Synthesis of bolaform surfactants from recycled poly(ethylene terephthalate) waste

Abstract

In this study, bolaform surfactants have been prepared from recycled poly(ethylene terephthalate) monomers through an efficient process. Bis(hydroxyethyl) terephthalate (BHET) and terephthalic acid (TPA) have been used as precursor molecules for the synthesis of organophosphorus surfactants. With a yield of 73%, the reaction between BHET and triethyl phosphate resulted in the bis(2-((triethoxy(hydroxy)-l5-phosphaneyl)oxy)ethyl) terephthalate (BHETEO) sample. From TPA as a precursor molecule in a three-step reaction process, TPTEOH compound has been obtained with a yield of 58%. The physicochemical properties such as solubility, photosensitivity, zeta potential, hydrodynamic size, and thermogravimetric analyses of both surfactants have been studied. The bolaform surfactants showed stability under ultraviolet radiation. The Dynamic Light Scattering analysis displayed an aggregate size of 65.7 nm for BHETEO sample, without the influence of temperature. In contrast, the aggregate size of 144 nm for TPTEOH was strongly influenced by temperature. The BHETEO and TPTEOH samples presented Zeta Potentials of −21.7 mV and −1.06 mV, respectively. The results showed BHETEO and TPTEOH samples to have self-assembling properties with aggregation forms dependent on the polarity of the solvents. Therefore, the development of bolaform surfactants represents an alternative way to use monomers from PET waste with promising applications.