scholarly journals Ionization behavior of nanoporous polyamide membranes

2020 ◽  
Vol 117 (48) ◽  
pp. 30191-30200
Author(s):  
Cody L. Ritt ◽  
Jay R. Werber ◽  
Mengyi Wang ◽  
Zhongyue Yang ◽  
Yumeng Zhao ◽  
...  
Keyword(s):  
High Performance ◽  
Interfacial Polymerization ◽  
Carboxyl Groups ◽  
Structure Property ◽  
Nanoconfined Water ◽  
Fundamental Understanding ◽  
Ionization Behavior ◽  
Water Salt ◽  
Low Permittivity ◽  
Polyamide Membranes

Escalating global water scarcity necessitates high-performance desalination membranes, for which fundamental understanding of structure–property–performance relationships is required. In this study, we comprehensively assess the ionization behavior of nanoporous polyamide selective layers in state-of-the-art nanofiltration (NF) membranes. In these films, residual carboxylic acids and amines influence permeability and selectivity by imparting hydrophilicity and ionizable moieties that can exclude coions. We utilize layered interfacial polymerization to prepare physically and chemically similar selective layers of controlled thickness. We then demonstrate location-dependent ionization of carboxyl groups in NF polyamide films. Specifically, only surface carboxyl groups ionize under neutral pH, whereas interior carboxyl ionization requires pH >9. Conversely, amine ionization behaves invariably across the film. First-principles simulations reveal that the low permittivity of nanoconfined water drives the anomalous carboxyl ionization behavior. Furthermore, we report that interior carboxyl ionization could improve the water–salt permselectivity of NF membranes over fourfold, suggesting that interior charge density could be an important tool to enhance the selectivity of polyamide membranes. Our findings highlight the influence of nanoconfinement on membrane transport properties and provide enhanced fundamental understanding of ionization that could enable novel membrane design.

Technical viewpoint on polystyrene/graphene nanocomposite

2020 ◽  
pp. 089270572090765
Author(s):  
Ayesha Kausar
Keyword(s):  
Electromagnetic Interference ◽  
High Performance ◽  
State Of The Art ◽  
Synthetic Methods ◽  
Structure Property ◽  
Electromagnetic Interference Shielding ◽  
Graphene Nanocomposites ◽  
Structure Property Relationship ◽  
Fundamental Understanding ◽  
Graphene Nanocomposite

This review presents state-of-the-art progress in the field of polystyrene (PS)/graphene nanocomposite. Graphene is a monoatomic thick nanoallotrope of carbon. It has attracted tremendous research consideration owing to chemical functionalization aptitude and remarkable physical properties. Graphene has been used as a potential nanofiller to dramatically improve the performance of polymeric nanocomposite. PS is an important synthetic aromatic thermoplastic polymer. Graphene has been used to enhance the mechanical strength, thermal stability, electrical conductivity, and thermal conductivity of PS/graphene nanocomposite. Dispersion routes and synthetic methods of graphene and PS/graphene nanocomposite have also been reviewed. PS/graphene nanocomposites have been explored for anticorrosion, electromagnetic interference shielding, batteries, electrocatalysis, and microextraction applications. In spite of interesting developments, a lot remains to be done with regard to fundamental understanding of structure–property relationship and designing materials to operate for advanced high performance applications. This review is also concluded listing current challenges associated with processing and future perspectives of nanocomposite.

