Synthesis and assessment of poly(5-nitro-2-aminophenol) as a new scaling inhibitor to control the precipitation of CaCO3 and CaSO4 in solution

Abstract

The introduction of a -NO2 substituent in o-aminophenol would create an open-unit polymer suitable for different applications. We report the synthesis of poly(5-nitro-2-aminophenol) by aniline-catalyzed oxidative polymerization. The polymer structure was intensively characterized by spectroscopic techniques, elemental analysis, cyclic voltammetry, electrical conductivity and microscopic measurements such as SEM, TEM, TGA and DSC. The hydrophilic and hydrophobic nature of the substituents provided the formation of amphiphilicity, as judged by SEM. Thermal measurements reveal high stability up to 500 °C. Electrical conductivity decreases with increasing temperature at various frequencies. This behavior reflects the semiconducting nature in the extrinsic range, which is characterized by high carriers and low mobility. Dielectric measurements have shown that permittivity decreases gradually at lower levels, mainly due to the transport of charging carriers. Investigating the copolymer as a new scale blocker has resulted in moderate to high performance attributed to the change in polymer geometry because of the presence of different tautomers having equivalent ortho functionalities and could equally coordinate with free calcium ions and thus reduce the nucleation rate and block crystal growth. Thus, the abovementioned features indicate a new potential candidate for application as a scaling inhibitor of CaSO4 and CaCO3 precipitation, a common problem in industry.