Our group is engaged in exploring polymer, surface, and material science in areas such as shape memory, soft lithography, fluidics, and acoustics.

See Research Highlights

Currently, positions are available for postdocs with expertise in the following fields of material science:
polymers, thin-films, surfaces/interfaces, acoustics, scattering/microscopy, rheology, lithography.
Graduate and undergraduate positions also available. Contact Sergei Sheiko

UNC Chapel Hill received a $3.18 million National Science Foundation (NSF) grant to establish a Materials Interdisciplinary Research Team (MIRT)! (Read more…)

Some areas of research include thin polymer films, surface properties, wetting phenomena, molecular assembly, and the behavior of single molecules. Currently, we are focused on the design of molecular tensile machines, exploring new strategies in lithography, developing molecular fluidics, and mechanical activation of specific chemical bonds at interfaces. Using molecular imaging techniques we are able to observe how individual molecules move, self-organize, respond, and react on surfaces. These studies have direct implications on microelectronics, photonics, fluidics, and oil recovery, i.e. technologies that greatly exploit the microstructure and surface properties of thin polymer films

Research Highlights

Avalanche-like Breaking of Chemical Bonds

Mechanical activation of chemical bonds typically involves the application of external forces, which implies a broad distribution of bond tensions. Carolina’s Sheiko Group in collaboration with the Rubinstein and Matyjaszewski groups have demonstrated that controlling the flow profile of a macromolecular fluid generates and delineates mechanical force concentration. As reported inJACS, this enables a hierarchical activation of chemical bonds on different length scales from the macroscopic to the molecular. Bond tension is spontaneously generated within brushlike macromolecules as they spread on a solid substrate.

The molecular architecture creates an uneven distribution of tension in the covalent bonds, leading to spatially controlled bond scission. By controlling the flow rate and the gradient of the film pressure, one can sever the flowing macromolecules with high precision. Specific chemical bonds are activated within distinct macromolecules located in a defined area of a thin film. Furthermore, the flow-controlled loading rate enables quantitative analysis of the bond activation parameters.

Molecular Tensile Testing Machines

Mechanical activation of chemical bonds plays a vital role in biology, chemistry, and materials engineering. Usually, one should use an external tool to induce deformation of bond length and bond angles. UNC Chemistry’s Sheiko Groupin collaboration with the Matyjaszewski Group at Carnegie Mellon University and the Rubinstein Group, also at UNC Chemistry has discovered a class of macromolecules that self-generate tension in their covalent bonds without applying any external force.

One example is molecular bottle-brushes; highly branched macromolecules with side chains densely grafted to a long polymer backbone. These polymer architectures are regarded as molecular tensile testing machines, wherein the brush section generates force and transmits it to covalent bonds in the backbone. The bond tension depends on molecular architecture and interaction of macromolecules with the surrounding environment. Through variation of temperature, solvent, and substrate composition, one can control bond tension in a broad range from pico- to nano-Newtons, which is sufficient to break both weak H-bonds and strong covalent bonds. Furthermore, smart molecular design allows fine tuning of the tension distribution and enables mechanical activation of chemical reactions at specific chemical bonds within a macromolecule.

Sheiko Research Group