Crystallizable Material Research Articles

Fast Evaluation and Comparison of the Energy Performances of Elastomers from Relative Energy Stored Identification under Mechanical Loadings.

The way in which elastomers use mechanical energy to deform provides information about their mechanical performance in situations that require substantial characterization in terms of test time and cost. This is especially true since it is usually necessary to explore many chemical compositions to obtain the most relevant one. This paper presents a simple and fast approach to characterizing the mechanical and energy behavior of elastomers, that is, how they use the mechanical energy brought to them. The methodology consists of performing one uniaxial cyclic tensile test with a simultaneous temperature measurement. The temperature measurement at the specimen surface is processed with the heat diffusion equation to reconstruct the heat source fields, which in fact amounts to surface calorimetry. Then, the part of the energy involved in the mechanical hysteresis loop that is not converted into heat can be identified and a quantity is introduced for evaluating the energy performance of the materials. This quantity is defined as an energy ratio and assesses the ability of the material to store and release a certain amount of mechanical energy through reversible microstructure changes. Therefore, it quantifies the relative energy that is not used to damage the material, for example to propagate cracks, and that is not dissipated as heat. In this paper, different crystallizable materials have been considered, filled and unfilled. This approach opens many perspectives to discriminate, in an accelerated way, the factors affecting these energetic performances of elastomers, at the first order are obviously the formulation, the aging and the mechanical loading. In addition, such an approach is well adapted to better characterize the elastocaloric effects in elastomeric materials.

A Cross-Linking/Percolating-Integrated Strategy to Enhance Crystallizable Rubber Using Rod-Like Reactive Biobased Nanocrystals.

Cross-link-based and percolation-based methods have been separately applied to develop highly elastic crystallizable materials. However, cross-linking may exert a trade-off effect between the strength and the stretchability, and the heterogeneous nucleation of percolation fillers may change the crystalline behavior in an undesirable way and may decrease the toughness. We thus focused on exploring a method to increase the elastic properties of crystallizable polymers with no strength decrease. Using cellulose nanocrystals (CNCs) with high percolation properties due to their high aspect ratio, we integrated the two strategies of cross-link and percolation to improve the full mechanical properties of eucommia ulmoide gum (EUG), a sustainable polymer, for developing green composite materials. The crystallinity of EUG could decrease to 22% with thiol-functionalized CNCs (mCNCs), solving the urgent problem of EUG on its inevitably high crystallinity from its trans-double bonds. The thiol-functionalization was to offer CNC chemical activity to cross-link with EUG, which limited the segment movement of the EUG around CNC and decrease the heterogeneous nucleating ability of CNC. Then, the strength and elongation at break of EUG-based nanocomposite maximally increased to 16.2 MPa and 498%, respectively. Such an EUG-based material was prepared with biomass resources and was a qualified candidate for sustainable elastomers, which was of high industrial potential in packing materials.

About the elongation at break of unfilled natural rubber elastomers

This paper presents the characterization of the mechanical properties, of the ability to crystallize thermally or under strain, and of the Elastically Active Chains (EAC) network of Natural Rubber elastomer, whose EAC average density and length distribution were modified by thermo-oxidative ageing. EAC length distribution is not a critical parameter for λbreak in elastomers which do not crystallize (as far as the quantity of free and dangling chains stays negligible, which is the case in this study). However, it becomes important in crystallizable materials, since it controls the chains quantity which can be stretched enough to crystallize. When this quantity is large enough, the material can be stretched up to λc, and the crystallization process will enable to increase both λbreakand σbreak. Conversely when it is too low, λbreakis seemingly mainly governed by the average EAC density and a power law then links both quantities.

