Molecular Disorder Research Articles

Molecular versus Excitonic Disorder in Individual Artificial Light-Harvesting Systems.

Natural light-harvesting antennae employ a dense array of chromophores to optimize energy transport via the formation of delocalized excited states (excitons), which are critically sensitive to spatio-energetic variations of the molecular structure. Identifying the origin and impact of such variations is highly desirable for understanding and predicting functional properties yet hard to achieve due to averaging of many overlapping responses from individual systems. Here, we overcome this problem by measuring the heterogeneity of synthetic analogues of natural antennae–self-assembled molecular nanotubes–by two complementary approaches: single-nanotube photoluminescence spectroscopy and ultrafast 2D correlation. We demonstrate remarkable homogeneity of the nanotube ensemble and reveal that ultrafast (∼50 fs) modulation of the exciton frequencies governs spectral broadening. Using multiscale exciton modeling, we show that the dominance of homogeneous broadening at the exciton level results from exchange narrowing of strong static disorder found for individual molecules within the nanotube. The detailed characterization of static and dynamic disorder at the exciton as well as the molecular level presented here opens new avenues in analyzing and predicting dynamic exciton properties, such as excitation energy transport.

Enhanced shockwave-absorption ability of the molecular disorder rooting for the reactivity elevation of energetic materials

It is universally believed that the molecular disorder possesses a high reactivity compared to the molecular order and can start the ignition of shocked energetic materials (EMs) from defects, interfaces, and surfaces. However, the origin of this high reactivity is still not fully understood. To this end, this study performs a series of simulations of reactive molecular dynamics on a solid model and a liquid model of 1,3,5-trinitro-1,3,5-triazinane (RDX), which are the representatives of ordered and disordered energetic molecules with ReaxFF potentials, respectively. A total of five heating conditions and three shock conditions are considered. The high reactivity of the molecular disorder in liquid RDX is remarkably discriminated under shock, with the discrimination degree depending on shock strength, followed by adiabatic heating. This high reactivity is attributed to the increase in internal energy induced by stronger shock, which is originated from a high shockwave-absorption ability of the liquid RDX with amorphous structures compared to the solid RDX with ordered structures. Therefore, the high shockwave-absorption ability is just the root of the high reactivity of molecular disorder in defected EMs and usually starts the ignition. Thereby, for the first time, the high reactivity of molecular disorder in shocked EMs can be well understood through its high shockwave-absorption ability.

Local Disorder Facilitates Chain Stretching in Crowded Polymer Brushes.

Intermolecular crowding of densely tethered polymers promotes chain extension and anisotropy that induces many unique properties. In this study, we used conformation-sensitive infrared spectroscopy to determine that chain extension in a polymer brush is associated with local conformation rearrangements, i.e., contraction of side groups and increased proportion of gauche twists in the backbone, which served to increase molecular disorder at or below the segmental scale. This conformational transition points to a particular molecular mechanism for chain extension in densely tethered polymers, wherein increased local disorder facilitates global chain ordering (i.e., chain extension) and therefore supplements our current understanding of chain orientation at a molecular level.

Metabolic Dysregulation in Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a fibroproliferative disorder limited to the lung. New findings, starting from our proteomics studies on IPF, suggest that systemic involvement with altered molecular mechanisms and metabolic disorder is an underlying cause of fibrosis. The role of metabolic dysregulation in the pathogenesis of IPF has not been extensively studied, despite a recent surge of interest. In particular, our studies on bronchoalveolar lavage fluid have shown that the renin–angiotensin–aldosterone system (RAAS), the hypoxia/oxidative stress response, and changes in iron and lipid metabolism are involved in onset of IPF. These processes appear to interact in an intricate manner and to be related to different fibrosing pathologies not directly linked to the lung environment. The disordered metabolism of carbohydrates, lipids, proteins and hormones has been documented in lung, liver, and kidney fibrosis. Correcting these metabolic alterations may offer a new strategy for treating fibrosis. This paper focuses on the role of metabolic dysregulation in the pathogenesis of IPF and is a continuation of our previous studies, investigating metabolic dysregulation as a new target for fibrosis therapy.

