Tunable wavelength antireflective film by non-solvent-induced phase separation of amphiphilic block copolymer micelle solution

Polymer antireflection (AR) coatings have considerable practical value and wide-ranging applications because of their ability to adhere to flexible substrates and because they lend themselves easily to large-area processing. Preparing a suitable polymer porous structure with tunable wavelength AR by a simple approach is a challenge. In the present study, an inhomogeneous porous polymer film with a dense skin and porous structure underneath was obtained by spin coating a micelle solution of polystyrene-block-poly(4-vinypyridine) (PS-b-P4VP) with tetrahydrofuran (THF) and dimethyl formamide (DMF). The film was then subjected to non-solvent-induced phase separation before it reached a dry state. The dense skin surface morphology was fixed because of the rapid evaporation of THF during the spin coating. In the subsequent non-solvent immersion, an inner nanoporous structure was formed because the DMF was replaced by the non-solvent (with similar solubility to DMF). The inhomogeneous porous polymer film showed tunable wavelength AR controlled by the film thickness and immersion time in the non-solvent. The film exhibited an excellent transmittance of 99.6% at visible light wavelengths (400–800 nm) and 99.2% transmittance at near-infrared light wavelengths (800–2000 nm).