Chitosan-Nanocellulose Composites for Regenerative Medicine Applications

2020 ◽  
Vol 27 (28) ◽  
pp. 4584-4592 ◽  
Author(s):  
Avik Khan ◽  
Baobin Wang ◽  
Yonghao Ni
Keyword(s):  
Regenerative Medicine ◽  
Preparation Method ◽  
Chemical Properties ◽  
Biological Properties ◽  
Next Generation ◽  
Structure Property ◽  
Physico Chemical ◽  
Structure Property Relationship ◽  
Attractive Candidate ◽  
Fundamental Understanding

Regenerative medicine represents an emerging multidisciplinary field that brings together engineering methods and complexity of life sciences into a unified fundamental understanding of structure-property relationship in micro/nano environment to develop the next generation of scaffolds and hydrogels to restore or improve tissue functions. Chitosan has several unique physico-chemical properties that make it a highly desirable polysaccharide for various applications such as, biomedical, food, nutraceutical, agriculture, packaging, coating, etc. However, the utilization of chitosan in regenerative medicine is often limited due to its inadequate mechanical, barrier and thermal properties. Cellulosic nanomaterials (CNs), owing to their exceptional mechanical strength, ease of chemical modification, biocompatibility and favorable interaction with chitosan, represent an attractive candidate for the fabrication of chitosan/ CNs scaffolds and hydrogels. The unique mechanical and biological properties of the chitosan/CNs bio-nanocomposite make them a material of choice for the development of next generation bio-scaffolds and hydrogels for regenerative medicine applications. In this review, we have summarized the preparation method, mechanical properties, morphology, cytotoxicity/ biocompatibility of chitosan/CNs nanocomposites for regenerative medicine applications, which comprises tissue engineering and wound dressing applications.

scholarly journals Ab initio molecular dynamics and materials design for embedded phase-change memory

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Liang Sun ◽  
Yu-Xing Zhou ◽  
Xu-Dong Wang ◽  
Yu-Han Chen ◽  
Volker L. Deringer ◽  
...  
Keyword(s):  
Phase Change ◽  
High Performance ◽  
Materials Design ◽  
Atomic Scale ◽  
Ab Initio Molecular Dynamics ◽  
Core Material ◽  
Structure Property ◽  
Switching Speed ◽  
Atomic Structures ◽  
Memory Applications

AbstractThe Ge2Sb2Te5 alloy has served as the core material in phase-change memories with high switching speed and persistent storage capability at room temperature. However widely used, this composition is not suitable for embedded memories—for example, for automotive applications, which require very high working temperatures above 300 °C. Ge–Sb–Te alloys with higher Ge content, most prominently Ge2Sb1Te2 (‘212’), have been studied as suitable alternatives, but their atomic structures and structure–property relationships have remained widely unexplored. Here, we report comprehensive first-principles simulations that give insight into those emerging materials, located on the compositional tie-line between Ge2Sb1Te2 and elemental Ge, allowing for a direct comparison with the established Ge2Sb2Te5 material. Electronic-structure computations and smooth overlap of atomic positions (SOAP) similarity analyses explain the role of excess Ge content in the amorphous phases. Together with energetic analyses, a compositional threshold is identified for the viability of a homogeneous amorphous phase (‘zero bit’), which is required for memory applications. Based on the acquired knowledge at the atomic scale, we provide a materials design strategy for high-performance embedded phase-change memories with balanced speed and stability, as well as potentially good cycling capability.

Morphology of Rigid-Rod Molecular Composites: An Overview

1988 ◽  
Vol 134 ◽  
Author(s):  
Stephen J. Krause
Keyword(s):  
Mechanical Properties ◽  
High Performance ◽  
Morphological Characterization ◽  
High Ratio ◽  
Structure Property ◽  
Chain Polymer ◽  
Specific Strength ◽  
Composite Systems ◽  
Molecular Composites ◽  
Rigid Rod

ABSTRACTRigid-rod molecular composites are a new class of high performance structural polymers which have high specific strength and modulus and also high thermal and environmental resistance. A rigid-rod, extended chain polymer component is used to reinforce a matrix of a ductile polymer with the intent of achieving a “composite” on the molecular level. After synthesis, the key to producing a molecular composite is to control morphology to disperse the reinforcing rod molecules as finely as possible in the matrix polymer. Individual rod molecules or bundles of molecular rods must have dimensions which result in a high ratio of length to width (aspect ratio) for efficient reinforcement. To achieve this, the reinforcing rod component must not phase separate at any stage of processing. Morphological characterization techniques, which can measure the orientation and dispersion (or, conversely, the degree of phase separation) of rod molecules provide the tools for correlating theoretically predicted and experimentally observed mechanical properties. Various morphological techniques which have been applied to molecular composite systems will be reviewed, including wide angle x-ray scattering and scanning and transmission electron microscopy. Structure-property correlations for molecular composite systems will be discussed with regard to models for mechanical properties. Application of new morphological techniques will also be discussed.

