Abstract
In this study, we produced a new organic-inorganic hybrid pigment based on a natural chromophore. Lawsone was selected as the active organic compound and incorporated into aluminum-magnesium hydroxycarbonate (LH). The hydroxynaphthoquinone derivative lawsone (Lawsonia inermis L.) is a naturally occurring dye, which is commonly used as a colorant because of its nontoxicity and biological functions. The structure and stability of the hybrid colorant were investigated using 27-Al solid-state nuclear magnetic resonance (NMR) spectroscopy, X-ray diffraction (XRD), secondary ion mass spectrometry (TOF-SIMS), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and UV-Vis spectroscopy. TOF-SIMS and 27Al NMR spectroscopy revealed interactions between the dye molecules and metal ions present in the LH host, confirming successful formation of an LH-based hybrid (LH/lawsone). In the next part of the study, we examined the effect of the hybrid pigment on the mechanical and thermal properties of ethylene-norbornene (EN) materials, as well as the aging resistance of the colored composites to irradiation across the full solar spectrum. Dynamic mechanical analysis (DMA) and the results of tensile break tests revealed that the EN+LH/lawsone composite had significantly better resistance to solar irradiation in comparison to EN and EN with an unmodified carrier.
Highlights
Many colorants are recognized as carcinogenic or allergenic, leading to their disuse
The results demonstrated that layered double hydroxide can be used as a carrier for lawsone with controlled delivery capability
The modification of aluminum-magnesium hydroxycarbonate (LH) with lawsone was performed in an aquatic environment
Summary
Many colorants are recognized as carcinogenic or allergenic, leading to their disuse. There is growing interest in replacing artificial colorants with natural compounds or identical synthetic dyes [1,2,3]. Occurring substances as well as synthetic compounds are already widely used as colorants in various products, such as paints, plastics, fibers and rubbers. Many dyes are unstable under polymer processing conditions (e.g., heat, pH changes, the presence of other additives), resulting in loss of color. Organic-inorganic hybrid materials have emerged as an alternative form novel colorant with desirable characteristics. There has been sharp rise in the development of new organic-inorganic hybrid materials with unique or improved properties, such as enhanced resistance to migration and better chemical or thermal stability [4,5,6,7]. Intercalated/adsorbed hybrid colorants have been shown to be outstanding multifunctional hybrid pigments, able to act as coloring agents and fillers in polymer materials
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