Capillary suspensions: Particle networks formed through the capillary force

The addition of small amounts of a secondary fluid to a suspension can, through the attractive capillary force, lead to particle bridging and network formation. The capillary bridging phenomenon can be used to stabilize particle suspensions and precisely tune their rheological properties. This effect can even occur when the secondary fluid wets the particles less well than the bulk fluid. These materials, so-called capillary suspensions, have been the subject of recent research studying the mechanism for network formation, the properties of these suspensions, and how the material properties can be modified. Recent work in colloidal clusters is summarized and the relationship to capillary suspensions is discussed. Capillary suspensions can also be used as a pathway for new material design and some of these applications are highlighted. Results obtained to date are summarized and central questions that remain to be answered are proposed in this review.     

Fluorinated networks through photopolymerisation processes: synthesis, characterisation and properties

The study concerns the UV curing of systems containing fluorinated products. New difunctional and monofunctional monomers and oligomers bearing either radical or cationic photopolymerisable functionalities were synthesised. They were UV cured and the properties of the films obtained were investigated. In some cases biphasic structures were obtained, showing the separation between the fluorinated and hydrogenated domains at nanometric level. By copolymerising a low amount of the fluorinated additive with hydrogenated resins, the bulk properties of the films were not changed, but a deep modification of the surface was obtained. In all cases a selective enrichment of the fluorinated monomer at the film surface was observed. The dependence of the surface properties on the monomer structure, on its concentration and on the type of substrate was studied.     

"In-house likeness": comparison of large compound collections using artificial neural networks

Binary classification models able to discriminate between data sets of compounds are useful tools in a range of applications from compound acquisition to library design. In this paper we investigate the ability of artificial neural networks to discriminate between compound collections from various sources aiming at developing an "in-house likeness" scoring scheme (i.e. in-house vs external compounds) for compound acquisition. Our analysis shows atom-type based Ghose-Crippen fingerprints in combination with artificial neural networks to be an efficient way to construct such filters. A simple measure of the chemical overlap between different compound collections can be derived using the output scores from the neural net models.     

Molecularly "engineered" anode adsorbates for probing OLED interfacial structure-charge injection/luminance relationships: large, structure-dependent effects

Molecule-scale structure effects at organic light-emitting diodes (OLED) anode-organic transport layer interfaces are probed via a self-assembly approach. A series of ITO anode-linked silyltriarylamine molecules differing in aryl group and linker density are synthesized for this purpose and used to probe the relationship between nanoscale interfacial chemical structure, charge injection and electroluminescence properties. Dramatic variations in hole injection magnitude and OLED performance can be correlated with the molecular structures and electrochemically derived heterogeneous electron-transfer rates of such triarylamine fragments, placed precisely at the anode-hole transport layer interface. Very bright and efficient ( approximately 70 000 cd/m2 and approximately 2.5% forward external quantum efficiency) OLEDs have thereby been fabricated.     

Covalent networks through on-surface chemistry in ultra-high vacuum: state-of-the-art and recent developments

The fabrication of large molecular devices, directly on surfaces in UHV conditions, by covalent coupling of smaller precursors has become in the past years an attractive solution for Molecular Electronics. This review presents the state-of-the-art and an analysis of the potential of this new field, from Ullmann type C-C coupling, cyclodehydrogenation, and reactions involving heteroelements to 2D polymerisation on insulating thin films. Mechanistic insights are also mentioned, giving preliminary explanations on the influence of the substrate and the 2D confinement. Potential perspectives for further developments are then evoked.     

Template-controlled topochemical photodimerization based on "organometallic macrocycles" through single-crystal to single-crystal transformation

Organometallic macrocycles and undergo [2+2] photochemical cycloaddition to form and in quantitative yield, accompanied by a single-crystal to single-crystal transformation.     

Thermal analysis of interpenetrating polymer networks through molecular dynamics simulations: a comparison with experiments

Journal of Thermal Analysis and Calorimetry - In this work, we verified the synthesis of a novel sequential interpenetrating polymer network, composed of poly(2-hexyl-ethylacrylate) and...     

