Comprehensive study of the formation of stable colloids of Cu Al layered double hydroxide assisted by double hydrophilic block copolymers

Abstract

The formation of stable aqueous colloidal suspensions of Cu-Al layered double hydroxide (LDH) assisted by double-hydrophilic block copolymers was investigated. It was of utmost importance since the direct preparation LDH colloids of controlled size is still a major challenge ; moreover, regarding the Cu-Al system, the mechanism of formation of the LDH phase is not well understood yet. Cu-Al LDH nanoparticles were obtained by complexing Cu 2+ and Al 3+ cation mixture (Cu 2+ /Al 3+ = 2) with an asymmetric poly(acrylamide)-b-poly(acrylic acid) block copolymer, followed by metal cation hydroxylation. The mechanism of formation of the Cu-Al LDH was studied and compared to that of Mg-Al LDH. ICP-MS analysis of the hybrid polyion complex (HPIC) micelles obtained at increasing complexation ratio, i. e. the ratio of the molar concentration of complexing acrylate group of DHBC to M 2+ and Al 3+ cations (R = AA/(M 2+ + Al 3+)), showed higher selectivity of DHBC toward Al 3+ and, among M 2+ cations, for Cu 2+ than for Mg 2+. Hydroxylation of the HPIC micelles led to macroscopic precipitates at R values below flocculation thresholds, ie. R1 = 0.43 for DHBC/Cu-Al and 0.13 for and DHBC/Mg-Al suspensions, while stable suspensions were formed above R1. The hydrodynamic diameter (Dh) of the colloids determined by DLS decreased from 160 to 50 nm and from 350 to 50 nm in the DHBC/Cu-Al and DHBC/Mg-Al colloids, respectively, when R increased from R1 to 1. XRD and TEM analyses of the dried colloidal suspensions (R > R1) revealed the presence of Cu-Al LDH and Mg-Al LDH phases and elemental analyses confirmed that M(II)/Al = 2. Particle sizes were lower in Cu-Al LDH than in Mg-Al LDH. Titration curves corresponding to progressive hydroxylation of DHBC/Cu(or Mg)-Al solutions at fixed complexation ratio R allowed establishing that formation of Cu-Al and Mg-Al LDH obeyed to a similar sequential mechanism in two steps but involving different aluminum hydroxide precursors according to the different pH values of precipitation. Cu-Al LDH was obtained by combination of aluminum poly(hydr)oxide species with dissolved copper-based species at pH ~ 5.5, while Mg-Al LDH resulted from combination of Al(OH)3 and dissolved Mg 2+ at pH ~ 8.

On Complex Coacervate Core Micelles: Structure-Function Perspectives

“…The addition of different chemical functionalities to the neutral block can also avoid time-consuming post-synthetic surface modifications. C3Ms have been utilized to produce various types of metallic and semiconductor nanoparticles, including metals [ 174 , 180 , 181 , 182 , 183 , 184 ], metal oxides [ 185 , 186 , 187 , 188 , 189 ], and quantum dots [ 190 , 191 , 192 ]. The coacervate core can also be used for biomimetic mineralization of silica [ 193 ], barium carbonate [ 194 ], and calcium carbonate [ 195 ].…”

All-Aqueous Multi-phase Systems and Emulsions Formed via Low-Concentration Ultra-high-Molar Mass Polyacrylamides

“…DLS measurements of the LDH nanoparticles in combination with the polymer in aqueous solution showed the formation of large aggregates with sizes above 1 μm (Figure S19 and Table S4), which indicates an interaction between polymers and nanoparticles. Such an aggregate formation was described in the formation of nanocomposites from LDH nanoparticles and polymers for various polymers, for example, polyacrylamide − or double-hydrophilic block copolymers . As such, we assume that the aggregative phase separation behavior is due to the aggregation between the polymers and LDH nanoparticles.…”

“…Such an aggregate formation was described in the formation of nanocomposites from LDH nanoparticles and polymers for various polymers, for example, polyacrylamide 59−61 or double-hydrophilic block copolymers. 62 As such, we assume that the aggregative phase separation behavior is due to the aggregation between the polymers and LDH nanoparticles.…”

Pickering emulsions based on layered double hydroxides and metal hydroxides

“…In this method, the DHBC acts as both, growth control and stabilizing agents. For example, as shown by recently extended to synthetize a Cu-Al LDH phase with an efficient control of the size of the nano particles (Layrac, Harrisson et al 2020).…”