Soft Colloidal Particles at Fluid Interfaces

Abstract

The assembly of soft colloidal particles at fluid interfaces is reviewed in the present paper, with emphasis on the particular case of microgels formed by cross-linked polymer networks. The dual polymer/colloid character as well as the stimulus responsiveness of microgel particles pose a challenge in their experimental characterization and theoretical description when adsorbed to fluid interfaces. This has led to a controversial and, in some cases, contradictory picture that cannot be rationalized by considering microgels as simple colloids. Therefore, it is necessary to take into consideration the microgel polymer/colloid duality for a physically reliable description of the behavior of the microgel-laden interface. In fact, different aspects related to the above-mentioned duality control the organization of microgels at the fluid interface, and the properties and responsiveness of the obtained microgel-laden interfaces. This works present a critical revision of different physicochemical aspects involving the behavior of individual microgels confined at fluid interfaces, as well as the collective behaviors emerging in dense microgel assemblies.

3D Super-Resolution Fluorescence Imaging of Microgels

“…Virtanen et al (135) published a protocol on how to track single microgels in a concentrated matrix of nonlabeled microgels with wide-field fluorescence microscopy. SPT studies performed at fluid interfaces are powerful for investigating the adsorption, interaction, assembly, and rheology of hard and soft colloids (136,137). The adsorption of large PNIPAMbased microgels with a size of several micrometers labeled with R6G was investigated via their fluorescence (138).…”

Pickering Emulsions: A Novel Tool for Cosmetic Formulators

“…It is common that the increase in the particle aspect ratio, i.e., asymmetry, can contribute to the stabilization of Pickering emulsions [20]. Moreover, other structural parameters of the particles, such as their flexibility or conformation, and the particle-laden interface can modify the interfacial coverage and, hence, the emulsion stability [26,36]. On the other hand, particle roughness may also modify the stability of emulsions due to their impact on the particle contact angle.…”

Stimuli-Responsive Langmuir Films Composed of Nanoparticles Decorated with Poly(N-isopropyl acrylamide) (PNIPAM) at the Air/Water Interface

“…Below the transition temperature, the polymer creates hydrogen bonds with water molecules, while above the LCST, inter- or intramolecular hydrogen bonds prevail . The behavior of such polymers at fluid interfaces was recently described. , PNIPAM-decorated magnetic particles have already been reported in different contexts, mainly in three-dimensional (3D) systems. − These reports focus on aggregation properties or drug delivery potential, proving at the same time the temperature-dependent polymer transition on such nanoparticles. There is also a relatively large data set on PNIPAM-decorated graphene or graphene oxide and their applications. − Recently, PNIPAM-capped SiO 2 particles were shown as a promising adaptive material with tunable mechanical properties …”

“… 20 The behavior of such polymers at fluid interfaces was recently described. 21 , 22 PNIPAM-decorated magnetic particles have already been reported in different contexts, mainly in three-dimensional (3D) systems. 23 − 25 These reports focus on aggregation properties or drug delivery potential, proving at the same time the temperature-dependent polymer transition on such nanoparticles.…”