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The first synthesis of amine- or aniline-substituted thiophene polymers is reported, and field-effect transistor electronic responses to acetone are shown. 

Organic field-effect transistors (OFETs) were fabricated using three high-surface area and flexible expanded-poly(tetrafluoroethylene) (ePTFE) membranes in gate dielectrics, along with the semiconducting polymer poly[2,5-bis(2-octyldodecyl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione-3,6-diyl)-alt-(2,2’;5’,2’’;5’’,2’’’-quaterthiophen-5,5’’’-diyl)] (PDPP4T). The transistor behavior of these devices was investigated following annealing at 50°C, 100°C, 150°C, and 200°C, all sustained for 1 hour. For annealing temperatures above 50°C, the OFETs displayed improved transistor behavior and a significant increase in output current while maintaining similar magnitudes of Vth shifts when subject to static voltage, compared to those kept at ambient temperature. We also tested response to NO2 gas as further characterization and for possible applications. The ePTFE-PDPP4T interface of each membrane was characterized via scanning electron microscopy (SEM) for all four annealing temperatures to derive a model for the hole mobility of the ePTFE-PDPP4T OFETs that accounts for the microporous structure of the ePTFE and consequently adjusts the channel width of the OFET. Using this model, a maximum hole mobility of 1.8±1.0 cm2/V·s was calculated for the polymer in an ePTFE-PDPP4T OFET annealed at 200°C whereas a PDPP4T OFET using only the native silicon wafer oxide as a gate dielectric exhibited a hole mobility of just 0.09±0.03 cm2/V·s at the same annealing condition. This work demonstrates that responsive semiconducting polymer films can be deposited on nominally nonwetting and extremely bendable membranes, and the charge carrier mobility can be significantly increased compared to their as-prepared state by using thermally durable polymer membranes with unique microstructures as gate dielectrics. 

Abstract Doping of organic semiconductors has served as an effective method to achieve high electrical conductivity and large thermoelectric power factor. This is of importance to the development of flexible/wearable electronics and green energy‐harvesting technologies. The doping impact of the Lewis acid tris (pentafluorophenyl) borane (BCF) on the thermoelectric performance of poly(2‐(4,4′‐bis(2‐methoxyethoxy)‐5′‐methyl‐[2,2′‐bithiophen]‐5‐yl)‐5‐methylthieno[3,2‐b]thiophene (pgBTTT), a thiophene‐based polymer featuring oligoethylene glycol side chains is investigated. Tetrafluorotetracyanoquinodimethane (F4TCNQ), a well‐established dopant, is utilized as a comparison; however, its inability to co‐dissolve with pgBTTT in less polar solvents hinders the attainment of higher doping levels. Consequently, a comparative study is performed on the thermoelectric behavior of pgBTTT doped with BCF and F4TCNQ at a very low doping level. Subsequent investigation is carried out with BCF at higher doping levels. Remarkably, at 50 wt% BCF doping level, the highest power factor of 223 ± 4 µW m⁻¹K²is achieved with an electrical conductivity of 2180 ± 360 S cm⁻¹and a Seebeck coefficient of 32 ± 1.3 µV K⁻¹. This findings not only contribute valuable insights to the dopant interactions with oxygenated side chain polymers but also open up new avenues for high conductivity thermoelectric polymers in flexible electronic applications. 

Abstract The design of polymeric semiconductors exhibiting high electrical conductivity (σ) and thermoelectric power factor (PF) will be vital for flexible large‐area electronics. In this work, four polymers based on diketopyrrolopyrrole (DPP), 2,3‐dihydrothieno[3,4‐b][1,4]dioxine (EDOT), thieno[3,2‐b]thiophene (TT), and 3, 3′‐bis (2‐(2‐(2‐methoxyethoxy) ethoxy) ethoxy)‐2, 2′‐bithiophene (MEET) are investigated as side‐chains, with the MEET polymers newly synthesized for this study. These polymers are systematically doped with tetrafluorotetracyanoquinodimethane ( F₄TCNQ), CF3SO3H, and the synthesized dopant Cp(CN)₃‐(COOMe)₃, differing in geometry and electron affinity. The DPP‐EDOT‐based polymer containing MEET as side‐chains exhibits the highest conductivity (σ) ≈700 S cm−1 in this series with the acidic dopant (CF₃SO₃H). This polymer also shows the lowest oxidation potential by cyclic voltammetry (CV), the strongest intermolecular interactions evidenced by differential scanning calorimetry (DSC), and has the most oxygen‐based functionality for possible hydrogen bonding and ionic screening. Other polymers exhibit high σ ≈300–500 S cm−1 and power factor up to 300 µW m⁻¹K⁻². The mechanism of conductivity is predominantly electronic, as validated by time‐dependent conductance studies and transient thermo voltage monitoring over time, including for those doped with the acid. These materials maintain significant thermal stability and air stability over ≈6 weeks. Density functional theory calculations reveal molecular geometries and inform about frontier energy levels. Raman spectroscopy, in conjunction with scanning electron microscopy (SEM‐EDS) and x‐ray diffraction, provides insight into the solid‐state microstructure and degree of phase separation of the doped polymer films. Infrared spectroscopy enables this study to further quantify the degree of charge transfer from polymer to dopant. 

