Temperature-dependent Aggregation Research Articles

Unraveling the Solution Aggregation Structures and Processing Resiliency of High-Efficiency Organic Photovoltaic Blends.

The solution aggregation structure of conjugated polymers is crucial to the morphology and resultant optoelectronic properties of organic electronics and is of considerable interest in the field. Precise characterizations of the solution aggregation structures of organic photovoltaic (OPV) blends and their temperature-dependent variations remain challenging. In this work, the temperature-dependent solution aggregation structures of three representative high-efficiency OPV blends using small-angle X-ray/neutron scattering are systematically probed. Three cases of solution processing resiliency are elucidated in state-of-the-art OPV blends. The exceptional processing resiliency of high-efficiency PBQx-TF blends can be attributed to the minimal changes in the multiscale solution aggregation structure at elevated temperatures. Importantly, a new parameter, the percentage of acceptors distributed within polymer aggregates (Ф), for the first time in OPV blend solution, establishes a direct correlation between Ф and performance is quantified. The device performance is well correlated with the Kuhn length of the cylinder related to polymer aggregates L1 at the small scale and the Ф at the large scale. Optimal device performance is achieved with L1 at ≈30nm and Ф within the range of 60±5%. This study represents a significant advancement in the aggregation structure research of organic electronics.

A density of states-based approach to determine temperature-dependent aggregation rates.

Here, we establish an approach to determine temperature-dependent aggregation rates in terms of thermostatistical quantities, which can be obtained directly from flat-histogram and statistical temperature algorithms considering the density of states of the system. Our approach is validated through simulations of an Ising-like model with anisotropically interacting particles at temperatures close to its first-order phase transition. Quantitative comparisons between the numerically obtained forward and reverse rates to approximate analytical expressions corroborate its use as a model-independent approach.

An asymmetric polymerized small molecular acceptor with temperature-dependent aggregation and superior batch-to-batch reproducibility for efficient all-polymer solar cells

Polymerized small molecular acceptors (PSMAs) have been instrumental in driving the advancements in power conversion efficiencies (PCEs) of all-polymer solar cells (all-PSCs). However, PSMAs commonly face challenges such as low molecular weights and notable batch-to-batch variation, posing significant obstacles to the transition of all-PSCs from lab to fab. Herein, a novel PSMA, which we refer to PAY-IT with an asymmetric conjugated skeleton is reported. The A–D1A'D2–A-type asymmetric monomer endows PAY-IT a random conjugated backbone, thus offering a desired temperature dependent aggregation behavior, which is hardly observed in conventional PSMAs. This characteristic facilitates chain growth during polymerization, thus yielding high molecular weights and low batch-to-batch sensitivity for the polymer. Moreover, the “S-shape” configuration of the asymmetric monomer endows PAY-IT good planarity and excellent charge transport property. As a result, the all-PSC consisted of PAY-IT and PM6 showcased a remarkable PCE of 14.9 %. More importantly, three batches of PAY-IT with number-average molecular weights ranging from 18.3 to 26.2 kDa exhibited nearly identical PCE (14.4–14.9 %), demonstrating superior batch-to-batch reproducibility of this polymer acceptor. This work explored PSMAs with asymmetric skeleton for the first time, and the results demonstrated a new design concept for the development of state-of-the-art PSMAs with minimal batch-to-batch variation.

Regulating pre-aggregation in non-halogenated solvent to enhance the efficiency of organic solar cells

Optimizing the morphology of an active layer in organic solar cells (OSCs) through precise control of precursor solution aggregation is a crucial step in enhancing photovoltaic performance. However, the considerable difference in solubility among organic materials in environmentally friendly solvents, such as non-halogenated solvents, poses a challenge in simultaneously modulating the pre-aggregation of both donor and acceptor. Herein, we employ a synergistic approach that involves heat treatment and the addition of a solid additive to regulate the aggregation behavior of PM6 (donor) and BTP-ec9 (acceptor) within an o-xylene solvent. Our findings reveal that PM6 exhibits strong temperature-dependent aggregation tendencies, while the solid additive 1,4-diiodobenzene (DIB) notably influences the aggregation of BTP-ec9. Thus, treating the precursor solution at 90 °C and adding DIB result in a well-matched aggregation between donor and acceptor, effectively optimizing the crystallization and phase separation morphology of the active layer. This strategic intervention leads to an outstanding efficiency of 18.07%, with a fill factor of 78.65%, for the corresponding device, which ranks among the highest efficiencies for the non-halogenated solvent-processed OSCs. Importantly, this study also demonstrates the feasibility of fabricating thick-film and large-area OSCs by blade-coating, achieving efficiencies of 16.15% and 15.29%, showcasing substantial potential for commercial applications.

