Mechanical Properties of 3-Glycidoxypropyltrimethoxysilane Based Hybrid Organic-Inorganic Materials

Hybrid organic-inorganic materials were synthesized from acid catalysed sols of tetraethyl orthosilicate, 3-glycidoxypropyltrimethoxysilane and titanium or zirconium alkoxides. The mechanical properties of these materials were measured in different conditions of preparation. The elastic modulus E was determined by a resonance method and by Knoop microindentation. After a thermal treatment at 125°C for 120 h, E was around 3–5 and 1–2 GPa for the samples synthesized with titanium butoxide or zirconium butoxide, respectively. An increase in E in the samples cured for longer times was observed. Knoop microhardness also increased with the heating time and was larger in samples synthesized from titanium alkoxides than zirconium alkoxides. The two methods gave results in good agreement when applied to samples treated for shorter times. In the other samples Knoop microindentation gave a larger value of E compared to the resonance vibration method. Hardness to elastic modulus ratio, H/E, was evaluated by Knoop microindentation. The elastic recovery at the longest heat treatment time was similar to that of soda-lime glasses. Fracture toughness was measured by three points flexural test, a _KIc in the range of 0.4–0.5 MPa m^1/2 was evaluated for samples treated during 168 h.     

Au/CdS Hybrid Nanoparticles in Block Copolymer Micellar Shells

A polystyrene‐block‐poly(2‐vinylpyridine) (PS‐b‐P2VP) micellar structure with a P2VP core containing 5 nm CdS nanoparticles (NPs) and a PS shell formed in toluene that is a good solvent for PS block undergoes the core‐shell inversion by excess addition of methanol that is a good solvent for P2VP block. It leads to the formation of micellar shell‐embedded CdS NPs in the methanol major phase. The spontaneous crystalline growth of Au NPs on the CdS surfaces positioned at micellar shells without a further reduction process is newly demonstrated. The nanostructure of Au/CdS/PS‐b‐P2VP hybrid NPs is confirmed by transmission electron microscopy, energy‐dispersive X‐ray, and UV‐Vis absorption.

     

Hybrid Compound Block Copolymer Micelles Encapsulating Gold Nanoparticles

We report here on the formation of hybrid compound block copolymer micelles encapsulating gold nanoparticles, utilizing a direct and general preparation method. The giant hybrid compound micelles are structured with micelles of PS‐b‐P2VP with gold nanoparticles in their P2VP core and PI‐b‐PS chains as the outer part of the compound micelles. The gold nanoparticles were produced using gold ion‐loaded PS‐b‐P2VP micelles as a nanoreactor, in a PS selective solvent (toluene), by the subsequent reduction of gold ions. The synthesis of the gold nanoparticles was monitored by UV‐vis spectroscopy. The gold containing micelles were then encapsulated in larger micelles of PI‐b‐PS copolymer, by successive utilization of toluene and heptane with the intermediate evaporation of toluene. The nanoassembly of the compound materials comprised a PI corona and a PS compound core, with P2VP/Au⁰ domains, and was characterized using UV‐vis spectroscopy, dynamic light scattering and transmission electron microscopy.

     

Morphology and Micromechanical Behaviour of SBS Block Copolymer Systems

By means of transmission electron microscopy (TEM) and uniaxial tensile testing, the connection between the morphology and the micromechanical properties of selected styrene-rich styrene/butadiene block copolymers was studied with respect to their molecular architecture. In particular, the structure-property correlation of a lamellae forming asymmetric linear SBS triblock copolymer was examined by systematically varying the sample preparation techniques and testing temperature. The molecular architecture was found to influence directly the morphology formation of the block copolymers. Different mechanisms such as drawing of the lamellae, shearing in the rubbery phase and rotation of the lamellar axis were observed. From room temperature down to the temperature close to glass transition temperature of the soft phase, a homogeneous plastic drawing of glassy lamellae was perceptible.     

