Study of the nanostructure of free volume and ionic conductivity of polyvinyl alcohol doped with <scp>NaI</scp>

Hmamm, M. F. M.; Zedan, I.T.; Hamed, Mohamed; Hanafy, T. A.; Bekheet, A.E.

doi:10.1002/pat.5072

Cited by 10 publications

(13 citation statements)

References 73 publications

(107 reference statements)

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“…The S values are less than 1 for all the blended samples, which indicates that the conduction mechanism is a hopping mechanism. Such behaviour was obtained for PVA1-xNaIx in a previous study conducted by Hmamm et al [ 47 ].…”

Section: Resultssupporting

confidence: 76%

“…Region (II) represents the dispersion region due to the ac conduction. The ac conductivity σ ac obeys Jonscher’s universal power law, which is described as [ 47 ]:

where A is a temperature-dependent constant that identifies the polarizability strength, ω is the angular frequency, and S is the frequency exponent with values 0 < S < 1. The calculated value of S increased with an increase in the Nylon-6,6 concentration; it is 0.53, 0.68, 0.77, 0.78, 0.782, and 0.783 for 0, 20, 40, 60, 80, and 100 wt.% Nylon-6,6 concentration blended with PVA, respectively.…”

Section: Resultsmentioning

confidence: 99%

“…The measurements were performed under a vacuum at 25 °C. The out-of-plane value of the AC ionic conductivity σ AC can be acquired using the conductance G as [ 47 ]:

where L and A are the film thickness and the cross-sectional region of the electrodes, respectively.…”

Section: Methodsmentioning

confidence: 99%

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Investigation of Transport Mechanism and Nanostructure of Nylon-6,6/PVA Blend Polymers

2022

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A casting technique was used to prepare poly(vinyl alcohol) (PVA) blend polymers with different concentrations of Nylon-6,6 to increase the free-volume size and control the ionic conductivity of the blended polymers. The thermal activation energy for some blends is lower than that of pure polymers, indicating that their thermal stability is somewhere in between that of pure Nylon-6,6 and pure PVA. The degree of crystallinity of the blend sample (25.7%) was lower than that of the pure components (41.0 and 31.6% for pure Nylon-6,6 and PVA, respectively). The dielectric properties of the blended samples were investigated for different frequencies (50 Hz–5 MHz). The σac versus frequency was found to obey Jonscher’s universal power law. The calculated values of the s parameter were increased from 0.53 to 0.783 for 0 and 100 wt.% Nylon-6,6, respectively, and values less than 1 indicate the hopping conduction mechanism. The barrier height (Wm) was found to increase from 0.33 to 0.72 for 0 and 100 wt.% Nylon-6,6, respectively. The ionic conductivity decreases as the concentration of Nylon-6,6 is blended into PVA because increasing the Nylon-6,6 concentration reduces the number of mobile charge carriers. Positron annihilation lifetime (PAL) spectroscopy was used to investigate the free volume’s nanostructure. The hole volume size grows exponentially with the concentration of Nylon-6,6 mixed with PVA. The Nylon-6,6/PVA blends’ free-volume distribution indicates that there is no phase separation in the blended samples. Mixing PVA and Nylon-6,6 resulted in a negative deviation (miscible blends), as evidenced by the interaction parameter’s negative value. The strong correlation between the free-volume size and other macroscopic properties like ionic conductivity suggests that the free-volume size influences these macroscopic properties.

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Section: Resultssupporting

confidence: 76%

“…Region (II) represents the dispersion region due to the ac conduction. The ac conductivity σ ac obeys Jonscher’s universal power law, which is described as [ 47 ]:

Section: Resultsmentioning

confidence: 99%

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Investigation of Transport Mechanism and Nanostructure of Nylon-6,6/PVA Blend Polymers

2022

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“…Meanwhile, the concentration of the holes can be determined using the o ‐Ps intensity I 3. 16 The I 3 is influenced via the arranging of reactions about an energetic positron leading to the inhibition/formation of Ps as well as membrane structure changes such as membrane doped with an inhibitor 57,58 and change of the crystallinity 5 . The connection between the o‐ Ps lifetime τ 3 and the average value of hole radius R within spherical approximation is suggested by the Tao‐Eldrup model 59,60 as,

