RESUMO
The issue of information security has become a concern in all aspects of daily life, prompting the development of encryption technologies. Therein, optical encryption using color/graphical patterns holds great potential. However, current approaches generally rely on monochromic change upon one or more stimuli, limiting their further application in advanced confidential encryption. Herein, we propose a delicate strategy based on a co-assembly system of perylene bisimides (PBI)/polyvinyl alcohol (PVA) that demonstrates stepwise stimuli response and multicolor changes. The color of the supramolecular system changes from red to purple under the stimulus of UV light, and to orange when exposed to water. The multidimensional chromic response is achieved by an evolution process including the generation, packing rearrangement and quenching of PBI radical anions/dianions. With the virtues of photo- and hydrochromism, this novel co-assembly system was successfully employed for advanced anticounterfeiting and versatile information encryption applications.
RESUMO
As a novel polymer, polyurethane (PU) has been widely applied in leather, synthetic leather, and textiles due to its excellent overall performance. Nevertheless, conventional PU is flammable and its combustion is accompanied by severe melting and dripping, which then generates hazardous fumes and gases. This defect limits PU applications in various fields, including the leather industry. Hence, the development of environmentally friendly, flame-retardant PU is of great significance both theoretically and practically. Currently, phosphorus-nitrogen (P-N) reactive flame-retardant is a hot topic in the field of flame-retardant PU. Based on this, the preparation and flame-retardant mechanism of flame-retardant PU, as well as the current status of flame-retardant PU in the leather industry were reviewed.