The modified van der Waals equation of state

PVT data of crystallizable materials (CM), minerals, alkali, alkali halides, metals, mineral oxides and hydroxides, rare gas, water, organic compounds and polymers, published in the literature are reanalyzed. It is shown that all these materials under pressure verify the modified van der Waals equation of state (mVW-EOS), discussed recently [J. Rault, Eur. Phys. J. E 40, 82 (2017)]. The characteristic parameters P*V* of this EOS depend only on the nature of the material and not on its state (liquid, glassy, solid of different structure) and whatever are its conductivity and magnetic properties (insulator, conductor, superconductor, paramagnetic, ferromagnetic). This EOS explains the following properties: (a) the fan structure of the isobars V(T), and of the tangents to the isotherms V(P); (b) the superposition principle of the isotherms V(P); (c) the αB rule: the constancy of the thermal pressure coefficient (dP/dT)V = αB, product of the thermal expansion coefficient α and the bulk modulus B; (d) its relation with the Slater conjecture: (dP/dT)V ~ dP/dTm in crystallized materials, Tm being the melting temperature. The characteristic pressure P* (T and V independent) is compared with the various pressures: (i) Pcoh = Ecoh/V, the cohesive energy density; (ii) PLm = Lm/ΔVm, Lm and ΔVm being the enthalpy and volume jumps at the melting, respectively; (iii) PD = ΔHa/DVa, ratio of the activation parameters of the autodiffusion coefficient; (iv) PX = X∕X′, X being the bulk modulus B, shear modulus G, elastic constants Cij, and the yield stress σy of the CM, X′ their pressure derivative (at ambient conditions). All the elastic constants B, G, Cij and the yield stress σy are linear functions of P at low pressure (P < P*) and extrapolate to zero at the same negative pressure − PX = −P*. (e) PBγ = B∕γ* ratio of the bulk modulus B and Gruneisen parameter γ* at zero pressure. (f) PΔVm is the pressure deduced from the linear relation between the volume jump ΔVm(P) at the transition (melting or crystalline transition) and the pressure. The universal relation P* = Pcoh = PLm = PD = PB = PG = PCij = Pσy = PΔVm is observed and discussed. In molecular compounds such as H2O, H2, and polymers with different intra- and intermolecular interactions, the compression involves two different processes, at low and high pressures, verifying the mVW-EOS with characteristic pressures P1* and P2*. The ratio of these pressures is about the ratio of the weak intermolecular and strong intramolecular bond energies. The generalized modified equation of state (gmVW-EOS) describes the two-step process of compression in materials having two (or several) types of bonds.

Properties and thermal behavior of natural deep eutectic solvents

Natural deep eutectic solvents (NADES) have shown to be promising sustainable media for a wide range of applications. Nonetheless, very limited data is available on the properties of these solvents. A more comprehensive body of data on NADES is required for a deeper understanding of these solvents at molecular level, which will undoubtedly foster the development of new applications. NADES based on choline chloride, organic acids, amino acids and sugars were prepared, and their density, thermal behavior, conductivity and polarity were assessed, for different NADES compositions. The NADES studied can be stable up to 170°C, depending on their composition. The thermal characterization revealed that all the NADES are glass formers and some, after water removal, exhibit crystallinity. The morphological characterization of the crystallizable materials was performed using polarized optical microscopy which also provided evidence of homogeneity/phase separation. The conductivity of the NADES was also assessed from 0 to 40°C. The more polar, organic acid-based NADES presented the highest conductivities. The conductivity dependence on temperature was well described by the Vogel–Fulcher–Tammann equation for some of the NADES studied.

