Research & Initiatives

The Polymer Nanomaterials Laboratory at Chung-Ang University, Republic of Korea focuses on controlling the interfaces between neutral and charged (or highly polar) species in order to prepare polymeric (or hybrid) nanomaterials for energy, healthcare, and industrial applications.

We are now studying polymeric nanomaterials used in three research disciplines:

- Photocatalysts based on conjugated polymer-metal/metal oxide hybrids

- Fibers/textiles/composites with antiviral/antimicrobial properties

- Rubber-based nanocomposites for the semiconductor industry

Highly Ordered Structures in Conjugated Polymer Nanomaterials Assembled with Amphiphiles for Enhanced Optoelectronic Properties

Revealing the nature of chain packing in conjugated polymer nanoparticles (CPNs) is one of the important issues to polymer physics research. Surfactant-stabilized CPNs in water show significantly enhanced luminescence intinsity in comparison to small molecular organic dyes and single polymer chains dissolved in solvents. The importance of the conjutated polymer structure in nanomaterials is undoubted. However, details of the relationship between alignment of conjugated backbone in CPNs and its luminescent property have not been estabilished. Furthermore, there are yet no methods that can predict the atom-resolved structure of conjugated polymer in the CPNs. We empoly coarse-grained (CG) molecular dynaic simulations to investigate the structure of phase-separated film and the film shattering process for a mixture of a conjugated polymer and a phospholipid. The pi-pi stacked structure of the conjugated polymer is significantly enhanced when the ratio of the phospholipid increases in both dried and water exposed film. We also show that the amount of the phospholipid is at least 2.5 times larger than that of the conjugated polymer to wrap the conjugated polymer chain. We confirmed that conjugated backbones inside the nanoparticles were completely shielded from the aqueous solution by the dense layers of alkyl chains, resulting in remarkably enhanced chain packing. These simulated results are correlated with experimentally observed structure through UV-vis-near infrared (UV-vis-NIR) spectrometry, scanning electron microscopy (SEM), particle size analysis, transmission electron microscopy (TEM), and grazing-incidence X-ray diffraction (GIXD). [Macromolecules 2017, 50, 6935; Copyright 2017, ACS Publications]

Conjugated polymer nano-ellipsoids assembled with octanoic acid and their polyurethane nanocomposites with simultaneous thermal storage and antibacterial activity: Fatty acids for an antibacterial agent

We prepared conjugated polymer nano-ellipsoids (CPNs) via emulsification of chloroform phase using the octanoic acid (OA) in dimethyl formamide (DMF), followed by the removal of chloroform by heating. The resulting CPN DMF solutions were thoroughly mixed with polyurethane (PU) DMF solutions to form composite films upon solvent removal, with uniformly distributed CPNs due to hydrogen bonds between PU matrix and the CPNs. Superior photothermal and antibacterial properties of the PU:CPN composite films were observed, presenting the usefulness of CPNs as an efficient light harvester and thermal storage material, and the OA as an antibacterial material for multifunctional fiber applications. [J. Ind. Eng. Chem. 2018, 63, 33]

Strong Bathochromic Shift of Conjugated Polymer Nanowires Assembled with a Liquid Crystalline Alkyl Benzoic Acid via a Film Dispersion Process

We present aqueous dispersions of conjugated polymer nanowires (CPNWs) with improved light absorption properties aimed at aqueous-based applications. We assembled films of a donor–acceptor-type conjugated polymer and liquid crystalline 4-n-octylbenzoic acid by removing a cosolvent of their mixture solutions, followed by annealing of the films, and then formed aqueous-dispersed CPNWs with an aspect ratio >1000 by dispersing the films under ultrasonication at a basic pH. X-ray and spectroscopy studies showed that the polymer and liquid crystal molecules form independent domains in film assemblies and highly organized layer structures in CPNWs. Our ordered molecular assemblies in films and aqueous dispersions of CPNWs open up a new route to fabricate nanowires of low-band-gap linear conjugated polymers with the absorption maximum at 794 nm remarkably red-shifted from 666 nm of CPNWs prepared by an emulsion process. Our results suggest the presence of semicrystalline polymorphs β1 and β2 phases in CPNWs due to long-range π–π stacking of conjugated backbones in compactly organized lamellar structures. The resulting delocalization with a reduced energy bang gap should be beneficial for enhancing charge transfer and energy-conversion efficiencies in aqueous-based applications such as photocatalysis. [ACS Omega 2021, 6, 34876]