Vasileios Koutsos: Soft matter under confinement: droplets, bubbles and thin films

Soft matter systems consisting of two or more components (e.g. nanocolloid or polymer suspensions, polymer blends, block copolymers) exhibit unusual physical properties due to the geometric constraints imposed by the coexistence of the different phases. When such systems are confined on surfaces, in thin films, droplets and bubbles, there are additional geometric constraints which induce further changes in their behaviour. Soft matter systems on surfaces (and generally under confinement) have great potential for many applications ranging from micro/nanoelectronics and chemical sensor technology to biomedical implants and targeted drug/gene delivery. However, there are plenty of unsolved problems in our fundamental understanding of the behaviour of soft matter in confined spaces. The prediction and determination of materials properties at the nanoscale is not a trivial task and unexpected deviations from bulk behaviour are not uncommon. In this talk, I will present investigations of confined soft matter systems such as diblock copolymers and star polymers thin films, polymeric and nanocolloid droplets, polymer- and phospholipid-based microbubbles. The experimental studies show clearly the formation of nanostructures which are the direct consequence of confinement and/or interfacial interactions with the solid substrate. In many cases, the overall behaviour in confinement is remarkably different to what is expected from bulk behaviour. The phenomena studied include lamellae formation parallel to the substrate for asymmetric diblock copolymers, 2D jamming of star polymers, increased elastic modulus of polymer nanodroplets due to surface ‘pinning’. The experiments were complemented by (and discussed in terms of) scaling theory, continuum theory and computer simulations such as Langevin dynamics simulations using coarse-grained bead spring models and Monte Carlo simulations.