Multichromic copolymers based on 3,6-bis(2-(3,4-ethylenedioxythiophene))-N-alkylcarbazole derivatives

Electrochemical copolymers of 2,2'-bis(3,4-ethylenedioxythiophene) (BiEDOT) and 3,6-bis(2-(3,4-ethylenedioxy)thienyl)-N-methylcarbazole (BEDOT-NMeCz) were prepared from nine comonomer solutions of varying concentration. The monomers exhibit low peak oxidation potentials (E-p,E-m) that are in close proximity (BiEDOT = +0.56 V vs Ag/Ag+, BEDOT-NMeCz = +0.41 V), allowing for facile copolymerization. Spectroelectrochemical analysis revealed that the neutral copolymers possess unique, broad, neutral absorbance maxima and colors ranging from blue (587 nm), to red (464 nm), to orange (429 nm), and finally to yellow (420 nm) that were comonomer concentration dependent, while stepwise oxidation showed that the copolymers pass through a green intermediate state before reaching a blue oxidized state that is concentration independent. A soluble hybrid copolymer of 3,6-bis(2-(3,4-ethylenedioxy)thienyl)-N-eicosylcarbazole (BEDOT-NC(20)Cz) was prepared via FeCl3 polymerization. Molecular weights of this soluble polymer have been characterized by gel permeation chromatography (GPC) and vapor phase osmometry (VPO). Solution doping and cast film spectroelectrochemical analyses show that the copolymer has a maximum absorbance in the area of 430 nm and that upon sequential oxidation the copolymer passes though a green intermediate state before reaching the fully doped blue state. Photoluminescence experiments revealed emission maxima at 470 and 506 nm and an efficiency (of) of 0.12.