286 research outputs found
Glycolated Thiophene-Tetrafluorophenylene Copolymers for Bioelectronic Applications: Synthesis by Direct Heteroarylation Polymerisation
Mapping Microstructural Dynamics up to the Nanosecond of the Conjugated Polymer P3HT in the Solid State
We present a detailed study of the structure-dynamics relationship of
regio-regular and regio-random PEHT using different neutron scattering
techniques. Deuteration is employed to modulate the coherent and incoherent
cross-sections, allowing particularly to access both self-motions and
collective dynamics of the materials. The measurements are underpinned by
extensive quantitative calculations using classical MD, as well as first
principles quantum chemistry. MD reproduced well the main structural features
and slow motions, and shed light on differences in collective dynamics between
Q-values linked with the stacking and the lamellar stacking, with the
crystalline phase being the most impacted. On the other hand MD led to a
limited description of molecular vibrations. In this context, first principles
molecular calculations described well the high-energy vibrational features (
900 cm ), while periodic calculations allowed to better describe the
low- and mid-energy vibrational ranges ( 200-900 cm ). The mid-energy
range is predominantly associated with both intra-molecular and inter-molecular
mode coupling, which encloses information about both the polymer conformation
and the polymer packing at short range. One of the outcomes of this study is
the validation of the common assumption made that RRa-P3HT is a good
approximation for the amorphous phase of RR-P3HT at the macroscopic level. The
present work helps to clarify unambiguously the latter point which has been
largely overlooked in the literature. We highlight the importance to complement
optical spectroscopy techniques with inelastic neutron scattering. The latter
offering the advantage of being insensitive to the delocalized -electron
system, and thus enabling to infer relevant quantities like conjugation
lengths, for instance, impacting properties of conjugated polymer.Comment: Featured as ACS Editors' Choice. Featured on the Cover of the
December 10, 2019 issue of Chemistry of Material
The Influence of Regiochemistry on the Performance of Organic Mixed Ionic and Electronic Conductors
Aqueous processing of organic semiconductors enabled by stable nanoparticles with built-in surfactants
Resolving the backbone tilt of crystalline poly(3-hexylthiophene) with resonant tender X-ray diffraction
The way in which conjugated polymers pack in the solid state strongly affects the performance of polymer-based optoelectronic devices. However, even for the most crystalline conjugated polymers the precise packing of chains within the unit cell is not well established. Here we show that by performing resonant X-ray diffraction experiments at the sulfur K-edge we are able to resolve the tilting of the planar backbones of crystalline poly(3-hexylthiophene) (P3HT) within the unit cell. This approach exploits the anisotropic nature of the X-ray optical properties of conjugated polymers, enabling us to discern between different proposed crystal structures. By comparing our data with simulations based on different orientations, a tilting of the planar conjugated backbone with respect to the side chain stacking direction of 30 ± 5° is determined
Interplay between Side Chain Density and Polymer Alignment: Two Competing Strategies for Enhancing the Thermoelectric Performance of P3HT Analogues
A series of polythiophenes with varying side chain density was synthesized, and their electrical and thermoelectric properties were investigated. Aligned and non-aligned thin films of the polymers were characterized in the neutral and chemically doped states. Optical and diffraction measurements revealed an overall lower order in the thin films with lower side chain density, also confirmed using polarized optical experiments on aligned thin films. However, upon doping the non-aligned films, a sixfold increase in electrical conductivity was observed for the polythiophene with the lowest side chain density compared to poly(3-hexylthiophene) (P3HT). We found that the improvement in conductivity was not due to a larger charge carrier density but an increase in charge carrier mobility after doping with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ). On the other hand, doped aligned films did not show the same trend; lower side chain density instead led to a lower conductivity and Seebeck coefficient compared to those for P3HT. This was attributed to the poorer alignment of the polymer thin films with lower side chain density. The study demonstrates that optimizing side chain density is a synthetically simple and effective way to improve electrical conductivity in polythiophene films relevant to thermoelectric applications
A user-friendly web portal for T-Coffee on supercomputers
