Low Frequency Vibrations and Diffusion in Disordered Polymers Bearing an Intrinsic Microporosity as Revealed by Neutron Scattering

The microscopic diffusion and the low frequency density of states (VDOS) of PIM-EA-TB(CH3) are investigated by inelastic and quasi-elastic neutron scattering where also the demethylated counterpart of PIM-EA-TB(H2) is considered. These intrinsic microporous polymers are characterized by large BET surface area values of several hundred m2/g and pore sizes between 0.5 and 2 nm. Detailed comparison is made to the archetype of polymers of intrinsic microporosity, PIM-1, and polynorbornenes also bearing a microporosity. Due to the wavelength of neutrons, the diffusion and vibrations can be addressed on microscopic length and time scales. From the inelastic neutron scattering experiments the low frequency density of states (VDOS) is estimated which shows excess contributions to the Debye-type VDOS known as Boson peak. It was found that the maximum frequency of the Boson peak decreases with increasing microporosity characterized by the BET surface area. However, besides the BET surface area, additional factors such as the backbone stiffness govern the maximum frequency of the Boson peak. Further the mean squared displacement related to microscopic motions was estimated from elastic fixed window scans. At temperatures above 175 K, the mean squared displacement PIM-EA-TB(CH3) is higher than that for the demethylated counterpart PIM-EA-TB(H2). The additional contribution found for PIM-EA-TB(CH3) is ascribed to the rotation of the methyl group in this polymer because the only difference between the two structures is that PIM-EA-TB(CH3) has methyl groups where PIM-EA-TB(H2) has none. A detailed comparison of the molecular dynamics is also made to that of PIM-1 and the microporous polynorbornene PTCNSi1. The manuscript focuses on the importance of vibrations and the localized molecular mobility characterized by the microscopic diffusion on the gas transport in polymeric separation membranes. In the frame of the random gate model localized fluctuations can open or close bottlenecks between pores to enable the diffusion of gas molecules.

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Chemical modification of the polymer of intrinsic microporosity PIM-1 for enhanced hydrogen storage

Adsorption ◽

10.1007/s10450-020-00239-y ◽

2020 ◽

Vol 26 (7) ◽

pp. 1083-1091

Author(s):

Mi Tian ◽

Sébastien Rochat ◽

Hamish Fawcett ◽

Andrew D. Burrows ◽

Christopher R. Bowen ◽

...

Keyword(s):

Hydrogen Storage ◽

Surface Area ◽

Hydrogen Adsorption ◽

Sorption Properties ◽

Bet Surface Area ◽

Polymer Modification ◽

Gas Sorption ◽

Chemically Modified ◽

Polymer Of Intrinsic Microporosity ◽

Intrinsic Microporosity

Abstract A detailed investigation has been carried out of the pre-polymerisation modification of the polymer of intrinsic microporosity PIM-1 by the addition of two methyl (Me) groups to its spirobisindane unit to create a new chemically modified PIM-1 analogue, termed MePIM. Our work explores the effects of this modification on the porosity of PIM-1 and hence on its gas sorption properties. MePIM was successfully synthesised using either low (338 K) or high (423 K) temperature syntheses. It was observed that introduction of methyl groups to the spirobisindane part of PIM-1 generates additional microporous spaces, which significantly increases both surface area and hydrogen storage capacity. The BET surface area (N2 at 77 K) was increased by ~ 12.5%, resulting in a ~ 25% increase of hydrogen adsorption after modification. MePIM also maintains the advantages of good processability and thermal stability. This work provides new insights on a facile polymer modification that enables enhanced gas sorption properties.

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Platinum Nanoparticle Inclusion into a Carbonized Polymer of Intrinsic Microporosity: Electrochemical Characteristics of a Catalyst for Electroless Hydrogen Peroxide Production

Nanomaterials ◽

10.3390/nano8070542 ◽

2018 ◽

Vol 8 (7) ◽

pp. 542 ◽

Cited By ~ 4

Author(s):

Robert Adamik ◽

Naiara Hernández-Ibáñez ◽

Jesus Iniesta ◽

Jennifer Edwards ◽

Alexander Howe ◽

...