Phase-microstructure of Mo/Si nanoscale multilayer and intermetallic compound formation in interfaces

Microstructural investigation of the Mo/Si nanoscale multilayers (MLs) is essential to design high-reflective nanomirrors. Raman spectroscopy showed existence of silicon layer in the amorphous structure. Small fraction of the nanocrystalline silicon (nc-Si) phase was found to be embedded in the amorphous silicon (a-Si) matrix. The disorder in a-Si is increased with the decrease in the thickness of silicon layer in the Mo/Si MLs, determined by the increased bond-angle deviation (ΔΘ) of the Si–Si network. The MLs exposed to high-temperature (HT) showed a decrease in the ΔΘ value, which signifies the relaxation of both molecular disorder and residual stress. X-ray diffraction analysis confirmed the polycrystalline bcc phase of Mo and the formation of intermetallic t-Mo5Si3 phase in the interfaces. This phase is more prominent for higher value of β (thickness ratio of high atomic weight (z) layer to ML period d, i.e. β = dMo/d). Intensity of the Mo (110) plane is decreased for the sample annealed at HT, which is directly related to the degree of amorphization and the formation of intermetallic phases. However, HT annealed Mo/Si showed the growth of Mo (220) planes for higher β value of MLs. Current findings revealed that the disorder in the a-Si and microstructure of the Mo and intermetallic phase depend on the annealing temperature and the β value. The analysis of the intermetallic phase is critical for the development of high reflective mirrors.

Quantitative Effects of Disorder on Chemically Modified Amorphous Carbon Electrodes.

Real materials are disordered. This disorder influences the properties of these materials and the chemical processes that occur at their interfaces. Gaining a molecular-level understanding of the underlying physical manifestations caused by disordered materials is crucial to unraveling and ultimately controlling the efficiency and performance of these materials in a range of energy-related devices. This understanding necessitates measurement techniques through which disorder can be detected, quantified, and monitored. However, such quantitative measurements are notoriously difficult, as effects often average out in ensemble measurements. In this work, we describe how a combination of electrochemical and spatially resolved surface spectroscopy measurements illuminate a molecular-level picture of disorder in materials. Using amorphous carbon as an intrinsically disordered material, we covalently attached a monolayer of ferrocene. Interfacial electron transfer across the amorphous carbon-ferrocene interface is highly sensitive to disruptions of order. By systematically varying linker properties and surface loadings, the influence of lateral interactions between nonuniformly distributed ferrocene headgroups on ensemble electrochemical measurements is demonstrated. Electrochemical and imaging data collectively indicate that conformational flexibility of the ferrocene moieties provides a mechanism to elude repulsive and unbalanced lateral interactions, while rigid linkages provide direct information about the underlying disorder of the material. This study is the first of its kind to quantify and visualize molecular disorder and heterogeneity with an experimental model accessed through ensemble measurements.

Dynamics-Function Analysis in Catalytic RNA Using NMR Spin Relaxation and Conformationally Restricted Nucleotides.

A full understanding of biomolecular function requires an analysis of both the dynamic properties of the system of interest and the identification of those dynamics that are required for function. We describe NMR methods based on metabolically directed specific isotope labeling for the identification of molecular disorder and/or conformational transitions on the RNA backbone ribose groups. These analyses are complemented by the use of synthetic covalently modified nucleotides constrained to a single sugar pucker, which allow functional assessment of dynamics by selectively removing a minor conformer identified by NMR from the structural ensemble.

Understanding the Electrical Transport-Structure Relationship and Photovoltaic Properties of a [Succinonitrile-Ionic Liquid]-LiI-I2 Redox Electrolyte.

