Controlling electrostatic co-assembly using ion-containing copolymers: From surfactants to nanoparticles

Abstract

In this review, we address the issue of the electrostatic complexation between charged-neutral diblock copolymers and oppositely charged nanocolloids. We show that nanocolloids such as surfactant micelles and iron oxide magnetic nanoparticles share similar properties when mixed with charged-neutral diblocks. Above a critical charge ratio, core-shell hierarchical structures form spontaneously under direct mixing conditions. The core-shell structures are identified by a combination of small-angle scattering techniques and transmission electron microscopy. The formation of multi-level objects is driven by the electrostatic attraction between opposite charges and by the release of the condensed counterions. Alternative mixing processes inspired from molecular biology are also described. The protocols applied here consist in screening the electrostatic interactions of the mixed dispersions, and then removing the salt progressively as an example by dialysis. With these techniques, the oppositely charged species are intimately mixed before they can interact, and their association is monitored by the desalting kinetics. As a result, sphere- and wire-like aggregates with remarkable superparamagnetic and stability properties are obtained. These findings are discussed in the light of a new paradigm which deals with the possibility to use inorganic nanoparticles as building blocks for the design and fabrication of supracolloidal assemblies with enhanced functionalities.

Design of eco-friendly fabric softeners: Structure, rheology and interaction with cellulose nanocrystals

“…7a) [32,33]. The results suggest an interaction based on electrostatic association between opposite charged species [20,46,47]. There, the cationic guar particles are found to adsorb onto the CNCs, eventually reversing the sign of the electrophoretic mobility when added in excess and inducing aggregation at charge ratio close to unity (Fig.…”

“…As a result, we could show that cellulose nanocrystals interact strongly with the TEQ vesicles via electrostatic charge complexation leading to the formation of large-scale aggregates in which the vesicles remain intact and adsorbed at the cellulose surface [6]. Here we extend this approach and investigate the interaction of CNCs with guar polymers using the continuous variation method [22,23,45,46]. C-Guar/CNC dispersions were prepared by mixing stock solutions at different volumetric ratios between 10 -3 and 10 3 .…”

Block copolymers as bile salt sequestrants: intriguing structures formed in a mixture of an oppositely charged amphiphilic block copolymer and bile salt

“…As discussed above, DC À molecules are expected to interact preferentially with the cationic PAMPTMA(+) blocks suggesting that attractive electrostatic forces drive the formation of a charge-neutralized complex with a coacervate core surrounded by a PNIPAM corona in a similar way as to what is found for other oppositely charged block copolymer-surfactant systems, see, e.g., ref. 21. In this scenario, the measured interparticle distance of 40 nm could thus be the shortest distance reachable before the globules experience a strong increase in the steric repulsive force as dictated by the overlap of the PNIPAM coronas.…”

“…The resultant nanostructures sometimes with a liquid crystalline interior 13 are referred to as polyion complex micelles, block ionomer complexes, inter-polyelectrolyte complexes, complex coacervate core micelles or colloidal complexes (in this work mixed complexes). [14][15][16][17][18][19][20][21] Interestingly, the solution behavior of these nanostructures is much more versatile than the one of those formed by self-assembly of traditional amphiphiles (surfactants or amphiphilic block copolymers). This is because the electrostatic driving force is tunable through variables such as mixing ratio and added salt and also affected by the presence of counterions and additional hydrophobic interactions to list a few.…”

BCC Grain Formation Triggered by Miscibility Jump on Temperature Drop

“…The temporal increase rate in the storage modulus at 0.292 s −1 (G′ 0292 (t)) is given as follows; (4) which followed the Avrami equation, φ(t) ∼ 1 − exp(−Kt a ). φ(t)'s at 28 and 60°C are hereafter designated φ 28 (t) and φ 60 (t).…”