Keyword(s):

Oxygen Reduction ◽

Surface Area ◽

Hydrogen Oxidation ◽

Pt Nanoparticles ◽

Bet Surface Area ◽

Electrochemical Characteristics ◽

Platinum Nanoparticle ◽

Nano Catalyst ◽

The One ◽

Intrinsic Microporosity

The one-step vacuum carbonization synthesis of a platinum nano-catalyst embedded in a microporous heterocarbon (Pt@cPIM) is demonstrated. A nitrogen-rich polymer of an intrinsic microporosity (PIM) precursor is impregnated with PtCl62− to give (after vacuum carbonization at 700 °C) a nitrogen-containing heterocarbon with embedded Pt nanoparticles of typically 1–4 nm diameter (with some particles up to 20 nm diameter). The Brunauer-Emmett-Teller (BET) surface area of this hybrid material is 518 m2 g−1 (with a cumulative pore volume of 1.1 cm3 g−1) consistent with the surface area of the corresponding platinum-free heterocarbon. In electrochemical experiments, the heterocarbon-embedded nano-platinum is observed as reactive towards hydrogen oxidation, but essentially non-reactive towards bigger molecules during methanol oxidation or during oxygen reduction. Therefore, oxygen reduction under electrochemical conditions is suggested to occur mainly via a 2-electron pathway on the outer carbon shell to give H2O2. Kinetic selectivity is confirmed in exploratory catalysis experiments in the presence of H2 gas (which is oxidized on Pt) and O2 gas (which is reduced on the heterocarbon surface) to result in the direct formation of H2O2.

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Synthesis and Gas-Permeation Characterization of a Novel High-Surface Area Polyamide Derived from 1,3,6,8-Tetramethyl-2,7-diaminotriptycene: Towards Polyamides of Intrinsic Microporosity (PIM-PAs)

Polymers ◽

10.3390/polym11020361 ◽

2019 ◽

Vol 11 (2) ◽

pp. 361 ◽

Cited By ~ 6

Author(s):

Giuseppe Genduso ◽

Bader Ghanem ◽

Yingge Wang ◽

Ingo Pinnau

Keyword(s):

Surface Area ◽

Gas Permeability ◽

High Surface ◽

High Surface Area ◽

Gas Permeation ◽

Bet Surface Area ◽

Mixed Gas ◽

Fractional Free Volume ◽

Intrinsic Microporosity

A triptycene-based diamine, 1,3,6,8-tetramethyl-2,7-diamino-triptycene (TMDAT), was used for the synthesis of a novel solution-processable polyamide obtained via polycondensation reaction with 4,4′-(hexafluoroisopropylidene)bis(benzoic acid) (6FBBA). Molecular simulations confirmed that the tetrasubstitution with ortho-methyl groups in the triptycene building block reduced rotations around the C–N bond of the amide group leading to enhanced fractional free volume. Based on N2 sorption at 77 K, 6FBBA-TMDAT revealed microporosity with a Brunauer–Emmett–Teller (BET) surface area of 396 m2 g−1; to date, this is the highest value reported for a linear polyamide. The aged 6FBBA-TMDAT sample showed moderate pure-gas permeabilities (e.g., 198 barrer for H2, ~109 for CO2, and ~25 for O2) and permselectivities (e.g., αH2/CH4 of ~50) that position this polyamide close to the 2008 H2/CH4 and H2/N2 upper bounds. CO2–CH4 mixed-gas permeability experiments at 35 °C demonstrated poor plasticization resistance; mixed-gas permselectivity negatively deviated from the pure-gas values likely, due to the enhancement of CH4 diffusion induced by mixing effects.

