Search

High dielectric constant organic semiconductors, often obtained by the use of ethylene glycol (EG) side chains, have gained attention in recent years in the efforts of improving the device performance for various applications. Dielectric constant enhancements due to EGs have been demonstrated extensively, but various effects, such as the choice of the particular molecule and the frequency and temperature regime, that determine the extent of this enhancement require further understanding. In this work, we study these effects by means of polarizable molecular dynamics simulations on a carefully selected set of fullerene derivatives with EG side chains. The selection allows studying the dielectric response in terms of both the number and length of EG chains and also the choice of the group connecting the fullerene to the EG chain. The computed time- and frequency-dependent dielectric responses reveal that the experimentally observed rise of the dielectric constant within the kilo/megahertz regime for some molecules is likely due to the highly stretched dielectric response of the EGs: the initial sharp increase over the first few nanoseconds is followed by a smaller but persistent increase in the range of microseconds. Additionally, our computational protocol allows the separation of different factors that contribute to the overall dielectric constant, providing insights to make several molecular design guides for future organic materials in order to enhance their dielectric constant further.

Self-assembly is a ubiquitous process spanning from biomolecular aggregates to nanomaterials. Even though the resulting aggregates can be studied through experimental techniques, the dynamic pathways of the process and the molecular details of the final structures are not necessarily easy to resolve. Consequently, rational design of self-assembling aggregates and their properties remains extremely challenging. At the same time, modelling the self-assembly with computational methods is not trivial, because its spatio-temporal scales are usually beyond the limits of all-atom based simulations. The use of coarse-grained (CG) models can alleviate this limitation, but usually suffers from the lack of optimised parameters for the molecular constituents. In this work, we describe the procedure of parametrizing a CG Martini model for a cyanine dye (C8S3) that self-assembles into hollow double-walled nanotubes. We optimised the model based on quantum mechanics calculations and all-atom reference simulations, in combination with available experimental data. Then, we performed random self-assembly simulations and the performance of our model was tested on preformed assemblies. Our simulations provide information on the time-dependent local arrangement of this cyanine dye, when aggregates are being formed. Furthermore, we provide guidelines for designing and optimising parameters for similar self-assembling nanomaterials.

The Martini force-field for molecular dynamics (MD) simulations is suitable for running MD simulations of complex bio(molecular) systems and nano-materials. Recently, titratable Martini was developed, which is an extension of the popular force-field that is suitable for running constant pH simulations within the Martini framework. In this chapter, the key concepts behind the titratable Martini model are summarized, followed by a tutorial style presentation of three application cases. These application cases demonstrate how to generate coordinates, run titration simulations, and analyze them with the help of the martini_sour package. Martini_sour is a dedicated Python suite for facilitating all aspects of titratable Martini simulations. Finally, a series of notes containing useful information, limitations, and tips are described in the last section.

For many years, fullerene derivatives have been the main n-type material of organic electronics and optoelectronics. Recently, fullerene derivatives functionalized with ethylene glycol (EG) side chains have been showing important properties such as enhanced dielectric constants, facile doping and enhanced self-assembly capabilities. Here, we have prepared field-effect transistors using a series of these fullerene derivatives equipped with EG side chains of different lengths. Transport data show the beneficial effect of increasing the EG side chain. In order to understand the material properties, full structural determination of these fullerene derivatives has been achieved by coupling the X-ray data with molecular dynamics (MD) simulations. The increase in transport properties is paired with the formation of extended layered structures, efficient molecular packing and an increase in the crystallite alignment. The layer-like structure is composed of conducting layers, containing of closely packed C60 balls approaching the inter-distance of 1 nm, that are separated by well-defined EG layers, where the EG chains are rather splayed with the chain direction almost perpendicular to the layer normal. Such a layered structure appears highly ordered and highly aligned with the C60 planes oriented parallel to the substrate in the thin film configuration. The order inside the thin film increases with the EG chain length, allowing the systems to achieve mobilities as high as 0.053 cm2 V−1 s−1. Our work elucidates the structure of these interesting semiconducting organic molecules and shows that the synergistic use of X-ray structural analysis and MD simulations is a powerful tool to identify the structure of thin organic films for optoelectronic applications., The synergistic use of X-ray scattering and molecular dynamics simulations reveals the structure–property relationships of [60]fullerene derivatives with oligoethylene–glycol side chains.