The properties of succinonitrile-based electrolytes can be enhanced by the addition of an ionic liquid (IL). Here, we have reported the relationship between the electrical transport properties and the structure of a new [(1 – x)succinonitrile:xIL]–LiI–I2 electrolyte, where the mole fraction (x) of the IL (1-butyl-3-methyl imidazolium iodide) was varied from 0 to 40%. Compositional variation revealed the optimum conducting electrolyte (OCE) at x = 10 mol %, possessing an electrical conductivity (σ25°C) of ∼7.5 mS cm–1 with an enhancement of ∼369%. The partial replacement of succinonitrile by the IL eliminated the abrupt change in the slope of the log σ vs T–1 plot at the melting temperature of the succinonitrile–LiI–I2 system, showing the Vogel–Tamman–Fulcher-type behavior owing to molecular chain disorder. Raman spectroscopy showed the I3– concentration nearly twice the I5– concentration for the OCE. Vibrational spectroscopy exhibited red shifts in the νC≡N, νCH2, νa,CC, νa,N-CH3, and νs,N-butyl modes, indicating an interaction between succinonitrile and the IL. The area ratio ACH2/AC≡N increased slightly for x = 10 mol % (OCE) and largely for x > 10 mol %, indicating an increase in the C–H bond length. These observations indicated that the interaction between succinonitrile and the IL was enhanced at x > 10 mol %, which decreased the electrical conductivity of these electrolytes. Owing to fast ion transport, an OCE-based dye-sensitized solar cell showed a 40–55% decrease in the charge-transfer and Warburg resistances, resulting in ∼139 and ∼122% increases in JSC and η, respectively.

HMGA2 Variants in Silver-Russell Syndrome: Homozygous and Heterozygous Occurrence.

Silver-Russell syndrome (SRS) is a clinical and molecular heterogeneous disorder associated with short stature, typical facial gestalt, and body asymmetry. Though molecular causes of SRS can be identified in a significant number of patients, about one-half of patients currently remain without a molecular diagnosis. However, determination of the molecular cause is required for a targeted treatment and genetic counselling. The aim of this study was to corroborate the role of HMGA2 as an SRS-causing gene and reevaluate its mode of inheritance. Patients were part of an ongoing study aiming on SRS-causing genes. They were classified according to the Netchine-Harbison clinical scoring system, and DNA samples were investigated by whole exome sequencing. Common molecular causes of SRS were excluded before. Three novel pathogenic HMGA2 variants were identified in 5 patients from 3 SRS families, and fulfilling diagnostic criteria of SRS. For the first time, homozygosity for a variant in HMGA2 could be identified in a severely affected sibpair, whereas parents carrying heterozygous variants had a mild phenotype. Treatment with recombinant growth hormone led to a catch-up growth in 1 patient, whereas all others did not receive growth hormone and stayed small. One patient developed type 2 diabetes at age 30 years. Identification of novel pathogenic variants confirms HMGA2 as an SRS-causing gene; thus, HMGA2 testing should be implemented in molecular SRS diagnostic workup. Furthermore, inheritance of HMGA2 is variable depending on the severity of the variant and its consequence for protein function.

Synthesis, crystal structure, DFT studies and biological evaluation of N-benzamido derivatives of oxahexacycloundecyl amines: A case of enantiomerism leading to molecular disorder

