Structure-property Relationships Research Articles

Unraveling the structure-property relationship of novel thiophene and furan-fused cyclopentadienyl chromophores for nonlinear optical applications.

Development of organic nonlinear optical materials has become progressively more important due to their emerging applications in new-generation photonic devices. A novel series of chromophores based on innovative thiophene and furan-fused cyclopentadienyl bridge with various powerful donor and acceptor moieties were designed and theoretically investigated for applications in nonlinear optics. To unravel the structure-property relationship between this new push-pull conjugated systems and their nonlinear optical property, multiple methods, including density of states analysis, coupled perturbed Kohn-Sham (CPKS) method, sum-over-states (SOS) model, the two-level model (TSM), hyperpolarizability density analysis, and the (hyper)polarizability contribution decomposition, were performed to comprehensively investigated the nonlinear optical and electronic properties of this new π-system. Due to excellent charge transfer ability of new bridge and distinctive structure of donor and acceptor, the designed chromophores exhibit deep HOMO levels, low excitation energy, high dipole moment difference and large hyperpolarizability, indicating the appealing air-stable property and remarkable electrooptic performance of them. Importantly, THQ-CS-A3 and PA-CS-A3 shows outstanding NLO response properties with βtot value of 6953.9 × 10-30 and 5066.0 × 10-30 esu in AN, respectively. The influence of the push-pull strength, the heterocycle and the π-conjugation of new bridge on the nonlinear optical properties of this novel powerful systems are clarified. This new series of chromophores exhibit remarkable electro-optical Pockels and optical rectification effect. More interestingly, PA-CS-A3 and THQ-CS-A2 also show appealing SHG effect. This study will help people understand the nature of nonlinear optical properties of innovative heteroarene-fused based cyclopentadienyl chromophores and offer guidance for the rational design of chromophores with outstanding electrooptic (EO) performance in the future.

Enhancing the Performance of Perovskite Solar Cells by Extending the Terminal Conjugation of Spiro‐Type Hole Transport Material

Hole transport materials (HTM) play a vital role in the performance of perovskite solar cells (PSCs). Optimizing the molecular structure of HTMs has been proven to be an important method for improving PSCs’ efficiency and stability. Herein, a novel dibenzofuran‐terminated spiro‐type HTM with extending π‐conjugation is designed and developed, named spiro‐BNF. The structure–property relationship is also studied with spiro‐OMeTAD and spiro‐DBF as the reference. The results show that spiro‐BNF has improved hole mobility and glass transition temperature (reaching 198 °C) than spiro‐OMeTAD and spiro‐BDF. spiro‐BNF also exhibits matched highest occupied molecular orbital level with perovskite and superior morphology on the perovskite layer. Accordingly, the PSCs employing spiro‐BNF display a higher power conversion efficiency of 23.65% and improved stability than the device employing spiro‐OMeTAD or spiro‐BDF. The findings provide a new insight for enhancing the performance of PSCs.

Multifunctional Catalysts for Cascade Reactions in Biomass Processing

Multifunctional catalysts have received considerable attention in the cascade reactions of biomass processing. A cascade (or tandem) reaction is realized when multiple reaction steps that require different catalysts are performed in a one-step process. These reactions require bi- or multifunctional catalysts or catalyst mixtures to serve successfully at each reaction step. In this review article, we discuss the major factors of the catalyst design influencing the structure–property relationships, which could differ depending on the catalyst type. The major factors include the amounts and strengths of acidic and basic sites, interactions between those and metal sites, synergetic effects, nanoparticle sizes and morphology, nanostructures, porosity, etc. The catalysts described in this review are based on zeolites, mesoporous solids, MOFs, and enzymes. The importance of continuous cascade processes is also examined.

Topological Invariants for the Chemical Structures Used in Treatment of COVID-19

A topological index is a quantity expressed as a number that help us to catch symmetry of chemical compounds. With the help of quantitative structure property relationship (QSPR), we can guess physical and chemical properties of several chemical compounds. Here, we will compute Shingali & Kanabour, Gourava and hype Gourava indices for the chemical compounds, used in treatment of COVID-19, namely Remdesivir, Chloroquine, Hydroxychloroquine Theaflavin.

Closed-Loop Chemical Recycling of a Biobased Poly(oxanorbornene-fused γ-butyrolactone).

