title: Interplay between solid state transitions, conductivity mechanisms, and electrical relaxations in a [PVBTMA] [Br]-b-PMB diblock copolymer membrane for electrochemical applications.
abstract: Understanding the structure-property relationships and the phenomena responsible for ion conduction is one of the keys in the design of novel ionomers with improved properties. In this report, the morphology and the mechanism of ion exchange in a model anion exchange membrane (AEM), poly(vinyl benzyl trimethyl ammonium bromide)-block-poly(methylbutylene) ([PVBTMA][Br]-b-PMB), is investigated with small angle X-ray scattering, high-resolution thermogravimetry, modulated differential scanning calorimetry, dynamic mechanical analysis, and broadband electrical spectroscopy. The hyper-morphology of the material consists of hydrophilic domains characterized by stacked sides of [PVBTMA][Br] which are sandwiched between "spaghetti-like" hydrophobic cylindrical parallel domains of the PMB block. The most important interactions in the hydrophilic domains occur between the dipoles of ammonium bromide ion pairs in the side chains of adjacent chains. A reordering of the ion pair dipoles is responsible for a disorder-order transition (Tδ) at high temperature, observed here for the first time in AEMs, which results in a dramatic decrease of the ionic conductivity. The overall mechanism of long range charge transfer, deduced from a congruent picture of all of the results, involves two distinct ion conduction pathways. In these pathways, hydration and the motion of the ionic side groups are crucial to the conductivity of the AEM. Unlike the typical perfluorinated sulfonated proton-conducting polymer, the segmental motion of the backbone is negligible.
authors.affiliation: Department of Industrial Engineering, Section of Chemistry for Technology and Energy & Department of Chemical Sciences, University of Padova, Via Marzolo 1, I-35131 Padova, Italy. vito.dinoto@unipd.it.
authors.forename: Vito
authors.initials: V
authors.lastname: Di Noto
authors.affiliation: Helmholtz Institute Ulm (HIU), Electrochemistry I, Helmholtzstrasse 11, 89081 Ulm, Germany & Karlsruhe Institute of Technology (KIT), P. O. Box 3640, 76021 Karlsruhe, Germany.
authors.forename: Guinevere A
authors.initials: GA
authors.lastname: Giffin
authors.affiliation: Department of Industrial Engineering, Section of Chemistry for Technology and Energy & Department of Chemical Sciences, University of Padova, Via Marzolo 1, I-35131 Padova, Italy. vito.dinoto@unipd.it.
authors.forename: Keti
authors.initials: K
authors.lastname: Vezzù
authors.affiliation: Department of Industrial Engineering, Section of Chemistry for Technology and Energy & Department of Chemical Sciences, University of Padova, Via Marzolo 1, I-35131 Padova, Italy. vito.dinoto@unipd.it.
authors.forename: Graeme
authors.initials: G
authors.lastname: Nawn
authors.affiliation: Department of Industrial Engineering, Section of Chemistry for Technology and Energy & Department of Chemical Sciences, University of Padova, Via Marzolo 1, I-35131 Padova, Italy. vito.dinoto@unipd.it.
authors.forename: Federico
authors.initials: F
authors.lastname: Bertasi
authors.affiliation: Department of Polymer Science and Engineering, University of Massachusetts Amherst, 120 Governors Drive, Amherst, MA 01003, USA.
authors.forename: Tsung-han
authors.initials: TH
authors.lastname: Tsai
authors.affiliation: Department of Chemical and Biological Engineering, Colorado School of Mines, Golden, CO 80401, USA. aherring@mines.edu.
authors.forename: Ashley M
authors.initials: AM
authors.lastname: Maes
authors.affiliation: X-Ray Sciences, Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors.forename: Soenke
authors.initials: S
authors.lastname: Seifert
authors.affiliation: Department of Polymer Science and Engineering, University of Massachusetts Amherst, 120 Governors Drive, Amherst, MA 01003, USA.
authors.forename: E Bryan
authors.initials: EB
authors.lastname: Coughlin
authors.affiliation: Department of Chemical and Biological Engineering, Colorado School of Mines, Golden, CO 80401, USA. aherring@mines.edu.
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Herring