To explore the reactivity of the amine in oxahexacycloundecylamines and its effect on biological properties, two di-substituted N-benzamido-oxahexacycloundecylamine derivatives were synthesized. These compounds exhibited favourable biological properties in cytotoxicity, neuroprotection and calcium influx experiments. Steric and conformational factors are proposed to play an important role in the biological activities observed and X-ray crystallographic experiments were conducted in an attempt to gain insight into the structural features of these compounds. The propyl derivative, 3-(N-(8,11-oxahexacyclo[5.4.0.02,6.03,10.05,9]-undecyl)benzamido)propyl benzoate, crystallizes in the monoclinic space group P21/c with unit cell parameters: a = 6.2838(11) Å; b = 27.833(5) Å; c = 12.630(2) Å; β = 95.457(3) Å; V = 2199.0(7) Å3; Z = 4. The crystal structure revealed the existence of enantiomerism in the oxa-bridged polycycloundecylamine residue as a result of the nitrogen attached on either side of the oxa-bridge. This enantiomerism leads to molecular disorder of this residue in the crystal over two positions with refined site-occupancy factors (s.o.f.s) of x (= 0.774(2)) and 1-x (= 0.226(2)) corresponding to the respective enantiomeric residues with S- and R-configurations at partial atoms C18A and C18B in one molecule. For each two-fold disordered chiral atom, the presence of a centre of symmetry in the crystal generates the complementary pair of partial atoms within the crystal (s.o.f.s x and 1-x), thus rendering it racemic. DFT optimization studies on the two individual enantiomers corresponding to the two residues with S- and R-configurations at C18 within the disordered structure showed almost identical geometric parameters, indicating that the disorder observed is linked to the crystal packing. The ethyl derivative also showed similar geometric parameters to its propyl counterpart according to the DFT results. These findings correspond to earlier observations in that a number of steric and electronic factors could collectively be responsible for the biological activities observed for these compounds.

Microsatellite instability as a unique characteristic of tumors and a predictor of response to immune therapy

Deficiency of the mismatch repair system is a unique molecular disorder that occurs in most types of tumors and leads to development of microsatellite instability (MSI) in them. The development of a hypermutated phenotype and related high immunogenicity are typically associated with more favorable prognosis as well as a high sensitivity to immunotherapy with inhibitors of immune checkpoint inhibitors. This review presents the current views on the diagnosis, prognostic and predictive significance of MSI in various tumors, as well as their response to immunotherapy.

Thermodynamic and Morphological Properties of Trastuzumab Regulated by the Lipid Composition of Cell Membrane Models at the Air-Water Interface

Trastuzumab (Tmab) is an antibody with anti-cancer properties, whose action occurs when the tumor is associated to the overexpression of the human epidermal growth factor receptor. This drug binds to the receptor, blocking downstream signaling pathways, which controls the cancer progression. Tmab also interacts with glycosaminoglycans and proteoglycans of the cell surface and extracellular matrix so that this interaction helps control cellular events in tumorigenic endothelial cells. In this sense, it is interesting, to study the action of this drug in cellular membrane models to understand its action in cellular membranes and in other lipid surfaces with pharmaceutical interest. In this work, Tmab was incorporated in lipid monolayers at the air-water interface and their thermodynamic, morphological and structural effects were investigated with tensiometry, Brewster angle microscopy (BAM) and polarization-modulation reflection-absorption infrared spectroscopy (PM-IRRAS), respectively. For that, we employed the phospholipids dipalmitoylphosphatidylcholine (DPPC), and dipalmitoylphosphoethanolamine (DPPE), and their mixtures with cholesterol. Tmab expanded all lipid films and affected the compressional and structural properties as observed by surface pressure isotherms, in-plane elasticity, and PM-IRRAS, respectively. BAM showed distinctive morphological patterns for the monolayers and infrared spectroscopy showed an increased number of gauche conformers related to the CH2 stretching mode, indicating film molecular disorder. Also, the antibody kept the beta-sheet structure of the polypeptide backbone adsorbed at the lipid monolayers though the secondary conformation changed according to the monolayer composition. The results then suggest that the membrane lipid profile affects the adsorption of Tmab at lipid monolayers, which can be associated to the fact that antibody-receptor interactions at the lipid membrane environment can possibly be tuned by changing the lipid composition at the receptor vicinity.

