From ordinary rhelogy concrete to self compacting concrete: A transition between frictional and hydrodynamic interactions

This paper focuses on the physical phenomena involved in the transition between ordinary fluidity concrete and high fluidity concrete according to the aggregate content of the mixture. It is shown that there exists a strong transition in the rheological behavior of concrete between a regime dominated by the friction between aggregate particles and a regime dominated by hydrodynamic interactions far less dissipative. It is also demonstrated that it is possible to define a transition criterion between these two regimes. Finally, the consequences of these changes in mix design on the mechanical strengths of the concretes are studied showing that a small decrease in granular skeleton volume fraction, which may generate a decrease in yield stress of almost two orders of magnitude, only reduces the mechanical strength of a few percents.     

Toward an understanding of thermoresponsive transition behavior of hydrophobically modified N-isopropylacrylamide copolymer solution

Poly(N-isopropylacrylamide-co-vinyl laurate)(PNIPAAm-co-VL) copolymers were prepared at various feed ratios via conventional radical random copolymerization. The formation, composition ratios and molecular weight of copolymers were examined. The thermoresponsive behaviors of PNIPAAm and PNIPAAm-co-VL solutions at low and high concentrations were intensively investigated by turbidity measurement, Micro-DSC, temperature-variable state fluorescence, ¹H NMR and dynamic light scattering (DLS). Several important results were obtained that (1) incorporation of PVL results in much lower and broader LCST regions of the copolymer solutions, and facilitates the formation of hydrophobic microdomains far below LCST, causing a pronounced aggregation in solutions (2) temperature-variable ¹H NMR spectra shows that during the phase transition, the ‘penetration’ of PNIPAAm into the hydrophobic core is a process accompanied with a transition of isopropyl from hydration to dehydration as well as a self-aggregation of hydrophobic chains at different temperature stages (3) according to the ¹H NMR spectra of polymer solutions obtained at varied temperatures, the microdomains from hydrophobic VL moieties have a different accessibility for isopropyl groups and the entire chains during phase transition (4) temperature-variable DLS demonstrates that the temperature-induced transition behavior of copolymers is supposedly divided into three stages: pre-LCST aggregation (<20 °C), coil-globule transition at LCST (20-25 °C) and post-LCST aggregation (>25 °C).     

Three-dimensional shape analysis of coarse aggregates: New techniques for and preliminary results on several different coarse aggregates and reference rocks

The shape of aggregates used in concrete is an important parameter that helps determine many concrete properties, especially the rheology of fresh concrete and early-age mechanical properties. This paper discusses the sample preparation and image analysis techniques necessary for obtaining an aggregate particle image in 3-D, using X-ray computed tomography, which is then suitable for spherical harmonic analysis. The shapes of three reference rocks are analyzed for uncertainty determination via direct comparison to the geometry of their reconstructed images. A Virtual Reality Modeling Language technique is demonstrated that can give quick and accurate 3-D views of aggregates. Shape data on several different kinds of coarse aggregates are compared and used to illustrate potential mathematical shape analyses made possible by the spherical harmonic information.     

The EU “PARTNER” Project — European standard tests to prevent alkali reactions in aggregates: Final results and recommendations

This paper presents the main findings in the EU PARTNER Project (2002-2006) providing the basis for a unified European test approach for evaluating the potential alkali-reactivity of aggregates. The project evaluated the tests developed by RILEM and some regional tests for their suitability for use with the wide variety of aggregates and geological types found across Europe. The project had 24 partners from 14 countries, covering most of Europe, from Iceland to Greece. 22 different types of aggregates from 10 different European countries were evaluated. It was found that in most cases the RILEM tests could successfully identify the reactivity of the aggregates tested. They were most successful with normally reactive and non-reactive aggregates, but with aggregates that react very slowly an extended test period may be necessary for some of the RILEM methods. Overall, the accelerated mortar bar test and the accelerated concrete prism test seemed most effective and to have the best precision.     

