Synthesis of polyurethanes by polyaddition using diol compounds with methacrylate-derived functional groups

To functionalize polyurethane, a novel synthetic reaction of diol compounds derived from methacrylates with various functional groups was investigated. The methacrylates were reacted with α-thioglycerol via a Michael-type addition to obtain the corresponding diol compounds under mild conditions. In this reaction, diisopropylamine was a much better catalyst than triethylamine. The conversion was dependent on the functional group in the methacrylate. The fluoroalkyl group in 2,2,2-trifluoroethyl methacrylate was better than the alkyl group in butyl methacrylate. No reaction was observed in the case of styrene. Using these diol compounds, polyurethanes were prepared by polyaddition with 4,4-diphenylmethane diisocyanate. When the polyurethanes were casted on the substrate, the functional groups influenced surface hydrophilicity and protein adsorption resistance property of the polyurethane significantly. In particular, phosphorylcholine group was the best to reduced protein adsorption. Based on these findings, the variety of these diol compounds synthesized from methacrylates has the potential for use in the production of novel polyurethanes.     

氟气氟化含氢氟聚醚制备双端官能团全氟聚醚

以含氢氟聚醚（E10H）为原料，利用氟氮混合气进行氟化制备了双端羟基全氟聚醚（F-E10H-AL），分别探索了常温氟化、低温氟化及先低温后常温氟化的3种氟化工艺。然后与双三氟甲烷磺酸亚胺锂（LiTFSI）制备成锂离子电解质。采用红外光谱、核磁氢谱和氟谱分析氟化后的产物结构，并采用电化学工作站测试了阻抗和计时电流。结果表明，低温氟化工艺具有较高的氟化效率，在-10℃对E10H直接氟化12h后，分子链上有21.0%的H被F取代，但是产生较多的封端基团CF3O-。当利用六氟环氧丙烷二聚体酯化保护E10H上的羟基时，采用先低温后常温氟化工艺，分子链上有48.3%的H被F取代。最后将氟化产物还原，得到F-E10H-AL，分子链末端基本没有CF3O-，含量为0.7%。结合阻抗和计时电流的数据，计算出F-E10H-AL/LiTFSI的离子迁移数为0.32，高于PFPE-OH/LiTFSI（0.07）。     

Theory of chromatography of linear and cyclic polymers with functional groups

We discuss the chromatographic behavior of linear polymers and rings having specific (functional) adsorption-active groups. Functionalized eight-shaped, daisy-like and theta-shaped macromolecules are considered as well. By using a model of an ideal chain with point-type defects in a slit-like pore we derive equations for the distribution coefficient covering all modes of chromatography of functionalized polymers of any molar mass in both narrow and wide pores. Additionally simple approximate formulae are obtained for a number of important modes of chromatography; chromatograms are simulated for model mixtures of polydisperse non-functional and functional polymers. By using the theory we analyze separation of polymers by molar mass, functionality and topology. Although there is a principal possibility to use adsorption chromatography or size-exclusion chromatography (SEC), we conclude that the liquid chromatography at the critical condition (LCCC) is especially efficient for separation of polydisperse polymers by both functionality and topology. The theory predicts that functionalized linear and cyclic polymers can be separated from each others by LCCC even better than non-functionalized ones. The LCCC behavior of some other types of polymers such as comb-like and semicyclic ones is discussed as well.     

Investigation of hygroscopic properties in electronic packages using molecular dynamics simulation

Moisture-induced package failures such as interfacial delamination and pop-corn cracking are common failure phenomena that occur during the solder reflow process in the semiconductor industry. Therefore, the hygroscopic properties of the package materials are crucial factors in the reliability of electronic packaging products. In this work, molecular dynamics (MD) simulation was performed to study the hygroscopic properties, including diffusivity and swelling strain, of epoxy materials with respect to temperature and moisture concentration. Hygroscopic material properties predicted by MD are discussed and compared with the experimental data.     

