Kinetically Controlled Formation of Semi-crystalline Conjugated Polymer Nanostructures

Peter Kei, Mitchell T. Howell, Carlos A. Chavez, Joseph C. Mai, Changwoo Do, Kunlun Hong, Evgueni E. Nesterov

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

Conjugated polymer (CP) materials that are considered as an attractive choice for various electronic and optoelectronic applications possess highly heterogeneous complex structures that can span several orders of magnitude in length scale. This is due to the intricate coupling effects of weak secondary interactions and entropic forces that determine molecular organization in bulk polymer materials. Understanding the influence of molecular interactions on the emergence and evolution of nano- and microscale structures is of paramount importance to the guided design and development of condensed CP materials. Such understanding is even more critical for the rational design of hierarchical systems away from equilibrium, where weak molecular interactions can guide the system along competing kinetic pathways toward local energy minima and metastable architectures. In this work, we studied a promising concept for accessing various kinetically stabilized semi-crystalline CP nanostructures that are formed in the process of controlled chain-growth Kumada catalyst-transfer polymerization initiated by a small-molecule catalytic species which can exist in equilibrium between free and aggregated states. Specifically, we chose a small-molecule perylenedicarboximide (PDCI) polymerization catalytic initiator which has a strong tendency toward reversible supramolecular assembly-disassembly that can be controlled by temperature. Addition of a thiophene monomer to a solution of the PDCI initiator starts the chain-growth polymerization process, which produces distinct nanoscale semi-crystalline polythiophene structures formed under predominant kinetic control. We demonstrated that, depending on the reaction temperature (which affects the fine balance between the position of PDCI assembly-disassembly equilibrium, rate of polymerization, and solvent-solute interactions for the growing polythiophene chains), a range of kinetically trapped hierarchically organized semi-crystalline CP systems with substantially varying optoelectronic properties could be obtained. In addition to spectroscopic and electron microscopic studies, in order to better reveal the structural aspects of the generated polymer nanoscale systems, we carried out a series of X-ray diffraction and neutron scattering experiments which indicated complex hierarchical organization in these kinetically stabilized CP assembled materials. We expect that this in situ polymerization-based approach can lead to a general way to expand access to various semi-crystalline CP nanostructured materials with broadly tunable electronic and optical properties.

Original languageEnglish
Pages (from-to)2162-2177
Number of pages16
JournalMacromolecules
Volume54
Issue number5
DOIs
StatePublished - Mar 9 2021

Funding

This research was supported by the U.S. Department of Energy (DOE) under EPSCoR grant no. DE-SC0012432 with additional support from the Louisiana Board of Regents. P.K. was supported by the DOE Office of Science Graduate Student Research Fellowship for his experimental work at Oak Ridge National Laboratory (ORNL). This research used resources at Spallation Neutron Source and Center for Nanophase Materials Sciences, the DOE Office of Science User Facilities operated by ORNL, and resources of the Advanced Photon Source and Center for Nanoscale Materials, the DOE Office of Science User Facilities operated for the DOE Office of Science by Argonne National Laboratory under contract no. DE-AC02-06CH11357. We thank Dr. Saul H. Lapidus (Argonne National Laboratory) for assistance with acquiring powder XRD data. We acknowledge the NSF MRI program (grant CHE-1726931 to Northern Illinois University) for the purchase of a high-resolution mass spectrometer.

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