Fluorescent cellulose nanocrystals/waterborne polyurethane nanocomposites for anti-counterfeiting applications.

The development of eco-friendly anti-counterfeiting materials with high optical transparency and bright luminescence in the aggregate state is tremendously challenging. Herein, waterborne polyurethane/tetraphenylethylene-cellulose nanocrystal (WPU/TPE-CNC) nanocomposite aqueous solutions and films were prepared direct blending aggregation-induced emission (AIE) active fluorescent CNCs (TPE-CNCs) with WPU and then applied in the anti-counterfeiting field. TPE-CNCs are compatible with WPU and dispersed homogeneously in the nanocomposite aqueous solutions and films. The thermal stability and mechanical properties of these films significantly improved with the increase in the content of TPE-CNCs. WPU/TPE-CNC nanocomposite films display high transparency (above 80%), excellent fluorescence properties, high mechanical strength, and good flexibility and then successfully applied to anti-counterfeit marking. Moreover, the dispersions of the aqueous WPU/TPE-CNC nanocomposite were nearly colorless and demonstrated promise as fluorescent anti-counterfeiting inks. This novel eco-friendly nanocomposite exhibited the potential for applications in anti-counterfeiting, fluorescent transparent paper and coating, fluorescent 3D printing, and optical/sensing devices.