In WP1 of COLLDENSE we had 5 specific projects, encompassing synthesis, experimental analysis, simulations and theoretical modelling of the properties of deformable colloids under external drive. We started with single droplets, using optical microscopy describe their pair interaction. It turned out that the composition of droplets is a key parameter to tune in order to change their behaviour. Another project that studied in computer simulations the mobility of a single 3D droplet depending on its composition and the properties of the solvent, showed that the transition from the osmosis to the electrophoresis could be found changing the solvation energy of the droplet. The ensemble of droplets has been also addressed in the simulations of the 3rd project, where the soft-hard transition in a 2D system was found and the discontinuous shear thinning was discovered. The effects of shear have been also studied by the 4th project experimentally. It showed that dense star polymers in melt could exhibit the properties of both polymers and colloids, namely they form a soft solid above the glass temperature, leading to a practical jamming of the system. Finally, to elucidate the mechanical properties and the phase diagram, a new theoretical approach (5th project) has been developed.
In WP2 we investigated hybrid colloids: DNA coated droplets, functionalized micelles, micro gels, telechelic star polymers and dipolar colloids. In the 1st project, using optical tweezers and microscopy, DNA coated droplets were synthesized, whose interactions can be tuned by light. It was shown that the rheological behaviour of the functionalized telechelic stars can be controlled by changing their topology. For that, in the 2nd project, a special molecular dynamics method was developed. Experimentally, in the 3rd project special micelles and microgels were synthesized with tuneable isotropic attractive interaction. Extensive comparison of the rheology and relaxation of the gels made of these hybrid colloids to those made of simple particles were studied. In simulations, relaxations of these systems were addressed in the 4th project of WP2. It was shown that shear can change their behaviour from percolation to phase separation. Talking about percolations and phase transitions in hybrid colloids is impossible without having a stable method to calculate cluster partition functions. This method has been developed in the frame-work of the 5th project in WP2 and tested for hybrid dipolar colloids.
One of the most versatile and efficient strategies for designing new materials with unconventional behaviour is based on competitive interactions. This was the part of COLLDENSE (WP3), in which we studied mixtures of complex colloids. The first project in WP3 was studying the mixture of two population of colloids, and as a result, gels with controllable strength were constructed. Such mixtures prove to have a large potential for industrial applications. The 2nd industrial project is dedicated to the study of self-filtration and jamming in gels. It has been shown that the rheology of these systems can be controlled by tuning the process of gel drying under different conditions and confinements. Rheological measurements were also the subject of the 3rd project. Here, however, the mixture of various grafted anisotropic nanoparticles were investigated. It turned out that soft rods are the most promising candidates to show the richest phase diagram. The last two projects addressed the study of DNA gels. The purpose of one of them was to develop a simulation hybrid Monte Carlo method for DNA origami. The method was developed and tested. In the second one, the experimental synthesis and light/neutron scattering characterization of DNA stars was performed. These stars turned out to be the first known system to form a gel if heated and melt if cooled down.
Along with the fundamental scientific value that all the results obtained within the project possess, the outcome will be used as a guideline for synthesis of new smart colloid-based materials with a fine-tuneable properties and responses, such as foods, cosmetics, industrial and domestic chemistry products.
