Preparation and characterization of a poly(vinylbenzyl sulfonic acid)-grafted FEP membrane

One-Pot Synthesis of Proton Exchange Membranes from Anion Exchange Membrane Precursors

Proton exchange membranes (PEMs) play a critical role in many electrochemical devices that could solve the shortcomings of current energy storage and conversion systems. Hydrocarbon-based PEMs are an attractive alternative for replacing the state-of-the-art perfluorosulfonic acid PEMs; however, synthetic routes are generally limited to sulfonation of aromatic units (pre- or postpolymerization functionalization). Here we disclose a facile and scalable one-pot synthetic method of converting an alkyl halide functionality to a sulfonate in polymer systems. With this method, sulfonated hydrocarbon PEMs can be conveniently prepared from a precursor polymer of anion exchange membranes which have recently experienced significant advances. Polyphenylene type PEMs (BPSA and mTPSA in this report) were generated in one-pot S_N2 reaction of bromoalkyl side chains of polymers followed by oxidation. These PEMs showed excellent proton conductivity with BPSA showing 250 mS/cm in water at 80 °C, nearly 1.5 times higher than that of Nafion 212. Furthermore, the separation of the sulfonic acid group from the rigid backbone with a flexible alkyl chain mitigates excessive water uptake and in-plane swelling ratio of the polymer, despite having a high ion exchange capacity of 2.6 mequiv/g. Oxidative stability was also shown to be superior for hydrocarbon-based PEMs with negligible changes in mass, NMR, and proton conductivity.

A greener approach for impressive removal of As(iii)/As(v) from an ultra-low concentration using a highly efficient chitosan thiomer as a new adsorbent

Contamination of ground water with arsenic is a serious problem all over the world.

New Chitosan-Thiomer: An Efficient Colorimetric Sensor and Effective Sorbent for Mercury at Ultralow Concentration

This paper describes an innovative procedure for the fabrication of a facile colorimetric sensor in one step with thiol functional group for Hg(2+) detection at trace level. The sensor was successfully synthesized via chitosan isothiouronium salt intermediate with innocuous low cost thiourea reagent under microwave irradiation. It is an innovative green approach to achieve thiol functionalization with a high degree of substitution. Thiomer was characterized by titrimetry, FTIR, (1)H NMR, elemental analysis (CHNS), and EDX for extent of modification with detail structure. The synthesized and well characterized thiomer was screened for sensor application. The sensing solution of thiomer resulted in an instantaneous sharp color change from colorless, yellow, to brown with increase in Hg(2+) concentration. Chitosan thiomer also exhibited high sensitivity and selectivity for Hg(2+) over other possible interfering ions in aqueous media. The sensing responses were visualized quantitatively with quick response, good selectivity, high sensitivity, and a low detection limit of ∼0.465 ppb by the naked eye. The same was tested with a paper strip method for technological applications. Furthermore, the as-prepared sensors also exhibited exceptional sorption potential for Hg(2+) even from ultralow concentration aqueous solution and reduced the Hg(2+) concentration from 10 ppb to the extremely low level of ∼0.04 ppb as studied by cyclic voltammetry. Thus, the proposed method is simple, promising, and rapid without any complicated modifying step and is an economical alternative to traditional Hg(2+) sensors for rapid sensor application in environmental water samples at ppb levels.

Synthesis of diverse α,ω-telechelic polystyrenes with di- and tri-functionality via tandem or one-pot strategies combining aminolysis of RAFT-polystyrene and a thiol–ene “click” reaction

Diverse new α,ω-telechelic polystyrenes with di-/tri-functionality were synthesized via tandem/one-pot strategies combining aminolysis of RAFT-polystyrene and a thiol–ene “click” reaction.

A green and highly efficient sulfur functionalization of starch

An innovative green approach to achieve thiol functionalization of starch with a degree of substitution ≥ 2.

A study on the characterization of FEP-g-PVBSA membranes as polymer electrolytes for direct methanol fuel cells

Poly(vinylbenzyl sulfonic acid)-grafted poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP- g-PVBSA) electrolyte membrane was prepared by radiation-induced grafting of vinylbenzyl chloride onto FEP film with subsequent sulfonation processes. An energy dispersive X-ray analysis was used to observe the cross-sectional distribution behaviors of the hydrophilic sulfonic acid groups and hydrophobic fluorine groups. The characteristics of an ion-exchange capacity (IEC), water and methanol uptake, methanol permeability, and proton conductivity as a function of the degree of grafting were studied. The IECs and water uptakes of membranes with different degrees of grafting (36 to 102%) were measured in the range of 0.8 to 1.62 meq g−1 and 10 to 30%, respectively. The proton conductivity was higher than that of a Nafion 212 membrane (6.1 E−02 S cm−1), when the degree of grafting reached 60%. The methanol permeability and uptake of the FEP- g-PVBSA membrane was significantly lower than that of the Nafion 212 membrane, and even the degree of grafting reached 102%.