Ionomer solution to film solidification dependence upon solvent type and its impact upon morphology and ion transport

Donghui Wang, Yan Fang Fan, Mingqiang Zhang, Robert B. Moore, Christopher J Cornelius

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

Ionomer chain and solvent molecule interactions during solution-casting, solvent evaporation, and solidification impacts chain entanglements, spatial arrangement of functional groups, microstructure development, morphology, and physical properties. These concepts were investigated using poly(t-butylstyrene-b-ethylene-alt-propylene-b-sulfonatedstyrene-b-ethylene-alt-propylene-b-t-butylstyrene) with a fixed ion-exchange capacity of 1.0, and estimated solubility parameter of 21.8 (J/cm3)1/2. Films were solution-cast using an equal volume cyclohexane:heptane mixture (C:H), chloroform (CHCl3), and tetrahydrofuran (THF). Subsequent film structures were evaluated using transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS), FT-IR, and electrochemical impedance spectroscopy. A commercially supplied film had sulfonated domains randomly distributed throughout it, and its initial proton conductivity was 11.8 mS/cm. A film created by solution-casting from C:H had a morphology containing randomly distributed sulfonated domains. This random morphology became more ordered with a lamella-like morphology when solution-cast using THF. The film produced from CHCl3 had a morphology that was between random and ordered. Film morphology differences were attributed to a poorer solvent system that inhibited chain solvation. The solution-cast film's proton conductivity was 1.0 mS/cm for a random morphology, and 15.3 mS/cm with a lamella-like structure. Increasing the ionomer-THF solution-casting temperature to 40 °C produced a film with a 103% increase in conductivity (31.2 mS/cm). This led to a water uptake change from 29 wt% to 80 wt%. Cycling a THF solution-cast film from its dry to a wet state revealed that a lamella-like morphology would maintain its conductivity, but the commercial film's conductivity decreased from 11.8 mS/cm to 0.98 mS/cm. Ionomer film properties were found to be dependent upon solvent quality and processing.

Original languageEnglish (US)
Pages (from-to)169-177
Number of pages9
JournalEuropean Polymer Journal
Volume97
DOIs
StatePublished - Dec 1 2017

Fingerprint

Ionomers
solidification
Solidification
Ions
ions
tetrahydrofuran
casts
lamella
conductivity
Heptanes
Casting
Proton conductivity
Heptane
Cyclohexane
heptanes
propylene
cyclohexane
Propylene
Ethylene
ethylene

Keywords

  • FTIR
  • Film solution-casting method and processing temperature
  • Ionomer
  • Morphology
  • Proton conductivity
  • SAXS

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Polymers and Plastics
  • Organic Chemistry
  • Materials Chemistry

Cite this

Ionomer solution to film solidification dependence upon solvent type and its impact upon morphology and ion transport. / Wang, Donghui; Fan, Yan Fang; Zhang, Mingqiang; Moore, Robert B.; Cornelius, Christopher J.

In: European Polymer Journal, Vol. 97, 01.12.2017, p. 169-177.

Research output: Contribution to journalArticle

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