Recent advances in stimuli-responsive core-shell microgel particles: synthesis, characterisation, and applications

Abstract

Inspired by the path followed by Matthias Ballauff over the past 20 years, the development of thermosensitive core-shell microgel structures is reviewed. Different chemical structures, from hard nanoparticle cores to double stimuli-responsive microgels have been devised and successfully implemented by many different groups. Some of the rich variety of these systems is presented, as well as some recent progress in structural analysis of such microstructures by small-angle scattering of neutrons or X-rays, including modelling approaches. In the last part, again following early work by the group of Matthias Ballauff, applications with particular emphasis on incorporation of catalytic nanoparticles inside core-shell structures-stabilising the nanoparticles and granting external control over activity-will be discussed, as well as core-shell microgels at interfaces.

Osmotic pressure of suspensions comprised of charged microgels

“…Microgels, which are cross-linked polymer networks in the colloidal-size domain, are an example of such compressible particles. Indeed, they are known to respond to external stimuli, including pH, T , solvent composition, or salt concentration by swelling or deswelling [34][35][36][37][38][39]. While in the deswollen state the particle bulk modulus, K p , is comparable to that of hard-sphere-like colloids, in the swollen state, K p can be significantly smaller [40].…”

Microgels at Interfaces Behave as 2D Elastic Particles Featuring Reentrant Dynamics

“…This is especially true for soft polymeric colloids that possess internal degrees of freedom endowing them with elasticity and deformability. Among the available library of soft deformable particles, microgels, colloidal-sized crosslinked polymer networks, are one of the finest illustrations of this concept [3][4][5][6][7]. Their structure is determined by the chemical synthesis conditions that, in the common procedure of precipitation polymerization [8], lead to the formation of spherical particles made of a compact core and a fluffy external corona [9].…”

Smart Microgels from Unconventional Acrylamides

“…Furthermore, microgels made of NnPAM are described by Kano et al., [ 49 ] Matsumara et al., [ 54 ] Uchiyama et al., [ 55 ] and since 2012 by our group in several publications. [ 37,38,56–60 ] But to our knowledge, the preparation and characterization of microgels based on the other monomers mentioned above (see Figures 1 and 4–6) has only been described once for NnPMAM by our group. [ 37 ]…”