New polymers, properly designed for end-of-life and efficiently formed from renewable carbon, are key to the transition to a more sustainable circular plastics economy. Ring-opening polymerization (ROP) of bicyclic lactones is a promising method for the production of intrinsically recyclable polyesters, but most lactone monomers lack an efficient synthesis route from biobased starting materials, even though this is essential to sustainably account for material loss during the life cycle. Herein, we present the exceptionally rapid and controlled polymerization of a fully biobased tricyclic oxanorbornene-fused γ-butyrolactone monomer (M1). Polyester P(M1) was formed in low dispersity (D̵ = 1.2-1.3) and controllable molecular weight up to Mn = 76.8 kg mol-1 and exhibits a high glass transition temperature (Tg = 120 °C). The orthogonal olefin and lactone functionalities offer access to a wide range of promising materials, as showcased by postpolymerization modification by hydrogenation of the olefin, which increased polymer thermal stability by over 100 °C. Next to rapid hydrolytic degradation and solvolysis, the poly(oxanorbornene-fused γ-butyrolactone) could be cleanly chemically recycled back to the monomer (CRM), in line with its favorable ceiling temperature (Tc) of 73 °C. The density functional theory (DFT)-computed ΔH° of ring-opening with methanol of γ-butyrolactone-based monomers provided a model to predict Tc, and the DFT-computed and X-ray crystal structure-derived structural parameters of M1, hydrogenated analogue M1-H2, and regioisomer M2 offered insights into the structural descriptors that cause the high polymerizability of M1, which is key to establishing structure-property relations.

Influence of hydrogen bonding interactions, entanglement, and covalent crosslinking on the viscoelasticity of acrylic viscoelastomers containing urea group

The structure–property relationship of acrylic clear viscoelastomer films (acrylic CVFs) as foldable optical clear adhesives (OCAs) has always been unclear. In our work, a series of acrylic CVFs with different hydrogen-bonding interactions (H-bondings) and cross-linking densities (namely, CL-H-copolymers) were synthesized. The effects of entanglement, H-bonding, and covalent crosslinking on the recovery and adhesive properties of CL-H copolymers were analyzed by rheology, equilibrium swelling, and tensile stress–strain tests (tensile tests). The structural parameter Mx/MeH was obtained by combining the affine deformation model, the Flory-Rehner equation, and the UCM-Gent model, where Mx is the molecular weight between covalent crosslinkers and MeH is the a physical crosslinking molecular weight affected by H-bondings. The experimental results showed that the CL-H-copolymers had an obvious dependence on Mx/MeH. Recovery properties tended to stabilize (>90 %) at Mx/MeH < 1, while adhesion strengths continued to decrease with decreasing Mx/MeH. This conclusion and methodology are instructive for the design of foldable OCAs with high elasticity and high adhesion performance.

Synthesis and Mesomorphism of New Calamitic Schiff Bases-Ester Possessing Dialkylamino Terminal Substituent

: New calamitic liquid crystals, 4-[{[4-(diethylamino)phenyl]methylidene}amino]phenyl 4- alkyloxybenzoate (nEABAA) containing mesogenic core system which made of three phenyl rings were reported. The ester and imine linkages connected the phenyl rings. At one end of the molecule, the core system was attached to an alkyloxy chain with a variable length -(CH2)n- (where n = 2-10, 12, 14, 16 and 18). At the other end of the molecule, the para position of the phenyl ring is bonded to the diethylamino group. The molecular structure of the current compounds was confirmed by using spectroscopic methods. The mesomorphic characteristics of the title compounds were studied by using a differential scanning calorimeter and a polarizing optical microscope attached to a heating stage. Through observation under microscopy, it was found that all synthesized compounds exhibited only a single (nematic) phase. The exhibition of the monophase variance (nematic) in the current compounds is caused by the presence of the diethylamino group that is attached to the terminal position of the benzylideneaniline core system. The diethylamino group has caused the molecular breadth to increase and this results in a weaker overall lateral intermolecular attraction. Subsequently, it depressed the mesophase thermal stability of the compounds. Thermal properties of the current compounds were compared with the earlier reported analogous and the structure-property relationships of the current compounds have been inferred through this comparison.