Mechanical Behavior of a Series of Copolyester Blends near the Glass Transition: Monotonic and Load-Hold Behavior in Compression

Monotonic loading tests were conducted on five commercial blends of poly(ethylene terephthalate) (PET) and poly(1,4-cyclohexylenedimethylene terephthalate) (PCT) at temperatures of 90°C and 100°C and strain rates of 0.1/s, 0.05/s, and 0.005/s in uniaxial and plane strain compression. On comparing the mechanical behavior of the five materials, it was found that the behavior of the low-PCT content materials was different from the high-PCT content materials only at conditions that favored strain-induced crystallization, particularly in plane strain compression. Load-hold tests were also conducted on three of the blends with similar results to the monotonic tests. Material differences were only pronounced at certain conditions, and in these cases the low-PCT content materials showed increased strain hardening after the hold period while the high-PCT content material did not. Therefore, it was found that the addition of a hold period was not exclusively required to observe differences in the crystallizable materials over the noncrystallizing blends. The increased strain hardening likely associated with crystallization in PET was only observed when the following conditions were met: (i) strain rates of 0.1/s and above, (ii) temperatures of 90°C–100°C, (iii) plane strain compression, and (iv) after a certain level of deformation.

924 POSTER Radiosensitization of chlorogenic acid in Lewis lung carcinoma through inhibiting NF-úB mediated cIAP2

The role of sample preparation and purification cannot be overestimated in experimental structural biology studies, especially for the crystallization of macromolecules. Purity, homogeneity, conformational state, and sample yield are major considerations in the preparation and purification of biological materials for structural studies. This chapter delineates some of the techniques used to produce large quantities of crystallizable material for chromatin studies. The scale of the procedures can be adapted to suit the situation. The first protocol described is for the isolation of histones from eukaryotic sources. Subsequent topics include isolation and purification of defined sequence DNA from recombinant sources. Reconstitution of nucleosome core particles (NCP) from histone octamer and defined sequence DNA is detailed, followed by descriptions for crystallizing NCP.

Real time observation of crystallization in polyethylene oxide with video rate atomic force microscopy

Video rate atomic force microscopy (VideoAFM), with a frame rate of 14 frames/s and a tip velocity of up to 15 cms −1, is used to image polyethylene oxide films during crystal growth. The capabilities of VideoAFM when applied to semicrystalline polymer surfaces are explored. Image quality comparable to that found with conventional contact AFM is achieved but with a nearly 1000 times improvement in time resolution. By applying the technique to the real-time observation of crystal growth, different modes of rapid crystallization are followed in real time. Observation of the spherulite growth front allows measurement of growth rates at the lamellar scale, from which a factor of two difference in the rate of radial growth to the rate of tangential growth is observed, confirming that the elongated nature of spherulite lamellae is due to geometric constraints rather than an inherent fibrillar character. Measurements on screw dislocation growth, when large amounts of crystallizable material is trapped at the surface show that the terrace height does not influence the rate of crystal growth, confirming that under these conditions processes at the lamellar growth front control the rate of growth. When only a thin film of molten material is left on the surface of the already crystallized film dendritic growth is observed, implying a diffusion controlled process under these far from equilibrium conditions.

Electron crystallography on polymorphic organics

Abstract Organic materials, such as non-linear optical active compounds (1-(2-furyl)-3-(4-aminophenyl)-2-propene-1-one (FBAPPO) and 1-(2-furyl)-3-(4-benzamidophenyl)-2-propene-1-one (FAPPO)), polymeric materials like the metal coordinated polyelectrolyte (Fe(II) [ditopic bis-terpyridin] (MEPE)) or polymorphic materials (e.g. Cu-phthalocyanine), which do not crystallize big enough for single crystal x-ray structure analysis have been investigated by electron diffraction (ED) at 100 and 300 kV acceleration voltage. Sample preparation (direct crystallization, ultra sonication, ultra microtomy), diffraction strategies (selected area diffraction, nano diffraction, use of double-tilt rotation holder), data collection and data processing as well as structure solution strategies have been chosen dependent on the different requirements of the compounds under investigation. Structure analysis was carried out by simulation using ab initio quantum-mechanical methods like density functional theory (DFT), semi-empirical approach (MNDO/AM1/PM3) and force field packing energy calculations (DREIDING). The structure models resulting from simulation were refined kinematically as rigid bodies. Subsequently, refinements by multi-slice least squares (MSLS) procedures taking dynamical scattering into account were performed. The described combination of different methods which was used successfully on crystallizable materials is also adaptable to insoluble organic materials (e.g. pigments) and polymorphic systems.

