Influence of poly(3-octylthiophene) on the water transport through methacrylic-acrylic based polymer membranes

Accumulation of water in ion-selective membranes, can lead to inconsistent potentiometric responses with solid-contact ion-selective electrode (SC-ISE) formats, and hence it is essential to restrain their water uptake. We have used FTIR-ATR spectroscopy to study how the water uptake is influenced by the intermixing of a poly(3-octylthiophene) (POT) SC and a poly(methyl methacrylate):poly(n-decyl methacrylate) (PMMA:PDMA) based polymeric membrane matrix, the only SC-ISE system for which direct evidence was provided on the aqueous layer elimination. Numerical simulations of the FTIR-ATR spectra of 1 or 5 wt% POT containing PMMA:PDMA membranes showed that the addition of 5 wt% POT to the membrane lowered the equilibrium water uptake, whereas the diffusion coefficients of water in the membrane were found to be less affected. Consequently, POT is beneficial for preventing the formation of detrimental water layers in the SC-ISE structure.