Non-covalent planarizing interactions yield highly ordered and thermotropic liquid crystalline conjugated polymers.

Controlling the multi-level assembly and morphological properties of conjugated polymers through structural manipulation has contributed significantly to the advancement of organic electronics. In this work, a redox active conjugated polymer, TPT-TT, composed of alternating 1,4-(2-thienyl)-2,5-dialkoxyphenylene (TPT) and thienothiophene (TT) units is reported with non-covalent intramolecular S⋯O and S⋯H-C interactions that induce controlled main-chain planarity and solid-state order. As confirmed by density functional theory (DFT) calculations, these intramolecular interactions influence the main chain conformation, promoting backbone planarization, while still allowing dihedral rotations at higher kinetic energies (higher temperature), and give rise to temperature-dependent aggregation properties. Thermotropic liquid crystalline (LC) behavior is confirmed by cross-polarized optical microscopy (CPOM) and closely correlated with multiple thermal transitions observed by differential scanning calorimetry (DSC). This LC behavior allows us to develop and utilize a thermal annealing treatment that results in thin films with notable long-range order, as shown by grazing-incidence X-ray diffraction (GIXD). Specifically, we identified a first LC phase, ranging from 218 °C to 107 °C, as a nematic phase featuring preferential face-on π-π stacking and edge-on lamellar stacking exhibiting a large extent of disorder and broad orientation distribution. A second LC phase is observed from 107 °C to 48 °C, as a smectic A phase featuring sharp, highly ordered out-of-plane lamellar stacking features and sharp tilted backbone stacking peaks, while the structure of a third LC phase with a transition at 48 °C remains unclear, but resembles that of the solid state at ambient temperature. Furthermore, the significance of thermal annealing is evident in the ∼3-fold enhancement of the electrical conductivity of ferric tosylate-doped annealed films reaching 55 S cm-1. More importantly, thermally annealed TPT-TT films exhibit both a narrow distribution of charge-carrier mobilities (1.4 ± 0.1) × 10-2 cm2 V-1 s-1 along with a remarkable device yield of 100% in an organic field-effect transistor (OFET) configuration. This molecular design approach to obtain highly ordered conjugated polymers in the solid state affords a deeper understanding of how intramolecular interactions and repeat-unit symmetry impact liquid crystallinity, solution aggregation, solution to solid-state transformation, solid-state morphology, and ultimately device applications.

Strain and temperature dependent aggregation of Candida auris is attenuated by inhibition of surface amyloid proteins

Candida auris is a multi-drug resistant human fungal pathogen that has become a global threat to human health due to its drug resistant phenotype, persistence in the hospital environment and propensity for patient to patient spread. Isolates display variable aggregation that may affect the relative virulence of strains. Therefore, dissection of this phenotype has gained substantial interest in recent years. We studied eight clinical isolates from four different clades (I-IV); four of which had a strongly aggregating phenotype and four of which did not. Genome analysis identified polymorphisms associated with loss of cell surface proteins were enriched in weakly-aggregating strains. Additionally, we identified down-regulation of chitin synthase genes involved in the synthesis of the chitinous septum. Characterisation of the cells revealed no ultrastructural defects in cytokinesis or cell separation in aggregating isolates. Strongly and weakly aggregating strains did not differ in net surface charge or in cell surface hydrophobicity. The capacity for aggregation and for adhesion to polystyrene microspheres were also not correlated. However, aggregation and extracellular matrix formation were all increased at higher growth temperatures, and treatment with the amyloid protein inhibitor Thioflavin-T markedly attenuated aggregation. Genome analysis further indicated strain specific differences in the genome content of GPI-anchored proteins including those encoding genes with the potential to form amyloid proteins. Collectively our data suggests that aggregation is a complex strain and temperature dependent phenomenon that may be linked in part to the ability to form extracellular matrix and cell surface amyloids.

