data on chlorinated gold species, a common interpretation is made with Au 4 f. [48][49][50][51][52][53][54][55][56] It has been reported that Cl 2p 3/2 appears around 200.1 eV in a tetrachloroaurate environment (HAuCl 4 ) while for a low chlorine content such as Au(I)-Cl complexes lead to Cl 2p 3/2 at a lower BE of 199.5 eV. 48 Consequently, for AuPc, the peak at 198.3 eV (FWHM = 1.1 eV; at% = 78) and 200.1 eV (FWHM = 1.1; at% = 22) could be assigned, respectively, to Cl bonded to Au in the phthalocyanine referred to as N-Au III Cl-N (Scheme 1, with an axial ligand Cl) and the few residual traces of the HAuCl 4 precursor (given that XPS is a highly sensitive surface technique).…”

“…[48][49][50] The peak at 84.3 eV (FWHM = 1.2 eV) belongs to Au 4f 7/2 of metallic gold, which can come from the observed aggregates in SEM-EDX images as well as photo-reduction of gold (I/II/III) species by the photo-emission process during XPS analysis. [53][54][55][56][57][58] The peak at 88.0 eV (FWHM = 1.2 eV) for AuPc can be assigned to Au 4f 7/2 of gold (III) surrounded by nitrogen and chlorine in N-Au III Cl-N (Scheme 1, with an axial ligand Cl). We note that due to the overlap with the dominant pyridinic-N and pyrrolic-N moieties of the phthalocyanine macrocycle, the previous N 1 s could not provide access to an N-Au bond.…”

On the Differences in the Mechanisms of Reduction of AuCl2– and Ag(H2O)2+ with BH4–

“…26,27 AuCl 2 − has a negligible absorption around 300 nm. 37,38 Therefore, the results at 295 nm point out that the first reaction observed is not the reduction of AuCl 4 − as the first reaction observed causes an increase in the absorption at 295 nm. Stopped-flow measurements were performed to get a better time resolution.…”

Aggregation behavior of symmetric poly(n‐butyl acrylate)‐block‐poly(acrylic acid) on subphases of different ionic strengths

“…Studies on the aggregation behavior of amphiphilic block polyelectrolytes have been conducted in recent years, which include the vinylpyridine based copolymers polystyrene‐ b ‐poly(n‐vinyl pyridine) (PS‐ b ‐PnVP, n being 2 or 4), 16–22 some acrylic acid based copolymers polystyrene‐ b ‐poly(acrylic acid) (PS‐ b ‐PAA), 23–25 poly( n ‐butyl acrylate)‐ b ‐poly(acrylic acid) (PnBA‐ b ‐PAA), 26,27 and poly(1,1‐diethylsilacyclobutane)‐ b ‐poly(methacrylic acid), 28 and some other systems such as poly( n ‐benzyl methacrylate)‐ b ‐poly( N , N‐ dimethylaminoethyl methacrylate), 29 poly[2‐(dimethylamino)ethyl methacrylate]‐ b ‐poly(lauryl methacrylate) (PDMAEMA‐ b ‐PLMA), 30 and poly( N ‐isopropyl acrylamide)‐ b ‐poly[oligo(ethylene glycol) acrylate] (PNIPAM‐ b ‐POEGA) 31 . Besides of the factors mentioned above, subphase pH value placed an important role on their interfacial aggregation behavior characterized with the surface pressure–molecular area ( π–A ) isotherms and the morphologies of their LB films.…”