Synthesis and characterization of amphiphilic star copolymer of polyaniline and polyacrylic acid based on calix[4]resorcinarene as an efficient adsorbent for removal of paraquat herbicide from water

Abstract

In this study a novel star copolymer of acrylic acid with aniline was prepared using calix[4]resorcinarene as a multifunctional core. The prepared star copolymer was characterized and its physical properties were investigated. In this regard, firstly, the calix[4]resorcinarene was prepared via condensation of resorcinol with butanal. Then in order to synthesis the multifunctional RAFT (Reversible addition-fragmentation chain transfer) initiator, the calix[4]resorcinarene was treated with CS2 and the resulting mixture reacted with vilsmeier-haack reagent in the presence of aniline. In the next step, acrylic acid was added and the resulting polyacrylic acid star polymer was obtained via RAFT living polymerization. Finally, the acrylic acid-aniline (PAA-b-PANI) star copolymer was produced by oxidation polymerization of aniline with as prepared polyacrylic acid star prepolymer using ammonium persulfate as initiator and HCl as a doping agent. The characterization of all synthesized materials was done using FT-IR and 1H NMR. The morphology of PAA-b-PANI star copolymer determined using FE-SEM and TEM analyses. The conductivity of star copolymer was measured by four-probe method. According to XRD analysis, the PAA-b-PANI star co-polymer showed a semi-crystalline nature. The thermal properties of PAA-b-PANI star co-polymer were investigated using TGA and DSC apparatus. Eventually, PAA-b-PANI star copolymer was assessed for the removal of paraquat herbicide. Optimization of paraquat adsorption by PAA-b-PANI star copolymer in aqueous solution was performed. Langmuir and Freundlich isotherms and pseudo first and second order kinetics were studied.