Saccharide Recognition by Oligo( meta-ethynylpyridine)s in Protic Media

1Introduction Previously, we have reported tris(ethynylpyridine) macrocycles as synthetic receptors for ribofuranosides, deoxyribofuranosides, and glucopyranosides[1]. The hydrogen-bonding skeletons of the macrocycles consisted of "meta"-tethered ethynylpyridine trimers. If the ethynylpyridine unit is polymerized, the resulting oligo- and poly(meta-ethynylpyridine) s would adopt unfolded, somewhat zigzag conformations because each pyridine nitrogen is mainly located on opposite sides of the ethynediyl bonds to cancel the dipoles. When the polymer meets with a saccharide, its pseudolinear conformation may be guided to a well-ordered helical structure in order that the nitrogen atoms of the pyridine rings inwardly interact with peripheral saccharide-OH groups in a manner similar to those of the macrocycles (Fig. 1). Thus, the chirality of saccharides added can be transferred to the helical sense of the polymer, depending on the stereochemistry of the saccharides.     

Translocation of polymer through nanopore: dissipative particle dynamics simulation

Dissipative particle dynamics simulations are performed to study the forced translocation of polymer through a nanopore inside which the polymer experiences a driving force F. Hydrodynamic interaction （HI） is taken into account for the polymer in good solvent. We find that the mean translocation time 〈t〉 scales with the polymer length N as 〈t〉 ~ N^a with α = 1.26 ± 0.03 close to a theoretical pre- diction, and the probability distribution of t can be described by a Gaussian function. Our results show that the dynamics of polymer translocation with the HI is different from that without the HI. However, the exponent 6 in the scaling 〈t〉 ~ F^-δ is found not to be affected by the HI effect.     

Efficiency Improvement of Heterojunction Polymer Photovoltaic Cells through Controlling the Morphology of the Polymer Film

1 Results Polymer photovoltaic cells, which provide clean and renewable energy sources, have gained more and more attention. Polymer photovoltaic cells have the advantage of low fabrication cost and high mechanical flexibility. Polymers can be processed through a solution process, so that a homogeneous polymer film could be readily prepared in a large area. Recently, the light-to-electricity conversion efficiency of the polymer photovoltaic cells was improved significantly[1-2]. Polymer donor and organic acceptor are the two components in the active layer of the polymer photovoltaic cells. The photovoltaic performance is strongly dependent on morphology of the polymer donor/organic acceptor film. The dependences of the film morphology and the device performance on the temperature, solvent and ratio of the polymer donor to acceptor will be reported. Baking of the polymer film at a high temperature significantly affects the absorption and the morphology of the polymer film, which is account for the effect of baking polymer film on the photovoltaic performance. Similar effect on the polymer film morphology and absorption can be achieved by adding small amount of organic molecule into the polymer solution. The photovoltaic performance is related to the structure of the additives.     

Study on the HPHT synthetic diamond crystal from Fe-C（H） system and its significance

Investigations of crystal habit, micro-topographic imaging, micro-composition and micro-structural analysis of HPHT synthetic diamonds from the Fe-C（H） system indicate that most of them have an octahedral habit. The crystals grow mainly layer-to-layer from center to periphery. HPHT synthetic diamond is smaller in size than natural diamond because it only goes through nucleation and growth in the early stage. In the middle and late stages, due to the coalescence of diamond grains related to differences of surface energy, the growth of HPHT synthetic diamond is limited. The active energy （E） of transforming single nitrogen into a nitrogen-pair is lowered and the time of transforming single nitrogen into a nitrOgen-pair is shortened because of the existence of hydrogen. Therefore, aggregate nitrogen （A-centers） may exist in synthetic diamond from HPHT and explosive detonation processes. It needs further discussion on a worldwide view that the time of natural diamond formation extracted from nitrogen aggregation is some hundred million years. Consideration of the way in which surface energy influences the growth of diamond can help to understand some of the remaining issues （e.g. growth mechanism, etc.） in the HPHT synthetic process and effectively explain the formation of natural diamond in terms of HPHT thermodynamic theory. Especially, it is important to pay more attention to the influence of hydrogen on surface energy in that hydrogen may be a ＂bridge＂ for explaining the formation of HPHT synthetic and natural diamond.     

A novel high-sensitivity pressure sensor: Thinned fiber Bragg grating with pressure-sensing polymer

Based on thinned fiber Bragg grating and polymer material, we propose a novel high-sensitivity pressure sensor and obtained a new contribution to the pressure sensitivity, which is dependent on the derivative of the effective refractive index (RI) of core mode with respect to the surrounding medium RI, as well as on the relationship between the polymer RI and the pressure; moreover, it is inversely proportional to Young’s modulus of the polymer material. For the polymer with Young’s modulus of 1.0 MPa, the total pressure sensitivity 1.54×10-2 MPa-1 can be obtained.     