Side chain engineering of fluorinated benzothiadiazole‐based polymers: Improving the charge transport in organic field‐effect transistors

AbstractThree donor‐acceptor (D‐A) polymers P1–P3 are designed and synthesized, with 4,7‐dibromo‐5,6‐difluorobenzo[c][1,2,5]thiadiazole (FBT) as A and thiophene derivatives as D. All polymers show good thermal stability. The UV–vis absorption spectra show that P1 has too strong aggregation in solution, and it has no obvious temperature‐dependent aggregation (TDA) performance, which is also revealed in the variable temperature UV–vis absorption spectra. P2 film shows the same aggregation as in solution, P3 film shows stronger aggregation than that in solution. Polymers P1 and P2 both have strong TDA properties. Organic field effect transistors (OFETs) are prepared based on polymers P1, P2, and P3. OFETs devices prepared with high molecular weight polymers have better performance, and the polymer with 2‐nonyltridecyl side chain leads to the highest hole mobility around 0.252 cm2 V−1 s−1. The results show that the application of high molecular weight polymers and the selection of appropriate side chains are very important for the charge transport performance of OFETs.

TRPM8 thermosensation in poikilotherms mediates both skin colour and locomotor performance responses to cold temperature

Thermoregulation is a homeostatic process to maintain an organism’s internal temperature within a physiological range compatible with life. In poikilotherms, body temperature fluctuates with that of the environment, with both physiological and behavioral responses employed to modify body temperature. Changing skin colour/reflectance and locomotor activity are both well-recognized temperature regulatory mechanisms, but little is known of the participating thermosensor/s. We find that Xenopus laevis tadpoles put in the cold exhibit a temperature-dependent, systemic, and rapid melanosome aggregation in melanophores, which lightens the skin. Cooling also induces a reduction in the locomotor performance. To identify the cold-sensor, we focus on transient receptor potential (trp) channel genes from a Trpm family. mRNAs for several Trpms are present in Xenopus tails, and Trpm8 protein is present in skin melanophores. Temperature-induced melanosome aggregation is mimicked by the Trpm8 agonist menthol (WS12) and blocked by a Trpm8 antagonist. The degree of skin lightening induced by cooling is correlated with locomotor performance, and both responses are rapidly regulated in a dose-dependent and correlated manner by the WS12 Trpm8 agonist. We propose that TRPM8 serves as a cool thermosensor in poikilotherms that helps coordinate skin lightening and behavioural locomotor performance as adaptive thermoregulatory responses to cold.

Observation of alumina nanoparticles generated from aqueous solutions of a "flat" aluminum-13 cluster.

Amorphous alumina nanoparticles were synthesized via dynamic processes during the dissolution of aluminum hydroxide by nitric acid, a method commonly used to produce aqueous solutions of aluminum oxide molecular clusters. These particles were characterized by DLS measurements, and corroborated by other solution and solid state analyses. The methods used represent a highly tuneable, facile synthetic pathway that allows for size targeting and scalability for industrial purposes, and provides insight into pH- and temperature-dependent alumina speciation and aggregation.

Intrachain and Interchain Excited-State Dynamics of Temperature-Dependent Aggregation Copolymer in Solution.

Poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene)-co-(1,3-di(5-thiophene-2-yl)-5,7-bis (2-ethylhexyl)benzo[1,2-c:4,5-c']dithiophene-4,8-dione)] (PBDB-T) is a donor-acceptor copolymer widely used as a donor material in high-efficiency organic solar cells. In this work, we studied the temperature-dependent aggregation properties of PBDB-T in solution. Through the characterization of UV-vis absorption and the photoluminescence spectrum, we found that PBDB-T formed strong interchain interactions that facilitate aggregation at room temperature. In contrast, warmer temperatures cause PBDB-T to coil and increase intrachain interactions, thus reducing aggregation. We further use transient absorption spectroscopy to explore the effect of temperature-dependent aggregation behavior on excited-state dynamics. The results show that the intrachain interaction is beneficial to increase the production of polaron pairs, and the interchain interaction is beneficial to accelerate the production of free polarons. Finally, we investigated the corresponding films and demonstrated that regulating the solution aggregation is an effective way to control the crystallinity, and morphology of the corresponding films.