Computer simulation of diffusion within and through membranes using nonequilibrium molecular dynamics

A novel nonequilibrium molecular dynamics (NEMD) method introduced in 1994 and its recent application to investigations of the transport properties of gases and dense fluids within strongly inhomogeneous pore structures are reviewed. In this technique molecular simulations are conducted under realistic nonequilibrium (experimental) conditions thus enabling direct insight into the underlying microscopic processes taking place during transport within pores. The case studies reviewed in this paper establish the versatility and scope of the NEMD technique and also demonstrate its significant advantages over prior molecular simulation procedures as a tool to assist in the design and tailoring of novel nanopore systems.     

钙催化苯酚反应的分子动力学模拟

钙催化煤热解焦油二次反应的过程较为复杂，通过实验研究手段难以深入探究其机理。采用基于反应力场的分子动力学模拟方法研究了钙对焦油模型化合物苯酚反应的影响。结果表明，钙提高了苯酚的反应速率，促进了苯酚向气体产物、重质焦油和焦炭产物转化。在较低温度下，没有发现与气体产物键结的钙，钙主要迁移转化到重质焦油和焦炭产物中，促进了苯酚的缩聚反应。在较高温度下，有大量的钙与气体产物键结，促进了苯酚的裂解反应，提高了H₂的生成量，但对CO的生成几乎没有影响。根据一级反应动力学模型，钙对苯酚裂解反应的活化能影响较小，但显著降低了苯酚缩聚反应的活化能。     

Microstructure characterization of low molecular weight polybutadiene using the chain end groups by nuclear magnetic resonance spectroscopy

Polymer Bulletin - Four laboratory types of low molecular weight polybutadiene (PBD) with different 1,2-vinyl isomer contents were selected for microstructure characterization by nuclear magnetic...     

Molecular dynamics simulation of AlN thin films under nanoindentation

A large-scale molecular dynamics (MD) simulation of nanoindentation was performed to study the structural deformation on wurtzite aluminum nitride (B4-AlN). The nanoindentation induced B4-B1 phase-transition, amorphization and dislocation glide in AlN (0001) thin films were found. It shows that the B4-B1 phase-transition path includes two processes: an anti-parallel vertical movement of N and Al atoms along the [0001] axis, followed by horizontal rearrangements of the two types of atoms. Indentation force-depth (P-h) curve shows minor and major pop-in events. Detailed analysis of the results shows that the first three minor load drops in the P-h curve are related to the nucleation of amorphous structure, whereas the subsequent major load drop is related to the dislocation nucleation and expansion. The dislocations in AlN thin film involve perfect dislocations and Shockley partial dislocations, the latter is associated with the formation of intrinsic stacking faults (SFs) type I₂ during the expansion of dislocation loops.     

Motional heterogeneity of segmented polyurethane-polymethacrylate mixtures: an influence of functional groups concentration

The motional heterogeneity in the polymer mixtures of segmented polyether polyurethane (PU) with carboxylic groups and methacrylic copolymer (PM) with tertiary amine groups was studied by the electron spin resonance (ESR)—spin probe and spin label methods. Pure polymer components containing varying amounts of functional groups and their 1:1 mass ratio mixtures have been analysed. The results of motional heterogeneity and polymer interaction were complemented with the glass transition temperatures, structural and morphological characteristics. Spin probed PU/PM mixtures indicate that the probe motion and the phase separation deduced from the temperature-dependent ESR spectra are sensitive to a free volume determined by the polymer-polymer interactions. The interaction between the two components in PU/PM mixture with the highest functional groups concentration disorganizes hard segment domains with spherulitic character at the microscopic level as compared with the ordered hard phase in the corresponding pure PU sample. The influence of PU hard and soft segments on the motional dynamics of PM chains is analysed from the ESR spectra of spin labelled PM chains in the mixtures with unlabelled PU components. The fractional amount of the PM fast motion depends on the temperature and concentration of functional groups.     

