We are studying special organic molecules known as rotaxanes that have switchable structures such that the application of a mechanical force on these molecules leads to structural changes that store chemical energy. The figure shows an example of this in which the rings are initially tightly bound to the spine of the molecule, but eventually unfold as the molecule is stretched. Such molecules allow for the conversion of chemical energy into mechanical energy at the molecule unfolds. This can be used to prepare molecular batteries for energy storage applications.

We investigate the equilibrium properties and the underlying dynamics of emulsions formed in asymmetric A-B copolymers in matrices of immiscible B and C molecular fluids using coarse-grained molecular dynamics simulations. This monolayer collapse mechanism can be exploited to generate nano- reactors or containers that enhance the delivery of molecular components into immiscible molecular fluid environments.

Dissociation of ionizable ligands (or apparent pK a) immobilized on nanopaticles (NPs) depends on and can be regulated by the curvature of these particles as well as the size and the concentration of counterions. The experimental dependencies are reproduced well by a theoretical model that accounts fully for all molecular details (size, shape, conformation, and charge
distribution). Understanding how and why the NPs regulates the degree of dissociation of its coating is of prime importance for nanotechnological applications such as self-assembled materials for energy applications.

Our goal is to theoretically understand the transport properties of nanochannels modified with different molecular species, in particular polyelectrolyte brushes. We have developed a model that predicts the pH dependent conductivity of a single polyelectrolyte modified nanopore device in excellent agreement with the experiments and provided physical insights on the molecular organization and ion fluxes inside the channel.

The kinetics of pattern formation of cationic-anionic co-assembly leads to the formation of modulated phases of opposite charge. We developed a formalism to compute time-dependent potentials that revealed a non-equilibrium screening processes. A strong deviation from the standard Debye-Huckel theory is demonstrated.

Contact electrification is a phenomenon that we encounter everyday, from little shocks that we get when we touch to doorknobs to large problems it causes in manufacture of many products. However, its mechanism has been a mystery to scientist for more than a 2000 years. We study the contact electrified polymer surfaces with various electrical modes of force microscopy. The images show that despite the common belief, surfaces are not charged uniformly but a mosaic of negatively and positively charges reside on surfaces side by side.

Contrary to previous estimates, we showed that contact electrification of polymers can take place in absence of water . By examining the charging and the discharging behaviour of such surfaces at "zero water" conditions help us understand the identity of charge carriers and the mechanism of contact electrification which is a millenia-old problem.

• Novel mathematical theories used to studymulti-component fibers arising in biological systems.

• Computational simulations reveal the existence of highly complex polymer structures arising in nature.

• Theoretical analysis shows that semi-flexible polymers undergo dramatic changes in conformation through dynamic alteration of mechanical properties.

In this project, we investigate the icosahedral and spherical nanoparticles grafted with charge end group ligands in solutions. Different conformations of grafted ligands are observed. We found that for certain ratio of electostatic repulsion between the end groups over Van der Waals attraction between ligands, ridges are formed on the nanoparticle surface.

We study interaction between two grafted nano-particles with
functional groups on the end of each tethered chain. We considered that the system is charge regulated, i.e. dissociation of the functional groups determinates self consistently by configuration of the system, salt concentration and pH of the bulk. Due to the high strength of electrostatic interactions, even weak charging of grafted chains (one group at the end) leads to significant changing in magnitude of interaction potential.

Using theory, modeling and computer simulation, we seek
to understand and design far-from-equilibrium materials,
including those suitable for energy conversion.