Mechanical Properties of SiO2-PMMA Based Hybrid Organic-Inorganic Thin Films

Nano-indentations using a Berkovich indenter were performed in order to analyze the mechanical properties of hybrid organic-inorganic coatings. This technique allows to measure low load deformations and therefore to estimate quantitatively mechanical properties of the coatings. The elastic modulus and the hardness were determined on the basis of the load-displacement curve. We report results obtained for class II hybrid coatings based on SiO₂-PMMA prepared by sol-gel process. The effects of coating composition were investigated.     

Polymer‐Coated PtCo Nanoparticles Deposited on Diblock Copolymer Templates: Chemical Selectivity versus Topographical Effects

Metal–polymer hybrid films are prepared by deposition of polymer‐coated PtCo nanoparticles onto block copolymer templates. For templating, a thin film of the lamella‐forming diblock copolymer poly(styrene‐b‐methyl methacrylate) P(S‐b‐MMA) is chemically etched and a topographical surface relief with 3 nm height difference is created. Two types of polymer‐grafted PtCo nanoparticles are compared to explore the impact of chemical selectivity versus the topographical effect of the nanotemplate. A preferable wetting of the polystyrene (PS) domains with poly(styrenesulfonate) (PSS)‐coated PtCo nanoparticles (instead of residing in the space between the domains) is observed. Our investigation reveals that the interaction between PSS‐coated nanoparticles and PS domains dominates over the topographical effects of the polymer surface. In contrast, a non‐selective deposition of poly(N‐vinyl‐2‐pyrrolidone) (PVP)‐coated PtCo nanoparticles and the formation of large metal‐particle aggregates on the film is observed.     

Hierarchical Nanoporous Structures by Self‐Assembled Hybrid Materials Based on Block Copolymers

Hierarchical nanoporous structures are fabricated by adsorption of micelles of diblock copolymer‐templated Au‐nanoparticles onto a hydrophilic solid substrate. Gold nanoparticles are prepared using micelles (19 nm) of polystyrene‐block‐poly(4‐vinylpyridine) (PS‐b‐P4VP) as nanoreactors. Deposition of thin films of the micellar solution, modified with a non‐selective solvent (THF), on hydrophilic surfaces leads to the formation of hierarchical nanoporous morphologies. The thin films exhibit two different pore diameters and a total pore density of 15 × 10⁸ holes per cm². The structure was analyzed in terms of topography and chemical composition using AFM, TEM and XPS measurements. The PS‐b‐P4VP template was subsequently removed by oxygen plasma etching, to leave behind metallic nanopores that mimic the original thin film morphology.

     

Effect of Epoxidation of Diene Component of SBS Block Copolymer on Morphology and Mechanical Properties

In this work, the polybutadiene (PB) block of an asymmetric lamellae forming polystyrene/polybutadiene based triblock copolymer was epoxidized to different extent in order to study its effect on morphology and mechanical behaviour of the copolymer. The products were analyzed by means of different microscopic techniques, Fourier transform infrared (FTIR) spectroscopy and microhardness measurements. It was found that the microphase separation behavior and hence the mechanical properties of the materials were drastically altered through epoxidation of the diene block of the styrene/diene triblock copolymer. With the increase in the extent of epoxidation the lamellar structure changed to distorted lamellae and then to disordered domains. Consequently, inhomogeneous mechanical performance of the samples was observed at higher degree of chemical modification.     

锂电池用嵌段共聚物电解质的研究进展

离子导体嵌段共聚物电解质作为一种固态锂电池导离子材料引起了人们的广泛关注。嵌段共聚物的自组装行为为设计微观尺寸有序结构提供了一种可能。这种有序纳米结构既保证聚合物电解质良好的机械性能,同时又拥有与其它聚合物电解质相当的离子电导率,为进一步组装高性能、易加工的锂电池器件提供了一种可能。本文综述了聚氧化乙烯型嵌段共聚物和单离子型嵌段共聚物,并总结了近期嵌段共聚物电解质的形貌影响离子电导率的实验研究结果,最后评述了嵌段共聚物电解质面临的挑战,并对未来研究进行了展望。     

Double Yielding in a Styrene/Butadiene Star Block Copolymer

Summary: The morphology and tensile deformation behaviour of a highly asymmetric styrene/butadiene star block copolymer (polystyrene (PS) content = 74%) containing random PS‐co‐PB (polybutadiene) copolymer as a rubbery phase were investigated. The existence of double yielding, similar to that observed in some semicrystalline polymers, was detected in this nanostructured amorphous polymer. The observed phenomenon may be correlated with two different micromechanical processes taking place at the initial stage of deformation.