Block copolymer aggregates with photo-responsive switches: Towards a controllable supramolecular container

Herein, we present a concept of combining host-guest chemistry with block copolymer self-assembly to fabricate an inner cross-linking block copolymer aggregate with photo-responsive switches on the basis of the reversible interaction between azobenzene and β-cyclodextrin, which can serve as a controllable supramolecular container to load and release guest molecules reversibly. The inner cross-link makes the block copolymer aggregates exhibit good stability, and the aggregates can keep their spherical morphologies during photo-irradiation treatment. When the switches are in on-state, cyclodextrins can bind with hydrophobic pyrene molecules; and when the switches are in off-state, pyrene molecules will get away from the cyclodextrins. The photo-controllable switches embedded in the aggregates endow this new supramolecular container with the capability to load and release guest molecules reversibly without structure disruption. It is anticipated that this line of work may open an avenue for fabricating new polymeric containers which can be used for controllable molecular transfer and catalysis.     

Functional mesoporous poly(ionic liquid)-based copolymer monoliths: From synthesis to catalysis and microporous carbon production

Ionic liquid-functionalized mesoporous polymeric networks with specific surface area up to 935 m²/g have been successfully synthesized one pot by solvothermal copolymerization of divinylbenzene and monomeric ionic liquids. The as-obtained polymers exhibit a monolithic structure featuring large pore volumes, an abundant mesoporosity and an adjustable content of ionic liquids. The effect of the reaction conditions on the pore structure has been studied in detail. These poly(ionic liquid)-based porous networks (PILPNs) have then been employed as precursors in two distinct applications, namely organocatalysis and production of microporous carbon monoliths. Selected organocatalyzed reactions, including carbonatation of propylene oxide by cycloaddition with carbon dioxide, benzoin condensation, and cyanosilylation of benzaldehyde have been readily triggered by PILPNs acting as crosslinked polymer-supported (pre)catalysts. The two latter reactions required the prior deprotonation of the imidazolium salt units with a strong base to successfully generate polymer-supported N-heterocyclic carbenes, referred to as poly(NHC)s. Facile recycling and reuse of polymer-supported (pre)catalysts was achieved by simple filtration owing to the heterogeneous reaction conditions. Furthermore, PILPNs could be easily converted into microporous carbon monoliths via CO₂ activation.     

Characterization of the fragmentation of protein aggregates in suspension subjected to flow

Suspensions of flocculated aggregates subjected to flow present two distinct typical fragmentation mechanisms: cleavage and erosion. In this paper, a mathematical model is developed to concurrently evaluate the two phenomena. Erosion is tackled by a perturbative calculation, while cleavage is treated according to an exact calculation. The model is implemented on experimental data on the fragment size distribution in suspension of protein aggregates subjected to flow. Both cleavage and erosion are seen to gradually rise in significance as the flow rate increases. Their respective extent are each quantified with one chosen single parameter: cleavage with the number of fragments and erosion with the amount of eroded material. A relation found between the two parameters indicates a proportionality between the amount of eroded material and the surface area newly exposed by the process of cleavage.     

A water-solubilized, segmented, alternating block copolymer of a 1,4-bis-styrylbenzene with polyethylene glycol

The synthesis and characterization of a new segmented alternating copolymer is described, having monodisperse, partially methoxy-substituted bis-1,4-styrylbenzene chromophores linked with polyethylene glycol segments (average MW 1000) at the terminal aryl rings, so that the chromophore long axis lies along the polymerization vector. The product polymer is a blue-emitting material that is soluble in organic solvents and water. It is a waxy solid with a degree of polymerization of ∼3-6, a melting transition at 35 °C and good thermogravimetric stability up to 300 °C. It exhibits blue photoluminescence (PL) at 437 nm in chloroform, and at 445-465 nm in water, with relative PL quantum yields of 0.7 and 0.3, respectively. Its neat film luminescence maximum is 460 nm; solid state blending with PMMA blue shifts the emission to 440 nm at 10% polymer in PMMA.     

