Synthesis, characterization of multi-arm copolymers and linear blocks based on PEG and PCL: Effect of topology on dye adsorption

Abstract

Three poly (ethylene glycol)-poly (ε-carprolactone) (PEG-PCL) copolymers with different topologies but identical molar ratio between PEG to PCL were designed. These samples, namely, diblock (Di-PEG-PCL), triblock (Tri-PEG-PCL), and multi arm (Multi-PEG-PCL) copolymers, were characterized by different techniques including Fourier transform infrared spectroscopy, X-ray diffraction, Transmission electron microscopy, and thermogravimetric analysis. The effect of topology on the removal of methylene blue efficiency from aqueous solutions was investigated.The effects of the initial concentration of MB, contact time, and temperature on the adsorption phenomena, were investigated. Pseudo-first/second-order isotherms were applied to determine the efficiency of the copolymers. The experimental data fitted well with the pseudo-second-order and Freundlich model for MB dye adsorption. The Freundlich isotherm exhibited the best fit.The endothermic and spontaneous nature of the MB adsorption was demonstrated by thermodynamic analysis. Compared to the various topologies, the produced Multi arm copolymer showed an effective MB dye separation from the aqueous solution. The findings of this work point to the potential utility of the synthetic Multi arm PEG-PCL for the efficient removal of cationic dyes from aquatic settings.