<p>Abstract</p> <p>Background</p> <p>Parallel T-Coffee (PTC) was the first parallel implementation of the T-Coffee multiple sequence alignment tool. It is based on MPI and RMA mechanisms. Its purpose is to reduce the execution time of the large-scale sequence alignments. It can be run on distributed memory clusters allowing users to align data sets consisting of hundreds of proteins within a reasonable time. However, most of the potential users of this tool are not familiar with the use of grids or supercomputers.</p> <p>Results</p> <p>In this paper we show how PTC can be easily deployed and controlled on a super computer architecture using a web portal developed using Rapid. Rapid is a tool for efficiently generating standardized portlets for a wide range of applications and the approach described here is generic enough to be applied to other applications, or to deploy PTC on different HPC environments.</p> <p>Conclusions</p> <p>The PTC portal allows users to upload a large number of sequences to be aligned by the parallel version of TC that cannot be aligned by a single machine due to memory and execution time constraints. The web portal provides a user-friendly solution.</p
Side chain engineering in indacenodithiophene- co -benzothiadiazole and its impact on mixed ionicâelectronic transport properties
Organic semiconductors are increasingly being decorated with hydrophilic solubilising chains to create materials that can function as mixed ionicâelectronic conductors, which are promising candidates for interfacing biological systems with organic electronics. While numerous organic semiconductors, including p- and n-type materials, small molecules and polymers, have been successfully tailored to encompass mixed conduction properties, common to all these systems is that they have been semicrystalline materials. Here, we explore how side chain engineering in the nano-crystalline indacenodithiophene-co-benzothiadiazole (IDTBT) polymer can be used to instil ionic transport properties and how this in turn influences the electronic transport properties. This allows us to ultimately assess the mixed ionicâelectronic transport properties of these new IDTBT polymers using the organic electrochemical transistor as the testing platform. Using a complementary experimental and computational approach, we find that polar IDTBT derivatives can be infiltrated by water and solvated ions, they can be electrochemically doped efficiently in aqueous electrolyte with fast doping kinetics, and upon aqueous swelling there is no deterioration of the close interchain contacts that are vital for efficient charge transport in the IDTBT system. Despite these promising attributes, mixed ionicâelectronic charge transport properties are surprisingly poor in all the polar IDTBT derivatives. Albeit a âânegativeââ result, this finding clearly contradicts established side chain engineering rules for mixed ionicâelectronic conductors, which motivated our continued investigation of this system. We eventually find this anomalous behaviour to be caused by increasing energetic disorder in the polymers with increasing polar side chain content. We have investigated computationally how the polar side chain motifs contribute to this detrimental energetic inhomogeneity and ultimately use the learnings to propose new molecular design criteria for side chains that can facilitate ion transport without impeding electronic transport
Prognostic value of nuclear morphometry in patients with TNM stage T1 ovarian clear cell adenocarcinoma
In 40 patients with TNM stage T1 ovarian clear cell adenocarcinoma, we used nuclear morphometry to study the relations among morphometric variables, clinical prognostic factors and outcome. The presence of one or more giant nuclear cells was positively associated with death (OR = 10.6, P = 0.02) and tended to be associated with disease recurrence (OR = 5.1, P = 0.07). Nuclear irregularity (expressed in terms of the nuclear roundness factor) was positively associated with both death (OR = 8.6, P = 0.02) and disease recurrence (OR = 8.2, P = 0.02). A combination of giant nuclear cell presence or nuclear irregularity proved to be a useful prognostic indicator, with a sensitivity and specificity of 83% and 71% in the prediction of death, and 75% and 71% in the prediction of disease recurrence. Patients' age and substage were of no prognostic value. We conclude that the nuclear morphometric characteristics, especially the presence of giant nuclear cells and nuclear irregularity, may be useful in predicting outcome in patients with early stage ovarian clear cell adenocarcinoma. © 1999 Cancer Research Campaig
Liquid-gas phase transition in nuclear multifragmentation
The equation of state of nuclear matter suggests that at suitable beam
energies the disassembling hot system formed in heavy ion collisions will pass
through a liquid-gas coexistence region. Searching for the signatures of the
phase transition has been a very important focal point of experimental
endeavours in heavy ion collisions, in the last fifteen years. Simultaneously
theoretical models have been developed to provide information about the
equation of state and reaction mechanisms consistent with the experimental
observables. This article is a review of this endeavour.Comment: 63 pages, 27 figures, submitted to Adv. Nucl. Phys. Some typos
corrected, minor text change
- âŠ