We introduce a novel and versatile approach for preparing self-assembled nanoporous
multilayered films with tunable optical properties. Protonated polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) and anionic polystyrene-block-poly(acrylic acid) (PS-b-PAA) block copolymer micelles (BCM) were
used as building blocks for the layer-by-layer assembly of BCM multilayer films. BCM film growth is governed
by electrostatic and hydrogen-bonding interactions between the opposite BCMs. Both film porosity and
film thickness are dependent upon the charge density of the micelles, with the porosity of the film controlled
by the solution pH and the molecular weight (Mw) of the constituents. PS7K-b-P4VP28K/PS2K-b-PAA8K films
prepared at pH 4 (for PS7K-b-P4VP28K) and pH 6 (for PS2K-b-PAA8K) are highly nanoporous and antireflective.
In contrast, PS7K-b-P4VP28K/PS2K-b-PAA8K films assembled at pH 4/4 show a relatively dense surface
morphology due to the decreased charge density of PS2K-b-PAA8K. Films formed from BCMs with increased
PS block and decreased hydrophilic block (P4VP or PAA) size (e.g., PS36K-b-P4VP12K/PS16K-b-PAA4K at
pH 4/4) were also nanoporous. This is attributed to a decrease in interdigitation between the adjacent
corona shells of the low Mw BCMs, thus creating more void space between the micelles. Multilayer films
with antireflective and photochromic properties were obtained by incorporating a water-insoluble photochromic dye (spiropyran) into the hydrophobic PS core of the BCMs assembled in the films. The optical
properties of these films can be modulated by UV irradiation to selectively and reversibly control the
transmission of light. Light transmission of higher than 99% was observed with accompanying photochromism
in the (PS7K-b-P4VP28K/PS2K-b-PAA8K) multilayer films assembled at pH 4/6. Our approach highlights the
potential to incorporate a range of materials, ranging from conventional hydrophilic materials with specific
interactions to hydrophobic compounds, into the assembled BCMs to yield multifunctional nanoporous films
