Smaller Counter Cation for Higher Transconductance in Anionic Conjugated Polyelectrolytes

© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Conjugated polyelectrolytes (CPEs) are a focus of research because combine their inherent electrical conductivity and the ability to interact with ions in aqueous solutions or biological systems. However, it is still not understood to what degree the counter ion in CPEs influences the properties of the CPE itself and the performance of electron ic transducers. In order to investigate this, three different conjugated polyelectrolytes, poly(6-(thiophen-3-yl)hexane-1-sulfonate)s (PTHS − X + ), are synthesized, which have the same polythiophene backbone but different X + counter ions: the bulky tetrabutylammonium (TBA + ), tetraethylammonium (TEA + ), and the smallest tetramethylammonium (TMA + ). At the interface with biological systems, thin CPE films have to be stable in an aqueous environment and should allow the inward and outward flow of ions from the electrolyte. Since the studied PTHS − X + have different solubilities in water, the optical properties of pristine PTHS − X + as well as of crosslinked PTHS − X + via UV–vis absorption spectroscopy are investigated additionally. PTHS − TMA + exhibits better aggregation, fast interdiffusion of ions, and fast recovery from the oxidized state. Additionally, spectroelectrochemical and cyclic voltammetric as well as electrochemical capacitance investigations show that PTHS − TMA + can be oxidized to a higher degree. This leads to a better performance of PTHS − TMA + -based organic electrochemical transistors

Electrically controlled cellular migration on a periodically micropatterned PEDOT:PSS conducting polymer platform

© 2018 Wiley Periodicals, Inc. In the field of tissue engineering, the study of cellular adhesion and migration is of crucial interest. Conducting polymers such as poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) provide an outstanding interface with biology due to their soft nature, which is closer to the mechanical, chemical, and morphological properties of biological systems. In this work, periodically micropatterned PEDOT:PSS thin films are used as a platform to investigate cellular migration. Human cerebral microvascular endothelial cells (hCMEC) show alignment and linear motion along PEDOT:PSS microstripes of varying widths (10–30 μm). In addition, an electrochemical gradient is created on the PEDOT:PSS film along these microstripes to influence the cell behavior. hCMEC cells linearly change their velocities depending on the redox state of the conducting polymer film. This work demonstrates the potential of such conducting polymer platforms to combine, at the same time, several key physicochemical factors for controlling cellular migration. In the future, we envision that these conducting polymer platforms will deliver tools for tissue regeneration and lead to new opportunities in regenerative medicine. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 47029

Low-Temperature Cross-Linking of PEDOT:PSS Films Using Divinylsulfone

Recent interest in bioelectronics has prompted the exploration of properties of conducting polymer films at the interface with biological milieus. Poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT:PSS) from a commercially available source has been used as a model system for these studies. Different cross-linking schemes have been used to stabilize films of this material against delamination and redispersion, but the cost is a decrease in the electrical conductivity and/or additional heat treatment. Here we introduce divinylsulfone (DVS) as a new cross-linker for PEDOT:PSS. Thanks to the higher reactiveness of the vinyl groups of DVS, the cross-linking can be performed at room temperature. In addition, DVS does not reduce electronic conductivity of PEDOT:PSS but rather increases it by acting as a secondary dopant. Cell culture studies show that PEDOT:PSS:DVS films are cytocompatible and support neuroregeneration. As an example, we showed that this material improved the transconductance value and stability of an organic electrochemical transistor (OECT) device. These results open the way for the utilization of DVS as an effective cross-linker for PEDOT:PSS in bioelectronics applications