Realization of the shape memory effect in a composite material PLA/Diopside with different supramolecular structures

This study explores the realization of the shape memory effect (SME) in composite materials composed of polylactide (PLA) filled with diopside particles exhibiting varied supramolecular structures, such as spherulites and amorphous lamellar structures. We investigated the influence of diopside filler on the thermomechanical properties and shape recovery behavior of PLA-based composites. Different supramolecular structures of PLA were achieved through controlled crystallization processes. Comprehensive characterization techniques, including differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and dynamic mechanical analysis (DMA), were employed to elucidate the structure-property relationships. The results indicate that the diopside enhances the SME of PLA composites, with the degree of improvement being dependent on the specific supramolecular structure of the polymer matrix. Our findings provide insights into the design of advanced SMPs with tailored properties for potential applications in medicine.

Comprehensive accurate prediction of critical jet fuel properties with multiple machine learning models

Quantitative structure–property relationship (QSPR) model development driven by emerging machine learning (ML) shows promise for accelerating design and preparation of jet fuels with complex hydrocarbon compositions. In this work, we collected 104 jet fuels from different refineries, determined the detailed components of the fuel composition, and tested the fuel properties (density, viscosity, net heat of combustion, freezing point and flash point) using standard methods to form a database of molecule structure/composition and properties. Subsequently, six mainstream ML algorithms were adopted to establish the QSPR models, in which the prediction accuracy of the best ML models for each property is improved to above 0.93. Finally, the best ML property models are applied to predict unseen RP-3 fuels, and all prediction errors are within acceptable limits. This effort not only provides valuable data for the construction of the jet fuel database, but also provides tools for predicting its critical properties.

On-demand reverse design of polymers with PolyTAO

The forward screening and reverse design of drug molecules, inorganic molecules, and polymers with enhanced properties are vital for accelerating the transition from laboratory research to market application. Specifically, due to the scarcity of large-scale datasets, the discovery of polymers via materials informatics is particularly challenging. Nonetheless, scientists have developed various machine learning models for polymer structure-property relationships using only small polymer datasets, thereby advancing the forward screening process of polymers. However, the success of this approach ultimately depends on the diversity of the candidate pool, and exhaustively enumerating all possible polymer structures through human imagination is impractical. Consequently, achieving on-demand reverse design of polymers is essential. In this work, we curate an immense polymer dataset containing nearly one million polymeric structure-property pairs based on expert knowledge. Leveraging this dataset, we propose a Transformer-Assisted Oriented pretrained model for on-demand polymer generation (PolyTAO). This model generates polymers with 99.27% chemical validity in top-1 generation mode (approximately 200k generated polymers), representing the highest reported success rate among polymer generative models, and this was achieved on the largest test set. Importantly, the average R2 between the properties of the generated polymers and their expected values across 15 predefined properties is 0.96, which underscores PolyTAO’s powerful on-demand polymer generation capabilities. To further evaluate the pretrained model’s performance in generating polymers with additional user-defined properties for downstream tasks, we conduct fine-tuning experiments on three publicly available small polymer datasets using both semi-template and template-free generation paradigms. Through these extensive experiments, we demonstrate that our pretrained model and its fine-tuned versions are capable of achieving the on-demand reverse design of polymers with specified properties, whether in a semi-template generation or the more challenging template-free generation scenarios, showcasing its potential as a unified pretrained foundation model for polymer generation.

One-step pyrolysis of ZIF-8 after recovering rare earth elements from mining wastewater as a functional fenton-like catalyst

The management of rare earth elements (REEs) from mining wastewater has consistently a key issue. Our previous research has demonstrated the selective adsorption of REEs in mining wastewater by ZIF-8. Herein, one-step pyrolysis of ZIF-8 after recovering REEs from mining wastewater as a high-value product was further proposed. The resulting REEs-based magnetic nanoporous carbon materials (REEs-MPC) was utilized for the activation of peroxymonosulfate (PMS) in the removal of bisphenol A (BPA). Experimental results indicate substantial BPA removal efficiencies of 74.62 %, 83.57 %, and 70.06 % with REEs-MPC synthesized at different pyrolysis temperatures (700 °C, 800 °C, and 900 °C). The detailed characterizations reveal the REEs-MPC at 800 °C was obtained (REEs-MPC/800) exhibit prominent graphitic and defective characteristics. In addition, electrochemical analysis revealed that the REEs-MPC/800 demonstrate elevated conductivity and superior capacitive current, with Tafel slopes as high as 294 mV/dec. Functional theory (DFT) calculations demonstrate that the presence of graphitic-N and REEs-N species significantly enhance PMS activation. Finally, a neural network model constructed through machine learning techniques provided a comprehensive overview of the structure–property relationship. Overall, the proposal to synthesize a high-value product using mining wastewater has been put forward. This initiative is expected to contribute to the advancement of the green economy within the rare earth mining industry.