How Does Temperature Affect the Dynamics of SARS-CoV-2 M Proteins? Insights from Molecular Dynamics Simulations.

Enveloped viruses, in general, have several transmembrane proteins and glycoproteins, which assist the virus in entry and attachment onto the host cells. These proteins also play a significant role in determining the shape and size of the newly formed virus particles. The lipid membrane and the embedded proteins affect each other in non-trivial ways during the course of the viral life cycle. Unraveling the nature of the protein–protein and protein–lipid interactions, under various environmental and physiological conditions, could therefore prove to be crucial in development of therapeutics. Here, we study the M protein of SARS-CoV-2 to understand the effect of temperature on the properties of the protein-membrane system. The membrane-embedded dimeric M proteins were studied using atomistic and coarse-grained molecular dynamics simulations at temperatures ranging between 10 and 50 °C. While temperature-induced fluctuations are expected to be monotonic, we observe a steady rise in the protein dynamics up to 40 °C, beyond which it surprisingly reverts back to the low-temperature behavior. Detailed investigation reveals disordering of the membrane lipids in the presence of the protein, which induces additional curvature around the transmembrane region. Coarse-grained simulations indicate temperature-dependent aggregation of M protein dimers. Our study clearly indicates that the dynamics of membrane lipids and integral M protein of SARS-CoV-2 enables it to better associate and aggregate only at a certain temperature range (i.e., ~ 30–40 °C). This can have important implications in the protein aggregation and subsequent viral budding/fission processes.Graphical Supplementary InformationThe online version contains supplementary material available at 10.1007/s00232-022-00244-y.

Enabling Roll-Processed and Flexible Organic Solar Cells Based On PffBT4T Through Temperature-Controlled Slot-Die Coating

Although the mark of 18% power conversion efficiency (PCE) was surpassed recently, organic solar cells (OSCs) still have several challenges to overcome in order to fully compete with silicon-based solar cells in the energy market. One of the main challenges is the upscaling of the technology. Despite the recent advances in PCEs, a big scalability gap still exists between the best lab-scale device and large-scale modules fabricated via roll-to-roll processing. The polymer donor PffBT4T-C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">9</sub> C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">13</sub> has already shown efficiencies of almost 12% together with PCBM. Combined with the nonfullerene acceptor O-IDTBR, a reduced voltage loss of 0.5 V between the optical band gap and V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OC</sub> is obtained, with an open-circuit voltage up to 1.12 V, which is one of the highest values reported for OSCs. In this work, we demonstrate a route to upscaling OSCs based on PffBT4T-C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">9</sub> C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">13</sub> :O-IDTBR through temperature-controlled slot-die coating, solving the challenges of the temperature dependent aggregation behavior, which strongly affects the efficiency of the device. Efficiencies above 4% were achieved in our flexible and roll-processed devices with an area of ∼1 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and the different origins of the scalability lag were studied. As an additional necessary step for scalability, we incorporate the use of a hydrocarbon-based solvent to remove the environmentally dangerous halogenated solvents. To the best of our knowledge, this is the first work reporting PffBT4T:O-IDTBR solar cells fabricated in open air using slot-die coating in a roll-platform with flexible substrates, that mimics large-scale roll-to-roll processing.

Aggregation Time Machine: A Platform for the Prediction and Optimization of Long-Term Antibody Stability Using Short-Term Kinetic Analysis.

