Here, we introduce polymer of intrinsic microporosity
1 (PIM-1)
to design single-layer and multilayered all-inorganic antireflective
coatings (ARCs) with excellent mechanical properties. Using PIM-1
as a template in sequential infiltration synthesis (SIS), we can fabricate
highly uniform, mechanically stable conformal coatings of AlO
x
with porosities of ∼50% and a refractive
index of 1.41 compared to 1.76 for nonporous AlO
x
that is perfectly suited for substrates commonly used in high-end
optical systems or touch screens (e.g., sapphire, conductive glass,
bendable glass, etc.). We show that such films can be used as a single-layer
ARC capable of reduction of the Fresnel reflections of sapphire to
as low as 0.1% at 500 nm being deposited only on one side of the substrate.
We also demonstrate that deposition of the second layer with higher
porosity using block copolymers enables the design of graded-index
double-layered coatings. AlO
x
structures
with just two layers and a total thickness of less than 200 nm are
capable of reduction of Fresnel reflections under normal illumination
to below 0.5% in a broad spectral range with 0.1% reflection at 700
nm. Additionally, and most importantly, we show that highly porous
single-layer and graded-index double-layered ARCs are characterized
by high hardness and scratch resistivity. The hardness and the maximum
reached load were 7.5 GPa and 13 mN with a scratch depth of about
130 nm, respectively, that is very promising for the structures consisting
of two porous AlO
x
layers with 50% and
85% porosities, correspondingly. Such mechanical properties of coatings
can also allow their application as protective layers for other optical
coatings.