Reconfigurable Anticounterfeiting Coatings Enabled by Macroporous Shape Memory Polymers

Here, we report a new type of reconfigurable anticounterfeiting coating enabled by integrating the scientific principles of photonic crystal and shape memory polymer (SMP). The autonomous infusion of uncured oligomers in a polydimethylsiloxane (PDMS) stamp into a templated macroporous SMP photonic crystal coating, which was confirmed by quantitative X-ray photoelectron spectroscopy analysis, can program an iridescent pattern on the transparent SMP membrane with deformed macropores. By manipulation of the unconventional all-room-temperature shape memory effects exhibited by the shape memory copolymer comprising polyethylene glycol diacrylate and ethoxylated trimethylolpropane triacrylate, the iridescent pattern can be easily and instantaneously concealed and revealed by immersing in common household liquids (e.g., ethanol and water). Systematic experiments and theoretical simulations using scanning electron microscopy, atomic force microscopy, optical spectroscopy, scalar wave approximation modeling, and contact angle measurements reveal the major mechanism underlying the anticounterfeiting concealing and revealing processes: the compressive deformation of periodic macropores induced by capillary pressure created by solvent evaporation. Apparent water contact angle measurements show that the infusion of hydrophobic PDMS oligomers into hydrophilic macroporous SMP coatings leads to a large increase in water contact angle from similar to 35 degrees to, similar to 70 degrees, which significantly changes the capillary pressure and the final configuration of the SMP photonic crystals. In addition to rendering a facile anticounterfeiting mechanism, the novel oligomer-infusion-induced chromogenic effects and modification of surface wettability might lead to important applications in developing new chromogenic sensors for noninvasively monitoring molecular diffusion at solid-solid interfaces and durable superhydrophobic and/or superomniphobic coatings.