FY2021 Annual Report

pi-Conjugated Polymers Unit​
Professor Christine Luscombe 


Pi-Conjugated semiconducting polymers are actively under development for use in organic light-emitting diodes, thin-film transistors, and solar cells. However, the understanding of their performance in many applications is limited because of the difficulty in establishing detailed structure-property relationships, which arises from the disconnect in our understanding of microstructure development. The lack of a unified understanding in microstructure formation, in turn, partly comes from our inability to precisely control defects in pi-conjugated semiconducting polymers. Additionally, due to our limitations in controlling the synthesis of these polymers, the majority of studies related to these classes of materials have focused on linear polymers with broad molecular weight distributions. While it is widely recognized that, for traditional insulating coiled polymers, the topology and architecture of the polymers will greatly affect their properties, a detailed structure-property relationship for how the topology of rigid rod polymers such as pi-conjugated semiconducting polymers affects the microstructure and thus their optoelectronic properties has remained limited. With these factors in mind, the primary goal in our group has focused on the development of controlled polymerizations to synthesize precise polymeric structures and hybrid materials to enable us to perform structure-property relationships that have not been possible to date.

Below are specific projects that we are working on:

  • Living polymerizations to synthesize semiconducting polymers
  • Inorganic-organic hybrid systems
  • Using CH-functionalization for the synthesis of semiconducting polymers – moving towards more environmentally sustainable reactions
  • Semiconducting polymers for stretchable electronics
  • Mixed ionic/electronic conducting polymers for use in energy storage, bioelectronics and robotic materials
  • Identifying the fate of microplastics in marine organisms

1. Staff

  • Dr. Christine Luscombe, Group Leader
  • Dr. Preeti Yadav, Researcher
  • Dr. Samantha Phan, Researcher
  • Dr. Isha Sanskriti, Researcher
  • Nivedha Velmurugan, Rotation Student (winter 2022)
  • Tom Whilfing, Rotation Student (winter 2022)
  • Callum Hudson, Rotation Student (spring 2022)
  • Daniel Gutierrez Del Rio, Rotation Student (spring 2022)
  • Midori Tanahara, Administrative Assistant

2. Collaborations

2.1 Cross Dehydrogenative Coupling Polymerization to synthesize semiconducting polymers

  • Type of collaboration: Joint research
  • Researchers:
    • Professor Kendall Houk, University of California, Los Angeles
    • Professor Xin Hong, Zhejiang University, China
    • Dr. Ji-Ren Liu, Zhejiang University, China

2.2 Use of Neutron and X-Ray Scattering to Elucidate the Structure of Conjugated Polymers

  • Type of collaboration: Joint research
  • Researchers:
    • Professor Lilo Pozzo, University of Washington, Seattle
    • Dr. Caitlyn Wolf, University of Washington, Seattle

2.3 The Development of Non-Fullerene Electron Acceptors for Bulk Heterojunction Solar Cells

  • Type of collaboration: Joint research
  • Researchers:
    • Professor Pakkirisamy Thilagar, Indian Institute of Science, Bangalore
    • Dr. Samir Kumar Sarkar, Indian Institute of Science, Bangalore

2.4 The Development of Mixed Ionic-Electronic Conducting Polymers

  • Type of collaboration: Joint research
  • Researchers:
    • Professor Christopher Ober, Cornell University
    • Professor Shraysh Patel, University of Chicago
    • Professor Paul Nealey, University of Chicago
    • Prof. David Ginger, University of Washington, Seattle
    • Dr. Lee Richter, NIST
    • Dr. Lucas Flagg, NIST
    • Dr. Adam Marks, Oxford University

2.5 Understanding the performance of donor-acceptor semiconducting polymers

  • Type of collaboration: Joint research
  • Researchers:
    • Professor Alberto Salleo, Stanford University
    • Professor Natalie Stingelin, Georgia Tech
    • Professor Frank Spano, Temple University

3. Activities and Findings

3.1 The Development of Mixed Ionic-Electronic Conducting Polymers

Bioelectronics focuses on the establishment of the connection between the ion-driven biosystems and readable electronic signals. Organic electrochemical transistors (OECTs) offer a viable solution for this task. Organic mixed ionic/electronic conductors (OMIECs) rest at the heart of OECTs. The balance between the ionic and electronic conductivities of OMIECs is closely connected to the OECT device performance. While modification of the OMIECs’ electronic properties is largely related to the development of conjugated scaffolds, properties such as ion permeability, solubility, flexibility, morphology, and sensitivity can be altered by side chain moieties. We have performed a number of studies to understand how the structure of OMIECs’ affect their performance. These results are summarized in refs. 10 and 11 below. We have also written two review papers, refs. 3 and 5 on this topic. 






