Through direct arylation polymerization, a series of mixed ion-electron conducting polymers with a low synthetic complexity index is synthesized. A thieno[3,2-b]thiophene monomer with oligoether side chains is used in direct arylation polymerization together with a wide range of aryl bromides with varying electronic character from electron-donating thiophene to electron-accepting benzothiadiazole. The obtained polymers are less synthetically complex than other mixed ion-electron conducting polymers due to higher yield, fewer synthetic steps and less toxic reagents. Organic electrochemical transistors (OECTs) based on a newly synthesized copolymer comprising thieno[3,2-b]thiophene with oligoether side chains and bithiophene exhibit excellent device performance. A high charge-carrier mobility of up to mu = 1.8 cm(2) V-1 s(-1) was observed, obtained by dividing the figure of merit [mu C*] from OECT measurements by the volumetric capacitance C* from electrochemical impedance spectroscopy, which reached a value of more than 215 F cm(-3).

Conjugated polymers with oligoether side chains make up a promising class of thermoelectric materials. In this work, the impact of the side-chain length on the thermoelectric and mechanical properties of polythiophenes is investigated. Polymers with tri-, tetra-, or hexaethylene glycol side chains are compared, and the shortest length is found to result in thin films with the highest degree of order upon doping with the p-dopant 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F(4)TCNQ). As a result, a stiff material with an electrical conductivity of up to 830 +/- 15 S cm(-1) is obtained, resulting in a thermoelectric power factor of about 21 mu W m(-1) K-2 in the case of as-cast films. Aging at ambient conditions results in an initial decrease in thermoelectric properties but then yields a highly stable performance for at least 3 months, with values of about 200 S cm(-1) and 5 mu W m(-1) K-2. Evidently, identification of the optimal side-chain length is an important criterion for the design of conjugated polymers for organic thermoelectrics.

Organic mixed ionic-electronic conductors are promising materials for interfacing and monitoring biological systems, with the aim of overcoming current challenges based on the mismatch between biological materials and convectional inorganic conductors. The conjugated polymer/polyelectrolyte complex poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT/PSS) is, up to date, the most widely used polymer for in vitro or in vivo measurements in the field of organic bioelectronics. However, PEDOT/PSS organic electrochemical transistors (OECTs) are limited by depletion mode operation and lack chemical groups that enable synthetic modifications for biointerfacing. Recently introduced thiophene-based polymers with oligoether side chains can operate in accumulation mode, and their chemical structure can be tuned during synthesis, for example, by the introduction of hydroxylated side chains. Here, we introduce a new thiophene-based conjugated polymer, p(g(4)2T-T)-8% OH, where 8% of the glycol side chains are functionalized with a hydroxyl group. We report for the first time the compatibility of conjugated polymers containing ethylene glycol side chains in direct contact with cells. The additional hydroxyl group allows covalent modification of the surface of polymer films, enabling fine-tuning of the surface interaction properties of p(g(4)2T-T)-8% OH with biological materials, either hindering or promoting cell adhesion. We further use p(g(4)2T-T)-8% OH to fabricate the OECTs and demonstrate for the first time the monitoring of epithelial barrier formation of Caco-2 cells in vitro using accumulation mode OECTs. The conjugated polymer p(g(4)2T-T)-8% OH allows organic-electronic-based materials to be easily modified and optimized to interface and monitor biological systems.

Herein, a binary cathode interface layer (CIL) strategy based on the industrial solvent fractionated LignoBoost kraft lignin (KL) is adopted for fabrication of organic solar cells (OSCs). The uniformly distributed phenol moieties in KL enable it to easily form hydrogen bonds with commonly used CIL materials, i.e., bathocuproine (BCP) and PFN-Br, resulting in binary CILs with tunable work function (WF). This work shows that the binary CILs work well in OSCs with large KL ratio compatibility, exhibiting equivalent or even higher efficiency to the traditional CILs in state of art OSCs. In addition, the combination of KL and BCP significantly enhanced OSC stability, owing to KL blocking the reaction between BCP and nonfullerene acceptors (NFAs). This work provides a simple and effective way to achieve high-efficient OSCs with better stability and sustainability by using wood-based materials. This work introduces industrial solvent fractionated LignoBoost kraft lignin (KL) in highly efficient organic solar cells (OSCs) by binary cathode interface layer (CIL) strategy, which can significantly improve the stability of both binary and ternary photoactive layer (PAL) OSC, owing to the passivation of diffusion and reaction between bathocuproine (BCP) and nonfullerene acceptors (NFAs). The results combine sustainable wood-based material with classic interface materials in advance NFA-OSCs.image

