Soft and flexible Interpenetrating Polymer Networks hosting electroreflective poly(3,4-ethylenedioxythiophene)

•A flexible electroreflective device with tunable IR optical properties is proposed.•PEDOT is synthesized within an IPN network as a soft and flexible host matrix.•The tow PEDOT layers play both as a current collector and an active material.•The optical and mechanical properties are studied according to PEDOT contents.

In this paper, we designed a flexible electroreflective device (ERD) with tunable optical properties in the near and mid infrared spectra. The ERD is made of a poly(3,4-ethylenedioxythiophene) (PEDOT) layer interpenetrated in a soft and flexible nitrile butadiene rubber (NBR)/polyethylene oxide (PEO) interpenetrating polymer network (IPN). The composition, structure and infrared properties of the semi-IPN were optimized according to the polymerization time of the EDOT monomer within the IPN. After the addition of an ionic liquid (IL), namely N-ethylmethylimidazolium bis(trifluoromethanesulfonyl)imide (EMITFSI), assuming the ionic conductivity of the system, the device exhibits middle infrared and tunable optical properties between 2 µm and 20 µm upon electrical switching between −1.5 V and +1.5 V. The modulation of the reflectivity in bands II (3–5 µm) and III (8–12 µm) regions is 26% and 41% respectively. Due to the presence of the soft NBR network, both IPN and ERD reveal improved mechanical properties compare to the single network and the ERD-only based on PEO. For instance, ERDs made with PEO/PEDOT semi-IPN possesses an elongation at break below 10%, for a stress at break lower than 1.4 MPa, while ERDs containing NBR show elongations at break from 45% to 15% for stresses at break from 3 to 8 MPa, depending on the amount of incorporated PEDOT. In parallel, the NBR/PEO/PEDOT devices showed robust and flexible behavior.

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