Photoresponsive liquid crystalline block copolymers: From photonics to nanotechnology

Being one of the most fascinating multi-functional materials, photoresponsive liquid crystalline block copolymers (PLCBCs) have attracted much attention because of their light controllable properties of supramolecularly self-assembled structures. These originate from their unique features combining the advanced function of photoresponsive liquid crystalline polymers (PLCPs) with the inherent property of microphase separation of block copolymers (BCs). Benefiting from recent progresses in materials chemistry, diverse PLCBCs have been designed and synthesized by controlled polymerization using different synthetic routes and strategies. Generally, PLCBCs show different performance depending on their self-organization and molecular composition, with the PLCP blocks in the minority phase or in the majority phase. One of the most important properties of PLCBCs is supramolecular cooperative motion, resulted from the interactions between liquid crystalline elastic deformation and microphase separation, which enables them to self-assemble into regularly ordered nanostructures in bulk films with high reliability. These nanostructures contribute to improving the optical performance of polymer films by eliminating the scattering of visible light, in favor of their photonic applications. With the help of liquid crystal alignment techniques, both parallel and perpendicular patterning of nanostructures has been fabricated in macroscopic scale with excellent reproducibility and mass production, which provides nanotemplates and nanofabrication processes for preparing varieties of nanomaterials. Recent findings about PLCBCs including their synthesis, diagram of microphase separation, structure-property relationship, precise control of nanostructure as well as their applications in photonics to nanotechnology are reviewed.     

Hierarchical self-assembly of fluorine-containing diblock copolymer:From onion-like nanospheres to superstructured microspheres

Superstructured microspheres were prepared via a two-tier hierarchical assembly of a fluorine-containing diblock copolymer, poly(tert-butyl acrylate)-b-poly(2-[(perfluorononenyl)oxy]ethyl methacrylate) (PtBA-b-PFNEMA) with well controlled block lengths. At tier 1, water induced self-assembly of the diblock copolymer produced nanospheres of low dispersity with onion-like multilayer inside structures, which were the consequence of the gradual aggregation of the fluorinated segments by accessing the super-strong segregation regime. And both the size and inner structure could be tuned by changing the water addition rate. At tier 2, nanospheres with different sizes were chosen as the building blocks for the formation of closely packed superstructural microspheres through an evaporation assisted process. The packing rules were governed by the volatility distinction between THF and water, the dispersity of nanospheres, and other various forces, such as the capillary force.     

Encapsulation of hydrophobic drugs in a copolymer: Glass transition behavior and miscibility evaluation

The knowledge of glass transition temperatures T_g in drug + polymer systems is indispensable for drug encapsulation. T_g values as a function of composition make possible the determination whether a given polymer is miscible or compatible with the drug and whether the polymer will provide release of the drug into organism within an acceptable rate range. We have used differential scanning calorimetry and Fourier‐transform infrared spectroscopy to evaluate miscibility in solid dispersions of the drugs carvedilol, itraconazole, nevirapine, and nimodipine in the pharmaceutical grade copolymer poly(vinyl pyrrolidone‐co‐vinyl acetate) (PLS‐630 Copovidone). Successful drug encapsulation is discussed in terms of thermophysical behavior (suppression of crystallization, negative excess volumes of mixing) and intermolecular interactions (concentrations of proton donating/accepting groups) in drug + polymer systems. Several equations were applied to the complex s‐shaped T_g(?) patterns obtained (? being the mass fraction of the drug). The best agreement of calculations with experiment is achieved using a recently proposed three‐parameter equation, symmetric with respect to the equal concentration of both components. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Polymer micellar aggregates of novel amphiphilic biodegradable graft copolymer composed of poly(aspartic acid) derivatives: Preparation,characterization, and effect of pH on aggregation

Novel amphiphilic biodegradable graft copolymer based on poly(aspartic acid) was prepared by attaching monomethoxy polyethylene glycol (mPEG) as hydrophiphic segment to poly(aspartic acid‐g‐octadecylamine) (PASP‐g‐ODA) as hydrophobic backbone. The chemical structures of amphiphilic copolymers were confirmed by FTIR and ¹H NMR spectroscopy. The polymeric micelles were prepared with solvent evaporation and their physicochemical properties in aqueous media were characterized by dynamic light scattering (DLS) and fluorescence spectroscopy. These micelles were confirmed to be pH‐sensitive by measuring optical transmittance of micelle solution and the size of micellar aggregates. The number average diameter of polymeric micelles prepared in medium at pH 2.5 was larger than that in neutral and basic medium and showed a bimodal size distribution because of the protonation of carboxyl groups in backbone. Furthermore, the polymeric micelle can load water‐insoluble drug (podophyllotoxin), and the drug release from micelles showed a pH‐dependency. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Self-assembly template during morphological transition of a linear ABC triblock copolymer from lamellar to Gyroid structure