Room temperature deposition of functional ceramic films on low-cost metal substrate

In various practical applications, such as high power actuators, high sensitivity sensors, and energy harvesting devices, polycrystalline piezoelectric films of 1–100?µm thickness and sizes ranging from several µm² to several cm² are required. With conventional film deposition processes, such as sol-gel, sputtering, chemical vapor deposition, or pulsed laser deposition, it is difficult to fabricate films with higher thickness due to their low deposition rate and high interfacial stress. The aerosol deposition method (AD), a relatively new deposition technique, can be used to fabricate highly dense thick films at room temperature by the consolidation of submicrometer-sized ceramic particles on various ceramic, metal, glass, and polymer substrates. Ferroelectric BaTiO₃ ceramic films of different thicknesses ranging from 1 to 30?µm were fabricated on a low-cost metallic substrate at room temperature using the AD method. Surface morphology and adhesion of the film were analyzed. Analysis of internal residual stresses revealed an equibiaxial compressive stress state in the as-processed film. Electrical characterization of films annealed at 500?°C shows an enhanced polarization value of ~?14?µC/cm² over that of the as-processed film. This improved property is related to the decreasing internal residual stress. In addition, the BT films prepared in this work were found to withstand electric fields greater than 100?kV/mm, which is possibly related to the inherent relatively defect-free structure of AD films.     

A study on hygrothermal degradation and recovery of an epoxy adhesive using molecular dynamics simulation

For application of epoxy adhesive to joining similar or dissimilar materials in vehicle bodies, its hygrothermal degradation (HTD) caused by severe environmental conditions of service will always be an issue until the relevant mechanism is clearly addressed and the remedy is found. This study provides experimental observations of an epoxy adhesive in terms of HTD and recoverability of the mechanical performance, and in the meantime, molecular dynamics (MD) simulations are performed to analyse the underlying mechanism. Comparing experimental results of the adhesive among states of the initial, HTD and dried manifests that the glass transition temperature (T_g) and the uniaxial tensile properties both reduced after HTD but partially recovered when dried. In the MD simulations, both of the dominant HTD factors, plasticization and hydrolysis, are accounted for via characterizations of water inclusion and bond scission. The simulation results reveal that both of the HTD factors reduce T_g, while only hydrolysis weakens the tensile properties. A quantitative comparison between the influences of plasticization and hydrolysis implies that hydrolysis is reversible for this specific epoxy adhesive.     

纳米流体中纳米颗粒微运动的分子动力学模拟

建立了以水分子为基础液、以铜纳米颗粒为悬浮粒子的纳米流体模型,利用分子动力学模拟方法对纳米颗粒的微运动行为进行分析。研究发现纳米颗粒在基础液中具有高速的随机旋转与平移运动,旋转运动的角速度为1×10⁹~1×10¹⁰ rad·s^-1,平移运动的速度为1~10 m·s^-1。纳米流体速度分布与温度分布主要区别于单相基础液的位置在近壁面附近,纳米流体无论是速度梯度还是温度梯度均比单相流体的情况大,其主要原因是纳米颗粒在基础液中的随机运动,而改变的流体速度特性又会进一步影响传热过程。     

纳米狭缝中水流动非平衡分子动力学模拟

采用非平衡分子动力学模拟（non-equilibrium molecular dynamics simulation）方法研究了不同间距纳米狭缝之间水的流动行为。研究了纳米狭缝间距、壁面性质和外部压力对水流动速度径向分布、有效黏度、壁面速度和滑移长度的影响,讨论了Navier-Stoke（N-S）方程的适用性。研究结果表明,N-S方程仅适用于3 nm以上的孔道;狭缝尺寸的增加和施加压力的增加均会使得管内流速增加,而造成表观黏度降低以及滑移长度增加。壁面亲水性的增加仅使得滑移长度降低,表观黏度并没有发生较大变化。     

