Optical percolation and oxygen diffusion in poly(divinylbenzene) doped poly(methyl methacrylate) latex flms

Abstract

A simple fluorescence technique is proposed for the measurement of the diffusion coefficient of oxygen into poly(methyl methacrylate) (PMMA) latex-poly(divinylbenzene) (PDVB) composite films. Percolation model was used by using photon transmission (PT) technique to interpret the distribution of PDVB particles in PMMA lattice. Optical results were interpreted according to site percolation theory. The optical percolation threshold value and critical exponent were calculated as, Rc = 0.03 and, beta = 0.34, respectively. PT measurements were performed for eight different PDVB content (0, 1.5, 3, 5, 10, 20, 40, and 60) wt%. Pyrene (P) functionalized PDVB cross-linked spherical microspheres with diameters of 2.5 mu m were synthesized by using precipitation polymerization technique followed by click coupling reaction. The diameter of the PMMA particles prepared by emulsion polymerization was in the range of 0.50.7 mu m. PMMA/PDVB composite films were then prepared by physically blending of PMMA latex with PDVB microspheres at various compositions. The steady-state fluorescence method was used to monitor oxygen diffusion into these (0, 5, 10, 20, and 40 wt%) latex films. Diffusion coefficients, D, of oxygen were determined by the fluorescence quenching method by assuming Fickian transport and were found to be increased from 1.8 x 10-11 to 36.6 x 10-11 cm2 s-1 with increasing PDVB content. This increase in D values was explained with formation of microvoids in the film by using PT technique. POLYM. COMPOS., 2013. (c) 2012 Society of Plastics Engineers