Monolayer subnanometric polymersomes with ultrabroad photochromism performance for multichromatic and multimodal information security
Photochromic Förster resonance energy transfer (pc-FRET)-based subnanometric polymersomes with accurate color control offer a transformative yet challenging tactic for advanced and custom-tailored information encryption. Herein, various amphiphilic alternating pyrene/azobenzene-containing copolymers were polymerized using one-pot Ugi four-component polycondensation. Subsequent self-assembly was performed to produce highly-integrated monolayer subnanometric polymersomes (MSNPSs) and their composites, with diameters of around ~250 nm and vesicular thicknesses of approximately ~12.0 Å. J-aggregated monolayer chain-folding mechanism was accountable for the donor-acceptor-donor stacking manner within the vesicular membrane, beneficial to achieve highly efficient energy transfer. The trans-to-cis photoisomerization of azobenzenes rendered MSNPSs and their composites with photo-triggered structural transitions in diameter and vesicular thickness. Benefitting from considerable spectral overlap between cis-azobenzene and pyrene, MSNPSs and their composites were capable of photo-controllable non-invasive pc-FRET performance with a wide Stokes shift (~320 nm). The accurate color variation from blue to red highly depended upon precise modulation of both irradiation duration and precursor-fixed donor/acceptor ratios. The proof-of-concept individually multichromatic 2D QR code was attained using photochromic MSNPSs and their composites in patterning lithography, displaying a multimodal decryption and favorable repeatability for high-level and personalized information protection. Our work paves a prospective avenue to meticulously craft stimuli-chromatic polymersomes for the potential of advanced information encryption.