Bottlebrush Polymers with Sequence-Controlled Backbones for Enhanced Oligonucleotide Delivery.

The clinical translation of oligonucleotide-based therapeutics continues to encounter challenges in delivery. In this study, we introduce a novel class of delivery vehicles for oligonucleotides that are based on poly(ethylene glycol) (PEG) bottlebrush polymers with sequence-defined backbones. Using solid-phase synthesis and bespoke phosphoramidites, the oligonucleotide and the polymer backbone can be assembled on the solid support. The synthesis allows chemical modifiers such as carbon 18 (C18) units to be incorporated into the backbone in specific patterns to modulate the cell-material interactions. Subsequently, PEG side chains were grafted onto the polymer segment of the resulting polymer-oligonucleotide conjugate, yielding bottlebrush polymers. We report an optimal pattern of the C18 modifier that leads to improved cellular uptake, plasma pharmacokinetics, biodistribution, and antisense activity in vivo. Our results provide valuable insights into the structure-property relationship of polymer-oligonucleotide conjugates and suggest the possibility of tuning the polymer backbone to meet the specific delivery requirements of various diseases.

Modeling and mechanism of the mechanical interlocking for the carbon fiber/epoxy interphase

The intricate details governing the carbon fiber/epoxy interfacial characteristics at the molecular level have yet to be comprehensively unraveled. One of the reasons is that the effects of carbon fiber (CF) surface structures are oversimplified, leading to misconceptions regarding adhesion mechanisms. To advance knowledge of structure-property relationships, we employed molecular dynamics simulations to provide insights into the complexity of the CF surface and CF/epoxy interphase. A series of turbostratic surface models with different protrusion heights were built via crosslinking basic structural units inside hexagonal prism virtual energy walls to better model the physical and chemical features of a CF surface. Epoxy precursor and curing agent molecules were added and crosslinked to generate the CF/epoxy interphase models before loading the systems in tension and shear. It was found that the spatial variation of composition determines the longitudinal and transversal moduli distribution in the interphase. Moreover, higher protrusion increases the tensile strength and toughness in the transverse direction by transferring part of the tensile loading into the shear component. The mechanical interlocking between the polymer and the CF surface with microvoids and protrusions enhances both the interfacial shear strength and the effectiveness of load transmission.

Characterization of Mycelium Biocomposites under Simulated Weathering Conditions.

Expanded polystyrene (EPS) remains a popular packaging material despite environmental concerns such as pollution, difficulty to recycle, and toxicity to wildlife. The goal of this study is to evaluate the potential of an ecofriendly alternative to traditional EPS composed of a mycelium biocomposite grown from agricultural waste. In this material, the mycelium spores are incorporated into cellulosic waste, resulting in a structurally sound biocomposite completely enveloped by mycelium fibers. One of the main criteria for shipping applications is the ability of a material to withstand extreme weather conditions. Accordingly, this study focused on evaluating a commercially available mycelium material before and after exposure to various weathering conditions, including high and low temperatures at different humidity levels. Fourier transform infrared spectroscopy (FTIR) was performed to examine any transformations in the mycelium structure and composition, whereas scanning electron microscopy (SEM) was used to reveal any changes in the morphology. Similarly, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analyses were conducted to evaluate the thermal behavior, whereas mechanical properties were measured by using shore hardness and Izod Impact testing. Although some irreversible changes were observed due to the exposure to high temperatures, the material exhibited good thermal stability and impact resistance. FTIR analysis demonstrated small changes in the biocomposite structure and protein rearrangement as a result of weathering, whereas SEM revealed some cracking in the cellulose substrate. A combination of low temperatures and humidity resulted in significant moisture absorption, as indicated by TGA and DSC. This in turn decreased the hardness of the fibers by nearly 2-fold; however, the impact strength of the entire biocomposite remained unchanged. Overall, these results provide important insight into the structure-property relationships of mycelium-based materials.

