Morphology, Molecular Orientation, and Solid-State Characterization of 2,3-Dihydrothieno[3,4-b][1,4]dioxine-2-carboxylic Acid (EDOTacid)

Abstract

2,3-Dihydrothieno[3,4-b][1,4]dioxine-2-carboxylic acid (EDOTacid) is a comonomer for polymers synthesized from 3,4-ethylenedioxythiophene (EDOT) or EDOT derivatives designed to introduce controlled amounts of hydrophilicity into the resulting copolymers. EDOTacid forms a crystalline solid at room temperature; however, its solid-state packing and physical properties were unknown, limiting its ability to be used in various applications. For this purpose, single crystals of EDOTacid grown by various solution and sublimation techniques were characterized by X-ray diffraction, electron microscopy, electron diffraction, thermogravimetric analysis, and polarized optical microscopy. The compound forms orthorhombic crystals with space group Pbca (a = 1.014 nm, b = 0.699 nm, c = 2.139 nm, Z = 8, density = 1.63 g/cm3) per single crystal X-ray diffraction with d-spacings confirmed by powder X-ray diffraction and electron diffraction. The molecules are arranged into hydrogen-bonded dimers, with each member of the pair...