Molecular dynamics simulation of a single polymer in hydrophilic nano-slits

The behavior of a single polyethylene polymer in aqueous solution confined between two hydrophilic walls is studied with molecular dynamics （MD） simulations. The thickness of the nano-slit ranges from 1.26 to 3.15 nm, which is comparative to the polymer dimension. A monotonic transition from 3D- to 2D-like configurations is observed as the distance between the two walls narrows. Monomers are compressed into several layers and the preferred bond orientations alternate between parallel and normal to the walls accordingly. The diffusivity in the direction parallel to the wall is always larger than the one perpendicular to it. Calculation of the entropy and enthalpy changes during the folding of the polymer chain alone cannot explain the spontaneous process. The corresponding increase in water entropy due to volume expansion may be large enough to result in the overall free energy decrease.     

Towards larger spatiotemporal scales in polymer simulations

Molecular dynamics simulations are useful tools to unveil molecular mechanisms of polymer phase separation,self-assembly,adsorption,and so on.Due to large molecular size and slow relaxation of the polymer chains,a great amount of issues related to large-distance chain displacement cannot be tackled easily with conventional molecular dynamic simulations.Systematic coarse-graining and enhanced sampling methods are two types of improvements that can boost spatiotemporal scales in polymer simulations.We present two typical ways to obtain the coarse-graining potential either by fitting to correct liquid structures or by fitting to available thermodynamic properties of polymer systems.The newly proposed anisotropic coarse-grained particle model can be used to describe aggregation and assembly of polymeric building blocks from disk-like micelles to Janus particles.We also present a stochastic polymerization model combined with coarse-grained simulations to investigate the problems strongly influenced by the coupling of polymerization and excluded volume effects.Finally,a facile implementation of integrated tempering sampling method is illustrated to be very efficient on bypassing local energy minima and having access to true equilibrium polymer structures.     

Fabrication and Properties of Porous Film/Fabric Composites for Vascular Scaffold Application

A composite vascular scaffold combining textile reinforced structure and biodegradable polymer is introduced, which may possess high porosity and connectivity. Moreover, the porous size could be controlled. The proposed scaffold consists of a warp-knitted poly （ethylene terephthalate ） （PET） fabric with well-defined macropores, which is embedded with a porous biodegradable polymer membrane. The aim of this paper is to study the fabrication and properties of porous polymer membrane through optimizing the parameter of composite methods from freeze drying/particle leaching （ FD/PL ） and gas foaming/particle leaching （ GF/PL ）, subsequently combining with the warp-knitted fabric. Weighing method was utilized to analyze the porosity of the samples and the scanning electron microscope （SEM） images were taken to observe the porous structure of the vascular membrane. In addition, ,the static contact angle （CA） was measured to estimate the hydrophilicity of the samples, and the tensile testing of the composites was performed on the universal mechanical tester. Furthermore, the water permeability of the membrane was also calculated. The results showed that the porosity and pore connectivity of the vascular membrane were diverse, became of solution concentration, particle size, ratio of content, etc. Meanwhile, the stress-strain curves and the bursting strength showed the different mechanical properties among composite scaffolds in different structures.     

Effects of Polyethylene Oxide Concentration on the Size of Beads in Electrospun Beaded Nanofibers

Embedding particle drugs in beaded nanofibers by electrospinning has been shown a potential approach to control drug release in tissue engineering. The bead size is one of the critical parameters in controlling the drug release rate. In this study,the relationship between polymer concentration and beads size was investigated. Aqueous polyethylene oxide（ PEO） solutions with different concentrations were prepared to obtain various beaded nanofibers by electrospnning. Optical microscope and scanning electron microscope（ SEM） were used to observe the variation tendency of bead size. With an increase in the polymer concentration,the diameter of fibers between beads became bigger,while the fiber uniformity improved. In addition, the polymer concentration influenced the distribution of bead diameter. Higher polymer concentration would reduce the possibility of small-sized beads formation and improve the uniformity of bead diameter. The study provides a possible way to control the size of beads,which is helpful for further research on the control of particle drug release.     

Effect of nitrogen introduction methods on the microstructure and properties of gradient cemented carbides

Gradient cemented carbides with the surface depleted in cubic phases were prepared following normal powder metallurgical procedures. Gradient zone formation and the influence of nitrogen introduction methods on the microstructure and performance of the alloys were investigated. The results show that the simple one-step vacuum sintering technique is doable for producing gradient cemented carbides. Gradient structure formation is attributed to the gradient in nitrogen activity during sintering, but is independent from nitrogen introduced methods. A uniform carbon distribution is found throughout the materials. Moreover, the transverse rupture strength of the cemented carbides can be increased by a gradient layer. Different nitrogen carriers give the alloys distinguishing microstructure and mechanical properties, and a gradient alloy with ultrafine-TiC_0.5N_0.5 is found optimal.     

