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dc.contributor.authorAnderson, Lindsey Janeen_US
dc.date.accessioned2020-08-01T06:00:30Z
dc.date.available2020-08-01T06:00:30Z
dc.date.issued2019-02-07
dc.identifier.othervt_gsexam:18577en_US
dc.identifier.urihttp://hdl.handle.net/10919/99463
dc.description.abstractSulfonated polyaromatic hydrocarbon membranes have emerged as desirable candidates for proton exchange membranes (PEMs) due to their excellent mechanical properties, high thermal and chemical stability, and low cost. Specifically, sulfonated multiblock copolymers are attractive because their phase-separated morphologies aide in facile proton transport. In this work, the functionalization of semicrystalline gels of poly(ether ether ketone) (PEEK) is explored as a novel post-polymerization method to prepared blocky copolymers, and the effect of copolymer architecture on membrane physical properties, structure, and performance is extensively investigated. First, the blocky sulfonation of PEEK was explored to prepare blocky copolymers (SPEEK) with densely sulfonated domains and unfunctionalized, crystallizable domains. Compared to random SPEEK ionomers at similar ion content, blocky SPEEK exhibited enhanced crystallizability, decreased melting point depression, and faster crystallization kinetics. Phase separation between the hydrophilic sulfonated blocks and hydrophobic PEEK blocks, aided by polymer crystallization, resulted in enhanced water uptake, superior proton conductivity, and more closely associated ionic domains than random SPEEK. Furthermore, the random and blocky bromination of PEEK was investigated to prepare PEEK derivatives (BrPEEK) with reactive aryl-bromides. Spectroscopic evidence revealed long domains of unfunctionalized homopolymer for blocky BrPEEK, and this translated to an increased degree of crystallinity, higher melting temperature, and more rapid crystallization kinetics than random BrPEEK at similar degrees of bromination. The subsequent sulfonation of blocky BrPEEK resulted in a hydrophilic-hydrophobic blocky copolymer with clear multi-phase behavior. The phase-separated morphology contributed to decreased water uptake and areal swelling compared to random SPEEK and resulted in considerably higher proton conductivity at much lower hydration levels. Moreover, Ullmann coupling introduced superacidic perfluorosulfonic acid side chains to the BrPEEK backbone, which yielded membranes with less water content and less dimensional swelling than random SPEEK. Superior proton transport than random SPEEK was observed due to the superacid side chain and wider hydrophilic channels within the membranes, resulting in more continuous pathways for proton transport. Overall, this work provided a novel platform for the preparation of functionalized PEEK membranes using a simple post-polymerization functionalization procedure. The established methods produced blocky-type copolymers with properties reminiscent of multiblock copolymers prepared by direct polymerization from monomers/oligomers.en_US
dc.format.mediumETDen_US
dc.publisherVirginia Techen_US
dc.rightsThis item is protected by copyright and/or related rights. Some uses of this item may be deemed fair and permitted by law even without permission from the rights holder(s), or the rights holder(s) may have licensed the work for use under certain conditions. For other uses you need to obtain permission from the rights holder(s).en_US
dc.subjectproton exchange membraneen_US
dc.subjectpost-polymerization functionalizationen_US
dc.subjectpoly(ether ether ketone)en_US
dc.subjectsemicrystalline ionomeren_US
dc.subjectblocky copolymeren_US
dc.titleChemical and Physical Modifications of Semicrystalline Gels to Achieve Controlled Heterogeneityen_US
dc.typeDissertationen_US
dc.contributor.departmentChemistryen_US
dc.description.degreePHDen_US
thesis.degree.namePHDen_US
thesis.degree.leveldoctoralen_US
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen_US
thesis.degree.disciplineChemistryen_US
dc.contributor.committeechairMoore, Robert Bowenen_US
dc.contributor.committeememberRiffle, Judy Sen_US
dc.contributor.committeememberLiu, Guoliangen_US
dc.contributor.committeememberLong, Timothy Een_US


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