RSA CE&C 2015-2021 Group descriptions

62 Major accomplishments in the evaluation period Research quality and scientific relevance Our most significant results in the period 2015-2018 are summarized below, covering the main research themes: 1. Colloid and polymer mixtures We have developed a combined synthesis-characterization-theory approach to study a block copolymer (BCP) system in solvent (mixtures) with tunable morphology transitions. The theoretical framework helps to predict the preferred morphology as a function of BCP- solvent combination and BCP composition, which serves as an excellent starting point for further studies. Furthermore, we have developed insights into the complexation of colorants/ dyes and polyelectrolytes and surfactants that enable the tuning of the absorption of these dyes. We studied the effects of polyamine chain length on silica particle growth and condensation and found that the particle diameter increased with an increase in polyamine chain length, whereas silica condensation showed the opposite trend. Combining theory and experiments, we proposed that particle formation occurs via a coacervate intermediate with the final particles having a core shell structure with an amine-rich core and silica-rich shell. For colloid-polymer mixtures, theory was extended to be able to predict the complex phase behavior of dispersions of anisotropic colloidal particles mixed with nonadsorbing polymers. This revealed the possibility of many multi-phase coexistences, including even four and five- phase coexistence regions. 2. Polymers and colloids at solid surfaces We have developed hydrophilic-hydrophobic polymer networks which contain functional surface-segregated polymer chains leading to special properties, like extremely low coefficient of friction, self-healing or anti-protein adhesion properties. We have gained insights into the surface-segregation behavior of block copolymers which act as leveling agents in coating formulations. This type of additive is present in nearly all paints currently in use and play a major role in achieving hydrophobic properties and defect-free coating films. We have developed fully skin-compatible graphene-based colloidal inks for the printing of stretchable conductors using a variety of printing approaches (screen, flexi, 3D). To this end, we gained new fundamental insights into the rheology of 2D colloid and polymer dispersions depending on the size and aspect ratio of the platelets to enable the tuning of viscosity, recovery time and thus print definition in order to manufacture stretchable conductors. When deposited on flexible substrates, conductivity and stretchability (including durability) could be further tuned by post-processing via photonic annealing. This brings us one step closer to roll-to-roll production of wearable technology for, e.g., health monitoring. 3. Polymers and colloids at interfaces We have prepared polymer latexes with well-defined compositions and specific functional groups on their surface. These emulsion polymers will be used to investigate interactions between polymer particles and other colloidal particles added to the emulsions, which are the drivers for the formation of supracolloids with potential use in waterborne coating formulations. We have investigated emulsions based upon hydrophobic eutectic solvents and increased our fundamental understanding of these systems, allowing us to explain their unexpectedly high stability. Furthermore, we showed a new possibility to stabilize W/W emulsions using polyelectrolytes. Additionally, we pioneered a new technique to probe the structure of such interfaces with nanometer precision using synchrotron X-ray studies.