Broadband dielectric spectroscopy studies of glassy‐state relaxations in annealed poly(2,5‐benzimidazole)

Nalawade, Amol; Hassan, Mohammad K.; Jarrett, William A.; Mauritz, Kenneth A.; Litt, Morton H.

doi:10.1002/pi.3147

Cited by 11 publications

(10 citation statements)

References 42 publications

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“…The tan δ as a function of temperature (at a frequency of 1.35 Hz) for all the membranes is shown in Figure ; this is an important plot, which approximately shows the temperature window in which a particular relaxation is observed at a given frequency. The peak observed in the temperature range of −50 to 50 °C (designated as δ relaxation) is attributed to the rotational motions of the backbone . This peak moves to lower temperature with acid doped samples.…”

Section: Resultsmentioning

confidence: 98%

“…The broad shoulder peak observed at 2θ value of 18.5° can be attributed to short‐range order in the polymer. This peak sharpens with heat‐treatment temperature, due to the increased ordering from chain stacking; the change is only with respect to the peak intensity and there is no peak shift as such [see Figure (a)] and it is negligible with undoped composite [Figure (b)] . However, a significant shift is observed with the peak at 10° to higher 2θ values with temperature.…”

Section: Resultsmentioning

confidence: 99%

“…This relaxation is assigned as γ relaxation. The relaxation at higher temperature (100–200 °C) is attributed to the polymer segment with relatively larger number of carbon atoms and it is assigned as β relaxation . The β relaxation can be related to the motion of the local chains near crystalline regions of the material; it is observed mainly at higher temperatures wherein the water evaporation and closer packing of the material occurs …”

Section: Resultsmentioning

confidence: 99%

“…The temperature and dopants have been shown to significantly alter the relaxation properties of the material those in‐turn affect the proton conduction behavior . However, similar studies with high temperature membranes are rare in the literature . Moreover, the incorporation of phosphoric acid and dopant nanoparticles makes the relaxation processes in these membranes even more complicated to analyze and understand.…”

Section: Introductionmentioning

confidence: 99%

“…The only report on BDS of ABPBI material deals with the relaxation properties of undoped membranes, wherein, Nalawade et al . explain the sub‐ T g relaxations and the effect of heat treatment on the polymer crystallinity …”

Section: Introductionmentioning

confidence: 99%

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Dielectric relaxations in phosphoric acid‐doped poly(2,5‐benzimidazole) and its composite membranes

Saleha

Rahul

Nalajala

et al. 2017

J of Applied Polymer Sci

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Poly(2,5‐benzimidazole) (ABPBI)—a promising high‐temperature polymer electrolyte membrane—is characterized over a wide range of temperature (−50 to 220 °C) using broadband dielectric spectroscopy (BDS) to understand the various relaxation processes. The undoped ABPBI membrane shows two major secondary relaxations and a primary α relaxation. The effect of phosphoric acid (PA) and phosphotungstic acid grafted zirconium dioxide (PWA/ZrO2) nanoparticles on the chain relaxation and the proton conductivity is investigated. The phosphoric acid alters the relaxation trends, increases the number of free ions in the polymer matrix, and therefore the conductivity. The shift in the peak frequencies of different chain relaxation processes in the presence of PA and PWA/ZrO2 is attributed to the increase in free volume and the consequent easy motion of the polymer chains. The Fourier transform infra‐red (FTIR) spectroscopy of ABPBI and the acid‐doped composites show all the relevant peaks corresponding to CC, CN stretching, and phosphoric acid/phosphates, confirming the formation of ABPBI and doping with PA. The proton conductivity of the membranes is estimated from electrochemical impedance spectroscopy (EIS). To establish the effect of change in crystallinity on relaxations and proton conductivity, the undoped and PA‐doped membranes are characterized using thermogravimetric analysis and in situ XRD at high temperatures. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44867.

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Section: Resultsmentioning

confidence: 98%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Dielectric relaxations in phosphoric acid‐doped poly(2,5‐benzimidazole) and its composite membranes

Saleha

Rahul

Nalajala

et al. 2017

J of Applied Polymer Sci

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The effect of poly[styrene-b-(ethylene-co-butylene)-b-styrene] on dielectric, thermal, and morphological characteristics of polypropylene/silica nanocomposites

et al. 2013

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The effect of poly[styrene-b-(ethylene-co-butylene)-bstyrene] (SEBS) copolymer on the thermal and dielectric properties of polypropylene (PP)-nanosilica (NS) composites in relation with morphological aspects revealed by atomic force microscopy (AFM) was investigated in this article. SEBS hindered the crystallization process of PP in PP/NS composites, leading to a smaller degree of crystallinity and lower perfection of crystalline structure. Broader lamellar thickness distribution was obtained in nanocomposites containing SEBS. Almost two times higher dielectric loss as compared to PP reference and two relaxation processes were detected in e 00 r (f) curves of nanocomposites. The first peak, in the same frequency domain as for the references, was assigned to a-relaxation of polymer components together with interfacial polarization. The relaxation time follows the Arrhenius law with an activation energy of 80-90 kJ/mol. For the second process, the temperature dependence of the relaxation times obeyed the VFT equation. The dielectric changes following the incorporation of SEBS support its tendency to hinder the motional processes in PP, in accordance with DSC results. A smooth transition from a phase rich in SEBS to one containing mainly PP was detected in the AFM image of the composite with the larger amount of SEBS, emphasizing the good compatibility at the PP/SEBS interface.

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Porous polyimide films obtained by using lithium chloride as pore-forming agent

Chişcă¹,

Sava²,

Brumă³

2013

Polym. Int.

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Porous polymer films have been obtained from polyimide based on benzophenonetetracarboxylic dianhydride and 4,4'-diamino-3,3'-dimethyl-diphenylmethane by incorporating lithium chloride (LiCl) in the poly(amidic acid) precursor and subsequently leaching out the maximum possible LiCl by water Soxhlet extraction for 6 h. The resulting porous polyimide films were characterized with regard to their pore size, thermal stability and dielectric properties. The morphology of the porous polyimide films showed a uniform distribution and various pore sizes depending on the initial quantity of added pore-forming agent.

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Broadband dielectric spectroscopy studies of glassy‐state relaxations in annealed poly(2,5‐benzimidazole)

Cited by 11 publications

References 42 publications

Dielectric relaxations in phosphoric acid‐doped poly(2,5‐benzimidazole) and its composite membranes

Dielectric relaxations in phosphoric acid‐doped poly(2,5‐benzimidazole) and its composite membranes

The effect of poly[styrene-b-(ethylene-co-butylene)-b-styrene] on dielectric, thermal, and morphological characteristics of polypropylene/silica nanocomposites

Porous polyimide films obtained by using lithium chloride as pore-forming agent

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