PHOTOINITIATED POLYMERIZATION OF 2-HYDROXYETHYL METHACRYLATE BY SAFRANIN T / TRIETHANOLAMINE IN AQUEOUS SOLUTION: A KINETIC STUDY
Journal Title: Baqai Journal of Health Sciences - Year 2016, Vol 19, Issue 2
Abstract
This study involves the polymerization of 2-hydroxyethyl metharylate (HEMA) (1–3 M), photoinitiated by safranin T (ST) / triethanolamine (TEOHA) system in the pH range 6.0–9.0. The kinetics of the reactions during the initial stages of polymerization (~5% HEMA conversion, within 150 s) has been evaluated to avoid the effects of any volume changes in the solution. The concentration of HEMA in polymerized solutions has been determined spectrometrically at 208 nm with a precision of ±3%. The apparent first-order rate constants (kobs) for the polymerization of HEMA by ST in the presence of 0.010 M TEOHA range from 2.57–6.08 (1 M), 2.14–5.44 (2 M) and 1.79–4.81×10–4 s–1 (3 M) at pH 6.0–9.0. The second-order rate constants for the interaction of TEOHA with HEMA (1–3 M) range from 1.79–6.08×10–2 M–1 s–1 at pH 6.0–9.0. This indicates that the reactivity of TEOHA radicals increases with an increase in pH of the solution. The viscosity of HEMA solutions exerts an influence on the rates of polymerization and the values of kobs show a linear relation with inverse of solution viscosity. This could be due to the quenching of the ST excited triplet state with an increase in the viscosity of the solution.
Authors and Affiliations
Iqbal Ahmad, Kefi Iqbal, Syed Abid Ali
Keywords
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