A molecular dynamics simulation of bacteriophage T4 lysozyme

An analysis of a 400 ps molecular dynamics simulation of the164 amino acid enzyme T4 lysozyme is presented. The simulationwas carried out with all hydrogen atoms modeled explicitly,the inclusion of all 152 crystallographic waters and at a temperatureof 300 K. Temporal analysis of the trajectory versus energy,hydrogen bond stability, r.m.s. deviation from the startingcrystal structure and radius of gyration, demonstrates thatthe simulation was both stable and representative of the averageexperimental structure. Average structural properties were calculatedfrom the enzyme trajectory and compared with the crystal structure.The mean value of the C displacements of the average simulatedstructure from the X-ray structure was 1.1 ± 0.1 Å;differences of the backbone and angles between the averagesimulated structure and the crystal structure were also examined.Thermal-B factors were calculated from the simulation for heavyand backbone atoms and both were in good agreement with experimentalvalues. Relationships between protein secondary structure elementsand internal motions were studied by examining the positionalfluctuations of individual helix, sheet and turn structures.The structural integrity in the secondary structure units waspreserved throughout the simulation; however, the A helix didshow some unusually high atomic fluctuations. The largest backboneatom r.m.s. fluctuations were found in non-secondary structureregions; similar results were observed for r.m.s. fluctuationsof non-secondary structure and angles. In general, the calculatedvalues of r.m.s. fluctuations were quite small for the secondarystructure elements. In contrast, surface loops and turns exhibitedmuch larger values, being able to sample larger regions of conformationalspace. The C difference distance matrix and super-positioninganalyses comparing the X-ray structure with the average dynamicsstructure suggest that a ‘hinge-bending’ motionoccurs between the N- and C-terminal domains.     

Mechanical properties of SWNT X-Junctions through molecular dynamics simulation

The mechanical behavior of seven different carbon nanotube (CNT) X-junctions with a varying number of bonds was investigated through molecular dynamics simulations. The X-junctions are composed of two (6,0) single-walled carbon nanotubes (SWNTs) created via vibration-assisted heat welding. The junctions, containing anywhere between one and seven bonds, are subject to uniaxial tensile, shear and torsional strain, and then the stiffness values are determined for each case. When subjected to tensile and shear strain, both the arrangement and orientation of bonds are found to affect the stiffness of junctions more substantially than the number of bonds, bond length or bond order. Surprisingly, anisotropic shear behavior is observed in the X-junctions, which can be attributed to the junction's bond orientation. Also, the stiffness of X-junctions tested under an applied torque (torsion) differs from the stiffness under tensile and shear strain, however, in that it is more substantially affected by the number of bonds present in the junction than by any other property.     

Temperature dependency of gas barrier properties of biodegradable PP/PLA/nanoclay films: Experimental analyses with a molecular dynamics simulation approach

Polypropylene (PP)/poly(lactic acid) (PLA)/clay nanocomposite films with various compositions (PP‐rich and PLA‐rich) were prepared. Their structural and barrier properties against CO₂, O₂, and N₂ were investigated. The microstructure of the nanocomposites was studied by scanning electron microscopy, transmission electron microscopy, and wide angle X‐ray scattering. The PP‐rich with 75/25 composition revealed the best barrier properties against all the gases which could be justified according to its microstructure. Selectivity of O₂/N₂ and CO₂/N₂ was also measured. It was found that the addition of nanoclay as a gas barrier component reduced the permeability in both systems. The permselectivity was also reduced in the PP‐rich films while it was increased in the PLA‐rich system. Moreover, the temperature dependency of permeability, selectivity, and permselectivity for PP, PLA, and PP/PLA (75/25) samples was examined. The results showed that the temperature dependence of permeability obeyed an Arrhenius equation and order of activation energy of permeability for O₂, CO₂, and N₂ gases was found to be E_P < E_P/PLA < E_PLA. According to solubility measurements, the order of solubility coefficient for gases was as follows: CO₂ > O₂ > N₂. Finally, the molecular dynamics (MD) simulation was performed to estimate the diffusivity coefficients of the gases and showed that solubility increases with increasing temperature, which was in accordance with the experiments. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46665.     