3.2 Cross Dehydrogenative Coupling Polymerization to synthesize semiconducting polymers

The Carothers equation is often used to predict the utility of a small molecule reaction in a polymerization. In this study, we present the mechanistic study of Pd/Ag cocatalyzed cross dehydrogenative coupling (CDC) polymerization to synthesize a donor–acceptor (D–A) polymer of 3,3′-dihexyl-2,2′-bithiophene and 2,2′,3,3′,5,5′,6,6′-octafluorobiphenyl, which go counter to the Carothers equation. It is uncovered that the second chain extension cross-coupling proceeds much more efficiently than the first cross-coupling and the homocoupling side reaction (at least 1 order of magnitude faster) leading to unexpectedly low homocoupling defects and high molecular weight polymers. Kinetic analyses show that C–H bond activation is rate-determining in the first cross-coupling but not in the second cross-coupling. Based on DFT calculations, the high cross-coupling rate in the second cross-coupling was ascribed to the strong Pd-thiophene interaction in the Pd-mediated C–H bond activation transition state, which decreases the energy barrier of the Pd-mediated C–H bond activation. These results have implications beyond polymerizations and can be used to ease the synthesis of a wide range of molecules where C–H bond activation may be the limiting factor.






3.3 Developing environmentally sustainable reactions to synthesize semiconducting polymers

For environmentally sustainability, it is important to develop reactions that are less energy intensive than those that are currently used. One way to do this is to develop room temperature reactions. A robust method of room temperature direct arylation for benzofuran was developed. This discovery allows for mild arylation by commercially available aryl iodides with complete C-2 regioselectivity and tolerates a range of functional groups, including heat sensitive groups. Mechanistically, a Heck-type oxyarylation product from a direct arylation process is reported as a key piece of evidence for a carbopalladation intermediate.