Valerolactone (GVL) is readily accessible by catalytic hydrogenation of carbohydrate-derived levulinic acid (LA) and is an attractive biobased chemical with a wide range of applications in both the chemical (e.g., as biomass-derived solvent) and the transportation fuel sector. In this study, we used isotopic labeling experiments to provide insights into the catalytic hydrogenation pathways involved in the conversion of LA to GVL under different reaction conditions using water as an environmentally benign solvent and Ru/C as a readily available catalyst. 2H NMR experiments combined with quantum chemical calculations revealed that deuterium atoms can be incorporated at different positions as well as the involvement of the different intermediates 4-hydroxypentanoic acid and α-angelica lactone (α-AL). The insight provided by these studies revealed an as of yet unexploited sequential deuteration route to synthesize fully deuterated LA and GVL. The route starts by the conversion of LA to α-AL followed by a selective deuteration of the acidic protons of α-AL by H/D exchange with D2O. Subsequent ring-opening in D2O (d2-AL to d3-LA) and exchange of the remaining protons of d3-LA via a keto-enol tautomerization by heating in D2O under acidic conditions gives d8-LA. Finally, the d8-LA is catalytically reduced at low temperature using Ru/C with D2 in D2O to d8-GVL.

The ‘phonon-glass electron-crystal’ concept has triggered most of the progress that has been achieved in inorganic thermoelectrics in the past two decades. Organic thermoelectric materials, unlike their inorganic counterparts, exhibit molecular diversity, flexible mechanical properties and easy fabrication, and are mostly ‘phonon glasses’. However, the thermoelectric performances of these organic materials are largely limited by low molecular order and they are therefore far from being ‘electron crystals’. Here, we report a molecularly n-doped fullerene derivative with meticulous design of the side chain that approaches an organic ‘PGEC’ thermoelectric material. This thermoelectric material exhibits an excellent electrical conductivity of >10 S cm−1 and an ultralow thermal conductivity of, Achieved high thermoelectric figure of merit (ZT) in organic thermoelectric materials remains a challenge due to their low packing order and poor host/dopant miscibility. Here, the authors report side chain-engineered n-doped fullerene derivatives with record ZT >0.3 for organic thermoelectrics.

Incorporating ethylene glycols (EGs) into organic semiconductors has become the prominent strategy to increase their dielectric constant. However, EG's contribution to the dielectric constant is due to nuclear relaxations, and therefore, its relevance for various organic electronic applications depends on the time scale of these relaxations, which remains unknown. In this work, by means of a new computational protocol based on polarizable molecular dynamics simulations, the time- and frequency-dependent dielectric constant of a representative fullerene derivative with EG side chains is predicted, the origin of its unusually high dielectric constant is explained, and design suggestions are made to further increase it. Finally, a dielectric relaxation time of ∼1 ns is extracted which suggests that EGs may be too slow to reduce the Coulombic screening in organic photovoltaics but are definitely fast enough for organic thermoelectrics with much lower charge carrier velocities.

We present a new software package called M-Chem that is designed from scratch in C++ and parallelised on shared-memory multi-core architectures to facilitate efficient molecular simulations. Currently, M-Chem is a fast molecular dynamics (MD) engine that supports the evaluation of energies and forces from two-body to many-body all-atom potentials, reactive force fields, coarse-grained models, combined quantum mechanics molecular mechanics (QM/MM) models, and external force drivers from machine learning, augmented by algorithms that are focused on gains in computational simulation times. M-Chem also includes a range of standard simulation capabilities including thermostats, barostats, multi-timestepping, and periodic cells, as well as newer methods such as fast extended Lagrangians and high quality electrostatic potential generation. At present M-Chem is a developer friendly environment in which we encourage new software contributors from diverse fields to build their algorithms, models, and methods in our modular framework. The long-term objective of M-Chem is to create an interdisciplinary platform for computational methods with applications ranging from biomolecular simulations, reactive chemistry, to materials research.

