Yi Pang

Research Interests

Research in our group is focused on the design and synthesis of novel p-conjugated macromolecules that has potential applications in chemistry, biology, and material science.  Examples of these applications include light-emitting, light-harvesting, and ion-sensing.

Luminescent Polymers

A major recent development in the field of molecular electronics has been the discovery of electroluminescent conjugated polymers. Emission of bright light when excited by flow of electricity through the conjugated polymers makes these materials attractive for commercial applications such as backlights for liquid crystal displays, large screen displays, and lasers. A reliable polymeric light-emitting diode device requires the polymer emissive layer to exhibit high efficiencies in photoluminescence and electroluminescence. Our goal is to develop such materials to meet the practical requirements, through design and synthesis of new polymers with high luminescence and improved stability. The applications include light-emitting diodes and photovoltaic devices.

Optical absorption and emission spectra at low temperature has been proven to be a useful tool in elucidating the vibronic and aggregate structure of a p-conjugated molecule.  Understanding the related phenomenon will aid the development of new polymers of high luminescence.   In the following example, the polymer in THF/MeOH solution reveals gradual aggregate formation as the temperature decreases.

Carbon Nanotubes

Solubilizing and purifying carbon nanotubes remains one of the foremost technological barriers in realization of their potential applications.  In this direction, we are interested in using soluble polymers to effectively disperse single-walled carbon nanotubes (SWNTs) into solutions.   The specific conformation associated with each polymer structure could play important roles in selective interaction with different types of SWNTs.  For example, poly[(m-phenylenevinylene)-alt-(p-phenylenevinylene)] forms a cavity of about 1.3 nm, which preferably wraps up the SWNT of comparable diameters (1.0-1.2 nm).  The vinylene bond geometry is also found to influence the metallic tube selectivity.

Chemical Sensors

The luminescence signals of a material change, sometimes drastically, with the chemical environment.  In this field, we will modify the polymer structure to develop sensor materials. With proper chelating groups, one can selectively bind the targeted metal ions, thereby enhancing the selectivity. We are also interested in the polymer systems which can generate large optical response upon binding analyte.

Selected Publications 

1. "Wrapping of Single-Walled Carbon Nanotubes by a p-Conjugated Polymer: The Role of Polymer Conformation-Controlled Size Selectivity." W. Yi, A. Malkovskiy, A. P. Sokolov, M. L. Colon, M. Meador, Y. Pang   Journal of Physical Chemistry B, 2008, 112, xxxx (in press).
2. "A Polymeric Sensor with Excited-State Intramolecular Proton Transfer: Its Response toAnionic Species." Q. Chu, D. A. Medvetz, Y. Pang   Chem. Mater., 2007, .
3. "Synthesis and Optical Properties of Light-Emitting p-Conjugated Polymers Containing Biphenyl and Dithienosilole." L. Liao, A. Cirpan, Q. Chu, F. E. Karasz, and Y. Pang   J. Polym. Sci. Part A: Polym. Chem.  2007, 45 (10), 2048-2058.
4. "Terpyridine-Substituted Fluorescent Polymers and Their Chelation with Zinc Ion: Ligand-to-Metal Ratio and Optical Properties." Q. Chu and Y. Pang, J. Polym. Sci. A.: Polym. Chem., 2006, 44, 2338-2345. 
5. "Aggregation and Self-Assembly of Oligo(2,5-dialkoxy-1, 4-phenyleneethynylene)]s: An Improved Probe to Study Inter- and Intra-Molecular Interaction." Q. Chu, Y. Pang; Macromolecules, 2005, 38, 517-520.
6. "Blue-Emitting Poly(1,3-phenylenevinylene) Derivatives: Effect of Substitution Patterns on the Optical Properties." L. Liao, Y. Pang, L. Ding, and F. E. Karasz; J. Polym. Sci. Part A: Polym. Chem., 2005, 43, 2800-2809.
7. "Synthesis and Luminescence of Yellow/Orange-Emitting Poly[tris(2,5-dihexyloxy-1,4-phenylenevinylene)-alt-(1,3-phenylenevinylene)]s" L. Liao, Y. Pang, L. Ding, F. E. Karasz, P. R. Smith, and M. A. Meador;  J. Polym. Sci. Part A: Polym. Chem., 2004, 42, 5853-5862.
8. "A Highly Efficient Light-Emitting Poly[5-(dipenylamino)-1,3-phenylene vinylene]-alt-(2,5-dihexyloxy-1,4-phenylene vinylene)]: Synthesis and Optical Properties." L. Liao, Y. Pang, L. Ding, and F. E. Karasz; Macromolecules, 2004, 37, 3970-3972.
9. "Molecular Aggregation of Poly[(1,3-phenyleethynylene)-alt-oligo(2,5-dialkoxy-1, 4-phenyleneethynylene)]: Effect of Solvent, Temperature, and Polymer Conformation." Q. Chu, Y. Pang; Macromolecules, 2003, 36, 4614-4618. 
10. "Green-Emitting PPE-PPV Hybrid Polymers: Efficient Energy Transfer across meta-Phenylene Bridge."  Q. Chu, Y. Pang, L. Ding, F. E. Karasz; Macromolecules, 2003, 36, 3848-3853.