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Polythiophenes (PTs) constitute a diverse array of promising materials for conducting polymer applications. However, many of the synthetic methods to produce PTs have been optimized only for the prototypical alkyl-substituted example poly(3-hexylthiophene) (P3HT). Improvement of these methods beyond P3HT is key to enabling the widespread application of PTs. In this work, P3HT and two ether-substituted PTs poly(2-dodecyl-2H,3H-thieno[3,4-b][1,4]dioxine) (PEDOT-C12) and poly(3,4-bis(hexyloxy)thiophene) (PBHOT) are synthesized by the FeCl3-initiated oxidative method under different conditions. Polymerization was carried out according to a common literature procedure (“reverse addition”) and a modified method (“standard addition”), which differ by the solvent system and the order of addition of reagents to the reaction mixture. Gel-permeation chromatography (GPC) was performed to determine the impact of the different methods on the molecular weights (Mw) and degree of polymerization (Xw) of the polymers relative to polystyrene standards. The standard addition method produced ether-substituted PTs with higher Mw and Xw than those produced using the reverse addition method for sterically unhindered monomers. For P3HT, the highest Mw and Xw were obtained using the reverse addition method. The results show the oxidation potential of the monomer and solution has the greatest impact on the yield and Xw obtained and should be carefully considered when optimizing the reaction conditions for different monomers. 

The Eastern Tropical North Atlantic Oxygen Minimum Zone (OMZ) is a biogeochemically important area. The low oxygen in this region is thought to be maintained by a balance between the slow mixing supply of O₂and its removal by respiration. We use data from 90 isopycnal RAFOS floats to characterize the mixing coefficients responsible for the supply of oxygen to the region. One group was ballasted to drift on the isopycnal where oxygen is at its minimum and the other about 300 m deeper. Using the record of the float positions at each 6‐hr interval, we calculate the relative dispersion of pairs of floats. The time derivative of this dispersion provides a diffusivity coefficient that captures the net effect of eddy‐driven mixing along each isopycnal. Float pairs deployed at shared locations but across the two target densities reveal that the influence of vertically sheared currents is to accelerate the dispersion by 10–15% relative to true isopycnal dispersion. Relative dispersion of the floats in the OMZ area obeyed the canonical four‐thirds power scaling, representative of two‐dimensional turbulence. At the length scale of the maximum energy‐containing eddy (approximately 100 km), the effective diffusivity is 1,400±500 m²/s in the zonal direction and 800±300 m²/s in the meridional. Within the uncertainty, the diffusivities on the two isopycnals are indistinguishable from one another. An idealized model suggests that meridional mixing across the large‐scale O₂gradient is the leading supply term of oxygen to the OMZ.