Synthesis and Characterization of New Organoammonium, Thiazolium, and Pyridinium Triiodide Salts: Crystal Structures, Polymorphism, and Thermal Stability

Triiodide salts are of interest for a variety of applications, including but not limited to electrochemical and photochemical devices, as antimicrobials and disinfectants, in supramolecular chemistry and crystal engineering, and in ionic liquids and deep eutectic solvents. Our work has focused on the design of salt–solvate cocrystals and deep eutectic solvents in which the triiodide anion interacts as a halogen bond acceptor with organoiodine molecules. To understand structure–property relationships in these hybrid materials, it is essential to have benchmark structural and physical data for the parent triiodide salt component. Herein, we report the structure and thermal properties of eight new triiodide salts, three of which exhibit polymorphism: tetrapentylammonium triiodide (1a and 1b), tetrahexylammonium triiodide (2), trimethylphenylammonium triiodide (3), trimethylbenzylammonium triiodide (4), triethylbenzylammonium triiodide (5), tri-n-butylbenzylammonium triiodide (6), 3-methylbenzothizolium triiodide (7a and 7b), and 2-chloro-1-methylpyridinium triiodide (8a and 8b). The structural features of the triiodide anion, Raman spectroscopic analysis, and melting and thermal decomposition behavior of the salts, as well as a computational analysis of the polymorphs, are discussed. The polymorphic pairs here are distinguished by symmetric versus asymmetric triiodide anions, as well as different packing patterns. Computational analyses revealed more subtle differences in their isosurface plots. Importantly, this study provides reference data for these new triiodide salts for comparison to hybrid cocrystals and deep eutectic solvents formed from their combination with various organoiodines.

Pressure-Engineered Through-Space Conjugation for Precise Control of Clusteroluminescence.

Clusteroluminogens (CLgens) represent an innovative class of nonconjugated luminophores that address the limitations of conventional π-conjugated molecules. Different from the through-bond conjugation mechanism in π-conjugated luminophores, through-space conjugation (TSC) plays dominant roles in CLgens. However, precisely controlling TSC to customize the optical properties of CLgens remains a significant challenge. This work proposes a novel strategy of high pressure to engineer TSC within tetraphenylalkanes (TPAs)-based CLgens at molecular level. High-pressure exploration enables accurate manipulation of clusteroluminescence and elucidates the intrinsic structure-property relationships involved. Upon initial compression, the predominant molecular distortions marked by increased interfacial angles between benzene rings diminish TSC, resulting in anomalous hypochromatic shift in emission. Subsequently, considerable structural contraction enhances TSC and suppresses molecular motion, resulting in a pronouncedly enhanced and bathochromic-shifted emission. Notably, a series of TPAs-based CLgens exhibit intense white-light emission upon pressure release, attributed to irreversible structural distortion and destruction. This study not only advances the understanding of CLgens, but also underscores the crucial structural factors for effective TSC control, paving the way for establishing new photophysical theories for aggregate science.

Operando elucidation of hydrogen production mechanisms on sub-nanometric high-entropy metallenes

Precise morphological control and identification of structure-property relationships pose formidable challenges for high-entropy alloys, severely limiting their rational design and application in multistep and tandem reactions. Herein, we report the synthesis of sub-nanometric high-entropy metallenes with up to eight metallic elements via a one-pot wet-chemical approach. The PdRhMoFeMn high-entropy metallenes exhibit high electrocatalytic hydrogen evolution performances with 6, 23, and 26 mV overpotentials at −10 mA cm−2 in acidic, neutral, and alkaline media, respectively, and high stability. The electrochemical measurements, theoretical simulations, and operando X-ray absorption spectroscopy reveal the actual active sites along with their dynamics and synergistic mechanisms in various electrolytes. Specially, Mn sites have strong binding affinity to hydroxyl groups, which enhances the water dissociation process at Pd sites with low energy barrier while Rh sites with optimal hydrogen adsorption free energy accelerate hydride coupling, thereby markedly boosting its intrinsic ability for hydrogen production.

