Developing a shape memory polyurethane with high mechanical properties, excellent self-healing has become a huge challenge for the development of smart materials. Herein, we report the design and fabrication of a shape memory polyurethane network terminated with coumarin units (HEOMC-PU) to address this conundrum. The synthesized HEOMC-PU exhibits exceptional mechanical performance with a breaking elongation of 746% and toughness of 55.5 MJ•m −3 . By utilizing the dynamically reversible behavior of coumarin units to repair the damaged network, the efficient self-healing performance (99.2%) of HEOMC-PU is obtained. In addition, the prepared network and light-induced dynamic reversibility endow the HEOMC-PU with both liquid-state remoldability and solid-state plasticity, respectively, enabling polyurethane to be recycled and processed multiple times. Furthermore, based on the fluorescence responsive characteristic of coumarin, HEOMC-PU with a fluorescent pattern can be deformed into specific threedimensional configurations by combining photolithography, self-healing, and the shape memory effect. Such a multilevel and multidimensional anti-counterfeiting platform with rewritable fluorescent patterns and reconfigurable shapes can open up a new encryption approach for future intelligent anti-counterfeiting.
In this work, Au nanoparticle (AuNP)
arrays on shape memory polyurethane
(SMPU) substrates serve as flexible materials for tunable localized
surface plasmon resonance (LSPR). AuNP arrays prepared by diblock
copolymer self-assembly are transferred from rigid silicon wafers
onto flexible SMPU substrates with ultrasonic treatment rather than
peeling off directly. The resultant AuNP array SMPU films have excellent
mechanical properties and stable thermodynamic properties. The LSPR
arising from AuNP arrays is increased by negative bending on SMPU
substrates, whereas the LSPR is decreased by positive bending. Besides,
upon uniaxial tension, the vertical LSPR is increased first then decreased,
whereas the parallel LSPR is similar, resulting in the overall LSPR
of AuNP arrays being increased first and then decreased with the mechanical
uniaxial tension of SMPU. Moreover, the resultant AuNP array SMPU
films exhibit excellent flexibility, stability, and homogeneity in
practical surface-enhanced Raman scattering (SERS) application. This
approach of incorporating AuNP arrays on SMPU substrates for tuning
plasmonic properties have great potential applications in SERS, fluorescence
enhancement, and newly optoelectronic materials.
Herein this study, plasmonic‐patterned nanostructures are applied to fabricate unclonable anti‐counterfeiting labels. Patterned Au nanoparticles (AuNPs) are constructed by the skillful combination of diblock copolymer polystyrene‐block‐poly(4‐vinyl pyridine) (PS‐b‐P4VP) self‐assembly with shadow mask lithography to provide a simple and universal approach for large‐area fabrication of patterned nanostructures. The AuNP pattern can be made visible by increasing the nanoparticle size. A surface‐enhanced Raman spectroscopy (SERS)‐based physical unclonable function (PUF) security label with a large encoding capacity is fabricated by depositing malachite green (MG) on the surface. The broadening of the size distribution of the AuNPs after their growth and the increased disorder in their arrangement confer the security label with unique and unclonable characteristics. The as‐prepared optical PUF security label is read out by a confocal Raman spectrometer to extract binary codes, which are then authenticated through comparison. These SERS‐based PUF security labels, which combine patterning with stochastic spectral encoding, not only provide rich and diverse patterns but are also promising for anti‐counterfeiting applications in areas such as rigid silicon‐based optoelectronic materials and devices.
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