Free Volume in Poly(ether imide) Membranes Measured by Positron Annihilation Lifetime Spectroscopy and Doppler Broadening of Annihilation Radiation

Abstract

In order to characterize the free volume of a homologous series all-aromatic poly­(ether imide) (PEI) membranes, two positron annihilation techniques were utilized: positron annihilation lifetime spectroscopy (PALS) and Doppler broadening (DB) of annihilation radiation. First, DB, which is a fast and convenient method, indicated differences in free volume of all PEIs investigated, whereas PALS experiments gave more quantitative information, with respect to the size and distribution of the voids. DB results show that S, W pairs for this PEI-series tend to group according to their dianhydride moiety, meaning that, in this series, dianhydrides govern the differences in the S parameter, indicating more free volume with increasing S value. The semicrystalline PEI samples exhibit the lowest S parameter, while the amorphous samples based on 3,3′,4,4′-oxydiphthalic dianhydride (ODPA) all lie on the higher S side of the S–W plot. With the 1,4-bis­(4-aminophenoxy)­benzene (P1)-based PEI (ODPA-P1) standing out with the highest S parameter. The same could be confirmed and quantified by PALS, where ODPA-P1 is the only membrane in this series with its free volume described by both smaller and larger free-volume elements. The larger voids in ODPA-P1 can be characterized as having a radius (R) of 3.3 Å, which is 5 times larger than the lowest measured free-volume content in this series observed for 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) and 1,3-bis­(4-aminophenoxy)­benzene (M1)-based PEI (BPDA-M1), which has voids with a radius of R ≈ 0.7 Å. When comparing results obtained by DB and PALS, a very good correlation is observed between the S parameter (determined by DB) and the free-volume content (quantified by PALS).

High‐pressure sorption of carbon dioxide and methane in all‐aromatic poly(etherimide)‐based membranes

“…The lack of a clear T g and the semicrystalline character of the PMDA‐P1 complicate the TEA analysis and therefore the PMDA‐P1 results should be treated with caution. Experiments to determine the EFV for all four PEIs using Positron Annihilation Lifetime Spectroscopy and Doppler Broadening (PALS and PADB) are in progress and the results will be reported elsewhere . In the rubbery state, the values for linear thermal expansion coefficient follow a consistent trend: a more rigid precursor gives a lower CTE.…”

Achieving Low-Energy-Barrier Ion Hopping in Adhesive Composite Polymer Electrolytes by Nanoabsorption

“…To quantitatively analyze the nanoabsorption effect, positron annihilation lifetime spectroscopy (PALS) measurements were conducted to investigate the free volume change caused by the nano-Al 2 O 3 . Table S1 summarizes the positron annihilation lifetime (τ) and its intensity ( I ) of A-CPEs, where τ 3 is considered to be the annihilation of o -Ps in free volume holes of polymers, which reflects the free volume size of polymer materials. , Figure f shows the average radius and volume of free volume holes in UHMWPEO–Li + and A-CPE-15%. After introducing 15 wt % nano-Al 2 O 3 in A-CPEs, the average radius and volume decrease from 3.027 to 3.006 Å and 116.137 to 113.664 Å 3 , respectively.…”

“…τ 1 , τ 2 , and τ 3 correspond to para -positronium ( p -Ps), free positron, and ortho -positronium (o -Ps), respectively. The free volume hole radius was calculated according to eq where τ 3 is the o -Ps lifetime, R is the free volume radius, and Δ R is the empirical electron layer thickness of around 1.66 Å.…”

Application Progress of PALS in the Correlation of Structure and Properties for Graphene/Polymer Nanocomposites

“…The positron lifetime in polymer composites is sensitive to the size of free volume, while the momentum distribution of electrons in DBS is more sensitive to their chemical environments [ 65 , 66 ]. In the investigation of polyzwitterion membrane via assembly of GO-based core-brush nanosheet [ 67 ], slow positron annihilation DBS was used to reveal the microstructure, the smaller S parameter indicates a more compact membrane structure.…”