Nature-inspired robust hydrochromic film for dual anticounterfeiting

Abstract

Micro-structures are formed by self-assembly of polyurethanepolyelectrolyte colloids Information changes from one pattern to another within 3 s when exposed to waterThe hydrochromic films are mechanically robust in both dry and wet state

Nano-enabled smart and functional materials toward human well-being and sustainable developments

“…Several researchers have investigated the application of WPU as a polymer matrix for anti-counterfeiting, encryption, or sensing applications. Si et al [94,95] utilized the interaction between anionic WPU and polyelectrolytes to develop anti-counterfeiting materials. They developed a dual anti-counterfeiting material by integrating WPU/polyethyleneimine (PEI, cationic polyelectrolyte) and WPU/Poly (methacrylic acid-sodium salt) solution (PMANa, anionic polyelectrolyte) on two sides of neat WPU film.…”

A Heat‐Resistant Polymer Based on the Reversible Change in Polymer Skeleton Structure for Self‐Anticounterfeiting

“…Because these materials can be colored or discolored by the induction of various external stimuli, it has a unique chromatic shift that makes it easy to observe and perform color processing. [18][19][20][21][22][23][24][25] Nowadays, there are two main methods for preparing stimulichromic polymers: i) The small molecule color-changing dye is combined with the polymer matrix by physical doping. [26][27][28] ii) The stimulating reactive chromophore is covalently linked to the polymer.…”

Crystal structures and stimuli-responsive properties for three novel D–A type salicylhydrazide–viologen compounds with free radical properties under ambient conditions

“…Viologen as a stimuli-reactive material can undergo reversible redox processes in response to external stimuli, accompanied by the generation and quenching of viologen radicals. [1][2][3][4][5][6][7] The radical properties of viologen make it rich in properties, such as photochromic properties, [8][9][10][11][12] pressure-chromic properties, 13 thermochromic properties, 14 hydrochromic properties, 15 photocurrent effects, 16 ammonia-chromic properties, 17 etc. Usually, the applied conditions that promote this redox process are often harsh, such as high energy light sources, [8][9][10][11][12] strong pressure, 13 high temperatures, 14 etc.…”