P(o-chlorophenol–co-o-hydroxyphenol): kinetic formation studies and pH-sensor application

Abstract

Electrochemical copolymerization of o-chlorophenol (o-ClPh) with o-hydroxyphenol (o-HOPh) was conducted in aqueous H2SO4 using cyclic voltammetry technique at the Pt electrode. The reaction rate was found to be of the second order in the monomer concentration and first order in the acid concentration. The activation energy, enthalpy, and entropy for the copolymerization were found to be 20.20 kJ mol-1, 19.24 kJ mol-1 and -281.47 J K-1 mol-1, respectively. The obtained copolymer films show smooth feature with amorphous nature. Copolymer films adhere Pt electrode very well and show less reactivity in the H2SO4 medium. The pH sensitivity of the poly(oClPh-co-HOPh)-modified electrode has been investigated potentiometrically using different polymer thicknesses. The potentiometric responses to pH change of the poly(oClPh-co-HOPh)-modified electrode appeared reversible and linear in the range from pH 2-11 with a maximum sub-Nernstian potentiometric response slope of 40.7 mV/pH (30 °C). The slope became close to 56.2 mV/pH in the range from pH 4 to 9 at (30 °C). The poly(oClPh-co-HOPh)-modified electrode readily responded to pH change but was not stable with time.

Keywords

• Pt-anode
• poly(o-chlorophenol-co-o-hydroxyphenol)
• electrocopolymerization
• kinetic study
• activation parameters
• potentiometric pH sensor