Design,Synthesis,and Analytical Application Of Tetraphenylethylene-terminated Quaternary Ammonium Surfactants

As one of the most widely used solubilizers,surfactants are widely used in the fields of environmental restoration,detergency of pollutants,crude oil mining,catalysis,sensing,drug delivery,and polymerization.Solubilization location of the solubilized substance in surfactant micelles usually affects its application fields and effects.Therefore,it is crucial to develop a suitable analytical method to accurately determine the solubilization locations of the solubilized substance.The current methods to measure the solubilization locations are based on the relationship between the signal of polar probe and the polar region of the micellar microenvironment.However,the difference in the response performance of the polar probes and the uncertainty of the polarities in micellar microenvironment bring many problems.This text aims to establish a new analytical method,not involving polarity of the probes and micellar microenvironment.We designed and synthesized a new type of aggregation-induced luminescence(AIE)surfactant,and used the Forster resonance energy transfer(FRET)distance formula to accurately measure solubilization locations on the nanoscale.The main contents are as follows:1.By altering the number of carbon atoms in hydrophobic alkyl chain(C4,C6,C8,C10),a series of triethylammonium bromide cationic surfactants(TPE-C4TEAB?TPE-C6TEAB?TPE-C8TEAB and TPE-C10TEAB)were successfully designed and synthesized with a hydrophobic tail group terminated by a tetraphenylethylene(TPE)fluorophore.Next,the basic properties such as hydrophobicity,critical micelle concentration(CMC),and optical properties were studied using theoretical calculations,conductivity measurement,UV-vis absorption spectra,and fluorescence emission spectra.The results showed that with the increase of alkyl chain length,the hydrophobicity increased,the CMC decreased,and the intensity of fluorescence increased.2.As a surfactant model,TPE-C10TEAB with low CMC and high-efficiency luminescence was used to develop a method to measure solubilization locations in micelles.The results of theoretical calculations,transmission electron microscope(TEM)and dynamic light scattering(DLS)proved that TPE-C10TEAB in water formed spherical micelles and TPE fluorophores were located at the inner core of the micelles.Using TPE fluorophores as FRET donors and five solubilized substances with different hydrophobicities and sizes as FRET acceptors,the nanometer distance between TPE donors and solubilized substances in micelles was calculated by the FRET distance formula,so as to accurately measure solubilization positions of solubilized substance in micelles.The results showed that solubilization locations of solubilized substances in the micellar interior and at the micellar surface depend on their size and hydrophobicity,respectively.In addition,we constructed the bright multicolour and pure white light-emitting micellar solutions and gels through tuning their FRET behaviors.