Photostabilization of organic thermochromic pigments: Action of benzotriazole type UV absorbers bearing an amphoteric counter-ion moiety on the light fastness of color formers

A mathematical analysis and elucidation of AB(2k,1ϕ) thermophotochromic kinetics: Analytical solutions using pure kinetic data and considering as unknown the rate constants, quantum yield, and both species' spectra

“…Thermochromism is a thermally induced reversible color change that is encountered for a large variety of photochromic organic substances such as spiropyrans, spirooxazines, Schiff's bases, and bianthrones 1,4. The attention received by such materials is largely due to their potential use in a variety of technological applications 1–10. However, the lack of an analytical kinetic elucidation method has made the results obtained so far insufficiently reliable for comparative studies and/or to represent a solid basis for the design and improvement of the properties of new structures.…”

“…From a reaction point of view, a number of these chromic systems can be described by a generic AB(2 k ,1 ϕ) kinetic mechanism 1–14, which consists of opposing thermal steps between the reactive species A and B in addition to a forward photochemical reaction involving the starting material (species A, Scheme ). Of course, the true mechanism will be more complex than that assumed by this generalization, but the other intermediate species (particularly excited states) involved in the overall reaction are characterized by lifetimes several orders of magnitude shorter (<ms) than those of species A and B (in the order of seconds/minutes) 2–4.…”

“…The elucidation approaches proposed, thus far, to solve such kinetics have necessarily involved independent estimation of the effective values of at least one of the unknown parameters, besides considering (or assuming) that the spectrum of the initial species is accessible 1–14. For example, to determine the thermal equilibrium constant ( K e = k AB / k BA ) at a given temperature, the spectrum of B has been estimated by undertaking measurements at low temperature (−75°C) 11, by using iterative methods 12,13, or by the total protonation of the charged species (open form isomers) 14.…”

From Murex Purpura to Sensory Photochromic Textiles

“…The mechanism by which the photochromism occurs is actually cleavage of the carbon-oxygen bond, caused exclusively by irradiation with UV light. The result is a ring-opened coloured species, called "merocyanine" form or MC, which can be cis-(1.2), trans-(1.3) or ortho-quinoidal form 1.4 (Bamfield, 2001, Oda, 2008. …”

Sıcaklığa Duyarlı Derilerin Yaşlanma Davranışları

“…Besides, the change occurred in these factors are lead to effect the aesthetic and performance properties as well as product life and usage areas of leather materials [11]. Nevertheless, the undesirable effect of ageing on thermochromic leathers could be prevented by the use of different chemicals that enhanced the fastness properties of thermochromic leathers [2,12,13].…”