Room temperature cured polyurea-urethane propellant with unique mechanical properties

A polyurea-urethane propellant based on an NCO-terminated prepolymer, a diamine and a triol has been developed. This is a room temperature curing propellant which is case-bondable. This has been standardized at 3-kg level and then scaled upto grains of 300-mm diameter and 2250-mm length weighing 250 kg. This propellant has a tensile strength of about 4 kg/cm² and an elongation of 150 percent. Because of low cost, case bondability and room temperature curability this can be used in large solid boosters.     

Detecting a single molecule using a micropore-nanopore hybrid chip

Nanopore-based DNA sequencing and biomolecule sensing have attracted more and more attention. In this work, novel sensing devices were built on the basis of the chips containing nanopore arrays in polycarbonate (PC) membranes and micropores in Si₃N₄ films. Using the integrated chips, the transmembrane ionic current induced by biomolecule''s translocation was recorded and analyzed, which suggested that the detected current did not change linearly as commonly expected with increasing biomolecule concentration. On the other hand, detailed translocation information (such as translocation gesture) was also extracted from the discrete current blockages in basic current curves. These results indicated that the nanofluidic device based on the chips integrated by micropores and nanopores possessed comparative potentials in biomolecule sensing.     

氯化聚乙烯与小分子化合物掺杂体

介绍了氯化聚乙烯与多官能团小分子掺杂体的特殊性质及其机理。目前,该领域的研究重点在于对掺杂体形态结构和动态力学性能的分析与控制,应用这方面的研究成果可以开发出一系列具有优异阻尼性能、形状记忆效应以及其他独特功能的新材料。     

A natural-synthetic hybrid copolymer of polyhydroxyoctanoate-diethylene glycol: biosynthesis and properties

The bacterium Pseudomonas oleovorans was utilized to produce a novel natural-synthetic hybrid block copolymer. This hybrid biomaterial consists of the natural hydrophobic polymer polyhydroxyoctanoate (PHO) end-capped with hydrophilic synthetic diethylene glycol (DEG). The addition of the synthetic component, in the form of PEG106, to the bioprocessing stage significantly affected polymer yield and properties compared to its non-hybridized counterpart. Compared to PHO polymer, the PHO-DEG hybrid possessed a significantly higher C8 component and reduced molecular mass. In contrast, thermal and crystalline properties were similar in both polymer types. While the molecular weight ratio of the natural and synthetic blocks is approximately 1000:1, the small hydrophilic component exerted a powerful influence during polymer processing. Under conditions of high humidity, solvent cast films of the PHO-DEG hybrid self-assembled into ordered microporous arrays. Thus, a novel natural-synthetic hybrid comprized of biocompatible components has been produced.     

Benefiting from the unique properties of lanthanide ions

The recent upsurge of interest in contrast agents for magnetic resonance imaging, of luminescent chemosensors for medical diagnostic, and lately, for optical imaging of cells has generated an impressive momentum for the coordination and supramolecular chemistry of trivalent lanthanide ions. We shortly review the synthetic methods allowing the introduction of these spherical ions with fascinating optical and magnetic properties into elaborate mono- and polymetallic edifices. We then illustrate these methods by selected examples describing the use of (i) a coronand to produce luminescent liquid crystals, (ii) derivatized calixarenes for 4f-5f element separation, (iii) podates for the production of nanoparticles with high relaxivity and for sensitizing the near-infrared (NIR) emission, and (iv) self-assembly processes for producing functional bimetallic edifices.     

Elastic properties of intermingled hybrid composites

The combination of different types of fibers in a common matrix, known as a hybrid composite, has the potential of achieving a balance between composite strength and ductility, as well as a more cost-effective use of expensive fibers, not re-alized in a single-fiber compostie. The elastic properties of a continuous Kevlar®/glass intermingled hybrid composite have been investigated. Theoretical predictions utilizing a self-consistent model and a bound approach are compared to the influence of the relative Kevlar®/glass fiber volume fraction on the elasstic material properties.     

A type I/type III polyketide synthase hybrid biosynthetic pathway for the structurally unique ansa compound kendomycin

Kendomycin is a bioactive polyketide that is produced by various Streptomyces strains. It displays strong antibiotic activities against a wide range of bacteria and exhibits remarkable cytotoxic effects on the growth of several human cancer cell lines. In this study we cloned the corresponding biosynthetic locus from the producer Streptomyces violaceoruber (strain 3844-33C). Our analysis shows that a mixed type I/type III polyketide synthase pathway is responsible for the formation of the fully carbogenic macrocyclic scaffold of kendomycin, which is unprecedented among all of the ansa compounds that have been isolated so far. Heterologous expression of a gene set in Streptomyces coelicolor shows that 3,5-dihydroxybenzoic acid is an intermediate in the starter unit biosynthesis that is initiated by the type III polyketide synthase. The identification of the kendomycin biosynthetic gene cluster sets the stage to study a novel chain termination mechanism by a type I PKS that leads to carbocycle formation and provides the starting material for the heterologous expression of the entire pathway, and the production of novel derivatives by genetic engineering.     

