Directional crystallization of semiconducting homopolymers and novel donor-acceptor diblock copolymers for control of nanostructure and optoelectronic properties

• Applicants: Professor Dr. Mukundan Thelakkat; Professor Dr. Thomas Thurn-Albrecht
• Subject Area: Preparatory and Physical Chemistry of Polymers ; Experimental and Theoretical Physics of Polymers
• Term: from 2018 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 407706940

• Final Report Year: 2024

Final Report Abstract

The objectives of the project were first to synthesize tailored donor and acceptor polymers as well as block copolymers and study their structure formation and crystallite alignment on substrates. In this context diverse polythiophenes with differing side chains and surface energies as well as polydiketopyrrolopyrroles having different flanking units were designed and their structure formation was studied in detail. We could show that the crystal orientation in films of substituted polythiophenes is determined by interfacial interactions at both the substrate and vacuum interfaces. Therefore, by tuning the surface energy of the polymers (via side chains), a uniform face-on crystal orientation induced by graphene can be realized in polythiophene films as thick as 200 nm. In one case, face-on crystal orientation of a modified polythiophene is even attained on amorphous surfaces. Due to the competition of interfacial interactions, the crystal orientation can be switched in the same sample depending on the crystallization conditions. These results demonstrate that directed crystallization can be used to control the orientation of semicrystalline functional polymers in thin films given that the surface energy of the polymers as well as the interaction with both interfaces is taken into account. Furthermore, the chemical structure of polydiketopyrrolopyrroles (PDPPs) could be varied in a very flexible manner by changing the flanking units on either side of DPP core and the comonomer used to obtain alternating copolymers. This also leads to hole transport or ambipolar transport or electron transport depending on the structural motive. Although the chemical structures of a series of model polymers differ only slightly from one another, namely by an additional side-chain or a different flanking unit, the modifications led to an increase in long-range order and thereby to a change in the phase state from sanidic ordered over sanidic rectangular or oblique to crystalline. Finally, an acceptor-acceptor copolymer based on DPP and thienopyrrolidone (TPD) units was realized and its n-type character was confirmed by Seebeck measurements and n-type transsitor character.

Publications

• Influence of ω-Bromo Substitution on Structure and Optoelectronic Properties of Homopolymers and Gradient Copolymers of 3-Hexylthiophene. Macromolecules, 53(7), 2474-2484.
  Schmode, Philip; Schötz, Konstantin; Dolynchuk, Oleksandr; Panzer, Fabian; Köhler, Anna; Thurn-Albrecht, Thomas & Thelakkat, Mukundan
  
• The Key Role of Side Chain Linkage in Structure Formation and Mixed Conduction of Ethylene Glycol Substituted Polythiophenes. ACS Applied Materials & Interfaces, 12(11), 13029-13039.
  Schmode, Philip; Savva, Achilleas; Kahl, Robert; Ohayon, David; Meichsner, Florian; Dolynchuk, Oleksandr; Thurn-Albrecht, Thomas; Inal, Sahika & Thelakkat, Mukundan
  
• Elucidating the Effect of Interfacial Interactions on Crystal Orientations in Thin Films of Polythiophenes. Macromolecules, 54(12), 5429-5439.
  Dolynchuk, Oleksandr; Schmode, Philip; Fischer, Matthias; Thelakkat, Mukundan & Thurn-Albrecht, Thomas
  
• Polydiketopyrrolopyrroles Carrying Ethylene Glycol Substituents as Efficient Mixed Ion‐Electron Conductors for Biocompatible Organic Electrochemical Transistors. Advanced Functional Materials, 31(20).
  Krauss, Gert; Meichsner, Florian; Hochgesang, Adrian; Mohanraj, John; Salehi, Sahar; Schmode, Philip & Thelakkat, Mukundan
  
• High electron mobility and tuneable glass transition temperature in fullerene-functionalized polynorbornenes. Journal of Materials Chemistry C, 10(16), 6419-6428.
  Erhardt, Andreas; Hochgesang, Adrian; Meichsner, Florian & Thelakkat, Mukundan
  
• A Competitive n‐Type OECT Material via Copolymerization of Electron Deficient Building Blocks. Advanced Electronic Materials, 9(7).
  Erhardt, Andreas; Hochgesang, Adrian; McNeill, Christopher R. & Thelakkat, Mukundan
  
• Highly Efficient n‐Doping via Proton Abstraction of an Acceptor1‐Acceptor2 Alternating Copolymer toward Thermoelectric Applications. Advanced Functional Materials, 33(30).
  Hochgesang, Adrian; Erhardt, Andreas; Mohanraj, John; Kuhn, Meike; Herzig, Eva M.; Olthof, Selina & Thelakkat, Mukundan