Solvent-assisted polymer micro-molding

The micro-molding technology has played an important role in fabrication of polymer micro-patterns and development of functional devices. In such a process, suitable solvent can swell or dissolve the polymer films to decrease their glass transition temperature （Tg） and viscosity and thereby improve flowing ability. Consequently, it is easy to obtain the 2D and 3D patterns with high fidelity by the solvent-assisted micro-molding. Compared with the high temperature molding, this technology overcomes some shortcomings such as shrinking after cooling, degradation at high temperature, difficulty in processing some functional materials having high Tg, etc. It can be applied to making patterns not only on polymer monolayers but also on polyelectrolyte multilayers. Moreover, the compressioninduced patterns on the multilayers are chemically homogenous but physically heterogeneous. In this review, the controlling factors on the pattern quality are also discussed, including materials of the mold, solvent, pressure, temperature and pattern density.     

The Effect of Initiator on Acrylate Emulsion Copolymerization Containing Hydroxyl Groups

Emulsion polymerization has become the important method to obtain polymer. A typical emulsion polymerization recipe comprises of monomer, emulsifier, initiator and other necessary ingredient. Among the recipe component the initiator takes up an exceptional position for a number of reasons： （1） determine the reaction temperature; （2） Influence polymer properties and end-use; （3） Cause some effect on particle morphology. Klaus etc. described the role of initiator in emulsion polymerization, and studied the influence of initiator on polymer properties taken styrene as example. Mukul etc. studied the kinetic of emulsion copolymerization of methylmethacrylate and ethylacrylate. The aim of this paper is to investigate the effect of initiator on the acrylate emulsion copolymerization with hydrophilic monomer （hydroxylethyl methacrylate, HEMA）.     

Polymer Photovoltaic Cells

Polymer photovoltaic cells （PPVCs） have attracted much attention recently because of its easy fabrication, low cost and possibility to make flexible devices. PPVC is composed of a conjugated polymer/C60 blend layer （photosensitive layer） sandwiched between a transparent ITO electrode and a metal electrode. When a light through ITO electrode irradiates on the photosensitive layer, the photons with appropriate energy will be absorbed by the conjugated polymer （CP） and excitons （electron-hole pair） are produced. The excitons move to the interface of CP/60 where the electrons transfer to the LUMO of C60 and holes leave on the HOMO of the CP. The separated electrons migrate through the C60 network to and are collected by the metal electrode, and the holes migrate through the CP network to and are collected by the ITO electrode, so that the photocurrent and photovoltage are attained.     

The Origin of Traditional Chinese Medicine and Thinking on Chinese Medicine Development

Although the traditional Chinese medicine （TCM） has developed a profound theory system and a fame of outstanding advantage in curative effect, it seems that the TCM is not quite adaptable to the deveiopment and requirement of the modern society. A principle of ＂Adopting the advanced part of Western medicine to serve the TCM＂ should be adhered to for the traditional Chinese medicine. First, TCM should strive for a consensus of TCM theory which focuses on the guiding principles of ＂diagnosis and treatment based on an overall analysis of the illness and the patient＇ s condition＂and ＂the opposite principle of five internal organs＂. Among these principles, ＂keeping relative balance of three internal systems＂is a valuable guidance of the diagnosis and treatment theory. Secondly, macroscopic should be integrated with microscopic, totality with parts, phenomenology with materialism. A dialectical law should be applied to guide analysis. In treatment, adjustment and balance are basic principles. It is necessary not only prepare the medicine in advance accoding to the predicted disease of the year, but also adopt methods to restrict disease in advance. Basides, TCM dose type should be ameliorated in order to meet the needs of society.     

Advanced Polymer Electrolytes for Highenergy-density Power Sources

The preparation of highly controlled thin films of lithium ion conducting organic materials is becoming a challenging but rewarding goal in view of obtaining high-performance technological devices like solid-state polymer batteries and capacitors. The classical polymer electrolyte consists of organic macromolecules （usually polyether polymer） that are doped with inorganic （typically lithium） salts. Poly（ethylene oxide） （PEO） is the most commonly employed polymer in PEs because of the peculiar array in the, （-CH2-CH2-O-）n chain providing the ability to solvate low-lattice-energy lithium salts.     