Monoclonal antibodies are the fastest growing class of therapeutics. However, aggregation limits their shelf life and can lead to adverse immune responses. Assessment and optimization of the long-term antibody stability are therefore key challenges in the biologic drug development. Here, we present a platform based on the analysis of temperature-dependent aggregation data that can dramatically shorten the assessment of the long-term aggregation stability and thus accelerate the optimization of antibody formulations. For a set of antibodies used in the therapeutic areas from oncology to rheumatology and osteoporosis, we obtain an accurate prediction of aggregate fractions for up to three years using the data obtained on a much shorter time scale. Significantly, the strategy combining kinetic and thermodynamic analysis not only contributes to a better understanding of the molecular mechanisms of antibody aggregation but has already proven to be very effective in the development and production of biological therapeutics.

Revealing temperature-dependent polymer aggregation in solution with small-angle X-ray scattering

Small-angle X-ray scattering is used to probe the solution behavior of two similar electron donor polymers. Differences in aggregate crystallinity are observed upon cooling for the two polymers which is then correlated with the film morphology.

Proteomic analysis demonstrates the role of the quality control protease LONP1 in mitochondrial protein aggregation

The mitochondrial matrix protease LONP1 is an essential part of the organellar protein quality control system. LONP1 has been shown to be involved in respiration control and apoptosis. Furthermore, a reduction in LONP1 level correlates with aging. Up to now, the effects of a LONP1 defect were mostly studied by utilizing transient, siRNA-mediated knockdown approaches. We generated a new cellular model system for studying the impact of LONP1 on mitochondrial protein homeostasis by a CRISPR/Cas-mediated genetic knockdown (gKD). These cells showed a stable reduction of LONP1 along with a mild phenotype characterized by absent morphological differences and only small negative effects on mitochondrial functions under normal culture conditions. To assess the consequences of a permanent LONP1 depletion on the mitochondrial proteome, we analyzed the alterations of protein levels by quantitative mass spectrometry, demonstrating small adaptive changes, in particular with respect to mitochondrial protein biogenesis. In an additional proteomic analysis, we determined the temperature-dependent aggregation behavior of mitochondrial proteins and its dependence on a reduction of LONP1 activity, demonstrating the important role of the protease for mitochondrial protein homeostasis in mammalian cells. We identified a significant number of mitochondrial proteins that are affected by a reduced LONP1 activity especially with respect to their stress-induced solubility. Taken together, our results suggest a very good applicability of the LONP1 gKD cell line as a model system for human aging processes.

Tuning Aggregation Behavior of Polymer Donor viaMolecular‐Weight Control for Achieving 17.1% Efficiency Inverted Polymer Solar Cells

Main observation and conclusionRecently, the polymer solar cells (PSCs) based on the PM6 and small molecular acceptor (SMA) Y6 have attracted considerable attention in this community for their outstanding photovoltaic performance. As well known, the molecular weight of polymer has dramatic impact on the blend morphology and photovoltaic performance in the polymer solar cells, especially for those polymers with temperature‐dependent aggregation (TDA) behavior. In this work, a series of PM6 polymers with different weight‐average molecular weights (Mw = 41, 67, 74, 84 and 114 kDa) were synthesized, and the effects of the Mw on the morphology and photovoltaic performance were systematically investigated. Notably, molecular weight induces dramatic influences on the aggregation behaviors of the polymers and their corresponding blend morphology, which were explored by the temperature‐dependent UV‐vis absorptions (TD‐Abs), grazing incidence wide‐angle X‐ray scattering (GIWAXS) and resonant soft X‐ray scattering (R‐SoXS) measurements. Increasing Mw promoted the strong face‐on molecular packing and reduced the blend film domain sizes for enhanced donor‐acceptor interfacial areas, resulting in increased short‐circuit current densities (Jsc) and fill factor (FF). However, polymer donor with high Mw value processed stronger tendency of forming excessive pure donor aggregate, which hampered forming the intermixed phase for efficient charge transport, resulting in the inferior FF. Therefore, the optimized OSCs based on PM6 with moderate molecular weight (Mw = 74 kDa) and Y6 exhibited suitable size and purity of the domains, facilitating well‐balanced charge transport, reducing trap‐assisted recombination and leading to significant enhancement of photovoltaic performance with the optimal PCE of 17.1%. This work indicates that proper and precisely tuning the molecular weight of polymer donor is critical to enhance the photovoltaic performance in PSCs.