Study on the structure and properties of SSBR with large-volume functional groups at the end of chains

Solution polymerized styrene-butadiene rubber (SSBR) and SSBR with tert-Butylchlorodiphenylsilane (TBCSi, large-volume functional groups) at the two ends of macromolecular chains (T-SSBR) were prepared by anionic polymerization. The molecular structure parameters of T-SSBR and SSBR were characterized and the ratio of the amount of macromolecular chain ends connected with TBCSi to total macromolecular chain ends (i.e., end-capping efficiency) was calculated. The comprehensive properties of T-SSBR and SSBR composites filled with carbon black (CB) were investigated. The results showed that T-SSBR composites presented lower Payne effect (namely better CB dispersion) than those of SSBR composites, which led to decrease in hardness, internal friction, dynamic compression heat built-up and permanent set of T-SSBR composites, significant increase in tensile strength, elongation at break, tear strength and resilience of T-SSBR composites, and excellent balance between wet-skid resistance and rolling resistance. However, compared with SSBR composites, T-SSBR composites presented longer stress-relaxation time, bigger die-swell and higher apparent viscosity, as well as slightly inferior dynamic-cutting resistance. All the above, owing to the end-capping of TBCSi, which could immobilize the free chain ends of T-SSBR (i.e., to reduce the friction loss of molecular chains and create a greater degree of orientation in the force field), and adsorb CB, the comprehensive performances of T-SSBR were better than those of SSBR and T-SSBR terminated with styrene-TBCSi (T_S-SSBR) were far superior to those of T-SSBR terminated with butadiene-TBCSi (T_B-SSBR). Accordingly, the former was suitable for the tread of green tires.     

Effect of carbon fiber surface functional groups on the mechanical properties of carbon-carbon composites with HTT

The present investigation describes the quantitative measurement of surface functional groups present on commercially available different PAN based carbon fibers, their effect on the development of interface with resol-type phenol formaldehyde resin matrix and its effect on the physico-mechanical properties of carbon-carbon composites at various stages of heat treatment. An ESCA study of the carbon fibers has revealed that high strength (ST-3) carbon fibers possess almost 10% reactive functional groups as compared to 5.5 and 4.5% in case of intermediate modulus (IM-500) and high modulus (HM-45) carbon fibers, respectively. As a result, ST-3 carbon fibers are in a position to make strong interactions with phenolic resin matrix and HM-45 carbon fibers make weak interactions, while IM-500 carbon fibers make intermediate interactions. This observation is also confirmed from the pyrolysis data (volume shrinkage) of the composites. Bulk density and kerosene density more or less increase in all the composites with heat treatment up to 2600 °C. It is further observed that bulk density is minimum and kerosene density is maximum upon heat treatment at 2600 °C in case of ST-3 based composites compared to HM-45 and IM-500 composites. It has been found for the first time that the deflection temperature (temperature at which the properties of the material start to decrease or increase) of flexural strength as well as interlaminar shear strength is different for the three composites (A, B and C) and is determined by the severity of interactions established at the polymer stage. Above this temperature, flexural strength and interlaminar shear strength increase in all the composites up to 2600 °C. The maximum value of flexural strength at 2600 °C is obtained for HM-45 composites and that of ILSS for ST-3 composites.     

Green lubricants production from Nile tilapia waste and prediction of physical properties through molecular dynamics simulations

Fish farming is a worldwide growing activity and a large amount of residues is produced in this process. The present work describes a cleaner and sustainable way to produce new lubricants from fish waste oil. Oil extracted from the Nile tilapia (Oreochromis niloticus) viscera was utilized as raw material to produce basic oil for lubricants. The products were synthesized by esterification with polyols, trimethylolpropane (TMP) and pentaerythritol (PE), using p-toluenesulfonic acid (p-TSA) as catalyst. The synthesized esters were characterized by infrared (IR) and nuclear magnetic resonance (NMR). Computational methods were used to predict the physical characteristics of the material. In addition, the main physicochemical properties were evaluated, as well as the thermal behavior and toxicity of the products against Artemia salina. The synthesized esters showed high viscosity indexes (VI > 150) and viscosities that fit the degree of application ISO-46 and 150. Molecular dynamics simulations indicated that at room temperature the lubricants Tilapia fatty acid - trimethylolpropane ester (T-TMPE) and Tilapia fatty acid - pentaerythritol ester (T-PEE) are in liquid and gel states, respectively, confirming the experimental data. The products did not present toxicity against A. salina. In this research, we reinforce the potential of using tilapia oil from waste to produce green lubricants as a strategy to reduce damage to the environment, as well as the use of computational methods that collaborate to predict physical properties of lubricants.