Preparation and Crystallization of Nucleosome Core Particle

Publisher Summary The role of sample preparation and purification cannot be overestimated in experimental structural biology studies, especially for the crystallization of macromolecules. Purity, homogeneity, conformational state, and sample yield are major considerations in the preparation and purification of biological materials for structural studies. This chapter delineates some of the techniques used to produce large quantities of crystallizable material for chromatin studies. The scale of the procedures can be adapted to suit the situation. The first protocol described is for the isolation of histones from eukaryotic sources. Subsequent topics include isolation and purification of defined sequence DNA from recombinant sources. Reconstitution of nucleosome core particles (NCP) from histone octamer and defined sequence DNA is detailed, followed by descriptions for crystallizing NCP.

Correction of biased time domain NMR estimates of the solid content of partially crystallized systems

The solid content values obtained from the intensity of the nuclear magnetic resonance free induction decay signal of partially crystallized samples such as fats, supersaturated solutions, solid dispersions of waxes, gels are biased due to the difference between the proton density and mass density of the samples. It is shown here that this can be easily corrected with the specific volumes (determined gravimetrically) and proton densities (determined by time-domain nuclear magnetic resonance) of completely liquefied models of the solid and liquid phases and provided that the total amount of crystallizable material is known. The corrected data are in excellent agreement with the values obtained by differential scanning calorimetry for both model systems and real petroleum samples.

X-ray microscopy

The subject of X-ray microscopy (high-resolution X-ray imaging of general nonperiodic structures), an area in which much progress has been made in recent years, is reviewed. The main techniques are briefly described. Achievable performance levels, which for many years were highly speculative, can now be understood with fair accuracy in terms of basic X-ray and specimen properties, and techniques have progressed to the point where actual results are nearing those levels. In terms of specimen size and imaging resolution, X-ray microscopies lie between electron and light microscopy, and are thus suited to imaging extremely large and complex structures; in addition, they demand little or no specimen preparation, and can be used to observe local composition and chemical state as well as structure. Thus X-rays, which have played the leading role in imaging crystallizable materials, may also prove to be highly valuable in the imaging of very large non-crystalline structures. Throughout the treatment, attention is paid to the relationships connecting the subject with X-ray crystallography.

Influence of copolymer composition on the crystallization in PCL/SAN blends

Blends of poly(ε-caprolactone) (PCL) and poly(styrene- co-acrylonitrile) (SAN) show a miscibility window, i.e. for a fixed blend ratio ф, they are able to form a one-phase mixture in the liquid state, which is dependent on the copolymer composition β, and the temperature T. For miscible blends the Flory interaction parameter χ is smaller than χ s , the χ parameter at the spinodal. The minimum of χ, for a fixed T and ф, is at approximately 20 wt% acrylonitrile in SAN. Below the melting point the homogeneous liquid undergoes a liquid-solid phase transition (i.e. crystallization). We have studied the crystallization kinetics of miscible PCL/SAN blends as a function of β, ф and the crystallization temperature T c. The rate of crystallization G, which is equivalent to the radial spherulite growth rate, also exhibits a minimum, at a fixed T c and ф, for blends containing SAN with 20 wt% acrylonitrile. This behaviour is described in terms of a modified Hoffman-Lauritzen (HL) theory. From secondary nucleation plots it was shown, in addition, that the surface free energy (σσ e ) 1 2 has a minimum at a copolymer composition with 20 wt% acrylonitrile, again for fixed values of ф and T c. In contrast, according to the HL theory the lower surface free energy would lead to a faster crystallization. In order to explain the influence of polymer-polymer interactions on the crystallization kinetics it has to be assumed that the reptation of a crystallizable polymer chain towards the growing front of the crystal is slowed down by favourable interactions. Therefore, an additional term, ΔU∗, was introduced into the mobility expression used in the HL theory. The experimental findings show that the influence of U∗, the activation energy for the transport of crystallizable material, on the rate of crystallization predominates over the influence of (σσ e ) 1 2 .