Discovery of a dual pathway aggregation mechanism for a therapeutic constrained peptide.

Constrained peptides (CPs) have emerged as attractive candidates for drug discovery and development. To fully unlock the therapeutic potential of CPs, it is crucial to understand their physical stability and minimize the formation of aggregates that could induce immune responses. Although amyloid like aggregates have been researched extensively, few studies have focused on aggregates from other peptide scaffolds (e.g., CPs). In this work, a streamlined approach to effectively profile the nature and formation pathway of CP aggregates was demonstrated. Aggregates of various sizes were detected and shown to be amorphous. Though no major changes were found in peptide structure upon aggregation, these aggregates appeared to have mixed natures, consisting of primarily non-covalent aggregates with a low level of covalent species. This co-existence phenomenon was also supported by two kinetic pathways observed in time- and temperature-dependent aggregation studies. Furthermore, a stability study with 8 additional peptide variants exhibited good correlation between aggregation propensity and peptide hydrophobicity. Therefore, a dual aggregation pathway was proposed, with the non-covalent aggregates driven by hydrophobic interactions, whereas the covalent ones formed through disulfide scrambling. Overall, the workflow presented here provides a powerful strategy for comprehensive characterization of peptide aggregates and understanding their mechanisms of formation.

Organic Photovoltaics: Understanding the Preaggregation of Polymer Donors in Solution and Its Morphological Impact.

In bulk-heterojunction organic solar cells, it is well established that the active-layer morphology significantly impacts device performance. However, morphology control remains very challenging. An interesting step in that direction was recently provided by the development of polymer donors that display a temperature-dependent aggregation behavior in solution; the aggregation characteristics were found indeed to play a determining role in the eventual active-layer morphology. Here, a combination of thermodynamic analyses, molecular dynamics simulations, and long-range corrected density functional theory calculations enables us (i) to establish the Flory-Huggins interaction parameter, χ, as a useful figure of merit that allows us to integrate the contributions from all inter-related molecular interactions and to describe the extent of polymer preaggregation in solution at room temperature; (ii) to correlate the χ values for various polymer solutions to the extent of polymer aggregation and the morphological characteristics of the active layers; and (iii) to assess how polymer-polymer and polymer-solvent intermolecular interactions contribute to the variations in χ values among different polymer solutions. We have chosen to examine four representative polymer donors (PBT4T-2OD, PBTff4T-2OD, PffBT4T-2OD, and PffBTff4T-2DT) in solution in chlorobenzene or dichlorobenzene. With χ as a robust bridge, our results provide an unprecedented, detailed description of the relationships among intermolecular interactions, extent of polymer solution aggregation, and morphological features of the active layers.

Polymer Donors with Temperature-Insensitive, Strong Aggregation Properties Enabling Additive-Free, Processing Temperature-Tolerant High-Performance All-Polymer Solar Cells

In this work, the impact of temperature-dependent aggregation behaviors in benzodithiophene (BDT)-based polymer donors (PDs) on the electrical, morphological, and photovoltaic performances of all-p...

Temperature dependent aggregation mechanism and pathway of lysozyme: By all atom and coarse grained molecular dynamics simulation

Aggregation of protein causes various diseases including Alzheimer’s disease, Parkinson’s disease, and type II diabetes. It was found that aggregation of protein depends on many factors like temperature, pH, salt type, salt concentration, ionic strength, protein concentration, co solutes. Here we have tried to capture the aggregation mechanism and pathway of hen egg white lysozyme using molecular dynamics simulations at two different temperatures; 300 K and 340 K. Along with the all atom simulations to get the atomistic details of aggregation mechanism, we have used coarse grained simulation with MARTINI force field to monitor the aggregation for longer duration. Our results suggest that due to the aggregation, changes in the conformation of lysozyme are more at 340 K than at 300 K. The change in the conformation of the lysozyme at 300 K is mainly due to aggregation where at 340 K change in conformation of lysozyme is due to both aggregation and temperature. Also, a more compact aggregated system is formed at 340 K.