Soft and stretchable nanocomposites can match the mechanical properties of neural tissue, thereby minimizing foreign body reactions to provide optimal stimulation and recording specificity. Soft materials for neural interfaces should simultaneously fulfill a wide range of requirements, including low Young's modulus (<<1 MPa), stretchability (>= 30%), high conductivity (>> 1000 S cm(-1)), biocompatibility, and chronic stability (>> 1 year). Current nanocomposites do not fulfill the above requirements, in particular not the combination of softness and high conductivity. Here, this challenge is addressed by developing a scalable and robust synthesis route based on polymeric reducing agents for smooth, high-aspect ratio gold nanowires (AuNWs) of controllable dimensions with excellent biocompatibility. AuNW-silicone composites show outstanding performance with nerve-like softness (250 kPa), high conductivity (16 000 S cm(-1)), and reversible stretchability. Soft multielectrode cuffs based on the composite achieve selective functional stimulation, recordings of sensory stimuli in rat sciatic nerves, and show an accelerated lifetime stability of >3 years. The scalable synthesis method provides a chemically stable alternative to the widely used AgNWs, thereby enabling new applications within electronics, biomedical devices, and electrochemistry.

The interactions between counterions and electronic carriers in electrically doped semiconducting polymers are important for delocalization of charge carriers, electronic conductivity, and thermal stability. The introduction of a dianions in semiconducting polymers leads to double doping where there is one counterion for two charge carriers. Double doping minimizes structural distortions, but changes the electrostatic interactions between the carriers and counterions. Polymeric ionic liquids (PIL) with croconate dianions are helpful to investigate the role of the counterion in p-type semiconducting polymers. PILs prevent diffusion of the cation into the semiconducting polymers during ion exchange. The redox-active croconate dianions undergo ion exchange with doped semiconducting polymers depending on their ionization energy. Croconate dianions are found to reduce doped films of poly(3-hexyl thiophene), but undergo ion exchange with a polythiophene with tetraethylene glycol side chains, P(g(4)2T-T), that has a lower ionization energy. The croconate dianion maintains crystalline order in P(g(4)2T-T) and leads to a lower activation energy for the electrical conductivity than PF6- counterions. The control of the doping level with croconate allows optimization of the thermoelectric performance of the semiconducting polymer. The thermal stability of the doped films of P(g(4)2T-T) is found to depend strongly on the nature of the counterion.

The interplay between the nanostructure of a doped polythiophene with oligoether side chains and its electrical as well as mechanical properties is investigated. The degree of order of the polymer is found to strongly vary when co-processed with bistriflimidic acid (H-TFSI). The neat polythiophene as well as strongly oxidized material are largely disordered while intermediate concentrations of H-TFSI give rise to a high degree of pi-stacking. The structural disorder of strongly oxidized material correlates with a decrease in the kinetic fragility with H-TFSI concentration, suggesting that positive interactions between TFSI anions and the polymer reduce the ability to crystallize. The electrical conductivity as well as the Youngs modulus first increase upon the addition of 4-10 mol% of H-TFSI, while the loss of pi-stacking observed for strongly oxidized material more significantly affects the latter. As a result, material comprising 25 mol% H-TFSI displays an electrical conductivity of 58 S cm(-1) but features a relatively low Youngs modulus of only 80 MPa. Decoupling of the electrical and mechanical properties of doped conjugated polymers may allow the design of soft conductors that are in high demand for wearable electronics and bioelectronics.