Purification and crystallization of glycogen phosphorylase from Saccharomyces cerevisiae

Glycogen phosphorylase from Saccharomyces cerevisiae is activated by the covalent phosphorylation of a single threonine residue in the N terminus of the protein. We have hypothesized that the structural features that effect activation must be distinct from those characterized in rabbit muscle phosphorylase because the two enzymes have unrelated phosphorylation sites located in dissimilar protein contexts. To understand this potentially novel mechanism of activation by phosphorylation, we require information at atomic resolution of the phosphorylated and unphosphorylated forms of the enzyme. To this end, we have purified, characterized and crystallized glycogen phosphorylase from S. cerevisiae. The enzyme was isolated from a phosphorylase-deficient strain harboring a multicopy plasmid containing the phosphorylase gene under the control of its own promoter. One liter of cultured cells yields 12 mg of crystallizable material. The purified protein was not phosphorylated and had an activity of 4.7 units/mg in the presence of saturating amounts of substrate. Yeast phosphorylase was crystallized in four different crystal forms, only one of which is suitable for diffraction studies at high resolution. The latter belongs to space group P4 12 12 with unit cell constants of a = 161.1 A ̊ and c = 175.5 A ̊ . Based on the density of the crystals, the solvent content is 49.7%, indicating that the asymmetric unit contains the functional dimer of yeast phosphorylase.

Crystallinity in chemically crosslinked low-density polyethylene: 5. Annealing behaviour of XLPE-2

The annealing behaviour of lightly crosslinked low-density polyethylenes having various levels of extractable non-crosslinked polyethylene present has been studied. Three separate processes can be identified, which are (a) solid-state annealing, (b) recrystallization and (c) gel-sol separation in the molten state. Unlike linear or linear low-density polyethylene, annealing for long times does not result in crystallization of all crystallizable material; there is always a component present that crystallizes only on cooling if the annealing temperature is in excess of 90°C. The multiple melting peaks observed are not associated with macroscopic morphological features but arise largely from differences in the perfection of crystals or in the character of the amorphous phase in the vicinity of the crystal.

Crystallization, morphology, structure and miscibility of poly(ethylene oxide) based blends

AbstractResults of an investigation on the morphology, structure, isothermal crystallization, thermal behaviour and miscibility of poly(ethylene oxide) (PEO) based binary blends are reported. In particular poly(vinyl acetate)(PVAc), poly(methyl methacrylate) (PMMA) at different tacticity and poly(ethyl methacrylate) (PEMA) were added to PEO.It was found that with the only exception of isotactic poly(methyl methacrylate) (IPMMA), the addition of the above cited components causes a depression in both the spherulite growth rate and the overall kinetic rate constant. The experimental G and Kn were analyzed by means of the latest kinetic theory in order to determine the influence of composition on the process of surface secondary nucleation. The optical microscopy of thin films of the sample revealed that the blends crystallized with volume filling crystals at least up to 50/50 blend composition. The small angle X‐ray scattering curves were analyzed using a recently developed methodology. The structural properties of the blends were attributed to the presence of the non crystallizable material in the interlamellar or interfibrillar regions of PEO. From the glass transition temperature it has been deduced that an homogeneous amorphous phase is present for all the blends except for the PEO/IPMMA amorphous system. For the system PEO/atactic poly(methyl methacrylate) (APMMA) the miscibility was also predicted by theoretical approaches.