4. Publications

4.1 Journals

  1. Liwen Xing, Ji-Ren Liu, Xin Hong, Kendall N. Houk, Christine K. Luscombe, "An Exception to the Carothers Equation Caused by the Accelerated Chain Extension in a Pd/Ag Cocatalyzed Cross Dehydrogenative Coupling Polymerization", J. Am. Chem. Soc., 2022, 144, 2311-2322. DOI: 10.1021/jacs.1c12599
  2. Richard R. Lunt et al., "Consensus statement: Standardized reporting of power-producing luminescent solar concentrator performance", Joule, 2022, 6, 8-15. DOI: 10.1016/j.joule.2021.12.004
  3. Yifei He, Nadzeya A. Kukhta, Adam Marks, Christine K. Luscombe, "The effect of side chain engineering on conjugated polymers in organic electrochemical transistors for bioelectronic applications", J. Mater. Chem. C, 2022, 2022,10, 2314-2332. DOI: 10.1039/D1TC05229B 
  4. Yunping Huang, Theodore A. Cohen, Breena M. Sperry, Helen Larson, Hao A. Nguyen, Micaela K. Homer, Florence Y. Dou, Laura M. Jacoby, Brandi M. Cossairt, Daniel R. Gamelin, Christine K. Luscombe, "Organic building blocks at inorganic nanomaterial interfaces", Mater. Horiz., 2022, 9, 61-97. DOI: 10.1039/D1MH01294K
  5. Nadzeya A. Kukhta, Adam Marks, Christine K. Luscombe, "Molecular Design Strategies toward Improvement of Charge Injection and Ionic Conduction in Organic Mixed Ionic–Electronic Conductors for Organic Electrochemical Transistors", Chem. Rev., 2022, 122, 13009– 13041. DOI: 10.1021/acs.chemrev.1c00266
  6. Jiří Vohlídal, Carlos F. O. Graeff, Roger C. Hiorns, Richard G. Jones, Christine Luscombe, Francois Schué, Natalie Stingelin, Michael G. Walter, "Glossary of terms relating to electronic, photonic and magnetic properties of polymers (IUPAC Recommendations 2021)", Pure Appl. Chem., 2022, 94, 15-69. DOI: 10.1515/pac-2020-0501
  7. Liwen Xing, Christine K. Luscombe, "Advances in applying C–H functionalization and naturally sourced building blocks in organic semiconductor synthesis", J. Mater. Chem. C, 2021, 9, 16391. DOI: 10.1039/D1TC04128B
  8. Caitlyn M. Wolf, Lorenzo Guio, Sage Scheiwiller, Viktoria Pakhnyuk, Christine K. Luscombe, Lilo D. Pozzo, "Strategies for the Development of Conjugated Polymer Molecular Dynamics Force Fields Validated with Neutron and X-ray Scattering", ACS Polym Au, 2021, 1, 134-152. DOI: 10.1021/acspolymersau.1c00027
  9. Samir Kumar Sarkar, Lauren J. Kang, Upendra Kumar Pandey, Christine K. Luscombe, Pakkirisamy Thilagar, "Triarylborane-BODIPY conjugate: An efficient non-fullerene electron acceptor for bulk heterojunction organic solar cell", Sol. Energy, 2021, 230, 242-249. DOI: 10.1016/j.solener.2021.10.048
  10. Tengzhou Ma, Ban Xuan Dong, Jonathan W. Onorato, Jens Niklas, Oleg Poluektov, Christine K. Luscombe, Shrayesh N. Patel, "Correlating conductivity and Seebeck coefficient to doping within crystalline and amorphous domains in poly(3-(methoxyethoxyethoxy)thiophene)", J. Polym. Sci., 2021, 59, 2797-2808. DOI: 10.1002/pol.20210608
  11. Ban Xuan Dong, Ziwei Liu, Jonathan W. Onorato, Tengzhou Ma, Joseph Strzalka, Peter Bennington, Christine K. Luscombe, Christopher K. Ober, Paul F. Nealey, Shrayesh N. Patel, "Ionic Dopant-Induced Ordering Enhances the Thermoelectric Properties of a Polythiophene-Based Block Copolymer", Adv. Funct. Mater., 2021, 31, 2106991. DOI: 10.1002/adfm.202106991
  12. Amy L. Mayhugh and Christine K. Luscombe, "Room Temperature C–H Arylation of Benzofurans by Aryl Iodides", Org. Lett. 2021, 23, 7079–7082. DOI: 10.1021/acs.orglett.1c02397
  13. Yunping Huang, Theodore A. Cohen, Christine K. Luscombe, "Naturally Derived Organic Dyes for LED Lightings of High Color Rendering and Fidelity Index", Adv. Sustain. Syst., 2022, 6, 2000300. DOI: 10.1002/adsu.202000300

4.2 Books and other one-time publications

Nothing to report

4.3 Oral and Poster Presentations

Presentations as Invited Speaker

  1. "Semiconducting polymers: New horizons and unmet future challenges", Bayreuth Polymer Symposium, September 2021
  2. "Organic dyes derived from molecules in cacao beans for use in lighting applications", Materials Research Society, Fall National Meeting, December 2021
  3. "Precise engineering of semiconducting polymers for organic electronics", Pacifichem, December 2021
  4. "Formation of Nanostructured Graphene Oxide during the Synthesis of Metal Chalcogenide Nanocrystals", Pacifichem, December 2021
  5. "Empowering Diversity in Science", Global Women's Breakfast, Joint OIST/University of Kyoto Event, February 2022
  6. "Side chain engineering control of mixed conduction in oligoethylene glycol-substituted polythiophenes", NanoGe Spring Meeting 2022, March 2022


  1. "Semiconducting polymers: New horizons and unmet future challenges", University of North Carolina, Chapel Hill, October 2021
  2. "Semiconducting polymers: New horizons and unmet future challenges", University of Illinois, Urbana Champaign, October 2021
  3. "Semiconducting polymers: New horizons and unmet future challenges", John Hopkins University, November 2021
  4. "Connecting the world through Chemistry", National Institute of Advanced Industrial Science and Technology, February 2022
  5. "Precise engineering of semiconducting polymers for organic electronics", Waseda University, March 2022

Workshops and symposia organized

  1. Symposium EN06—Sustainable Electronics—Green Chemistry, Circular Materials, End-of-Life and Eco-Design", Materials Research Society Fall National Meeting, December 2021
  2. Global Women's Breakfast, OIST/University of Kyoto Joint Event, February 2022

5. Intellectual Property Rights and Other Specific Achievements

Nothing to report

6. Meetings and Events

Nothing to report

7. Other


  1. Outstanding Reviewer for Chemical Science, 2021
  2. Outstanding Reviewer for Energy and Environmental Science, 2021