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Influence of NaCl Concentration on Food-Waste Biochar Structure and Templating Effects

Energies ◽

10.3390/en11092341 ◽

2018 ◽

Vol 11 (9) ◽

pp. 2341 ◽

Cited By ~ 3

Author(s):

Ye-Eun Lee ◽

Jun-Ho Jo ◽

I-Tae Kim ◽

Yeong-Seok Yoo

Keyword(s):

Surface Area ◽

Food Waste ◽

Pore Diameter ◽

Waste Treatment ◽

Bet Surface Area ◽

High Concentration ◽

Positive Effects ◽

Nacl Concentration ◽

The Mean ◽

Templating Effect

Food-waste-derived biochar structures obtained through pyrolysis and with different NaCl concentrations were investigated. Increased NaCl concentration in the samples inhibited cellulose and lignin decomposition, ultimately increasing the biochar yield by 2.7% for 20%-NaCl concentration. NaCl added in solution state exhibited templating effects, with maximum increases in the Brunauer–Emmett–Teller (BET) surface area and pore volume of 1.23 to 3.50 m2∙g−1 and 0.002 to 0.007 cm3∙g−1, respectively, after washing. Adding a high concentration (20%) of NaCl reduced the BET surface area. In contrast, the mean pore diameter increased owing to the increased NaCl clustering area. Increased NaCl clustering with increased added NaCl was shown to have positive effects on NaCl removal by washing. Furthermore, as the NaCl adhered to the KCl scattered in the food waste, a high NaCl concentration also had positive effects on KCl removal. This study reports on an investigation on the effects of varying NaCl concentrations injected in solution form on the structure of food-waste biochar during pyrolysis. The templating effect was considered using both added NaCl and NaCl already contained in the food waste, with implementation of a desalination process essential for food-waste treatment for recycling.

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Relaxation Processes and the Mixed Alkali Effect in Alkali Metasilicate Glasses

MRS Proceedings ◽

10.1557/proc-455-91 ◽

1996 ◽

Vol 455 ◽

Cited By ~ 14

Author(s):

J. Habasaki ◽

I. Okada ◽

Y. Hiwatari

Keyword(s):

Boson Peak ◽

Dynamics Simulation ◽

Relaxation Processes ◽

Lithium Metasilicate ◽

Mixed Alkali ◽

Mean Squared Displacement ◽

Mixed Alkali Effect ◽

Li Ion ◽

The Mean ◽

Β Relaxation

ABSTRACTA molecular dynamics simulation (MD) of lithium metasilicate (Li2SiO3) and related mixed alkali system (LiKSiO3) has been performed. Changes in the mean squared displacement and the corresponding clear two-step (β and α1) relaxations in a density correlation function have been observed at 700 K (self-part) for each ion in Li2SiO3 following an exponential decay by vibrational motion in a simulation up to 300 ps (run I). The mean squared displacement of the atoms shows the change in the slope at ca. 300 ps when the simulation is extended up to 1 ns (run II). Here we call the slowest relaxation (ca. 300 ps∼) the α2 region.Oscillation, which is clearer for O and Si than for Li, is found in the second (β-relaxation) region of the function, which is attributed to the so called “boson peak”. Both the β-relaxation and the boson peak are found to be due to the correlated motion.The slower relaxation (α1-relaxation) can be fitted to a stretched exponential form and the origin of this type of decay is confirmed to be waiting time distribution of jump motions. The back-correlated jumps also decrease the decay rate.Components A and B in α1 and α2 regions for Li ion are analyzed, where the Li ion of component A is located within the first neighboring sites and that of component B moves longer than the nearest neighbor distances by cooperative jump motion. The component B shows accelerated dynamics larger than t-linear ones (∼ t1.77) in the region 50–300 ps, and the dynamics can be characterized as Lévy flight.We have found that the contribution of the cooperative jumps decreases in the mixed alkali glass. This explains the maximum of the Haven ratio accompanied with the mixed alkali effect.

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New underwater and aerial vocalizations of captive harp seals (Pagophilus groenlandicus)

Canadian Journal of Zoology ◽

10.1139/z00-182 ◽

2001 ◽

Vol 79 (1) ◽

pp. 75-81 ◽

Cited By ~ 4

Author(s):

A Serrano

Keyword(s):

