Variable-Emittance Infrared Electrochromic Skins Combining Unique Conducting Polymers, Ionic Liquid Electrolytes, Microporous Polymer Membranes, and emiconductor/Polymer Coatings, for Spacecraft Thermal Control
Date of this Version
J. APPL. POLYM. SCI. 2014, DOI: 10.1002/APP.40850 DOI: 10.1002/app.40850
Variable emittance (ε) is a property vital for the increasing needs in thermal control of future microspacecraft. This article describes fabrication, function, and performance of thin-film, flexible, variable-emittance (V-E) electrochromic skins that use a conducting polymer/-Au/-microporous membrane (CP/Au/µP) base, and a new, unique ionic liquid electrolyte (IonEl). Poly(aniline-codiphenyl amine) with a long-chain polymeric dopant is used as the CP. A unique, patented device design yields no barrier between the active, electrochromic CP surface and the external environment, except for a thin, infrared-transparent semiconductor/polymer film that lowers solar absorptance [α(s)] and protects from atomic-O/far-UV. Use of the IonEl requires special activation methods. Data presented show tailorable e variations from 0.19 to 0.90, De values of >0.50 (which is the highest reported thus far for any functional V-E material, to our knowledge), α(s)<0.35, and nearly indefinite cyclability. Extended space durability testing, including calorimetric thermal vacuum and continuous light/dark cycling over >7 months under space conditions (<10-5 Pa vacuum, far- UV), show excellent durability. Other data show resistance to solar wind, atomic-O, electrostatic discharge, and micrometeoroids. These lightweight, inexpensive, advanced polymeric materials represent the only technology that can work with micro- (<20 kg) and nano- (<2 kg) spacecraft, thus eventually allowing for much greater flexibility in their design and potentially “democratizing” the entire space industry, for example, allowing small firms to launch their own, dedicated satellites.