Synthesising colloidal molecules with tunable interactions from soft responsive microgel particles

Sammanfattning: Colloidal self-assembly is an attractive bottom-up approach to new superstructures and materials with new properties. However, the typical spherical shape and isotropic interaction potential limit the repertoire of ordered structures that can be obtained from synthetic colloids. In order to expand the repertoire of structures, much effort has over the last decades been directed towards the preparation of colloids with anisotropic shapes and interactions and a more complex organisation. In an effort to replicate the concepts of valency and directionality that control the number, position and orientation of neighbours in molecular systems, the colloidal analogues have been prepared through controlled clustering of spherical colloids. However, as the lack of scientific publications in the field reveals, the typical charged hard sphere-nature of the constituent spheres - typically based on silica, polystyrene or poly(methyl methacrylate) - has made self-assembly of these so-called colloidal molecules difficult to control, resulting in jammed states where both translation and rotation are locked. The present thesis addresses this issue by reaching beyond classical electrostatic stabilisation, this by introducing poly(N -isopropylacrylamide) (PNIPAM) and poly(N-isopropylmethacrylamide) (PNIPMAM) microgel-based colloidal molecules that allow for both the strength and the range of the interactions, as well as the volume fraction, to be conveniently tuned with salt concentration, pH and temperature for a more successful assembly. This thesis foremost concerns design and development of methods for assembling microgels into colloidal molecules, and demonstration of the temperature-tunable interactions. Altogether, these results represent important steps towards assembly of novel superstructures and materials, and moreover, towards new colloidal model systems that capture the anisotropy of, for example, biological colloids such as proteins.