ML-based Read-Across Structure-Property Relationship (RASPR) strategy for predicting protein resistance of self-assembled monolayers (SAMs) as anti-biofouling materials

Designing highly effective antifouling materials is essential in many medical applications like implantable devices, regenerative medicine, biosensors etc. The experimental design based on a trial and error strategy of antifouling materials is difficult and requires a huge amount of time and money. Machine learning (ML) based read across strategy is a relatively novel strategy that may speed up the discovery of novel biofouling-resistant surfaces against protein adsorption making them suitably used in different medical applications. In this study, we developed data-driven machine learning-based quantitative read-across structure-property relationship (q-RASPR) models for protein adsorption data (in the case of fibrinogen and lysozyme) of self-assembled monolayers (SAMs) as antifouling materials by utilizing a mix of linear and non-linear algorithms, including Multiple Linear Regression (MLR), AdaBoost (ADB), Support Vector Regression (SVR), Linear Support Vector Regression (LSVR), Ridge Regression (RR), Random Forest (RF), Gradient Boost (GB), and Extreme Gradient Boost (XGB). The performances of all models were compared for their acceptable levels of goodness of fit, robustness, and external predictivity. The best q-RASPR models demonstrate superior performances (internal and external validation parameters) than the corresponding QSPR models and are interpreted concerning crucial molecular descriptors controlling the anti-biofouling property enabling further modifications of previous antifouling SAMs to novel antifouling SAMs with promising properties. Overall, the study demonstrates the effectiveness of the machine learning-based q-RASPR approach over the QSPR approach to understand the fundamental structure-anti-biofouling property relationships systematically with the potential to expedite the discovery of novel antifouling materials.

Advanced EXAFS analysis techniques applied to the L-edges of the lanthanide oxides.

The unique properties of the lanthanide (Ln) elements make them critical components of modern technologies, such as lasers, anti-corrosive films and catalysts. Thus, there is significant interest in establishing structure-property relationships for Ln-containing materials to advance these technologies. Extended X-ray absorption fine structure (EXAFS) is an excellent technique for this task considering its ability to determine the average local structure around the Ln atoms for both crystalline and amorphous materials. However, the limited availability of EXAFS reference spectra of the Ln oxides and challenges in the EXAFS analysis have hindered the application of this technique to these elements. The challenges include the limited k-range available for the analysis due to the superposition of L-edges on the EXAFS, multielectron excitations (MEEs) creating erroneous peaks in the EXAFS and the presence of inequivalent absorption sites. Herein, we removed MEEs to model the local atomic environment more accurately for light Ln oxides. Further, we investigated the use of cubic and non-cubic lattice expansion to minimize the fitting parameters needed and connect the fitting parameters to physically meaningful crystal parameters. The cubic expansion reduced the number of fitting parameters but resulted in a statistically worse fit. The non-cubic expansion resulted in a similar quality fit and showed non-isotropic expansion in the crystal lattice of Nd2O3. In total, the EXAFS spectra and the fits for the entire set of Ln oxides (excluding promethium) are included. The knowledge developed here can assist in the structural determination of a wide variety of Ln compounds and can further studies on their structure-property relationships.

Light-induced spin-state switching in heterospin complexes of Cu(hfac)2 with pyridine-based nitroxides.

Copper(II)-nitroxide based molecular magnets exhibit spin-crossover-like spin state switching, which is topical in field of molecular magnetism. However, establishing reliable structure-property relationships in these systems is still challenging, especially regarding the light-induced switching of spin states. In this paper, we report the investigation of photoswitching and relaxation in a series of heterospin Cu(hfac)2LR complexes with pyridine-based nitroxide ligands (LR), which belong to this family of materials. Using electron paramagnetic resonance (EPR) for detection, we demonstrate very long lifetimes of photoinduced spin states at liquid helium temperatures (<15 K), where relaxation to the ground state does not exceed 15% within two hours. At the same time, the efficiency of photoswitching strongly depends on the structure of the radical ligand in this series: the bulkier the ligand, the smaller the fraction of heterospin clusters that undergo photoswitching. These findings expand the understanding of mechanisms and factors behind photoswitching and relaxation in copper(II)-nitroxide molecular magnets and aid in further research aiming to optimize their functional properties.