Chemical Design of Stimuli Responsive Microgels: Recent Developments and Trends

Soft colloids with programmable chemical functionalities, size and shape are important building blocks for the fabrication of catalyst systems and adaptive biomaterials for tissue engineering. However, the development of the easy up-scalable and template-free synthesis methods to obtain such colloids lack of understanding of molecular interactions that occur during the synthesis step. We demonstrate that the use of “programmable” monomers able to undergo specific non-covalent interactions (electrostatic, hydrophobic or π-π-stacking) in aqueous solutions is a key to bottom-up synthesis of anisotropic microgels with controlled size, shape and chemical structure. 

A new synthesis approach based on the controlled self-assembly of growing polyelectrolyte microgel precursors during the precipitation polymerization process leading to the formation of polyampholyte Janus-like microgels was developed.<font size="1"> We confirmed the morphology of polyampholyte Janus-like microgels using super-resolution optical microscopy and demonstrated that they are capable of responding to changes in both pH and temperature in aqueous solutions. In another study, we first performed computer simulations for a series of pyrazole-modified monomers with different numbers of pyrazole groups, different length and polarity of spacers between pyrazole groups and the polymerizable group. Based on simulations, we synthesized monomers able to undergo π-π-stacking and guide the formation of supramolecular bonds between polymer segments and used them in precipitation polymerization to synthesize anisotropic microgels. We demonstrate that microgel morphologies can be tuned from spherical, raspberry-like to dumbbell-like by the increase of the pyrazole-modified monomer loading, which is concentrated at periphery of growing microgels.