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The introduction of oligoether side chains onto a polymer backbone can help to stabilise polymeric dispersions in water without the necessity of surfactants or additives when conjugated polymer nanoparticles are prepared. A series of poly(3-hexylthiophene) (P3HT) derivatives with different content of a polar thiophene derivative 3-((2-methoxyethoxy)methyl)thiophene was interrogated to find the effect of the polar chains on the stability of the formed nanoparticles, as well as their structural, optical, electrochemical, and electrical properties. Findings indicated that incorporation of 10–20 percent of the polar side chain led to particles that are stable over a period of 42 days, with constant particle size and polydispersity, however the particles from the polymer with 30 percent polar side chain showed aggregation effects. The polymer dispersions showed a stronger solid-like behaviour in water with decreasing polar side chain content, while thin film deposition from water was found to afford globular morphologies and crystallites with more isotropic orientation compared to conventional solution-processed films. As a proof-of-principle, field-effect transistors were fabricated directly from the aqueous dispersions demonstrating that polymers with hydrophilic moieties can be processed in water without the requirement of surfactants. 

Incorporation of polar side chains on organic semiconducting materials have been used recently in thermoelectric materials to increase dopant:semiconductor miscibility and stability to further increase the performance and durability of devices. However, investigations into how polar side chains can affect the structure and energetics of polythiophenes compared to non-polar alkyl side chains are usually carried out using materials with no common morphological structure. Within this work we systematically investigate the increase in polar side chain content on poly(3-hexylthiophene) (P3HT) and how the optical, electrochemical, and structural properties are affected. We find a decreasing degree of aggregation with increasing polar side chain content leading to lower charge carrier mobilities. Upon doping with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), we find that the electrical conductivity is reduced when incorporating the polar side chain and no stabilising effect is demonstrated when annealing the doped thin films at raised temperatures. This study emphasises that polar functionalities do not always increase dopant:semiconductor interactions and can harm desirable structural and electrical characteristics, and therefore should be incorporated into organic semiconductors with caution. 

Abstract A series of semiconducting small molecules with bithiophene or bis‐3,4‐ethylenedioxythiophene cores are designed and synthesized. The molecules display stable reversible oxidation in solution and can be reversibly oxidized in the solid state with aqueous electrolyte when functionalized with polar triethylene glycol side chains. Evidence of promising ion injection properties observed with cyclic voltammetry is complemented by strong electrochromism probed by spectroelectrochemistry. Blending these molecules with high molecular weight polyethylene oxide (PEO) is found to improve both ion injection and thin film stability. The molecules and their corresponding PEO blends are investigated as active layers in organic electrochemical transistors (OECTs). For the most promising molecule:polymer blend (P4E4:PEO), p‐type accumulation mode OECTs with µA drain currents, μS peak transconductances, and a µC* figure‐of‐merit value of 0.81 F V⁻¹cm⁻¹s⁻¹are obtained.