Poly(ethylene oxide)–silica hybrids entrapping sensitive dyes for biomedical optical pH sensors: Molecular dynamics and optical response

Polymer–silica hybrid nanocomposites prepared by sol–gel process based on triethoxisilane-terminatedpoly(ethylene oxide) chains and tetraethoxysilane as silica precursor, doped with organic pH sensitivedyes, have been prepared and their suitability for use as sensors coupled with plastic optic fibers has beenevaluated. Sensors were prepared by immobilizing a drop of the hybrid materials onto the tip of a multimodepoly(methyl methacrylate) optical fiber. The performance of the optical sensor in terms of sensitivityand response time was tested in different experimental conditions, and was found to be markedlyhigher than analogous sensors present on the market. The very fast kinetic of the hybrid’s opticalresponse was supported by studies performed at the molecular level by broadband dielectric relaxationspectroscopy (DRS), investigated over a wide range of frequency and temperature, showing that poly(ethyleneoxide) chains maintain their dynamics even when covalently bonded to silica domains, whichdecrease the self-association interactions and promote motions of polymer chain segments. Due to thefast response kinetic observed, these pH optical sensors result suitable for the fast-detection of biomedicalparameters, i.e. fast esophageous pH-metry.