The quality of molecular dynamics simulations strongly depends on the accuracy of the underlying force fields (FFs) that determine all intra- and intermolecular interactions of the system. Commonly, transferable FF parameters are determined based on a representative set of small molecules. However, such an approach sacrifices accuracy in favor of generality. In this work, an open-source and automated toolkit named Q-Force is presented, which augments these transferable FFs with molecule-specific bonded parameters and atomic charges that are derived from quantum mechanical (QM) calculations. The molecular fragmentation procedure allows treatment of large molecules (>200 atoms) with a low computational cost. The generated Q-Force FFs can be used at the same computational cost as transferable FFs, but with improved accuracy: We demonstrate this for the vibrational properties on a set of small molecules and for the potential energy surface on a complex molecule (186 atoms) with photovoltaic applications. Overall, the accuracy, user-friendliness, and minimal computational overhead of the Q-Force protocol make it widely applicable for atomistic molecular dynamics simulations.

1,2,4-Benzenetriol (BTO), sourced from the carbohydrate-derived platform chemical 5-hydroxylmethylfurfural (HMF), is an interesting starting point for the synthesis of various biobased aromatic products. However, BTO readily undergoes dimerization and other reactions under mild conditions, making analysis and isolation challenging. To both control and utilize the reactivity of BTO to produce biobased building blocks, its reactivity needs to be better understood. Here it was found that specific BTO aromatic C-H bonds are reactive toward deuterium exchange with D2O, which appears pronounced under acidic conditions at room temperature and can lead to the selective formation of BTO with an aromatic ring that contains one or two deuterium atoms, the first at the five and the second at the three position. By exposure to air, it was shown that BTO forms a 5,5'-linked BTO dimer [1,1'-biphenyl]-2,2',4,4',5,5'-hexaol (1) and subsequently a hydroxyquinone containing dimeric structure 2',4,4',5'-tetrahydroxy-[1,1'-biphenyl]-2,5-dione (2). Additionally, condensed dimer dibenzo[b,d]furan-2,3,7,8-tetraol (3) can be relatively easily accessed. The controlled formation of these symmetric and asymmetric multifunctional dimers illustrates diverse possibilities for BTO to be converted to valuable biobased aromatic compounds. Deuterium exchange was attributed to electrophilic aromatic substitution because this reactivity was found to be independent of oxygen and acid mediated. On the contrary, the dimerization was dependent on the presence of oxygen and thus likely involves radical intermediates. Thus this report overall displays different accessible reaction pathways for BTO that can be exploited for the production of BTO-derived compounds.

There is no molecular strategy for selectively increasing the Seebeck coefficient without reducing the electrical conductivity for organic thermoelectrics. Here, it is reported that the use of amphipathic side chains in an n-type donor-acceptor copolymer can selectively increase the Seebeck coefficient and thus increase the power factor by a factor of approximate to 5. The amphipathic side chain contains an alkyl chain segment as a spacer between the polymer backbone and an ethylene glycol type chain segment. The use of this alkyl spacer does not only reduce the energetic disorder in the conjugated polymer film but can also properly control the dopant sites away from the backbone, which minimizes the adverse influence of counterions. As confirmed by kinetic Monte Carlo simulations with the host-dopant distance as the only variable, a reduced Coulombic interaction resulting from a larger host-dopant distance contributes to a higher Seebeck coefficient for a given electrical conductivity. Finally, an optimized power factor of 18 mu W m(-1) K-2 is achieved in the doped polymer film. This work provides a facile molecular strategy for selectively improving the Seebeck coefficient and opens up a new route for optimizing the dopant location toward realizing better n-type polymeric thermoelectrics. Funding Agencies|STW/NWOTechnologiestichting STWNetherlands Organization for Scientific Research (NWO) [VIDI 13476]; China Scholarship CouncilChina Scholarship Council; Center for Information Technology of the University of Groningen; Swedish Research CouncilSwedish Research Council [2016-03979]; Olle Engkvists Stiftelse [204-0256]; Advanced Functional Materials center at LiU [2009 00971]; King Abdullah University of Science and Technology (KAUST) Office of Sponsored Research (OSR) [OSR-CRG2018-3737]; NWO Exact and Natural Sciences [2020/ENW/00852342]

