Research Overview

Our goal is to understand the properties of various polymeric, soft matter, and biological systems and to design new systems with even more interesting and useful properties. Our approach is based upon building and solving simple molecular models, as well as designing and performing experiments to test these models. Computer simulations of our models serve as an important bridge between analytical calculations, molecular modeling, and experiments.

Mucus

Mucus clearance is the primary defense mechanism that protects airways from inhaled infectious and toxic agents. We demonstrated a strong correlation between the extent of the chronic bronchitis disease and the state of hydration of the airway surface layer – mucus concentration and the corresponding osmotic pressure. We are using these ideas to develop biomarkers and treatment strategies for patients with different airway diseases.

Scale model shows configuration of chains in core and corona of diblock copolymer micelles of different geometries

Self-Assembly

The amphiphilic molecules contain both hydrophilic and hydrophobic units and often self-assemble into micelles. We are extending the micellization models to amphiphilic nanoparticles and self-assembled gels.

Reversible network with pairwise associating groups.

Reversible Networks and Gels

Association and formation of reversible bonds significantly modifies the dynamics and rheology of polymers. In spite of numerous experimental studies there was no fundamental understanding of these important systems. We are working on the theory of interpenetrating elastomers and gels containing both permanent and reversible components. We are studying the swelling and de-swelling kinetics of permanent and reversible networks both experimentally and theoretically.

A chain is topologically constrained to a tube by surrounding chains

Polymer Entanglements

The single most important feature that affects polymer dynamics is their entanglement. We are extending the theory of non-concatenated rings to model de-swollen networks and gels. We are modeling the dynamics of entangled bottle-brushes and nanocomposites with polymers grafted and adsorbed on nanoparticles. We are applying entangled polymer models to describe the conformations and interactions of DNA loops inside cell nuclei.

Illustration of the mapping procedure of sodium polystyrene sulfonate (NaPSS) in water.

Charged Polymers

Most of the water-soluble polymers are charged. If the charge on the chain is of one sign – such polymers are called polyelectrolytes(e.g. DNA). If polymers contain charges of both signs – they are called polyampholytes(e.g. proteins). We are working on extensions of the scaling theory of polyelectrolytes and polyampholytes to describe complexes and coacervates of oppositely charged polymers and to test theoretical predictions by computer simulations.