Our current research focus is two folds: i) Phase Behavior of Polymers and Related Materials and ii) Ion-containing Polymers.

 

Phase States and Phase Transitions of Polymer and Polyaromatic Hydrocaron Mixtures

Polyaromatic hydrocarbons (PAHs) have unique physical properties and are useful in designing self-assembling materials, organic electronics, and optical applications. PAHs are generated from combustion processes, also abundant in crude oils and coals, and even the universe. However, their delocalized π electrons and planar molecular structures make PAHs highly immiscible with many organic materials, and controlled incoproration of PAHs with other materials is often challenging. We are investigating the phase behavior of polymers and PAHs to understand the molecular structural factors governing the miscibility between PAHs and polymers.

We realized that characterization of the phase behaviors of mixtures of polymers and small PAHs can be conveniently conducted using differential scanning calorimetry (DSC), and even the DSC characterization can simultaneously extract the composition of polymer-rich phase. We chose pyrene as a representative PAH compound and investigated the phase behavior of pyrene and model polymers. This work is reported in Gagan N. Kangovi, Sangwoo Lee, "Phase Behavior of Pyrene and Vinyl Polymers with Aromatic Side Groups." Macromolecules 2017, ASAP.

We are currently investigating the phase separation behaviors relevant to destabilizations of multicomponent mixtures using polymer and PAH compounds to find a way to control the phase separation process.

 

Block Copolymer-based Fuel Cell Membranes

Fuell cell technology directly converts chemical energy to the electrical energy and has many advantages regarding storage and transportation of energy; and energy density. Fuel cell technology also accords very well with sustainable and renewable energy resources.

One challenge in the fuel cell technology is the preparation of cost-competitive and high-performance polymer electrolyte membranes with excellent thermal and chemical stability. We believe block copolymers can be the solutions for the cost-competitive and high-performance polymer electrolyte membranes. We are actively working on the development of new class of block copolymer-based fuel cell membranes.

 

Precisely Tailored Ionomers

Ionomers are polymers containing a small amount of ionic groups in non-ionic polymer chains. The ionic groups in the chains have strong inter-associations due to the Coulombic forces and result in new properties to ionomers.

We are currently establishing a new synthetic strategy to prepare precisely tailored ionomers that will open new opportunities to tune the structures and properties of ionomers.

 

Polymeric Micelles on Close-Pakced Lattices

Block copolymers are excellent model materials to explore self-assembled structures by microphase-separated domains. In recent years, packing structures known as Frank-Kasper phases by linear block copolymers melts are identified (see relevant publications 1, 2, and 3). The origin of Frank-Kasper phases of block copolymers is indirectly understood based on the surface area density of the Wigner-Seitz cells of these packing structures.

However, the origin of close-packed structures by block copolymer micelles is not known though the close-packed structures were identified much earlier than the other packing structures. More specifically, it is not known why block copolymer micelles select a certain close-packed structure among other ones at different conditions. We are investigating close-packed structures of block copolymer micelles to elucidate the fundamental origin of the close-packed structures of soft particles.