Organic electronics have a wide range of applications, from utilizing the solar energy for electricity generation to devices that seamlessly integrate with biological surfaces. The virtually unlimited chemical space of organic molecules, while offering the possibility of ideal molecules for each of these applications, also makes it more challenging to find them. A common approach to navigating through this vast chemical space towards better performing devices is identifying design rules by correlating changes in molecular or morphological structure to the improvement of specific properties. Functionalizing organic molecules with polar side chains is one such design rule that has become a ubiquitous strategy in the search for the next generation organic materials. This thesis elucidates, by advancing and applying computational methods, what happens at the molecular level by the inclusion of polar side chains and provides a deeper understanding of the interplay between molecular structure and dielectric and electronic properties, with the aim of guiding the field towards engineering better performing devices. A strong emphasis is given to both the accurate computation of the dielectric constant and the understanding of the relevant dielectric contributions for organic electronics. Additionally, the computational method introduced in this thesis, which is readily applicable in various materials science and biophysics studies, allows approaching quantum mechanical accuracy using computationally much more feasible molecular dynamics simulations. Overall, the findings of this thesis contribute to the goal of materials design based on computational approaches by improving existing models as well as the understanding of several property-structure relationships.

The low efficiency of organic photovoltaic (OPV) devices has often been attributed to the strong Coulombic interactions between the electron and hole, impeding the charge separation process. Recently, it has been argued that by increasing the dielectric constant of materials used in OPVs, this strong interaction could be screened. In this work, we report the application of periodic density functional theory together with the coupled perturbed Kohn Sham method to calculate the electronic contribution to the dielectric constant for fullerene C-60 derivatives, a ubiquitous class of molecules in the field of OPVs. The results show good agreement with experimental data when available and also reveal an important undesirable outcome when manipulating the side chain to maximize the static dielectric constant: in all cases, the electronic contribution to the dielectric constant decreases as the side chain increases in size. This information should encourage both theoreticians and experimentalists to further investigate the relevance of contributions to the dielectric constant from slower processes like vibrations and dipolar reorientations for facilitating the charge separation, because electronically, enlarging the side chain of conventional fullerene derivatives only lowers the dielectric constant, and consequently, their electronic dielectric constant is upper bound by the one of C-60.

Quantum mechanical calculations (QMC) and dissipative particle dynamics (DPD) simulations were utilized to understand the nature of the short and long-range hydrogen bonding and its influence on the microphase morphology in segmented polyurethanes and segmented polyureas prepared without chain extenders through the stoichiometric reactions of hydroxy or amine terminated poly(tetramethylene oxide) (PTMO-1000) with 1,4-phenylene diisocyanate (PPDI) and 1,3-phenylene diisocyanate (MPDI). The possibility of long-range connectivity due to a network of well-ordered hydrogen bonds between symmetrical PPDI and kinked MPDI based model urethane and urea compounds were also investigated. Special emphasis was given on the understanding of the influence of diisocyanate symmetry and nature of the hydrogen bonding between hard segments on the morphology development. QMC results obtained clearly indicated the possibility of long-range ordering of hydrogen bonds between PPDI based urethane and urea groups, while MPDI based systems did not display such a behavior. DPD results strongly supported the QMC studies and clearly demonstrated the possibility of long-range connectivity of hydrogen bonds between urethane and urea groups in PPDI based segmented copolymers, leading to the formation of microphase separated morphologies in these systems, which was not observed in the kinked MPDI based segmented urethane and urea copolymers. Computational results obtained strongly supported the experimental observations reported on the morphology and thermal and mechanical properties of these segmented polyurethanes and polyureas based on PPDI and MPDI.