The bulk-etch thickness for the formation of etched through tracks in CR-39 detectors as a tool for nuclear spectrometry: a computational study

The bulk-etch thickness which is removed from a single surface of CR-39 nuclear track detectors for the formation of etched through tracks has been calculated using various charged particles with ranges greater than the particle's trajectory in the detector. An attempt is made to explore the possibility of making use of the bulk-etch thickness at the moment of perforation for energy spectroscopy and particle identification. In the calculations track development kinetics were used for varying track etch rate ratio V. The value of V is determined for nuclei of Z≤26 and was found to be a function of the atomic number Z, the mass number A and the residual range of the nuclear particle. Also an empirical formula between the track length and the minor track diameter, the dip angle and the bulk-etch thickness is obtained. Present calculations show that the etched-off thickness from the detector surface at the moment of perforation of CR-39 depends upon REL and is also a function of Z/β of the nuclear particle. The obtained results have important applications in the fields of nuclear spectroscopy and the production of nuclear track filters.     

On searching in, sampling of, and dynamically moving through conformational space of biomolecular systems: A review

Methods to search for low-energy conformations, to generate a Boltzmann-weighted ensemble of configurations, or to generate classical-dynamical trajectories for molecular systems in the condensed liquid phase are briefly reviewed with an eye to application to biomolecular systems. After having chosen the degrees of freedom and method to generate molecular configurations, the efficiency of the search or sampling can be enhanced in various ways: (i) efficient calculation of the energy function and forces, (ii) application of a plethora of search enhancement techniques, (iii) use of a biasing potential energy term, and (iv) guiding the sampling using a reaction or transition pathway. The overview of the available methods should help the reader to choose the combination that is most suitable for the biomolecular system, degrees of freedom, interaction function, and molecular or thermodynamic properties of interest.     

Shedding light on helical microtubules: real-time observations of microtubule self-assembly by light microscopy

Helical tubules are a fascinating and an intriguing class of self-assemblies. They occur frequently in biology and are believed to be intermediates in formation of gallstones. The pathway by which amphiphiles transform from an initial state of vesicles or micelles into such tubules has puzzled soft matter physicists, and it has raised important questions about the interplay between molecular chirality and self-assembly. Here, for the first time, we demonstrate direct, real-time observations by light microscopy of the pathway to helical microtubules from an initial solution of nanoscale vesicles. The tubules are formed in aqueous mixtures of the single-tailed diacetylenic surfactant, 10,12-pentacosadiynoic acid (PCDA), and a short-chain alcohol. The stepwise process involves nucleation of thin helical microribbons from the vesicle solution. These ribbons then thicken, rearrange, and fold into closed tubules. Subsequently, most tubules further rearrange into plate-like structures, and once again, we are able to visualize this process in real time. A notable aspect of the above system is that the precursors are achiral; yet, the tubules are formed from helical ribbons. Our study provides new insights into tubule formation that will be valuable in clarifying and refining theoretical models for these fascinating structures.     

Carbon networks based on dehydrobenzoannulenes. 4. Synthesis of "star" and "trefoil" graphdiyne substructures via sixfold cross-coupling of hexaiodobenzene

The synthesis and characterization of star- and trefoil-shaped polyethynyl aromatic structures, which represent model substructures of the all-carbon network graphdiyne, are described. Assembly of these macrocycles is accomplished via 6-fold Sonogashira cross-coupling of hexaiodobenzene using Pd[P(o-Tol)(3)](2) and CuI as the catalytic system. The development of these modified Sonogashira conditions is detailed. This work has led to the synthesis of a new family of hexakis(phenylbutadiynyl)benzene derivatives (4a-c), the largest of which is the D(3)(h)()-symmetric "trefoil" 2 and is composed of three [18]annulenes fused at a common benzene ring. Attempts at the synthesis of "wheel" 3 are also described. Compound 2 represents the largest fragment of the graphdiyne network to date. UV-vis spectroscopic studies indicate enhanced electron delocalization throughout the extended pi-system.     

