Our research group is interested in understanding fundamental interactions in soft materials from molecular level and relating to bulk state properties.
While nanoparticles and polymers are widely used materials in industrial/daily products, it can exhibit unique properties when they are combined. Our research group is interested in understanding of particle-polymer interactions and controlling the structures to produce desired properties in complex nanoparticle-polymer composites. Upon the deep understanding of structural behavior of polymer composite materials, versatile thin film and novel 3-D nanostructures can be created; a special interest lies on block copolymer related composites.
Currently, the following topics are being investigated
- Colloids and polymer mixtures in non-equilibrium state
- Block copolymer related nanocomposites
- Functionalized particle-polymer composites
Structure and Dynamics of Colloidal Glasses
As a supercooled liquid approaches its glassy state without crystallization, unexpected physical properties can emerge; the most obvious change is that the viscosity increases by many orders of magnitude with small reductions in temperature. While this glass-like behavior is interesting and has been extensively studied in polymers, attentions has recently been given to colloidal systems, not only because colloidal particles are as an excellent model system for glasses, but because the transition of concentrated colloidal systems to the glassy state also has a great implication for the design and usage of many consumer products where particles are used as fillers to change the various physical properties. As the particles interact by volume exclusion and the volume fraction of colloidal particles increases, particles are localized within a cage of neighbor particles, slowing down the structural relaxation of particles dramatically.
Gelation of Graphene Oxide in Polymer Solutions
Graphene and its oxidized form of Graphene oxide (GO) have been of particular interest in material science due to their exceptional physical properties. However, relatively little attention has been paid to the GO dispersions although the state of dispersions directly affect to the material property. We systematically study the GO dispersion at various conditions and examine how GO gelation is affected by the presence of polymer.
Collaboration with S. O. Kim group at KAIST
Nanopatterning with Block Copolymers
Based on fundamental soft matter physics, we are interested in showing how soft materials can be employed in nanofabrication. More specifically, nanopatterning with block copolymers will be one of the promising applications. Since the characteristic size and spacing of block copolymer domains are on the order of 10- 100 nm, the range required by next-generation electronic and functional devices, nanopatterning with block copolymer thin films has emerged as a favorable technique. Furthermore, its distinct advantages in cost, fabrication and areal coverage are expected to overcome the shortcomings of conventional lithographic techniques.
Our focus was on
- Film structure of Block copolymers in a confined space
- Nanopattering with microfluidics
- Multilayer structure with nanoparticles
- Nano-contact printing system
Going into Details for Micro- Nano- structures
We use small angle scatterings extensively to study the microstructure of soft matter systems listed above. Small angle x-ray scattering (SAXS), small angle neutron scattering (SANS), Grazing Incidence SAXS (GI-SAXS) and light scattering (LS) are good experimental tools to study particle interactions and polymer microstructures. We are also interested in seeing their physical properties; rheological properties are examined with conventional rheometer and Diffusing Wave Spectroscopy (DWS).