Konut yapı kooperatiflerinde karşılıklı yardım, dayanışma ve kefalet asıl gaye olup, kâr elde etme amacı olmaması gerekir. Kooperatif ortaklarının gücünden istifade edilerek konut ihtiyaçlarının ucuz ve kolay temini asıl amacıdır. Bu nedenle, tüzel kişilik olarak faaliyeti, en üst yetkili organı olan genel kurulunu oluşturan üyelerinden, onlar tarafından belirlenen aidatı toplamak ve bunun karşılığında sadece ürettiği konutları, üyelerini konut sahibi yapmak amacıyla maliyet değeri ile onlara dağıtmak şeklinde bir faaliyet çerçevesi çizilebilir. Ancak, normal şartlarda konut edinmek genel kurul tarafından belirlenen aidatları toplamak, bu aidatlarla hisse sayısını karşılayacak konut üretimine yeter büyüklükte arsa alımı yapmak ve üzerine konut inşa etmek suretiyle üyelerinin konut ihtiyacını gerçekleştirme olması gereken kooperatiflerin, -İhtiyaç fazlası arsa almak ve hisse sayısından fazla konut karşılığı, başka bir kooperatife veya müteahhide daire karşılığı vermek suretiyle, hisse sayısından fazla konut sahibi olmak, -Başka bir kooperatifin veya şahsın Arsasını, müteahhit sıfatı ile Daire Karşılığı almak ve üye sayısı fazlası konut üretimi yapmak, -İhtiyaç fazlası arsa almak ve üye sayısından fazla konut inşa etmek, suretiyle, hisse sayısını aşan konut sahibi olmak ve bu konutları, Vergi muafiyetinden yararlanma anlamında Genel kurul kararı ile, üye kaydetmek veya üye kaydetmeksizin Yap-Say şeklinde tanımlanacak türden faaliyet içerisine girdikleri görülmektedir. Yargı kararları ile şartlı ortaklık olarak tanımlanmakta olan bu uygulamalar, a)Yönetim ve Genel Kurul kararı ile üye kaydetmeksizin satış(Yap-Sat) şeklinde olması yanı sıra, b)Yönetim Kurulu Kararı ile üye kaydetmek suretiyle satış, c)Genel kurul kararı ile üye kaydetmek suretiyle satış, şeklinde gerçekleşmektedir. Konut Yapı Kooperatiflerinin bu tür faaliyetlerinin yoğunlaşması neticesinde, ticari yönden haksız rekabet ve Vergi Kanunları yönünden kayıt dışı şeklinde tanımlanabilecek bu faaliyetin vergilenmesi yönünden, mali raporlarına nasıl yansıması gerektiği ve kooperatifin karşılaşabileceği ekonomik külfetin hesaplanmasının nasıl yapılacağı hususunda, mevcut yargı kararlarının uygulama şekilleri ile önerilen muhasebe kayıt uygulaması yönünde çalışma yapılmıştır.Anahtar Kelimeler : ġartlı ortaklık, konut, yapı, belge As it has been increased recently, Housing Construction Cooperatives selling residences without registering members in the way called `build & sell`, Corporate Tax Law (law no. 5520 came into force on 01/06/2006) ground says that, `It is principal that, members‟ jobs and their needs for subsist is providing by mutual contribution and cooperation of members`. Regarding that principle, today, for preventing the commercial activities‟ taxation staying out of the scope, the dispensation provided to cooperation has been limited. For this reason, they loose the dispensation conditions by violating both clauses; either with board decision or general assembly decision, in the both situation, both it is not count as beside partner transaction `acquiring residence or commercial for each share by flat for land`, and the clause `making business only with partners`. These implementations which are defined by jurisdiction decisions as conditional partnership are implementing with board or general assembly decisions and bringing different judicial conclusions with the following circumstances: a)Sales without registering members with board or general assembly decisions, b)Sales with registering members with board decision, c)Sales with registering members with general assembly decision. If it is sold with registering members with board decision; it is accepted that, restitution is just possible by implementing the principle of compensating justice and it is calculating by taking arithmetic mean of payments value from the first payment day until the lawsuit, taken into account the variables can effect the inflation rate like exchange rates, changes in the officer and worker wages etc. If it is sold with registering members with general assembly decision; it is accepted that, it has to be calculated that the partner has to derive a profit as much as provided by the rate proportioning the residence‟s current value and the current value of payments made by the partner who makes normal payment to defendant cooperative and the current value of residence made by that partner. Explaining of the basing method and reasons with cases and discussing with regard of account records are constituting the subject of this master thesis.Key Words : Conditional partnership, housing, construction, document 149