Fundamental Frequency ◽

Breeding Season ◽

High Frequency ◽

Low Frequency ◽

Time Of Day ◽

Vocal Repertoire ◽

Maximum Frequency ◽

Pagophilus Groenlandicus ◽

Vocal Activity ◽

The Mean

Pinnipeds are ecologically and socially diverse, attributes that are reflected in their systems of communication. The purpose of this investigation was to document the vocal repertoire and annual cycle of vocal activity in the harp seal (Pagophilus groenlandicus), a species that communicates mainly under water, but whose social and communicative systems outside the breeding season are poorly known. The repertoire comprised 18 vocal classes, or call types; 7 that had not been described previously are described here. Vocal activity varied seasonally and with time of day. Calls of low frequency and with few pulse repetitions were predominantly used outside the breeding season, and calls of high frequency and with a high number of pulse repetitions predominated in the breeding season. The new vocalizations described here differed in several ways from those described previously. First, calls were relatively brief, with an average duration of 1.75 s (except call types 22 and 23, which averaged >2 s in duration). Second, some calls differed in mean fundamental frequency, the average being 677 Hz. Call types 22 and 23 differed the most, with an average of 838 Hz. The vocal repertoire described previously comprise calls with a fundamental frequency of approximately 400500 Hz. Third, call types 22 and 25 differed from the rest of the vocalizations. The mean maximum frequency of call types 22 and 25 was 3.4 kHz, while the mean maximum frequency of the other call types is around 7.7 kHz.

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Anomalies in the low frequency vibrational density of states for a polymer with intrinsic microporosity – the Boson peak of PIM-1

Physical Chemistry Chemical Physics ◽

10.1039/c7cp07141h ◽

2018 ◽

Vol 20 (3) ◽

pp. 1355-1363 ◽

Cited By ~ 8

Author(s):

Reiner Zorn ◽

Huajie Yin ◽

Wiebke Lohstroh ◽

Wayne Harrison ◽

Peter M. Budd ◽

...

Keyword(s):

Density Of States ◽

Low Frequency ◽

Boson Peak ◽

Vibrational Density Of States ◽

First Time ◽

Intrinsic Microporosity ◽

Vibrational Density

For the first time the low frequency vibrational density of states is reported for a polymer with intrinsic microporosity.

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Synthesis and Characterization of Florfenicol-silver Nanocomposite and its Antibacterial Activity against some Gram Positive and Gram-negative Bacteria

International Journal of Veterinary Science ◽

10.37422/ijvs/20.050 ◽

2020 ◽

Keyword(s):

Silver Nanoparticles ◽

Electron Microscope ◽

Zeta Potential ◽

Surface Area ◽

Spherical Shape ◽

Bet Surface Area ◽

Sonochemical Method ◽

Raman Spectrometry ◽

Silver Nanocomposite ◽

Morphology Characterization

In this paper, easy, rapid and cheap synthetic method was described for florfenicol-silver nanocomposite by sonochemical method. Florfenicol-silver nanocomposite was characterized based on three classes namely index, identification and morphology class. Index characterization was carried out by zeta sizing, BET surface area and zeta potential. Identification characterization was performed using X-ray diffraction (XRD) and Raman spectrometry. Morphology characterization was done utilizing transmission electron microscope (TEM), scanning electron microscope (SEM) and atomic force microscope (AFM). Characterization results showed zeta sizing of florfenicol was 30.44nm, while florfenicol-silver nanocomposite was 33.5 nm with zeta potential -14.1 and -18, respectively. BET surface area was found to be 13.3, 73.2 and 103.69 m2/g for florfenicol, silver nanoparticles and florfenicol-silver nanocomposite respectively. XRD and Raman charts confirmed the formation of florfenicol-silver nanocomposite without any contamination. TEM, SEM and AFM spectral data illustrated spherical to sub spherical shape of silver nanoparticles on cubic to sheet shape of florfenicol with size less than 50 nm. Antimicrobial activity was screened where the average zone of inhibitions caused by the prepared nanocomposite were 28.3 mm, 24 mm, 27.3 mm and 24 mm compared to 17.7 mm, 16 mm, 18.7 mm and 13.3 mm of the native drug and 13 mm, 10 mm, 14.3 mm and 15 mm of the used positive reference standards against E. coli, Salmonella typhymurium, Staphylococcus aureus and Staph.aureus MRSA respectively.