Altered Thick and Thin Filament Structural Dynamics in Mouse Myocardium Due to Ablation and Phosphorylation of Myosin Binding Protein-C

Cardiac Myosin Binding Protein-C (cMyBP-C) is an important regulator of myocardial contraction and cross-bridge disposition; however, its contributions to thick and thin filament structural dynamics is unknown. Therefore, we performed time-resolved fluorescence (TR-F) experiments to quantify lifetime changes of environmentally-sensitive probes introduced in myofibrils isolated from ventricles of wild-type (WT) and cMyBP-C null (cMyBP-C-/-) mice. Mutant ventricular regulatory light chain (RLC V105C) labeled with CPM or cardiac troponin C (cTnC T53C) labeled with IANBD were exchanged in skinned myofibrils to replace the endogenous proteins. ATPase measurements demonstrated that the exchanges did not affect contractile function. TR-F measurements revealed differences in lifetimes of both RLC and cTnC between WT and cMyBP-C-/- myofibrils. PKA-mediated phosphorylation of myofibrils also affected lifetimes with greater effects observed in WT as compared to cMyBP-C-/-. For the RLC probe, the differences in lifetimes due to PKA phosphorylation were greatest with addition of myosin inhibitors: blebbistatin or vanadate. These results are consistent with the idea that cMyBP-C plays a role in stabilizing myosin on the thick filament and promoting the super-relaxed state, whereas its absence or phosphorylation leads to increased molecular disorder. For the cTnC probe, PKA treatment of myofibrils reduced the Ca2+-sensitivity of lifetime in both WT and cMyBP-C-/-. These results suggest unique phosphorylation-dependent roles for cMyBP-C and cardiac troponin I (cTnI) on thin filament structural dynamics. Our findings demonstrate that cMyBP-C and cTnI contribute to phosphorylation-dependent effects on thick and thin filament structural dynamics to influence force development. These TR-F probes can also be useful for screening of compounds that alter cMyBP-C interactions with the myofilaments.

Exploring the molecular disorder and dysfunction mechanism of human dental pulp cells under hypoxia by comprehensive multivariate analysis

Dental pulp cells (DPCs) are multipotent cells, which can differentiate into various tissues and have the potential to treat many diseases. However, little is known about the molecular disorder mechanism. To explore the mechanism of molecular disorders and dysfunction of DPCs under hypoxia, we investigated the molecular effects of two hypoxic time lengths on DPCs. Differential analysis, protein interaction network (PPI), enrichment analysis and coupling analysis were further synthesized to identify human dental pulp cell dysfunction modules under hypoxic conditions. Based on the module aggregation of 579 genes, 13 dental pulp cell dysfunction modules were obtained. Importantly, we found that up to 12 modules were significantly involved in positive regulation of neurogenesis, positive regulation of nervous system development. Based on the predictive analysis of regulators, we identified a series of ncRNAs (including CRNDE, MALAT1, microRNA-140-5p, microRNA-300 and microRNA-30a-5p) and transcription factors (including E2F1). Based on the comprehensive functional module analysis, we identified the dysfunction module of human dental pulp cells (HDPCs) under hypoxia. The results suggest that nerve regulation plays an important role in regulating the dysfunction module of DPCs. These prominent pivotal regulators in the module were used as an important part of the molecular disorders of DPCs, may be an important part of the subnetwork of the manipulation module and affect the molecular dysregulation mechanism of DPCs. This study provides new directions and potential targets for further research.

Polypeptide templating for designer hierarchical materials

Despite advances in directing the assembly of biomacromolecules into well-defined nanostructures, leveraging pathway complexity of molecular disorder to order transition while bridging materials fabrication from nano- to macroscale remains a challenge. Here, we present templated crystallization of structural proteins to nanofabricate hierarchically structured materials up to centimeter scale, using silk fibroin as an example. The process involves the use of ordered peptide supramolecular assemblies as templates to direct the folding and assembly of silk fibroin into nanofibrillar structures. Silk polymorphs can be engineered by varying the peptide seeds used. Modulation of the relative concentration between silk fibroin and peptide seeds, silk fibroin molecular weight and pH allows control over nanofibrils morphologies and mechanical properties. Finally, facile integration of the bottom-up templated crystallization with emerging top-down techniques enables the generation of macroscopic nanostructured materials with potential applications in information storage/encryption, surface functionalization, and printable three-dimensional constructs of customized architecture and controlled anisotropy.