scholarly journals RP-HPLC measurement and quantitative structure - property relationship analysis of the n-octanol - water partitioning coefficients of selected metabolites of polybrominated diphenyl ethers

2008 ◽  
Vol 5 (5) ◽  
pp. 332 ◽  
Author(s):  
Yijun Yu ◽  
Weihua Yang ◽  
Zishen Gao ◽  
Michael H. W. Lam ◽  
Xiaohua Liu ◽  
...  
Keyword(s):  
Polybrominated Diphenyl Ethers ◽  
High Performance ◽  
Reversed Phase ◽  
Retention Indices ◽  
Quantitative Structure ◽  
Structure Property ◽  
Rp Hplc ◽  
Structure Property Relationship ◽  
Water Partitioning ◽  
Log Kow

Environmental context. Polybrominated diphenyl ethers (PBDEs) are ubiquitous environmental contaminants and numerous studies have demonstrated a marked increase in the levels of PBDEs in human biological tissues and fluids, especially breast milk. How PBDEs are transported through the environment, taken up by biota, transported across membranes, and metabolised depends strongly on such fundamental properties as lipophilicity (log KOW). However, very little data on log KOW exist for PBDEs. In the present paper, the authors determine PBDE metabolites’ log KOW using reversed-phase high performance liquid chromatography, as recommended by the Organisation for Economic Co-operation and Development and US Environmental Protection Agency, along with quantitative structure–property relationships. Abstract. n-Octanol–water partitioning coefficient (log KOW) values of selected hydroxylated and methoxylated polybrominated diphenyl ether metabolites were measured for the first time by reversed-phase high performance liquid chromatography (RP-HPLC) using a C18 stationary phase with a water/methanol mixture as a mobile phase. The retention parameters, log kw (extrapolated retention indices) and k′ (gradient retention indices) were calibrated to log KOW by a set of calibration standards. For the PBDE metabolites investigated, extrapolated retention indices from isocratic elution seem to be more reliable and their RP-HPLC-derived log KOW values were found to range from 4.63 to 7.67. Some commonly available software, including ClogP, KowWin, AclogP, MlogP, AlogP, MilogP, and XlogP, was used to estimate the log KOW values of the analytes. Significant correlations were obtained between the RP-HPLC-derived log KOW and the software-computed log KOW, with squared correlation coefficients (R2) ranging from 0.793 to 0.922, but the difference between them was also significant. Then a quantitative structure–property relationship model based on topological descriptors was established and showed good reliability and predictive power for the estimation of RP-HPLC-derived log KOW values of PBDE metabolites. It was applied to estimate the log KOW values of some PBDE metabolites that are commercially available or have appeared in the literature. Lastly, factor analysis was carried out using the theoretical linear salvation/free-energy relationships, which indicated the average polarisability (α) and the most negative atomic partial Mulliken charge in the molecule (q–) were the most important parameters affecting their partition between n-octanol and water, supporting the factorisation of log KOW in bulk and electronic terms.

Fabrication of high-performance pervaporation membrane for sulfuric acid recovery via interfacial polymerization

2021 ◽  
Vol 624 ◽  
pp. 119108
Author(s):  
Huaqing Liu ◽  
Jianzhong Xia ◽  
Kangjie Cui ◽  
Junquan Meng ◽  
Rui Zhang ◽  
...  
Keyword(s):  
Sulfuric Acid ◽  
High Performance ◽  
Interfacial Polymerization ◽  
Pervaporation Membrane ◽  
Acid Recovery
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