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Life Time Improvement of Hierarchically Structured SAPO-34 Nanocatalyst in MTO Reaction via Applying Clinoptilolite, Investigating of Composite Design via RSM

Combinatorial Chemistry & High Throughput Screening ◽

10.2174/1386207323666200428093154 ◽

2020 ◽

Vol 23 ◽

Author(s):

Reza Yazdanpanah ◽

Eshagh Moradiyan ◽

Rouein Halladj ◽

Sima Askari

Keyword(s):

Surface Area ◽

Natural Zeolite ◽

Coke Formation ◽

Life Time ◽

Weight Percent ◽

Light Olefins ◽

Bet Surface Area ◽

Relative Crystallinity ◽

Mto Reaction ◽

The Common

Aim and Objective: The research focuses on recent progress in the production of light olefins. Hence, the common catalyst of the reaction (SAPO-34) deactivates quickly because of coke formation, we reorganized the mechanism combining SAPO-34 with a natural zeolite in order to delay the deactivation time. Materials and Methods: The synthesis of nanocomposite catalyst was conducted hydrothermally using experimental design. Firstly, Clinoptilolite was modified using nitric acid in order to achieve nano scaled material. Then, the initial gel of the SAPO-34 was prepared using DEA, aluminum isopropoxide, phosphoric acid and TEOS as the organic template, sources of Aluminum, Phosphor, and Silicate, respectively. Finally, the modified zeolite was combined with SAPO-34's gel. Results: 20 different catalysts due to D-Optimal design were synthesized and the nanocomposite with 50 weight percent of SAPO-34, 4 hours Crystallization and early Clinoptilolite precipitation showed the highest relative crystallinity, partly high BET surface area and hierarchical structure. Conclusion: Different analysis illustrated the existence of both components. The most important property alteration of nanocomposite was the increment of pore mean diameters and reduction in pore volumes in comparison with free SAPO-34. Due to low price of Clinoptilolite, the new catalyst develops the economy of the process. Using this composite, according to formation of multi-sized pores located hierarchically on the surface of the catalyst and increased surface area, significant amounts of Ethylene and Propylene, in comparison with free SAPO-34, were produced, as well as deactivation time that was improved.

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Hydrochloric Acid Modification and Lead Removal Studies on Naturally Occurring Zeolites from Nevada, New Mexico, and Arizona

Processes ◽

10.3390/pr9071238 ◽

2021 ◽

Vol 9 (7) ◽

pp. 1238

Author(s):

Garven M. Huntley ◽

Rudy L. Luck ◽

Michael E. Mullins ◽

Nick K. Newberry

Keyword(s):

New Mexico ◽

Surface Area ◽

Bet Surface Area ◽

Lead Removal ◽

X Ray Diffraction ◽

Sem Images ◽

X Ray ◽

Naturally Occurring ◽

27Al Mas Nmr ◽

Modified Zeolites

Four naturally occurring zeolites were examined to verify their assignments as chabazites AZLB-Ca and AZLB-Na (Bowie, Arizona) and clinoptilolites NM-Ca (Winston, New Mexico) and NV-Na (Ash Meadows, Nevada). Based on powder X-ray diffraction, NM-Ca was discovered to be mostly quartz with some clinoptilolite residues. Treatment with concentrated HCl (12.1 M) acid resulted in AZLB-Ca and AZLB-Na, the chabazite-like species, becoming amorphous, as confirmed by powder X-ray diffraction. In contrast, NM-Ca and NV-Na, which are clinoptilolite-like species, withstood boiling in concentrated HCl acid. This treatment removes calcium, magnesium, sodium, potassium, aluminum, and iron atoms or ions from the framework while leaving the silicon framework intact as confirmed via X-ray fluorescence and diffraction. SEM images on calcined and HCl treated NV-Na were obtained. BET surface area analysis confirmed an increase in surface area for the two zeolites after treatment, NM-Ca 20.0(1) to 111(4) m2/g and NV-Na 19.0(4) to 158(7) m2/g. 29Si and 27Al MAS NMR were performed on the natural and treated NV-Na zeolite, and the data for the natural NV-Na zeolite suggested a Si:Al ratio of 4.33 similar to that determined by X-Ray fluorescence of 4.55. Removal of lead ions from solution decreased from the native NM-Ca, 0.27(14), NV-Na, 1.50(17) meq/g compared to the modified zeolites, 30 min HCl treated NM-Ca 0.06(9) and NV-Na, 0.41(23) meq/g, and also decreased upon K+ ion pretreatment in the HCl modified zeolites.

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