Poly(N‑vinyl triazole‑b‑N‑vinyl imidazole) Graf ted on MWCNTs as Nanofillers to Improve Proton Conducting Membranes Nilanjan Mukherjee, Anupam Das, and Tushar Jana* Cite This: ACS Appl. Nano Mater. 2023, 6, 544-557 Read Online ACCESS Metrics & More Article Recommendations * sı Supporting Information ABSTRACT: Carbon nanotubes (CNTs) are of particular interest because of their ability to enhance the mechanical strength in the material; however, processing difculties of CNTs often restrict utilization up to its full potential. To resolve this, in the current study, we have developed a simple and efcient method to functionalize the surface of a multiwalled carbon nanotube (MWCNT) with precise functional polymer chains, which were covalently grafted onthesurfaceoftheMWCNT,anddelvedintoan application to demonstrate this material as an efcient nanofller in developing a proton conducting membrane (PEM) from poly- benzimidazole(PBI).Atfrst,theMWCNTsurfacewasconvertedto a polymerizable surface by attaching a trithiocarbonate based chain transfer agent (CTA). Then, a N-heterocyclic block copolymer, namely poly-N-vinyl-1,2,4-triazole-b-poly-N-vinyl imidazole (pNVT-b-pNVI), was grown from the CTA anchored surface with a one-potsurfaceinitiatedreversibleaddition−fragmentationchaintransfer(SI-RAFT)technique. Grafting ofblockcopolymerchain wasconfrmedbyGPC,NMR,TGA,TEM,FESEM,andEDXstudies.Tothebestofourknowledge,thiswillbethe frstreportofa growingblockcopolymerstructure grafted covalentlyonthesurfaceoftheMWCNT.Thenoveltyoftheworkwasfurtherenhanced by incorporating pNVT-b-pNVI-g-MWCNT as a nanofller into the oxypolybenzimidazole (OPBI) membrane to obtain homogeneousnanocompositemembraneswithexcellentthermomechanicalandtensileproperties,thermalstability,superiorproton conduction when doped with phosphoric acid (PA), and PA holding capacity. The nanocomposite membrane with 2.5 wt % nanofllerloadingdisplayedatensilestressof1.8MPaandastrainof176%atbreak.ThebasicN-heterocyclicringsdanglingfrom theblockcopolymerchains grafted ontheMWCNTsurfaceallowedformationofstrongH-bonding,acid−baseinteractionwithPA, whichisresponsibleforhighaciduptakeandsuperiorPAretention,andalsoexhibitedprotonconductivityashighas0.164Scm −1 at180 °C,whichisa2.6-foldincrementwhencomparedwithapristineOPBImembrane.Thissignifcantincreaseinconductivityis attributed to the proton conducting nanochannel pathway generated along the polymer-g-MWCNT surface. KEYWORDS: Block copolymer, RAFT polymerization, Multiwalled carbon nanotube, polybenzimidazole, proton exchange membrane ■ INTRODUCTION Carbonnanotubes(CNTs)haveattractedimmenseinterestof material scientists due to its versatile chemical characteristics and physical properties in catalysis, 1−3 gas adsorption, 4 water purifcation, 5,6 electrical and thermal conductivity, 7−10 and highmechanicalstability, 11,12 sincetheirdiscovery. 13 However, thereisasignifcantlimitationontheusageofCNTsbecause of the presence of strong van der Waals interaction which makes them insoluble in almost all the solvents, and they are heldtogethertightlytoformbundlesandropelikeaggregation in solution and also in the polymer matrix. 14−16 This strong aggregating nature restricts their processability and hampers the performance at the nano level. 17,18 To address these problems,diferentapproacheshaveevolvedinliteraturewhich include modifcation with surfactant, polymer absorption, encapsulation of polymer, and end group modifcation of CNT surface for covalent grafting of diferent molecules and polymers. 17,19−21 While investigating, we have observed that covalent functionalization of CNTs with polymer chains or surfacemodifcationofCNTwithstrategicallydesigned grafted blockcopolymerchainscanbeofgreatadvantageasthedesign of the polymer structure can enhance the material properties signifcantly and can be modifed to further improve the processability with the target matrix which can signifcantly improve to meet the requirements for particular applications. “Grafting to” and “grafting from” are the major two approaches toward the grafting of polymer chains on the Received: October 25, 2022 Accepted: December 2, 2022 Published: December 19, 2022 Article www.acsanm.org © 2022 American Chemical Society 544 https://doi.org/10.1021/acsanm.2c04603 ACS Appl. Nano Mater. 2023, 6, 544−557 Downloaded via UNIV OF HYDERABAD on January 13, 2023 at 11:20:54 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.