The stress‐strain curve of the star block copolymer prepared here (each curve represents a different method). The two yield points are clearly visible (labelled I and II).     

两亲嵌段共聚物胶束用作医用材料

两亲嵌段共聚物可以在水溶液中自组装形成亲水性链段为外壳、疏水性链段为内核的胶束,这种胶束能够用作药物载体而引起人们极大的关注。本文综述了两亲嵌段共聚物胶束用作医用材料的研究进展,主要内容包括医用两亲嵌段共聚物的种类,胶束化,以及用作诊断试剂载体、药物缓释载体、靶向载体等。两亲嵌段共聚物胶束用作磁共振造影剂载体有利于肿瘤的诊断,用作药物缓释载体可以有效增溶难溶性抗肿瘤药物,延长药物在体内的血液循环时间。此外,通过对胶束表面进行修饰或者施加外场,还可以实现靶向功能。因此,两亲嵌段共聚物胶束在医用材料领域有着广阔的发展前景。     

Extrusion Induced Morphologies and Properties of Layered Block Copolymer/Polystyrene Mixtures

Using transmission electron microscopy (TEM) and tensile testing, we investigated the morphology and the micro-deformation processes in a new kind of highly asymmetric polystyrene/polybutadiene based triblock copolymer and its blends with general purpose polystyrene (GPPS). The emphasis has been put on the analysis of blends morphology evolved under extrusion conditions and the impact of the later on the micromechanical behaviour of the blends. It was found that the phase separated structures were strongly oriented along the extrusion direction leading to the anisotropic mechanical behaviour. The blends showed more ductile performance and lesser strength on loading the sample perpendicular to the extrusion direction. The ductile to brittle transition was observed when the morphology of the blends was dominated by the glassy phase for 60 wt.-% GPPS.     

Optically Triggered Dissociation of Kinetically Stabilized Block Copolymer Vesicles in Aqueous Solution

We demonstrate a strategy for using an optical stimulus to trigger the dissociation of block copolymer (BCP) vesicles in aqueous solution. The BCP, comprising hydrophilic poly(ethylene oxide) (PEO) and a block of poly(methacrylic acid) bearing a number of spiropyran methacrylate comonomer units (P(MAA‐co‐SPMA)), was allowed to firstly self‐assemble into large vesicles in aqueous solution at pH = 3 with protonated carboxylic acid groups, and then become kinetically stable at pH = 8 due to the glassy vesicle membrane of P(MAA‐co‐SPMA). Fast dissociation of the vesicles was achieved through a cascade of events triggered by UV‐induced isomerization from neutral spiropyran to charged merocyanine in the membrane.

     

Mechanical and Thermal Properties of Organic/Inorganic Hybrid Coatings

Two types of organic/inorganic hybrid coatings were produced by the sol-gel route from (a) 80% tetra-ethoxy-silane (TEOS) and 20% glycidoxypropyl-trimethoxy-silane (GPTMS) and (b) GPTMS with varying amounts of diethylene-triamine (DETA). Residual stress was measured from substrate curvature and modulus and hardness were studied using nano-indentation.Coatings derived from 80TEOS/20GPTMS are relatively stiff and brittle. Tensile residual stress, elastic modulus and hardness all increase as the curing temperature is increased to 350°C. The organic components are not cross-linked and act as network modifiers.Coatings derived from GPTMS/DETA are less stiff and softer. Increasing the DETA content increases both E and H by increasing the connectivity of the organic network which dominates the mechanical properties. Thermal degradation begins at about 250°C in all cases, but is retarded when the connectivity of the organic network is high.     

