Research conducted in my group is primarily focused on understanding the physics of surfaces and interfaces at the molecular/atomic scale using classical simulation techniques, mainly molecular dynamics simulations technique. The physics (and also the chemistry for that matter) of surfaces and interfaces are the most exciting but very challenging research area of condensed matter science. Very challenging because interfacial properties are usually difficult to measure experimentally since it is hard to probe solely the interface and theoretically, the discontinuous nature of physical properties at interface makes it demanding to develop a general theory for them; most existing theories are therefore based on macroscopic continuum equations.

Polymer surfaces and interfaces have recently attracted a lot of attention from both theorists and experimentalists due to their potential applications in diverse areas ranging from telecommunication to biotechnology. On a fundamental level, understanding the behavior of polymer chains in the vicinity of surfaces and interfaces itself is of great importance and current research trends indicate that to be the main focus of polymer science in the 21st century. On a technological level, future nano-technological devices will be mainly composed of materials of differing properties that behave differently when brought together as a whole due to interfacial effects. A molecular or atomistic level understanding of surface/interface properties is thus essential to manipulate relevant surface/interface properties for numerous applications. Simulations are now making important contributions in understanding interfacial problems. Starting from models which have been developed and validated for bulk polymers it is now possible to treat interfaces.

Depending on the scope of the problem there are a number of simulation methods available. Atomistic simulations employing quantum mechanical methods, which are computationally very expensive, are used when knowledge of chemical properties is necessary. Atomistic simulations employing classical methods, which are still computationally expensive, are used when the detailed chemical bonding is not as crucial although the atomistic character is. For simulating polymers at a longer time and length scales a coarse-grained bead-spring model, where the polymers are represented by beads and are connected by flexible springs, is usually used. For example, we have used the bead-spring model to understand (a) the failure mechanism of highly crosslinked polymers attached to a solid surface, (b) the morphology of homopolymer films during solvent evaporation, and (c) the morphology of block copolymers during solvent evaporation; images (click to play movie) for these three different cases are shown below, respectively. Detailed discussion can be found in our recent publications.

Polymer

Click on an image to play a movie.

We also do atomistic simulation when the system under consideration is very sensitive to molecular details. The images shown below are the result of our recent large scale atomistic molecular dynamics simulations to understand the ordering of alkanes (hydrogenated and/or fluorinated) on crystalline and amorphous silicon dioxide surfaces. We are observing many interesting properties that have not been reported in past simulation studies. The work is in progess and will be reported in our future publications.
Polymer
Ordering of C16H34 and C16F34 on alpha quartz, respectively, at a temperature close to their corrsponding melting temperature.