Research on the Production Reaction Kinetics and Thermochromism of Salicylaldehyde Ethanolamine Schiff Base

A thermo chromic materials named Salicylaldehyde ethanolamine Schiff base was synthesized with ethanolamine and salicylaldehayde derivative in the medium of ethanol, and was characterized by means of UV-Vis absorption, GCMS. The reaction kinetics of Schiff base production was investigated through UV-Vis absorption spectra, and also the thermochromism of Schiff Base Condensed from ethanolamine and salicylaldehayde were studied by UV-Vis absorption spectra in different solvents. From the kinetics studies, the reaction rate constant at different temperature were obtained and the Ea of the reaction were calculated as 23.843KJ/mol. In thermochromism studies, Salicylalhayde-ethanolamine solution showed a reversible color change from dark yellow - to - light yellow as the temperature is varied between 30°C and 80°C, and repeated heating-cooling cycles can lead to the switches between dark yellow and light yellow colors.

I. Introduction

Thermochromic (TC) materials respond to changes of temperature by colour change [1]. Organic thermochromic material has become a hot topic because of its low toxicity, high sensitive and functional, especially for the compounds contained with Schiff base structure. Schiff bases in a broad sense have the general formula , where R is an organic side chain. On the Natural Hybrid Orbital, there is lone pair electrons from N atom which endowed it with important implications of biological and chemical. At present, its application domain involves topharmacy [2], catalysis [3], analytical chemistry [4], and corrosion [5] and so on. Along with the unceasing development of Schiff base material, the compounds with adjacent hydroxyl has been studied comprehensively. For example, someone has reported that the thermochromism of salicylideneanilines [6], salicylidene benzylamines [7], and 1-(Naphthalen-l-yliminomethyl)-naphthalen-2-o1 [8]. However, all of those are solid crystalline polymer, salicylaldehayde-ethanolamine Schiff base is liquid and water solubility. According to the literature, the relatively well known medical functionality of salicylaldehayde-ethanolamine [9], very little has been published about its colorimetric characteristics. This paper concerns the kinetic study and thermochromism properties of salicylaldehayde-ethanolamine Schiff base condensation reaction. Special attention was devoted to the thermochromism properties that describe colour hysteresis and the influence of temperatures in excess of the activation temperature on the reversibility of the thermochromic process.