Optical Patterning in Photoresponsive Azobenzene-Based Waterborne Coatings

Abstract

Reversible photoresponsive waterborne dispersions can be directly applied in the paint and printing industry and have several potential applications such as in rewritable optical patterns, security labeling, and sensing. However, the synthesis of such dispersions and application as waterborne coatings has rarely been reported. In this work, photoresponsive polymer dispersions containing light-responsive azobenzene were prepared by resin-stabilized emulsion polymerization. The aqueous dispersions consist of core/shell type polymer particles, where the resin forms the shell around the polymer core. The photoresponsive azobenzene was incorporated into the resin shell (azo-in-shell) or polymer core (azo-in-core). Waterborne coatings were easily prepared by applying the dispersions on glass or paperboard. The photoresponsive behavior of the azobenzene in the dispersions and coatings shows fast and reversible isomerization and a similar half-life of the cis-azobenzene regardless of its surrounding matrix in the coating, dispersion, or solution. Optical patterns were reversibly imprinted in the coatings on paperboard, which remain visible for several hours at room temperature and several weeks when stored in the freezer. The water barrier properties of the azobenzene-containing coatings on paperboard were unaffected by the addition of the azobenzene moieties and isomerization state. Our results reveal a class of photoresponsive azobenzene waterborne coatings that can be easily applied on different substrates.

Reconfigurable and Weldable Visible-Light-Driven Liquid-Crystalline Actuators with Enhanced Dynamic Performance

“…On removing the photomask is removed [Figure a­(iii)], the PNML letter pattern is clearly marked on the xLCE azo film. During UV-light exposure, the azobenzene linkages undergo trans-to-cis isomerism; hence, the shade of the exposed region is darker than that of the background; the color of the cis configuration is known to be red Figure b­(i–iii) shows the patterned xLCE azo film prepared at different UV exposure times ( t UV ).…”

“…During UV-light exposure, the azobenzene linkages undergo trans-to-cis isomerism; hence, the shade of the exposed region is darker than that of the background; the color of the cis configuration is known to be red. 63 8m), and unbending when the light is switched off (Figure 8n,o). This folding actuation of the xMLCE AB (front)/xMLCE azo bilayer film by blue-light irradiation is unique for mimicking the motions often observed in insects (e.g., Crustaceans, Octopoda, etc.).…”

Meta-Substituted Asymmetric Azobenzenes: Insights into Structure–Property Relationship

“…Its unique photoresponsive properties, arising from its ability to undergo E/Z isomerization upon absorption of light, have made it a popular choice for designing light-responsive molecular switches [4][5][6]. The facile and reversible nature of the photoisomerization process, which can be triggered by different wavelengths of light, has enabled a plethora of applications for azobenzene-containing systems, including photo-controlled cargo delivery [7][8][9][10], surface patterning [11][12][13][14], mechanical actuators [15][16][17][18][19], and biological process regulators [20][21][22]. The E/Z photoisomerization of azobenzenes occurs by electron transition from an occupied π molecular orbital (MO) to an unoccupied π* MO localized on the N=N bond.…”