Synthesizing polystyrene-block-poly(vinyl alcohol) (PS-b-PVA) via controlled radical polymerization of vinyl acetate, the traditional precursor to polyvinyl alcohol (PVA), is challenging due to the reactivity of the unconjugated α-acetoxy radical. We report the synthesis and characterization of PS-b-PVA block copolymers (BCPs) with tailorable PVA block lengths via RAFT polymerization of an alternative precursor, an aromatic organoborane comonomer BN 2-vinylnapthalene (BN2VN). RAFT homopolymerization of BN2VN (RB) using 2-cyano-2-propyl dodecyl trithiocarbonate (CPDT) is described. Solid-state NMR, ATR-IR, SEC and thermogravimetric analysis reveal significant differences between PS-b-PVA and RS-b-RB. The fate of the trithiocarbonate end-group during oxidative conversion of the C–B side chain to a C–OH side chain was studied; while a hydrated aldehyde (e.g., gem-diol) was hypothesized, conclusive evidence was not found. 

We investigated the enhanced vapor responses and altered response ratios of a series of thiophene (co)polymers with oxygenated side chains (CH 2 OH, linear polyethylene glycol, and crown ether), including the novel poly(3-hydroxymethylthiophene) (PTOH) and other newly synthesized polymers. Hydroxymethyl-containing copolymers had higher mobility compared to poly(3-hexylthiophene) (P3HT). The larger crown ether moiety promotes transistor characteristics of P3HT while the smaller one impairs them. Incorporating different oxygen bearing functionalities increased responses of thiophene polymers to NO 2 , NH 3 , and acetone. For example a polyether side chain increases the NO 2 response sensitivity of copolymers of both P3HT and PTOH, but sensitivity towards gas analytes was more prominent for glycol-based functionalities rather than the crown ethers. PTOH is very sensitive to NO 2 and the response likely includes a contribution from conductive protons on the OH group. The lack of correlation among the rank-ordered gas sensitivities imparted by each functional group was found to be useful for designing a selective sensor array. We specifically showed high classification accuracy for all the polymer responses to NO 2 and acetone vapors, both of which gave increased device currents but with response ratios different enough to allow highly classifying discriminant functions to be derived. 

Polythiophenes with differently functionalized side chains (alkyl, oligoethylene oxide, ester, hydroxy, and carboxylic acid) and varied counterions of potassium salt electrolytes were investigated in organic electrochemical transistors (OECTs). In addition, mixed blends were investigated to evaluate any synergistic effects between functionalities. Depending on the functional moiety attached, a large shift to lower potentials of Vth, an increase in drain current, and increase in transconductance can be observed compared to the base combination of alkyl side chain and Cl-. The newly designed and synthesized hydroxy polymer displayed stability to large shifts in VTH, slight increase in drain current, and little or no increase in transconductance when an ionic radius of the dopant is increased until a much larger anion, large polarizability, and low hydration number such as TSFI- was used. The acid-functionalized polymer, on the other hand had the same magnitude in shift with respect to any anion that is larger than Cl-. The polymers were characterized by spectroscopy, x-ray diffraction, thermal analysis, and cyclic voltammetry. This work demonstrates that side-chain engineering can have substantial difference in the level of interaction in the electrolyte which would require tailoring the ion for specific polymer interactions. 

Organic electronics offer a route toward electronically active biocompatible soft materials capable of interfacing with biological and living systems. One class of promising organic electronic materials are π-conjugated peptides, synthetic molecules comprising an aromatic core flanked by oligopeptides, that can be engineered to self-assemble into elongated nanostructures with emergent optoelectronic functionality. In this work, we combine molecular dynamics simulations with electronic structure and charge transport calculations to computationally screen for high charge mobility π-conjugated peptides and to elucidate design rules linking aromatic core character with charge mobility. We consider within our screening library variations in the aromatic core chemistry and length of the alkyl chains connecting the oligopeptide wings to the core. After completing our computational screen we identify particular π-conjugated peptides capable of producing self-assembled biocompatible nanoaggregates with predicted hole mobilities of 0.224 cm^2/(Vs) and electron mobilities of 0.143 cm^2/(Vs), and uncover design rules that enhance understanding of the molecular determinants of charge mobility within π-conjugated peptide assemblies.