Morphological transition of the ABC-type triblock copolymer from lameller to tricontinuous Gyroid structure has been observed. The sample used is a symmetric poly(isoprene-block-styrene-block-2-vinylpyridine), whose volume fractions of three components are 0.26, 0.48 and 0.26, and the total molecular weight is 1.0×10⁵. The solvent cast films were prepared and dried well, followed by annealing at 423 K, the temperature well above the glass transition temperatures of three polymer components. The structural transition was investigated by varying the annealing time from 1 h up to 7 days with two methods, transmission electron microscopy and small-angle X-ray scattering. It was confirmed that the as-cast film shows lamellar structure, however, the structure started to transform into Gyroid structure after annealing 14 h and it took more than 2 days to accomplish the transition. Furthermore, it was also confirmed that Gyroid structure is oriented with its (110) normal to the film surface, the length of its repeating unit along with (110), 55 nm, is similar to its original lamellar domain spacing, 58 nm.     

Alternating copolymer of bithiophene and dialkylbithiazole and its tendency to align on the surfaces

New five-membered ring π-conjugated polymers composed of 2,2′-bithiophene and 4,4′-dialkyl-2,2′-bithiazole units were prepared. The polymers were soluble in 1,2-dichlorobenzene and showed a UV-vis peak at about 490 nm above 120 °C. Cooling the solution led to the appearance of new UV-vis peaks at 550 and 600 nm, which were considered to originate from self-assembled polymer molecules. Powder XRD (X-ray diffraction) data supported a well-stacked solid structure of the polymers and a highly ordered structure of a polymer film formed on a quartz glass substrate. These data revealed a strong tendency of the new polymers to self-assemble and to form an aligned structure on the surface of the substrates.     

Electromagnetic activation of a shape memory copolymer matrix incorporating ferromagnetic nanoparticles

Modified magnetite (Fe₃O₄) was easily mixed in a matrix of a polynorbornene‐based copolymer to realize a nanocomposite of organic polymer and inorganic metal oxide nanoparticles. The crystalline structure and the diameter of the modified Fe₃O₄ were evaluated with X‐ray diffraction and atomic force microscopy, revealing the crystalline Fe₃O₄ nanoparticles in the nanometer size range with an average diameter of 55 nm, a value close to that indicated by dynamic light scattering (68 nm). The transition temperature of the composite of 51 °C was determined using differential scanning calorimetry and the thermal stability and dynamic mechanical properties of the easily formed composite were investigated using thermogravimetry and dynamic mechanical analysis. The shape memory effect was evaluated in terms of shape recovery rate and speed, while thermally and electromagnetically triggered shape memory properties were documented. The recovery time triggered by Fe₃O₄ is 186 s. Copyright © 2011 Society of Chemical Industry     

Encapsulation of inorganic nanoparticles into block copolymer micellar aggregates: Strategies and precise localization of nanoparticles

Precise assembly and localization of preformed inorganic nanoparticles (NPs) in block copolymer (BCP) assemblies are of great importance in realizing the formation of nano-hybrids with high performance. Properties of the nanocomposites depend not only on those of individual building blocks but also on their spatial organization at different length scales, demonstrating unique optical, electrical, and magnetic properties. With the aid of the BCPs, NPs can form a broader range of structures in the nanoscopically confined geometry. Thus, many studies have focused on the selective localization of NPs in BCP aggregates. In this paper, we will outline recent advances in the preparation strategies for precise localization of inorganic NPs into BCP micelles, including co-precipitation, supramolecular assembly, interfacial instabilities of emulsion droplets, heating–cooling, electrostatic interaction, and others. Manipulating the balance between enthalpic and entropic contributions provides one of the opportunities to precisely control the spatial distribution of NPs in BCPs assemblies. We will focus on the principles of precise control of dispersion and localization of the NPs in BCP micelles. Potential applications of the hybrid micelles will finally be discussed, followed by the summary and outlook of this emerging area.     

