IISER MOHALI

Abstract: I begin by describing the approach in my lab, which is deeply inspired by the world around us. We keep our eyes wide open, for today's content, keeping our eyes wide open to the wonders of nature-from the bustling shoreline to the creatures in the sea. Though we aren't directly studying these environments, our curiosity is sparked by the way they function.

In the first part of our work, we dive into the challenges of processing ultra-high molecular weight polymers. These polymers have an incredibly high viscosity, meaning they require a lot of energy to process, making large-scale production both costly and inefficient. In our recent study, we focused on how the shape of nanoparticles influences polymer flow. By comparing common shapes like nanospheres and nanorods to a unique structure, nanotetrapods, we made a surprising discovery: nanotetrapods significantly reduce the viscosity of the polymer melt without compromising its strength or stability. While other particle shapes typically increase viscosity, these tetrapods had the opposite effect. The magic lies in the geometry of the nanotetrapods. Their inner curvatures create confined spaces that prevent polymer chains from crowding and tangling, generating a "packing frustration" that allows the chains to move more freely, thereby reducing viscosity. This is something neither spherical nor rod-shaped nanoparticles could achieve. What's truly exciting about this discovery is how it aligns with both our experiments and molecular dynamics simulations, showing that even a small amount of nanotetrapods can drastically improve polymer processability. This idea was also inspired by the way large tetrapod-shaped concrete blocks work in the sea-disrupting flow and encouraging water to move through their arms. At the nanoscale, however, these tetrapods act differently, inhibiting the polymer flow and promoting the packing frustration that enhances molecular mobility.

In the second part of our work, we take inspiration from the humble squid - more specifically, the chromatophores on its skin, which serve as a biological example of a packed system on an expanding surface. We found that in polymer thin film dewetting, a process known for its scale-free growth, relative density fluctuations in cell numbers increase with spatial scale. We call this behavior "hyperdisorder," a term that contrasts with "hyperuniform" behavior, where fluctuations tend to zero at large scales. As the dewetting process progresses, it leads to a percolation-like phase transition with characteristic power laws, resulting in droplets that exhibit hyperdisorder. This phenomenon can be observed in both spinodal and nucleation-growth dewetting and can be tuned by adjusting key parameters such as molecular weight and slip length. It's particularly exciting because, in contrast to spinodal dewetting-which typically creates hyperuniform structures-our work shows how these structures can be broken down, revealing new insights into the underlying physics of polymer behavior.