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Research

IPOC - Functional Polymers

In our interdisciplinary research team of polymer chemists, organic chemists, physical chemists and material scientists, we are working on FUNCTIONAL POLYMERIC & HYBRID MATERIALS for applications in polymer electronics and electrochemical devices. The main aim is to control and manipulate structure-property relationships at the molecular and mesoscopic scale in films. On the mesoscopic scale self-assembly and crystallization are guided by bottom-up and top-down approaches. Functionalities include redox activity for electrochemical devices such as batteries and electrocatalysis, optical and electronic properties for polymer (opto)electronics and stimuli-responsive “intelligent” behavior for actuators.

Research Subjects

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Our fully equipped organic and polymer chemistry lab is specialized on chromophore synthesis and controlled polymerization techniques of functional (block) copolymers and semiconducting polymers. Tailor-made material design with architectural control is applied to further induce self-assembly and crystallization on hierarchical length scales in film geometries. Post-polymerization modification of polymers and films, e.g. by click chemistry, is among our specializations.

 Research examples include:

  • Triarylamine redox polymers[1] and conjugated redox polymers[2]
  • N-type semiconducting polymers with varying regioregularity[3]
  • Conjugated thiophene polymers with 2D- or 3D- architectures using oxidative, Ni-catalyzed or electro-polymerization methods[4,5]
  • Conjugated polyelectrolytes[6,7] for mixed conductivity
  • Chromophores for electro-optical applications[8]

[1]  E.J.W. Crossland et al. ACS Nano 4, 2010, 962.

[2] P. Reinold et al. Polymer Chemistry 8, 2017, 7351.

[3] Y. Gross et al. Macromolecules 50, 2017, 5353.

[4] M. Scheuble et al. Macromolecules 48, 2015, 7049.

[5] M. Scheuble et al. Macromol. Rapid Commun. 36, 2015, 115.

[6] T.V. Richter et al. J. Am. Chem. Soc. 134, 2012, 43.

[7] R. Merkle et al. Polymer 132, 2017, 216. 

[8] N. Hoppe et al. Adv. Radio Science 15, 2017, 141.

 

 In addition to electropolymerization as synthetic tool[1], we use cyclic voltammetry combined with in-situ spectroscopy, in-situ conductance and quartz crystal microbalance measurements to study electrochemical charging / doping and charge transport mechanisms of semiconducting polymers, such as polythiophenes, low bandgap copolymers and redox polymers bearing redox-active triarylamine groups [2]. Particular emphasis is put on the role of film deposition and polymer morphology on the electrochemical behavior and energy levels.[3,4] Ion transport of polyelectrolytes and conjugated polyelectrolytes is elucidated by ac impedance measurements under humidity control.[5]

https://opencms.uni-stuttgart.de/fak3/ipoc/fp/ipoc-functionlpolymers/electrochemie.jpg

In-situ spectroelectrochemistry for direct determination of neutral/charged species and HOMO/LUMO levels proved to be a very useful tool in the identification of charge separated states in organic solar cells [6] and for the analysis of photoreactions in light harvesting systems[7].

Electrochemical applications include batteries, sensors, actuators and electrocatalysis.

[1]  S. Link et al. Langmuir, 29, 2013, 15463.

[2]  O. Yurchenko et al. Chem. Phys. Chem. 11, 2010, 1637.

[3] K. Bruchlos et al. Electrochim. Acta 269, 2018, 299.

[4]  D. Trefz et al. J. Phys. Chem. C 119, 2015, 22760.

[5] R. Merkle et al. Polymer 132, 2017, 216.

[6]  S. Albrecht et al. Adv. Mater. 26, 2014, 2533.

[7]  L. Liu et al. Phys. Chem. Chem. Phys. 18, 2016, 18536.

 

 

Having a strong expertise in block copolymer self-assembly[1] we have focused on morphology control of semicrystalline polymers in recent years.[2,3] To gain control over mesoscopic order in thin films of polymers like poly(3-hexylthiophene) [4,5] and low band gap donor-acceptor copolymers such as PCPDTBT [6] and P(NDI2OD-T2) [7] aims at understanding structure formation starting from crystal structure analysis into macroscopic alignment.
Controlled solvent vapor annealing treatment[3], shear alignment [7] and crystallization under confinement [5] are some of the methods we use to reduce nucleation densities[4] and align and order polymer films. Methods include atomic force microscopy, electron microscopy and X-ray techniques.

Anisotropic charge transport is measured by field effect transistor (FET) and 4-point-probe conductivity techniques.

[1]  S. Ludwigs et al. Nature Mater. 2, 2003, 744.

[2] S. Ludwigs, Editor, P3HT revisited - from Molecular Scale to Solar Cell Devices, Adv. Polym. Sci., Springer, Heidelberg, 2014.

[3] G. Schulz, S. Ludwigs Adv. Funct. Mater. 27, 2017, 1603083.

[4] E.J.W. Crossland, et al. Adv. Funct. Mater. 21, 2011, 518. & Adv. Mater. 24, 2012,  839.

[5]  F.S.U. Fischer et al. Nanoscale 4, 2012, 2138.

[6]  F.S.U. Fischer et al. Adv. Mater. 27, 2015, 1223.

[7]  K. Tremel et al. Adv. Energy Mater. 2014, 1301659.

Block copolymer films [1] with their ability to self-assemble into highly ordered microdomain structures on length scales between 5 and 50 nm are high performance mesoporous templates for electrodeposition, bio-inspired material synthesis and catalysis under confinement.
In the case of electrodeposition we showed that poly(fluorostyrene)-block-polylactide block copolymers can be used as templates for the nanostructuring of inorganic semiconductors, e.g. Cu2O and TiO2 [2,3]. Both freestanding TiO2 nanowires and gyroid structures could be successfully incorporated into liquid-electrolyte and solid-state dye-sensitized solar cells [3]. Functional block copolymer templates include redox active blocks[4].
Additionally, we explore bio-inspired routes towards polymer/mineral hybrid materials by infiltration of block copolymer templates with inorganic species from aqueous solution at room temperature. Besides work on calcite we are interested in the synthesis of nanostructured functional oxides [5,6], e.g. Co3O4 for electrocatalytic applications.[7]

Within the SFB1333 we will explore catalysis under confinement within our project “Tunable Block Copolymer Templates for Spatially Controlled Immobilization of Molecular Catalysts”.

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[1] S. Ludwigs et al. Nature Mater. 2, 2003, 744.

[2]  E.J.W. Crossland et al. Soft Matter 3, 2007, 94.

[3]  E.J.W. Crossland, et al.  Nano Lett. 9, 2009, 2807. & Nano Lett. 9, 2009, 2813.

[4]  E.J.W. Crossland et al. ACS Nano 4, 2010, 962.

[5]  A. Finnemore et al. Adv. Mater. 21, 2009, 3928.

[6]  S. Ludwigs et al. Adv. Mater. 18, 2006, 2270.

[7] A.S. Schenk et al. Nanoscale 9, 2017, 6334.

 

 

Dieses Bild zeigt Ludwigs
Prof. Dr. rer. nat. habil.

Sabine Ludwigs

Head of Chair