Physical Science and Engineering (PSE) Division
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Article Catalyst-Free α-Acetyl Cinnamate/Acetoacetate Exchange to Enable High Creep-Resistant Vitrimers
(Wiley, 2024-03-15) Feng, Hongzhi; Wang, Sheng; Lim, Jason Y.C.; Li, Bofan; Rusli, Wendy; Liu, Feng; Hadjichristidis, Nikos; Li, Zibiao; Zhu, Jin; King Abdullah University of Science and Technology Physical Sciences and Engineering Division Physical Sciences and Engineering Division Bldg Ibn Sina (#3) West, Level 4 Room 4219 23955-6900 Thuwal SAUDI ARABIA; Chemical Science Program; KAUST Catalysis Center (KCC); Physical Science and Engineering (PSE) Division; Chinese Academy of Sciences Ningbo Institute of Materials Technology and Engineering CHINA; Institute of Sustainability for Chemicals Energy and Environment SGM SINGAPORE; A*STAR Research Entities IMRE SINGAPORE; A*STAR Research Entities ISCE2 SINGAPORE; Chinese Academy of Sciences Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences CHINAVitrimers represent an emerging class of polymeric materials that combine the desirable characteristics of both thermoplastics and thermosets achieved through the design of dynamic covalent bonds within the polymer networks. However, these materials are prone to creep due to the inherent instability of dynamic covalent bonds. Consequently, there are pressing demands for the development of robust and stable dynamic covalent chemistries. Here, we report a catalyst-free α-acetyl cinnamate/acetoacetate (α-AC/A) exchange reaction to develop vitrimers with remarkable creep resistance. Small-molecule model studies revealed that the α-AC/A exchange occurred at temperatures above 140 °C in bulk, whereas at 120 °C, this reaction was absent. For demonstration in the case of polymers, copolymers derived from common vinyl monomers were crosslinked with terephthalaldehyde to produce α-AC/A vitrimers with tunable thermal and mechanical performance. All resulting α-AC/A vitrimers exhibited high stability, especially in terms of creep resistance at 120 °C, while retaining commendable reprocessability when subjected to high temperatures. This work showcases the α-AC/A exchange reaction as a novel and robust dynamic covalent chemistry capable of imparting both reprocessability and high stability to cross-linked networks.
Article Biobased Interpenetrating Polymer Network Membranes for Sustainable Molecular Sieving
(American Chemical Society (ACS), 2024-02-20) Cavalcante, Joyce; Oldal, Diana Gulyas; Peskov, Maxim; Beke, Aron K.; Hardian, Rifan; Schwingenschlögl, Udo; Szekely, Gyorgy; Chemical Engineering Program; Physical Science and Engineering (PSE) Division; Advanced Membranes and Porous Materials Research Center; Material Science and Engineering Program; Applied Physics; KAUST Solar Center (KSC)There is an urgent need for sustainable alternatives to fossil-based polymer materials. Through nanodomain engineering, we developed, without using toxic cross-linking agents, interpenetrating biopolymer network membranes from natural compounds that have opposing polarity in water. Agarose and natural rubber latex were consecutively self-assembled and self-cross-linked to form patchlike nanodomains. Both nano-Fourier transform infrared (nano-FTIR) spectroscopy and computational methods revealed the biopolymers’ molecular-level entanglement. The membranes exhibited excellent solvent resistance and offered tunable molecular sieving. We demonstrated control over separation performance in the range of 227–623 g mol–1 via two methodologies: adjusting the molecular composition of the membranes and activating them in water. A carcinogenic impurity at a concentration of 5 ppm, which corresponds to the threshold of toxicological concern, was successfully purged at a negligible 0.56% pharmaceutical loss. The biodegradable nature of the membranes enables an environmentally friendly end-of-life phase; therefore, the membranes have a sustainable lifecycle from cradle to grave.
