Synthesis and characterization of highly hydrophilic self-associating terpolymers: Rheological, thermal, and corrosion protection studies

[Display omitted] •Acrylamide-based terpolymer was synthesized via inverse emulsion polymerization.•Rheological properties of terpolymer solutions were studied at different conditions.•Salt resistance, thermal resistance and stability of the terpolymer were studied.•Corrosion inhibition properties of terpolymer solutions were evaluated. In this study, water-soluble terpolymers containing highly hydrophilic monomers of acrylamide and maleic anhydride and highly hydrophobic monomers of styrene were synthesized (ASM) through the one-step inverse emulsion polymerization. Protonnuclear magnetic resonance (1H NMR), fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction pattern (XRD) were performed to investigate the chemical structures and structural transformations of ASM. Thermal stability and thermal decomposition steps of ASM were studied by thermogravimetric analysis (TGA). An Ubbelhode capillary viscometer and a rheological mechanical spectrometer (RMS) were employed to obtain the specific, relative, and intrinsic viscosities and rheological properties of ASM solutions at different temperatures and in the presence of different concentrations of salts. Gel permeation chromatography (GPC) test and the capillary viscometry method were utilized to obtain the molecular weight of ASM chains. The obtained results showed that the shear viscosity of ASM solutions increased by the increment of the temperature and salts’ concentration. Long-term thermal stability of the ASM solutions was assessed by an aging test in which long-lasting exposure endurance attained and the shear viscosity increased after the thermal aging due to the branching of ASM chains through ring-opening anhydride reactions. Corrosion protection properties of mild steel samples immersed in terpolymer solutions before and after aging at 150 °C were studied via the electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests. Corrosion protection properties of solutions were enhanced after the thermal aging. The inhibition efficiency of ASM and thermally aged ASM (A/ASM) were obtained ~52% and ~94%, respectively.