The lipid composition affects Trastuzumab adsorption at monolayers at the air-water interface

Trastuzumab (Tmab), an antibody for breast cancer, was incorporated in Langmuir monolayers with different lipidic compositions to investigate the drug action in lipidic interfaces of pharmaceutical interest. Tmab caused all lipid films to expand as confirmed with by surface pressure-area isotherm, proving its incorporation. It also affected the compressional and structural properties as observed by in-plane elasticity curves and polarization modulation reflection-absorption infrared spectroscopy (PM-IRRAS), respectively. Although Tmab did not change significantly the compressional modulus for dipalmitoylphosphatidylcholine (DPPC) monolayers, it decreased it for the mixtures of DPPC with cholesterol. In contrast, for dipalmitoylphosphoethanolamine (DPPE), Tmab increased the compressional modulus for both monolayers, pure DPPE or mixed with cholesterol. While Brewster Angle Microscopy showed discrete distinctive morphological patterns for the monolayers investigated, PM-IRRAS showed that Tmab caused an increased number of gauche conformers related to the CH2 stretching mode for the lipid acyl chains, suggesting molecular disorder. Furthermore, the antibody kept the β-sheet structure of the polypeptide backbone adsorbed at the lipid monolayers although the secondary conformation altered according to the film composition at the air-water interface. As a result, the results suggest that the membrane lipid profile affects the adsorption of Tmab at lipid monolayers, which can be important for the incorporation of this drug in lipidic supramolecular systems like in liposomes for drug delivery and in biomembranes.

Blood Profile of Lymphocyte Lineage Determining Transcription Factor Gata3 May Influence Malaria Disease Outcome of Children in the South of Benin

Background: Child morbidity in African countries including the Republic of Benin, is mostly attributed to parasitic infectious diseases involving malaria. Molecular disorder often underlies the vulnerability of children immune system to infectious diseases. This reduces the ability of immune system to combat appropriately exogen organisms including parasites larva, bacteria or viruses. GATA-3 is a nuclear protein expressed by immune cells and belongs to a family member of the lymphocyte CD4 lineage determining transcription factors inducible by retinoic acid. Thus, GATA3 is one of the main regulators of lymphocyte T-helper 2 (Th2) cell differentiation into mature CD4+ T cells that mediate immunity tocombat exogenmicroorganism involving plasmodium falciparum (pf). The objective of the study is to investigate if children with low or absence of GATA3 expression will be more vulnerable to pf infection and malaria. Methods: This study has received an institutional ethical approval.Preliminary study carried out on cell lysates of peripheral white blood cells isolated from blood samples used for pf counts in Benin Zonal hospital of Calavi/So-Ava diagnosis laboratory involving eighteen children (5-9 years) admitted for fever associated or not to malaria. Immunoblotting (western blot) technic was used to evaluate GATA3 expression in all samples.The presence of pf was determined with microscopic observation of blood thick smears stained with Giemsa. Results: Among the eighteen samples, normal expression of GATA3 was observed in ten, low expression in six while no expression was observed in two samples. Overall, seven samples were positive for pf counts ranging from 350-1500 per mm3 of red blood cells. Infection with pf was not observed in eleven samples. Conclusion: Immune system of children with low GATA3 and high level of pf count will be more vulnerable to infection. Thus, the absence of GATA3 transcription factor could influence the outcome of malaria disease and render children too weak to fight pf infection.The absence of GATA3 may also render them vulnerable to develop allergy or lymphoma in the future.

