Antireflection Performance Of Nanoporous Latex Coatings Prepared By Controlled Aggregation

The fabrication of nano-porous structured antireflection surfaces from spin coating of latex particles have been well demonstrated.However,the preparation of flexible coatings with tunable transmitted peaks covering the full visible range,showing low light-scattering loss and without using organic solvent is still challenging.Herein,we successfully tackled with the task by spin coating of crosslinked polymethyl methacrylate/polybutyl acrylate?PMMA/PBA?latex blend comprising ammonium bicarbonate?NH₄HCO₃?.Within the coatings,the coalesced PBA particles acted as binders that enhanced the mechanical integrity and adhesion of the PMMA structured coatings to the substrates.This endowed the coating with deformability and nearly unchanged antireflection properties even after 20 repeated cycles of 180°bending-relaxation.The concentration of NH₄HCO₃ was a crucial parameter not only for the formation of nano-porous structure,but also for the fabrication of coatings with good repeatability in antireflection performance.Within the calculated NH₄HCO₃ range window,the latex blend exhibited rather high dispersion stability,ensuring high repeatability of the coating process.On the other hand,after being coated onto the substrates,the growing of NH₄HCO₃ concentration with water evaporation led to latex destabilization,fractal particle aggregates and formation of nano-porous coatings.The light-scattering loss caused by the coatings remained at a level less than 0.45%,being much smaller than any reported data.The effective refraction indices(n_eff)of the coatings changed regularly with the concentration of NH₄HCO₃,while n_eff could remain almost constant at 1.27 as the coating thickness increased linearly with the polymer fraction of the coating dispersion.This allowed the transmitted peaks of the coatings being able to cover a range from 442 to 750 nm without sacrifice of the maximum transmittance.Moreover,the NH₄HCO₃ could be completely removed from the final coatings when drying the coatings at 100°C as a result of thermal decomposition.Therefore,we provide a straightforward method to prepare flexible nano-porous antireflection coating without applying long-time aging or sophisticated post-treatment process,like lithography or organic solvent etching.