A novel organometallic ReI complex with favourable properties for bioimaging and applicability in solid-phase peptide synthesis

Organometallic complexes possess great potential for imaging applications in biology, due to their kinetic stability and often favourable intrinsic properties. In this work we present a new class of Re(I) -tricarbonyl complexes with a substituted bis(phenanthridinylmethyl)amine (bpm) ligand. The complex Re(CO)(3) (R-bpm) could be conveniently prepared by microwave synthesis from [Re(CO)(3)(H(2)O)(3) ]Br and a suitably substituted bis(phenanthridinylmethyl)amine (R-bpm). Complex 5, with R=CH(2)-CO(2)-CH(3) , was characterized by a single-crystal X-ray structure. Complex 6 (R=CH(2)-C(6)H(4)-CO(2)H) was used in solid-phase peptide synthesis (SPPS) to label the neurotensin(8-13) (NT) fragment N-terminally. The complexes show luminescence emission with large Stokes shifts (λ(ex) =350 nm, λ(em) =570 nm). Cellular uptake and intracellular localization studies in several cell lines demonstrate the utility of the new Re(CO)(3) (R-bpm) complexes for fluorescence imaging and reveal significant differences between the simple methyl ester 5 and the NT bioconjugate 7.     

Si3N4-BN-SiCN ceramics with unique hetero-interfaces for enhancing microwave absorption properties

SiCN-based ceramics with broadband and strong microwave absorption properties are desired for the structural and functional integration of ceramic matrix composites. The elemental composition and thermal expansion coefficients of the ceramics matrix crucially affect its microstructure and electromagnetic wave (EMW) absorption properties. BN layer with lower electrical conductivity and higher specific area, exhibits both the impedance matching characteristic and EMW attenuation in the process of multiple reflections, electrical conductivity loss, dipole polarization and interfacial polarization. Therefore, Si₃N₄-BN-SiCN ceramics, which were synthesized using chemical vapor infiltration (CVI) method, construct unique hetero-interface of Si₃N₄-BN, Si₃N₄–SiCN and BN-SiCN. Therefore, the Si₃N₄-BN-SiCN ceramics have outstanding EMW absorption performance and realize an effective absorption bandwidth (EAB) that covers the whole X band and the minimum reflection coefficient (RC) reaches -18.43 dB at a thickness of 3.37 mm.     

Preparation and properties of polymerizable silica hybrid nanoparticles with tertiary amine structure

To increase the photopolymerization rate and improve the properties of UV coatings, polymerizable silica hybrid nanoparticles with tertiary amine structure were prepared. Organic compound with isocyanate group was first grafted onto the surface of nanosilica by reaction of nanosilica with isophorone diisocyanate, then the nanosilica bearing isocyanate group reacted with N,N-di(3-propionic acid, 1,4,7-trimethyl-3,6-dioxaoctane-8-yl acrylate, ester) ethanolamine synthesized from tripropylene glycol diacrylate and ethanolamine. The preparation was characterized by ¹H nuclear magnetic resonance (NMR) and Fourier transform infrared spectrometry (FT-IR). Thermogravimetric analysis (TGA) showed that the organic compounds grafted onto the silica decomposed from 256 °C to 650 °C and the grafting percentage based on nanosilica was 105%. The morphology analysis of nanosilica and modified silica by field-emission scanning electron microscopy (FE-SEM) indicated that the silica kept nanosized scale after modification, while the nanosilica dispersion was improved and formation of agglomerates unlikely. Determination of viscosities of coatings with modified nanosilica, it was found that viscosities of the coatings decreased in comparison with the viscosities of coatings with unmodified nanosilica. Compared with pure organic coating, the photopolymerization rate of coatings were faster when modified nanosilica was used from 1 wt% to 5 wt%, but slower when the loadings of modified nanosilica was 7 wt% because co-initiating effects of tertiary amine compound grafted on nanosilica counterbalanced the effects of UV scattering by silica on photopolymerization rate. The hardness and abrasive resistance of cured films also increased and improvement degree was different when the various amounts of modified nanosilica were used.     

纳米SiO_2杂化粒子的制备及其性能研究

以异佛尔酮二异氰酸酯（IPDI）与纳米SiO2表面Si—OH基团进行反应,制备了表面含—NCO基团的功能化纳米SiO2粒子,进一步用丙烯酸羟乙酯（HEA）对剩余—NCO基进行封端,制备出纳米SiO2/丙烯酸酯粒子,并用红外光谱（FI-IR）、热失重（TGA）、扫描电镜（SEM）等对改性前、后纳米SiO2的分散性进行表征。结果表明,IPDI和HEA均成功地以化学键形式接枝到纳米SiO2表面,接枝率为46.80%;改性纳米SiO2的分散性显著提高,团聚现象明显改善;将不同含量纳米SiO2杂化材料加入紫外光固化涂料中,同比加入未改性纳米SiO2的涂料,改性后的纳米SiO2在使涂料获得较低黏度和较快CC转化率的同时,可以显著地提高固化膜的硬度。     