LLDPE/TiO2 nanocomposites produced from different crystallite sizes of TiO2 via in situ polymerization

Nano-TiO2 particles with a range of crystallite sizes were synthesized by a conventional sol-gel method,and then used as nanoparticle substrates in the synthesis of LLDPE/TiO2 nanocomposites via in situ polymerization of ethylene/1-hexene with zirconocene/MMAO catalyst.It was found that the size of the nano-TiO2 crystallite nanoparticles can influence the catalytic activity in the polymerization system.The larger nano-TiO2 crystallites provided better catalytic activity in the polymerization system due to more space for monomer attack.In addition,by thermo-gravimetric analysis,it can be seen that the larger nano-TiO2 crystallites also exhibited lower interaction with available MMAO.Consequently,the MMAO reacted more efficiently with the zirconocene catalyst during the activation process,and enhanced polymerization catalysis.All the polymer nanocomposites products did not have well defined melting temperature indicating non-crystalline polymers.This is due to the high amount of hexene incorporation(based on 13C NMR).The difference in crystallite sizes of the nano-TiO2 also affected how 1-hexene became incorporated into the polymer nanocomposites.The smaller crystallite size of nano-TiO2 allowed greater 1-hexene incorporation due to depression of the reactivity of the ethylene.The contribution of this work helps develop a better understanding of the role of nano-TiO2 in the catalytic activity of the polymerization system and in the microstructure of the polymer composite product.However,this study only considers work on the laboratory scale,so for commercial application of these results,it is necessary to scale up the polymerization process.It is only at this stage,that other physical properties,such as the mechanical properties of these materials can be sensibly determined.     

Enzyme-Mediated Hydrolysis of Poly（ethylene glycol）-Supported Carbonates

Enzymatic kinetic resolution of racemic alcohols or esters is known as a useful method for the preparation of optically active secondary alcohols. However, the work-up including the separation of the mixture of the remaining substrate and the resulting compound spend a lot of time and waste much amount of solvents. On the other hand, organic synthesis based on polymer supports has made rapid progress. Although the methodology is potentially useful for the easy separation of compounds obtained by the enzymatic reaction, there have been relatively few reports on enzymatic resolutions of using a polymer so far. We have noticed that using a watersoluble polymer could be suitable for enzymatic transformation. Here, we report the first example of an enzyme-mediated enantioseleetive hydrolysis of poly（ethylene glycol）（PEG）-supported substrates with a carbonate moiety to afford optically active compounds, and the method enables us to achieve the easy separation of the products. See Scheme 1.     

Micro-friction of diazoresin/polyacrylic acid self-assembly films in water with atomic force microscopy

Ultrathin films composed of diazoresin（DR）and polyacrylic acid（PAA）were fabricated.The surface morphology of the films in water was measured using an atomic force microscopy（AFM）.The self-assembly technique makes the surface rather flat and uniform.The friction force and its dependence on the velocity differ from the surface charge of the thin films.The friction force of repulsive DR/PAA film increases linearly with velocity and has lower values than that of attractive DR film over the full range of velocity.As the velocity increases,the attractive friction of DR film first decreases to a minimum at a velocity of 2 line/s and then increases all the way.When the surface is repulsive to the friction substrate,the friction of thin films that is determined by hydrated lubrication of polymer chains that is ultralubricated;when it is adhesive to the friction substrate,the friction is mainly contributed from the elastic deformation of adsorbed polymer chains in the low velocity region and from viscous sliding in the presence of hydrated-layer lubrication of the polymer chains in the higher velocity region.     

Growth kinetics of cubic carbide free layers in graded cemented carbides

In order to reveal the formation mechanism of cubic carbide free layers (CCFL), graded cemented carbides with CCFL in the surface zone were fabricated by a one-step sintering procedure in vacuum, and the analysis on microstructure and element distribution were performed by scanning electron microscopy (SEM) and electron probe micro-analyzer (EPMA), respectively. A new physical model and kinetic equation were established based on experimental results. Being different from previous models, this model suggests that nitrogen diffusion outward is only considered as an induction factor, and the diffusion of titanium through liquid phase plays a dominative role. The driving force of diffusion is expressed as the differential value between nitrogen partial pressure and nitrogen equilibrium pressure essentially. Simulation results by the kinetic equation are in good agreement with experimental values, and the effect of process parameters on the growth kinetics of CCFL can also be explained reasonably by the current model.     

A nut-type ultrasonic motor and its application in the focus system

This article reports a screw-driven polyhedron linear ultrasonic motor （USM） of nut-type. It is comprised of a stator, which is a threaded metal nut bonded with piezoelectric plates on its external surface, and a rotor with external threads, which engage with the internal threads of the stator. A traveling wave in the plane is stimulated on the stator when harmonic electric signals are applied to the piezoelectric plates. The traveling wave drives the rotor to rotate, and the threads transform the rotation into a linear motion. The lens can be fixed in the rotor and realize the integrated design of the auto focus system. This structure can omit retarder and directly drive to obtain a high accuracy of positioning, and it is shockproof. A mini AF cellular phone module （8.5 mm×8.5 mm×5.9 mm） driven by this motor was made and an image resolution of 3-5 MP was obtained in the module prototypes of the cellular phone.