Inorganic-Macroion-Induced Formation of Bicontinuous Block Copolymer Nanocomposites with Enhanced Conductivity and Modulus

A facile and electrostatically driven approach has been developed to prepare bicontinuous polymer nanocomposites that is based on the polyoxometalate (POM) macroion induced phase transition of PS-b-P2VP from an initial lamellar phase to a stable bicontinuous phase. The multi-charged POMs can electrostatically cross-link P2VP blocks and give rise to bicontinuous phases in which the POM hybrid conductive domains occupy a large volume fraction of more than 50 %. Furthermore, the POMs can give rise to high proton conductivity and serve as nanoenhancers, endowing the bicontinuous nanocomposites with a conductivity of 0.1 mS cm⁻¹ and a Young's modulus of 7.4 GPa at room temperature; these values are greater than those of pristine PS-b-P2VP by two orders of magnitude and a factor of 1.8, respectively. This approach can provide a new concept based on electrostatic control to design functional bicontinuous polymer materials.     

Isoporous Block Copolymer Membranes

The developments in membranes based on tailored block copolymers are reported with an emphasis on isoporous membranes. These membranes can be prepared in different geometries, namely flat sheets and hollow fibers. They display narrow pore size distributions due to their formation by self‐assembly. The preparation of these membranes and possibilities to further functionalize such membranes will be discussed. Different ways to control the pore size will be addressed, and the potential of block copolymer blends to fabricate membranes with tailored pore sizes will be shown.

     

Pincushion of Tubule Discovery and Tubular Morphology Landscape Establishment of Block Copolymer Self‐Assemblies

Block copolymer (BCP) self‐assembly is a versatile technique in the preparation of polymeric aggregates with varieties of morphologies. However, its morphology library is limited. Here, the discovery of pincushion of tubules is reported for the first time, via BCP self‐assembly of poly(4‐vinylpyridine)‐b‐polystyrene (P4VP‐b‐PS) with very high molecular weight (500 kDa) and asymmetry (2 mol% P4VP). The investigation confirms the importance of core‐forming block length on morphology control of BCP self‐assemblies, especially with respect to tubular structures. The morphology landscape of tubular structures is successfully established, where dumbbell of tubule, tubule, loose clew of tubules, tight clew of tubules, and pincushion of tubules can be prepared by adjusting the core‐forming block length. This work therefore expands the structure library of BCP self‐assemblies and opens up a new avenue for the further applications of these tubular materials.     

Mechanical Properties of Gel-Derived Materials

The mechanical behaviour of xerogels and aerogels is generally described in terms of brittle and elastic materials, like glasses or ceramics. The main difference compared to silica glass is the order of magnitude of the elastic and rupture moduli which are 10⁴ times lower. However, if this analogy is pertinent when gels are under a tension stress (bending test) they exhibit a more complicated response when the structure is submitted to a compressive stress. The network is linearly elastic under small strains, then exhibits yield followed by densification and plastic hardening. As a consequence of the plastic shrinkage it is possible to densify and stiffen the gel at room temperature. These opposite behaviours (elastic and plastic) are surprisingly related to the same two kinds of gel features: the silanol content and the pore volume. Both elastic modulus and plastic shrinkage depend strongly on the volume fraction of pores and on the condensation reaction between silanols. On the mechanical point of view (rupture modulus and toughness), it is shown that pores and silanols play also an important role. Pores can be considered as flaws in the terms of fracture mechanics and the flaw size, calculated from rupture strength and toughness is related to the pore size distribution. Different kinds of gels structure (fractal or not fractal) have been synthesized by a control of the different steps of transformation such as sintering and plastic compaction. The relationships between structural and the elastic properties are discussed in terms of the percolation theory and fractal structure.     

聚丙烯/PMMA/CaCO3纳米复合材料的制备、结构与力学性能

分别将经不同表面处理的纳米碳酸钙粒子与聚合物PP共混,制备PP／CaCO3和PP／PMMA／CaCO3纳米复合材料。用TEM观察了表面处理后纳米粒子的粒径与分散情况,发现复合粒子分散较均匀。用DSC与WAXD研究了复合材料的结晶行为,发现原位聚合制备的PMMA／CaCO3纳米复合粒子与PP共混后,PP有异相成核作用,出现了不稳定的PPβ晶型。PP／PMMA／CaCO3纳米复合材料力学性能有大幅度的提高。