ESR study on the effect of temperature on the diffusion of oxygen into PMMA and PVAC polymers

Abstract

ABSTRACT:The free radicals produced by ␥ irradiation in the polymer network are formed with ionizing radiation. The decay rates of radicals in the temperature range were used to estimate the diffusion coefficient of oxygen into polymeric spheres by an electron spin resonance (ESR) technique. The ESR results showed that the activation energy of the diffusion of oxygen into poly(methyl methacrylate) (PMMA) in the temperature range 10 -40°C is 29.6 kJ/mol. There are two activation energies of the diffusion of oxygen into poly(vinyl acetate) (PVAc) in the temperature range 25-50°C. The activation energies below and above 35°C, which is the glass transition temperature of PVAc, were found to be 16.8 and 82.5 kJ/mol, respectively.

Influence of electrical operating conditions and active layer thickness on electroluminescence degradation in polyfluorene–phenylene based light emitting diodes

“…To the best of our knowledge, no research has been performed to study the oxygen diffusion length in polyfluorene layers. Few studies on the incorporation of oxygen via creation of free radicals in polymers such as PMMA and PVA reveal diffusion coefficients of the order of 10 À12 m 2 /s [25], which guarantee fast oxygen diffusion in these materials. In fact, the average diffusion distance, hdi, scales with diffusion coefficient, D, and time, t, as hdi ¼ ffiffiffiffiffi ffi Dt p , (according to the Flick's Law), resulting in a diffusion distance of 1 lm in 1 s of exposure.…”

Investigation of Various Organic Radicals Dispersed in Polymethylmethacrylate Matrices Using the Electron Spin Resonance Spectroscopy Technique

“…Herein, several 2- X -NN ( X = Ph ( 3 ), p -NO 2 Ph ( 4 ), or cyclohexyl (CH; 5 )), 4- Y -PhBzNN ( Y = Ph ( 6 ) or NO 2 ( 7 )), and iminonitroxide (IN) radicals substituted at the 2-position of the IN group (2- Z -IN, Z = Ph ( 8 ) or p- NO 2 Ph ( 9 ); Figure d) , dispersed in polymethylmethacrylate (poly­(methyl 2-methylpropenoate); PMMA) − matrices have been reported. The ESR spectra of these species were recorded.…”

“…The tacticity of the polymers and the synthetic method followed also influence the cavity sizes. − Unpaired electrons in PMMA can be produced via a numerous pathways. The process of mechanical fracture of PMMA, methods used to generate gamma-rays for sample irradiation, , the spin-label method for the functionalization of PMMA, and the method reported herein can be used to generate unpaired electrons. The spin probe technique can be used to study the adsorption and dispersion of the molecules containing unpaired electrons. , The principal values of the g and A tensors of the organic radicals (other than TEMPO derivatives) dispersed in the PMMA matrices can be potentially used in the future for the further development of the field.…”

“…40−42 Unpaired electrons in PMMA can be produced via a numerous pathways. The process of mechanical fracture of PMMA, 41 methods used to generate gamma-rays for sample irradiation, 43,44 the spinlabel method for the functionalization of PMMA, 45 and the method reported herein can be used to generate unpaired electrons. The spin probe technique can be used to study the adsorption and dispersion of the molecules containing unpaired electrons.…”

Investigation of liquid diffusion into contact lenses using an electron spin resonance technique

“…This equation forms the theoretical basis for determining D in this study. Similar equations are also derivates and are used for other geometries, such as cylinders and spheres 10, 13–15…”