University of Alicante develops innovative family of colouring agents for plastics
The study has appeared recently in Green Chemistry, a research journal published by The Royal Society of Chemistry
Family of colouring agents developed by the UA Institute of Organic Synthesis (ISO). Photo by UA Audiovisual Studio
Alicante. Thursday 22 March 2018
The University of Alicante’s Institute of Organic Synthesis (ISO) has synthesised 14 new colouring agents with solvatochromic properties, i.e. their colour changes depending on the substance in which they dissolve or the type of plastic they are applied on.This fundamental and applied research project is part of the PhD theses undertaken by María José Albaladejo and María José González and directed by professor of Organic Chemistry and ISO director Francisco Alonso.
The process involved is fascinating from the point of view of fundamental research, as only one starting substance is employed, indolizine, which then self-transforms into a colourant. According to Francisco Alonso, “The original molecular structure remains the same, with only an hydrogen atom being replaced by a fragment from another identical indolizine molecule, so the transformation process as a whole can be described as a ‘transplant between molecular clones’, which is highly unusual in organic synthesis.”
“Oddly enough, these colourants exhibit a single molecular structure when they are solid, but two in solution (rotamers). An even more surprising fact is that the solvatochromic behaviour has been displayed at very low concentrations also in plastic materials. This means that different plastics which do not absorb visible light and are perceived as colourless or whitish can switch to a different colour by means of the same colouring agent,” the UA professor explains.
The process whereby the colouring agents are obtained is environmentally friendly, as no harmful solvents or metals are present, and has proved to be efficient on a multigram scale. In this sense, their colouring power is very high. Plastic plaques of several materials were dyed during laboratory tests with just 0.05-0.2% of a colouring agent.
Since 2014 the ISO has been working to synthesise indolizine-derived dyes with potential applications in laser recording and reading devices, thermography and photothermography, electrochromic devices, optical filters and photoelectric converters for solar cells. After several years of hard work, the UA researchers have managed to design up to 14 different colourants for colourless plastics.
The study has appeared recently in Green Chemistry, a journal published by The Royal Society of Chemistry. This Valencia Region Government-funded project has been patented. Alicante-based plastics companies IQAP Masterbach Group S.L. and Colortec Química S.L. and ISO PhD researcher Diana Almasi, in charge of process scaling, have also taken part.