Practical aspects of computational chemistry calculations through PC networks: the RAMSES–Beowulf implementation

We have built clusters of PC using up to 320 processors in parallel. The first cluster was built in 1996 from 64 computers. The parallel architectures are named RAMSES. In this article, we share our experience and discuss our choices. The architecture is composed of Pentium processors connected by a 100 Mbits/s Ethernet network. Because RAMSES are built of independent computers, the system is easily maintained, and can be modified by adding or removing machines. Two programs, which are dedicated to molecular modeling and were previously developed on single machines (OSIRIS and IMPALA), have been adapted. IMPALA models peptide and protein interaction with membranes, OSIRIS simulates an ab initio folding of globular proteins. After parallelization, each program consists of two parts: one is the human/RAMSES interface, and the second is the simulation per se. The parallel architecture is transparent for the users. Tests of the IMPALA and OSIRIS efficiencies are shown and discussed. © 2000 John Wiley & Sons, Inc. J Comput Chem 22: 172–177, 2001     

Structural diversity through ligand flexibility: two novel metal-organic nets via ligand-to-ligand cross-linking of "paddlewheels"

Solvothermal reaction of a partially flexible ligand, H(4)L, and Cu(NO(3))(2)·2.5H(2)O afforded two cross-linked Kagomé lattices of formula [Cu(2)(L)](n): an acs net sustained by novel trigonal prismatic supermolecular building blocks (SBBs) and the first example of a partially pillared Kagomé net.     

通过实验教学加深对理论知识的理解——以“气相色谱实验”教学为例

仪器分析是化学专业学生的必修课,其中涉及的基本概念原理比较抽象、难以理解。将理论知识与实验教学相结合可加深学生对理论知识的理解。本文以气相色谱实验为例,通过研究实验条件如柱温、载气流量、进样量以及毛细管气相色谱分流比对分离度的影响,帮助学生理解书本知识,同时也培养了学生科研思维以及分析问题、解决问题的能力。     

"Biologic" level structures through chemistry: A total synthesis of a unimolecular pentavalent MUCI glycopeptide construct

A convergent synthesis of a unimolecular pentavalent-MUC1 glycopeptide has been accomplished. A tandem repeat of unglycosylated human tumor-associated MUC1, a potential target for cancer immunotherapy, was incorporated into the known unimolecular pentavalent carbohydrate construct (5). This is an important step toward the development of a new fully synthetic anticancer vaccine candidate (1).     

Ensembles of engineered cardiac tissues for physiological and pharmacological study: heart on a chip

Traditionally, muscle physiology experiments require multiple tissue samples to obtain morphometric, electrophysiological, and contractility data. Furthermore, these experiments are commonly completed one at a time on cover slips of single cells, isotropic monolayers, or in isolated muscle strips. In all of these cases, variability of the samples hinders quantitative comparisons among experimental groups. Here, we report the design of a "heart on a chip" that exploits muscular thin film technology--biohybrid constructs of an engineered, anisotropic ventricular myocardium on an elastomeric thin film--to measure contractility, combined with a quantification of action potential propagation, and cytoskeletal architecture in multiple tissues in the same experiment. We report techniques for real-time data collection and analysis during pharmacological intervention. The chip is an efficient means of measuring structure-function relationships in constructs that replicate the hierarchical tissue architectures of laminar cardiac muscle.     