高折射率钛杂化硅树脂制备及性能研究

采用非水解溶胶-凝胶法制备一系列高折射率透明钛杂化硅树脂,采用红外、核磁、拉曼光谱、MALDI-TOF(飞行时间质谱)等手段对其缩合反应、钛杂化硅树脂的分子结构和分子量进行分析。研究结果表明:钛元素以Si—O—Ti化学键形式成功引入到硅树脂主链中,在可见光区域不同钛含量的固化物显示较高透光率(85%);随着TPT(钛酸四异丙酯)用量增加,杂化树脂的分子量增加,折射率从1.57增加到1.62,呈线性变化;硅树脂的缩合度由91%增加到96%,固化物的玻璃化转变温度也从42.5℃提高到54℃。     

Fracture properties of natural rubber filled with hybrid carbon black/nanoclay

Hybrid carbon black (CB) and nanoclay (NC) in a rubber matrix have provided superior mechanical performances over conventional composites. Yet the fracture and fatigue properties have not been fully explored. In this paper, the mechanical properties of the hybrid-filled natural rubber (NR) were investigated with regard to the tensile strength, fatigue crack growth (FCG) and cut resistance. The ruptured crack tip and the torn surface were studied by using optical microscopy and scanning electron microscopy (SEM), respectively. It was found that the fatigue resistance at large tearing energy and cut strength were enhanced with hybrid filler. Subsidiary cracks were observed at the ruptured tip in rubber with NC. Morphology analysis revealed that the hybrid filler led to a rougher torn surface than rubber with non-hybrid filler. It was proposed that the clay layers constructed a dual phase filler network with CB aggregates. The filler network could cause strength anisotropy in the matrix and introduce more energy dissipation mechanisms to the system, resulting in enhanced fatigue resistance.     

聚氨酯-丙烯酸酯复合乳液的合成与性能

采用甲基丙烯酸甲酯(MMA)与水性聚氨酯乳液共聚反应制备聚氨酯-丙烯酸酯(PUA)复合乳液,研究了MMA添加量、引发剂种类和聚合温度对PUA复合乳液及涂膜性能的影响,确定了PUA复合乳液合成的工艺参数。用傅立叶红外光谱(FTIR)测定反应产物的结构。研究发现油溶性引发剂比水溶性引发剂更适合PUA体系的乳液聚合。随着MMA添加量的增大,PUA复合乳液胶粒粒径增大,黏度减小,涂膜光泽度下降,机械性能增强,耐水性增加。     

Polybenzoxazine alloys and blends: Some unique properties and applications

Polybenzoxazine (PBZ), a novel class of high performance thermosetting phenolic resin, has been developed in order to overcome many shortcomings of conventional phenolic materials from either novolac or resole type resins. The paper first provides the overview of this high temperature material including main types, chemical structure of each type, and properties of the polymer, especially the synergistic behavior in thermal properties. It then describes the manufacturing technique to produce the monomeric resin as well as some applications of the polymer.     

Thermal and pH dual stimuli-responsive hybrid inclusion complex with tunable nonlinear optical properties

A novel dual-responsive core-shell type hybrid inclusion complex composed of an azobenzene-terminated copolymer PNIPAM-b-PAA and β-cyclodextrin-modified silver/polydiacetylene (β-CD@Ag/PDA) nanocrystals had been fabricated based on the host-guest interaction between azobenzene unit in the block copolymer and β-CD cavities on the surface of the hybrid nanocrystals. While the hybrid nanocrystals provide necessary nonlinear optical properties, the copolymer shells exhibit dual sensitivity to temperature and pH variation. The dual stimuli-responsive behavior of the copolymer shells was used to act as the driving force to adjust the relative spatial distances between neighboring hybrid nanocrystals, further controlling the localized surface plasmon resonance enhancement and the corresponding NLO effect. It is expected that this research will introduce a new way for preparing novel smart NLO materials.     

MEMO改性硅溶胶增强甲基硅树脂薄膜结构及性能

以甲基三甲氧基硅烷(MTMS)水解聚合产物作为成膜材料,甲基丙烯酰氧基丙基三甲氧基硅烷(MEMO)改性硅溶胶为无机增强剂,采用溶胶-凝胶法在聚碳酸酯(PC)表面制备透明硅溶胶增强甲基硅树脂薄膜;探讨了MEMO改性硅溶胶前后涂膜液的稳定特征及薄膜特性,采用envelope方法计算了薄膜厚度。研究结果表明,MEMO改性硅溶胶增强硅树脂涂膜液与未经MEMO改性的涂膜液相比,凝胶时间延长,稳定性提高,易制备厚膜而不开裂;薄膜对PC片有增透作用,MEMO改性对薄膜增透性能及硬度影响不大;薄膜厚度随着陈化时间的延长而增加,理论计算所得的膜厚与SEM实测结果相近。