Volume Fraction of Ether Is a Significant Factor in Controlling Conductivity in Proton Conducting Polyether Based Polymer Sol–Gel Electrolytes

Abstract

We have synthesized several copolymers of methyl polyethylene glycol siloxane (MePEG7SiO3)m and methyl polypropylene glycol siloxane (MePPGnSiO3)m as hydrogen ion (H(+)) conducting polymer electrolytes. These copolymers were prepared by a sol-gel polymerization of mixtures of the MePEG and MePPG monomers. We synthesized these H(+) conducting polymer electrolytes in order to study the relationship between observed ionic conductivity and structural properties such as viscosity, fractional free volume, and volume fraction of ether. We found that viscosity increased as the fraction of the smaller comonomer increased. For the MePPG2/MePPG3 copolymer, an increase in fractional free volume increased the fluidity. The heterogeneous copolymers (PEG/PPG copolymers) obeyed the Doolittle equation, while the homogeneous (PEG/PEG and PPG/PPG) copolymers did not. The increase of FFV did not, however, correspond to an increase in conductivity, as would have been predicted by the Forsythe equation. The conductivity data did correspond to a modified Forsythe equation substituting Volume Fraction of Ether (V(f,ether)) for FFV. We conclude that the proton conductivity of MePEG copolymers is more dependent on the volume fraction of ether than on the fractional free volume.

Insight into the role of free volume in irradiation resistance to discoloration of lead‐containing plexiglass

“…Positron annihilation lifetime spectroscopy (PALS) was carried out by a conventional fast-fast coincidence spectrometer at room temperature. Two samples with the same size sandwiched the positron source 22 Na, and the thickness of samples was about 1.2 mm, enough to absorb more than 99% of the positrons. Each spectrum was recorded with 1 million counts, and a commonly used positron fitting procedure was employed to resolve the spectrum into three components.…”

“…The larger the free volume, the better the mobility of polymer chain. 22 Since the mobility of polymer chains is dependent on the free volume strongly, the irradiation resistance of polymer is also related to the free volume. 21 On the other hand, the free volume is commonly used as scale to correlate structural changes and performance of polymers after aging (including γ ray, ion irradiation, and UV radiation, etc.).…”

Ab Initio Molecular Dynamics Simulations of an Excess Proton in a Triethylene Glycol–Water Solution: Solvation Structure, Mechanism, and Kinetics

“…Polyethylene glycol (PEG) (also known as poly­(ethylene oxide) (PEO) in its long chain form) is a water-soluble polymer that has been widely studied for its interesting properties in aqueous environments. These properties include interactions of its ethylene oxide (EO) chains in aqueous solutions, − the ability to adsorb on surfaces and interfaces, and proton conductivity in polymer electrolytes. − The interaction of water with the PEG chain backbone has been widely studied to date, both by experiment ,, and simulation ,− due to the interesting ability of PEG to form bridged hydrogen bonds (HBs) from EO monomer units to water molecules to other EO monomer units within the same chain . These properties give PEG a wide variety of applications such as biphasic (two-phase) liquid–liquid catalysis, electrochemical energy conversion as a proton exchange membrane additive, − , and in drug delivery via modification of therapeutic molecules (known as PEGylation). − …”

“…6−18 The interaction of water with the PEG chain backbone has been widely studied to date, both by experiment 2,3,19 and simulation 4,20−26 due to the interesting ability of PEG to form bridged hydrogen bonds (HBs) from EO monomer units to water molecules to other EO monomer units within the same chain. 4 These properties give PEG a wide variety of applications such as biphasic (twophase) liquid−liquid catalysis, 27 electrochemical energy conversion as a proton exchange membrane additive, [8][9][10][11][12][13][14]28 and in drug delivery via modification of therapeutic molecules (known as PEGylation). 29−31 The conductivity of various ions with PEG in aqueous solution has also been of research interest in past years.…”