The design and properties study of a novel styryl-pyridinium-based water-soluble fluorescent copolymer as tracing agent

A water-soluble fluorescent copolymer poly(acrylamide-acrylic acid-styrene pyridinium) (PAAS) for detecting polymer concentration in real time was synthesized via micellar free-radical polymerization by acrylamide, acrylic acid, and styryl-pyridinium salt derivative (SP- 4 ). The special Donor-π-Acceptor unit and ionic structure of SP- 4 endued the copolymer with excellent fluorescent properties and remarkable water solubility. The fluorescent copolymer was fully characterized by Fourier transform infrared, ¹H nuclear magnetic resonance, thermogravimetry, Ubbelohde viscosity, ultraviolet–visible spectroscopy, and fluorescence measurements. Furthermore, the fluorescence intensity and the concentration of PAAS were verified to have ideal linear relationship with a correlation coefficient up to 0.9993, indicating that the copolymer's concentration can be easily measured by detecting its fluorescence intensity. Most importantly, the introduction of water-soluble fluorescent monomer SP- 4 endowed the PAAS with good fluorescent stability in a wide range of temperature, pH, and brine concentrations. This study demonstrated that the fluorescent copolymer PAAS exhibits great potential application in detecting polymer concentration in various environments. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47062.     

Synthesis of a soluble conjugated copolymer based on dialkyl-substituted dithienothiophene and its application in photovoltaic cells

A soluble conjugated alternating 3,5-didecanyldithieno[3,2-b:2′,3′-d]thiophene-thiophene copolymer was synthesized by palladium(0)-catalyzed Stille coupling reaction. The thermal, absorption, emission, electrochemical, and photovoltaic properties of the polymer were examined. A weight-average molecular weight around 6.2 × 10⁴ and a polydispersity index of 1.8 was estimated for the polymer using gel permeation chromatography. The polymer exhibits good thermal stability with decomposition temperature of 340 °C and glass-transition temperature of 136 °C. The polymer shows strong absorption peaked at 505 nm in diluted solution and 518 nm in thin film with an optical band gap 2.0 eV. The polymer exhibits intense emission located at 550 nm in solution and 603 nm in film. The HOMO and LUMO energies of the polymer were estimated to be −5.4 and −3.4 eV, respectively, by cyclic voltammetry. Polymer solar cells were fabricated based on the blend of the polymer and methanofullerene [6,6]-phenyl C61-butyric acid methyl ester (PCBM). The power conversion efficiency of 0.7% was achieved under AM 1.5, 100 mW/cm² using polymer:PCBM (1:4, w/w) as active layer.     

Polymer reaction engineering: From reaction kinetics to polymer reactor control

Polymer reaction engineering is a relatively “young”, very broad, multidisciplinary, rapidly developing field. It is the combination of polymer science, chemistry and technology with process engineering principles. The outcome of this high degree of synergism has evolved over the last fifteen or so years towards an area that includes any or all of the following: polymerization and post-polymerization (chemical modification) reaction kinetics; mathematical modelling and process simulation; polymer reactor design and scale-up; sensor development and process monitoring; and polymer reactor optimization, state estimation and computer control. This article will attempt to give an overview of the results obtained in our laboratory over the last seven years from systematic studies of polymer reaction engineering and polymer production technology problems. These problems cover all aspects of polymer reaction engineering mentioned above. Going from fundamentals to practice, the basic premise of the article is that only by adopting a holistic approach can one devise effective strategies in order to achieve the final objective of more efficient polymer reactor design and control, and hence improved production systems of polymeric materials.     

Grafting of hyperbranched polymers: From unusual complex polymer topologies to multivalent surface functionalization

In this feature article, the grafting of hyperbranched polymers to different substrates is reviewed. Both grafting onto macromolecules with different topologies (homogeneous grafting) and the resulting complex polymer architectures containing highly branched segments as well as their applications are discussed. In the second part grafting of hyperbranched polymers on surfaces, i.e., planar surfaces and spherical particles (heterogeneous grafting), with respect to specific applications, such as bio-repellent surfaces or soluble carbon nanotubes is described. In all cases, the one-step synthesis and the resulting highly branched topology of the hyperbranched building blocks is beneficial for the convenient introduction of a large number of functional groups to the substrates. These multifunctional hybrid materials open interesting options for applications, e.g., for highly functional nanoparticles or nanocomposites.