Tailoring heterogeneous polymer networks through polymerization‐induced phase separation: influence of composition and processing conditions on reaction kinetics and optical properties

Polymerization‐induced phase separation from an all‐monomeric system by direct copolymerization offers the formation of heterogeneous polymeric structures without reliance on polymer blends, block copolymers, or interpenetrating polymer networks. This study examines the potential for the formation of compositional heterogeneity in copolymer networks obtained by free‐radical photopolymerizations of initially homogeneous mixtures of bisphenol A glycidyl dimethacrylate and isodecyl methacrylate as the comonomer ratios and polymerization conditions are varied. Comonomer proportions that control thermodynamic stability prior to (as determined by cloud point measurements) and during [as determined by turbidity measurements coupled with near‐infrared (IR) spectroscopy] polymerization were shown to be a more influential factor on phase separation than irradiance‐imposed kinetic control of the photopolymerization process. Through photorheometry coupled with near‐IR and ultraviolet–visible (UV–Vis), the onset of phase separation was shown to occur at very low conversions and always prior to gelation (as estimated by the crossover of G′/G″). © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1796–1806     

Intermolecular interactions of substituted benzenes on multi-walled carbon nanotubes grafted on HPLC silica microspheres and interaction study through artificial neural networks

Purified multi-walled carbon nanotubes (MWCNTs) grafted onto silica microspheres by gamma-radiation were applied as a HPLC stationary phase for investigating the intermolecular interactions between MWCNTs and substituted benzenes. The synthetic route, simple and not requiring CNTs derivatization, involved no alteration of the nanotube original morphology and physical–chemical properties. The affinity of a set of substituted benzenes for the MWCNTs was studied by correlating the capacity factor (k′) of each probe to its physico-chemical characteristics (calculated by Density Functional Theory). The correlation was found through a theoretical approach based on feedforward neural networks. This strategy was adopted because today these calculations are easily affordable for small molecules (like the analytes), and many critical parameters needed are not known. This might increase the applicability of the proposed method to other cases of study. Moreover, it was seen that the normal linear fit does not provide a good model. The interaction on the MWCNT phase was compared to that of an octadecyl (C18) reversed phase, under the same elution conditions. Results from trained neural networks indicated that the main role in the interactions between the analytes and the stationary phases is due to dipole moment, polarizability and LUMO energy. As expected for the C18 stationary phase correlation, is due to dipole moment and polarizability, while for the MWCNT stationary phase primarily to LUMO energy followed by polarizability, evidence for a specific interaction between MWCNTs and analytes. The CNT-based hybrid material proved to be not only a chromatographic phase but also a useful tool to investigate the MWCNT-molecular interactions with variously substituted benzenes.     

Crystallization on confined engineered surfaces: a method to control crystal size and generate different polymorphs

Patterned glycine crystals nucleated on functionalized metallic square islands. This approach can be used to fabricate particles with micron dimensions and screen solid forms under different conditions. The size of the glycine crystals is controlled by the dimensions of the islands. High energy metastable beta-glycine crystallizes on small metallic islands, whereas for large islands, the polymorphic outcome becomes biased toward the alpha-form.     

Polyurethane/polystyrene one-shot interpenetrating polymer networks with good damping ability: Transition broadening through crosslinking,internetwork grafting and compatibilization

Good damping materials should exhibit a high loss factor value over a broad temperature range. Polyurethane and polystyrene are highly immiscible polymers with glass transition regions far apart. The interpenetrating polymer network topology can restrict phase separation and result in materials with a broad transition region. Simultaneous polyurethane/polystyrene interpenetrating polymer networks were synthesized by the one-shot route. Different methods of improving the miscibility of the two polymers were investigated. These included the vanation of the crosslink level in both polymer networks, the controlled introduction of internetwork grafting and the incorporation of compatibilizers into the polystyrene network. Dynamic mechanical thermal analysis indicated that the latter two were successful in achieving a compatibilization of the polymer components. With some materials, a high, broad transition region exhibiting a loss factor > 0.3 over more than 135°C was obtained. The morphology observed via transmission electron microscopy ranged from macrophase separated materials in the lightly crosslinked IPNs to a fine, microheterogeneous morphology in the grafted ones. Modulated differential scanning calorimetry measurements confirmed the trend of the glass transition locations observed with dynamic mechanical thermal analysis.