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

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 gm and 20 mu m upon electrical switching between -1.5 V and +1.5 V. The modulation of the reflectivity in bands II (3-5 mu m) and III (8-12 mu m) 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. (C) 2014 Elsevier B.V. All rights reserved.