Article Nanodomain Control in Carbon Molecular Sieve Membranes via Nanomaterial Footprinting
(Wiley, 2023-12-03) Hardian, Rifan; Abdulhamid, Mahmoud. A.; Szekely, Gyorgy; Advanced Membranes and Porous Materials Research Center; Physical Science and Engineering (PSE) Division; Chemical Engineering ProgramCarbon molecular sieve (CMS) membranes, fabricated via pyrolysis, are attracting attention owing to their stability under harsh environments, including high temperatures, organic media, and extreme pH. Herein, the fabrication of composite CMS (CCMS) membranes by incorporating sphere-shaped C60(OH) and ellipsoid-shaped C70(OH) fullerenol nanomaterials into intrinsically microporous 4,4′-(hexafluoroisopropylidene) diphthalic anhydride 3,3′-dimethyl-naphthidine polyimide is reported. The encapsulation of the nanomaterials by the polymer matrix, their chemical footprint, and the variation in the local chemistry of the pyrolyzed membranes are successfully revealed via nanodomain analysis using nano-Fourier-transform infrared spectroscopy. The incorporation of fullerenol nanomaterials into CMS membranes can induce the formation of fractional free volume upon pyrolysis, which can translate into molecular sieving enhancement. The effects of the concentration and geometrical shape of the fullerenol nanomaterials are successfully correlated with the membrane separation performance. The CCMS membranes demonstrate excellent stability and pharmaceutical and dye separation performance in organic media. Herein, nanodomain control is pioneered in CCMS membranes via nanomaterial footprinting to induce porosity during pyrolysis and subsequent control molecular sieving performance.
Article Leveraging the Stereochemical Complexity of Octahedral Diastereomeric-at-Metal Catalysts to Unlock Regio-, Diastereo-, and Enantioselectivity in Alcohol-Mediated C–C Couplings via Hydrogen Transfer
(American Chemical Society (ACS), 2024-03-13) Shezaf, Jonathan Z.; Santana, Catherine G.; Ortiz, Eliezer; Meyer, Cole C.; Liu, Peng; Sakata, Ken; Huang, Kuo-Wei; Krische, Michael J.; Chemical Science Program; KAUST Catalysis Center (KCC); Physical Science and Engineering (PSE) Division; Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States; Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States; Faculty of Pharmaceutical Sciences, Toho University, Funabashi, Chiba 274-8510, JapanExperimental and computational studies illuminating the factors that guide metal-centered stereogenicity and, therefrom, selectivity in transfer hydrogenative carbonyl additions of alcohol proelectrophiles catalyzed by chiral-at-metal-and-ligand octahedral d6 metal ions, iridium(III) and ruthenium(II), are described. To augment or invert regio-, diastereo-, and enantioselectivity, predominantly one from among as many as 15 diastereomeric-at-metal complexes is required. For iridium(III) catalysts, cyclometalation assists in defining the metal stereocenter, and for ruthenium(II) catalysts, iodide counterions play a key role. Whereas classical strategies to promote selectivity in metal catalysis aim for high-symmetry transition states, well-defined low-symmetry transition states can unlock selectivities that are otherwise difficult to achieve or inaccessible.
Article Deep Learning Peak Ground Acceleration Prediction Using Single-Station Waveforms
(Institute of Electrical and Electronics Engineers (IEEE), 2024) Saad, Omar M.; Helmy, Islam; Mohammed, Mona; Savvaidis, Alexandros; Chatterjee, Avigyan; Chen, Yangkang; Physical Science and Engineering (PSE) Division; National Research Institute of Astronomy and Geophysics (NRIAG), Seismology Department, Helwan, Egypt, 11731; National Research Institute of Astronomy and Geophysics (NRIAG), Helwan, Egypt, 11731; The University of Texas at Austin, Bureau of Economic Geology, Austin, TX, USA, 78712; University of Nevada, Nevada Seismological Laboratory, Reno, NV, USA, 89557Predicting the peak ground acceleration (PGA) from the first few seconds after the P-wave arrival time is crucial in estimating the ground motion intensity of the earthquake. The early estimation of PGA supports the earthquake-early warning (EEW) system to generate the warning. Here, we propose to use the vision transformer (ViT) to predict the PGA using 4-s three-channel single-station seismograms, i.e., 1 s prior to the P-wave arrival and 3 s subsequent to the arrival. The ViT can significantly extract remarkable information from the data resulting in superior prediction performance. The core layer of the ViT is the multihead attention (MHA) network which highlights the significant features of the input data. We train and evaluate the proposed algorithm using the Italian earthquake waveform data, where the proposed algorithm shows a promising result. The proposed ViT network utilizes an augmentation strategy to improve the learning ability of the model. Our proposed method is compared to the benchmark deep learning (DL) methods and empirical ground-motion models (GMMs) and outperforms all of them. The proposed algorithm can even predict the PGA accurately using only 2-s data after the P-wave arrival time. The proposed ViT architecture can also be integrated into a PGA classification framework. Finally, the proposed algorithm is tested using real-time data and shows accurate results, indicating its applicability in real-time monitoring.