Prepared self-growing supported nickel catalyst by recovering Ni (Ⅱ) from metal wastewater using geopolymer microspheres

Here, new and effective microsphere adsorbents were synthesized by NaOH activating slag based geopolymer (Na-SGS). These microsphere adsorbents upset the adsorption equilibrium with the maximum Ni2+ adsorption capacity of 414.38 mg/g which is much larger than that of other geopolymer materials. After Ni2+ adsorption from simulated nickel electroplating wastewater, more active positions for the adsorption Ni2+ ions on Na-SGS were provided as shifts from the average pore diameter of 22.00–7.44 nm, the pore volume of 0.06 to 0.25 cm3/g, the Brunauer-Emmett-Teller (BET) surface area of 10.46–125.35 m2/g and the apparent change of new morphology. Moreover, the adsorbed Ni2+ species were distributed uniformly on Na-SGS. Thermodynamic performance reflected an exothermic, spontaneous and molecular disorder adsorption process, which can be easily controlled by the pH, dosage, initial concentration, contact time and temperature. Through the controllable adsorption, Na-SGS after Ni2+ adsorption (Na-SGS-Ni) was recycled and then reduced to be directly supported nickel catalysts (red-Na-SGS-Ni), which showed superior catalytic activity for CO2 methanation. Although the highest percent of CO2 conversation (XCO2 =99.54%) and methane selectivity (SCH4 =99.5%) are both at 300 °C, red-Na-SGS-Ni performed good XCO2 (99.48%) and SCH4 (98.2%) at low temperatures (100 °C).

CP MAS kinetics in soft matter: Spin diffusion, local disorder and thermal equilibration in poly(2-hydroxyethyl methacrylate)

The 1H–13C cross-polarization magic angle spinning kinetics was studied in poly(2-hydroxyethyl methacrylate) (pHEMA), i.e. a soft material with high degrees of internal freedom and molecular disorder, having the purpose to track the influence of increasing local incoherent contributions to the effects of coherent nature in the open quantum spin systems. The experimental CP MAS kinetic curves were analyzed in the frame of the models of isotropic and anisotropic spin diffusion with thermal equilibration. The rates of spin diffusion and spin-lattice relaxation as well as the profiles of distribution of dipolar coupling, the parameters accounting the effective size of spin clusters and the local order parameters were determined. The intensities of the peaks of periodic quasi-equilibrium origin gradually decrease with increasing disorder, i.e. going from most ordered to more disordered sites in the polymer. Assuming that the thermal motion induced by the temperature gradients is much faster than the equilibration driven by spin diffusion due the difference in spin temperatures, it was deduced that the thermal equilibration in pHEMA occurs in the time scale of 10−4 s. This is one order of magnitude faster than the spectral spin diffusion, which occurs between spins having different resonance frequencies. The thermal equilibration in the case of remote spin clusters was described by the ‘stretched exponent’ decay. This led to the fractal dimension Dp ≈ 1.65 for both carbon sites (quaternary and carbonyl). The obtained Dp value corresponds to the aggregates, which images are very similar to those for pHEMA and some other related polymer structures are usually conceived.

A Large Anisotropic Enhancement of the Charge Carrier Mobility of Flexible Organic Transistors with Strain: A Hall Effect and Raman Study.

Utilizing the intrinsic mobility–strain relationship in semiconductors is critical for enabling strain engineering applications in high‐performance flexible electronics. Here, measurements of Hall effect and Raman spectra of an organic semiconductor as a function of uniaxial mechanical strain are reported. This study reveals a very strong, anisotropic, and reversible modulation of the intrinsic (trap‐free) charge carrier mobility of single‐crystal rubrene transistors with strain, showing that the effective mobility of organic circuits can be enhanced by up to 100% with only 1% of compressive strain. Consistently, Raman spectroscopy reveals a systematic shift of the low‐frequency Raman modes of rubrene to higher (lower) frequencies with compressive (tensile) strain, which is indicative of a reduction (enhancement) of thermal molecular disorder in the crystal with strain. This study lays the foundation of the strain engineering in organic electronics and advances the knowledge of the relationship between the carrier mobility, low‐frequency vibrational modes, strain, and molecular disorder in organic semiconductors.