τ_{3} goodbreak= 0.5 {\{1 - \frac{R}{R o} + \frac{1}{2 π} \sin (\frac{2 italicπR}{Ro})\}}^{- 1} ((), ns),

where R o = R + Δ R and Δ R = 0.166 nm is the thickness of the homogenous electron layer in which the positron in o‐ Ps annihilates 61 .…”

Section: Resultsmentioning

confidence: 99%

Humidity effect on the transport properties of per‐fluorinated sulfonic acid/PTFE proton exchange membranes: Positron annihilation study

El-Sharkawy

Mohamed

Hassanien

et al. 2021

Polymers for Advanced Techs

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The positron annihilation lifetime (PAL) technique was used to investigate the yield and lifetime of positronium (Ps) in three different samples of per‐fluorinated sulfonic acid/polytetrafluoroethylene (PTFE) proton exchange membranes. The high probability of Ps formation enables the study of the hole volume size by the PAL technique and explains the mechanism of both methanol permeation and proton conductivity of the membranes in relation to the relative humidity (RH). The influence of various membrane parameters, including water uptake, proton conductivity, and mechanical properties, was studied. The concentration of water molecules and SO3−–H3O+groups is correlated with the ion exchange capacity (IEC) of the membranes where higher IEC leads to high absorbance of water. The proton conductivity is enhanced by increasing the IEC value of the membrane. The activation energies of decomposition temperature for the F‐950 membrane are the lowest (Eb = 2.856 and 1.030 eV for the 1st and 2nd decomposition peaks, respectively, implying that the membrane with high IEC is thermally less stable. With increasing the IEC of the membranes, the concentration of the water molecules/SO3 group increases. In addition, the proton conductivity of the membrane is positively influenced by increasing water content at high RH. The fact that the variations in hole volume size and both methanol permeability and proton conductivity are highly dependent on RH suggests that hole volume size plays an important role in many parameters of hydrated perfluorinated sulfonic acid/PTFE proton exchange membranes. The outcomes data were introduced and interpreted appropriately with a theoretical model and compared with the literature.

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“…Nowadays, PALS is a unique nondestructive tool that has been used widely as a physical–chemical tool for directly probing the nanoatomic free volume holes sized and their concentration within a polymer 2‐5 . In PALS, when the positrons emerged from a 22 Na radioactive source, they entered the condensed medium such as polymers and quickly got thermalized by collisions with electrons of the medium.…”

Section: Introductionmentioning

confidence: 99%

Non‐fluorinated PVA/SSA proton exchange membrane studied by positron annihilation technique for fuel cell application

Awad

Abdel-Hady

Hamed

et al. 2021

Polymers for Advanced Techs

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Poly(vinyl alcohol) (PVA) with sulfosuccinic acid (SSA) membrane was prepared with different concentrations of SSA (wt.%) and thermally crosslinked successfully at 100 °C. Ion exchange capacity and proton conductivity were found to increase with increasing the SSA content in the meantime the water uptake and hydration number were declined with the rise in the degree of sulfonation. This anomalous behavior was discussed based on Nerst equation parameters which confirm the results discussion with enhancement with data of contact angle. Tensile strength results suggest the deterioration of the PVA/SSA membranes with increasing SSA content because of the chemical reaction of SSA and PVA chains. Positron annihilation results were found to enhance the electrochemical‐mechanical results of the membranes. The o‐Ps lifetime was found to increase with increasing degree of sulfonation while SO3 was working as an inhibitor agent of PS formation as o‐Ps Intensity was declined with an elevated percentage of SSA content. The o‐Ps lifetime as a function of temperature for different PVA/SSA membranes having different SSA content increased with increasing SSA content. Furthermore, the glass transition temperature of PVA/SSA membranes was found to decrease with increasing the SSA content. The results were discussed based on the free volume theory.

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Study of the nanostructure of free volume and ionic conductivity of polyvinyl alcohol doped with NaI

Cited by 10 publications

References 73 publications

Investigation of Transport Mechanism and Nanostructure of Nylon-6,6/PVA Blend Polymers

Investigation of Transport Mechanism and Nanostructure of Nylon-6,6/PVA Blend Polymers

Humidity effect on the transport properties of per‐fluorinated sulfonic acid/PTFE proton exchange membranes: Positron annihilation study

Non‐fluorinated PVA/SSA proton exchange membrane studied by positron annihilation technique for fuel cell application

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