The Synthesis of Some Alkyl Hex-3-enopyranosiduloses

Routes to methyl 3,4-dideoxy-α-D-glycero-hex-3-enopyranosidulose 1a have been developed which use cheap readily-available chemicals, which are operable on a large scale and which have readily crystallizable materials as key intermediates (Scheme 4). Extensive use is made of reductive elimination of vicinal sulfonyloxy groups which is shown to operate equally well whether these groups on the pyranoside ring are in cis or trans relationship. Contrary to other reported cases, it is found that the carbon-2 allylic hydroxyl goup is oxidized with manganese dioxide whether it is in pseudoaxial or equatorial orientation.

Thermal behavior of annealed organic glasses

AbstractThe influence of annealing processes on the thermal behavior of organic glasses in the glass‐transition interval has been investigated and analyzed quantitatively. In detailed annealing studies of atactic polystyrene and Aroclor 5460, the absorption of thermal energy superposed on the increase in the specific heat at the glass transition, observed with suitably chosen heating rates, was followed by the differential thermal method. It is concluded that the absorption of thermal energy observed under these conditions parallels the extent of molecular relaxation that has taken place during the annealing period. It is not necessary to postulate a first‐order process to account for the energy absorption. Moreover, such a postulate leads to severe conceptual difficulties regarding the development of crystallinity in crystallizable materials. The areas and the shapes of the endotherms are considered in terms of the original physical properties of the quenched glasses and the anticipated equilibrium properties. Relationships between the extent of energy absorption and time‐dependent processes such as volume relaxation are discussed.

Crystalline Papain Derivative Containing an Intramolecular Mercury Bridge

Abstract A partially reduced derivative of papain, in which only the disulfide bond connecting the cysteine residues in positions 43 and 152 had been opened, was reacted with mercury chloride. The resulting crystallizable material contained 2 g atoms of mercury per mole of papain, and is denoted Pap·2Hg. One of the mercury atoms in this derivative is joined in complex with the free sulfhydryl group of papain which is involved in the catalytic site, whereas the second one is present in the form of an —S-Hg-S— bridge, which replaces the original —S—S— bond that had been reduced. Pap·2Hg is enzymatically active on a range of substrates; in respect to the hydrolysis of benzoyl-l-arginine ethyl ester its Vmax is similar to that of native papain, but its Km value is 0.042 compared to a value of 0.023 obtained for native papain. The internal mercury atom, in contrast to the one bound to the active sulfhydryl, is retained in the molecule under the conditions required for activating papain (0.005 m cysteine and 0.002 m EDTA). It is, however, totally removed upon extensive dialysis (48 hours) against 0.02 m EDTA, or when Pap·2Hg is exposed to the activating agents in the presence of 8 m urea. Fluorometric titrations of Pap·2Hg, in comparison to those of native papain and of commercial mercuripapain, show very high quenching effect of the 2 mercury atoms, but again indicate that during activation conditions 1 mercury atom is still present in the molecule. On the other hand, under the conditions leading to complete elimination of the mercury from Pap·2Hg, its titration curve is identical with that of native papain. The immunological reactivity of Pap·2Hg with antipapain serum is essentially identical with that of native papain.

On the origin of crystallizable RNA from yeast

Low molecular weight RNA, extracted from yeast by a warm detergent method, has previously been crystallized. It was at first thought to be transfer RNA. The RNA was later found to have a lower molecular weight than intact transfer RNA, though it had some arnino-acid acceptor activity. Intact transfer RNA could not be made to crystallize. In the present work, intact purified yeast transfer RNA was degraded by various means and attempts were made to isolate crystallizable fragments. All these attempts failed. Isolated yeast ribosomes were then degraded by limited treatment with alkali and the RNA fragments isolated. These fragments crystallized in the same way as the RNA extracted with detergent from whole cells. It is concluded that the crystallizable RNA extracted from whole cells was probably derived mainly from ribosomes and not from transfer RNA. The conclusion is consistent with observations on Sephadex fractions of the original crystallizable material; it probably contains less than 20% transfer RNA, with more than 80% RNA of ribosomal origin. Experiments with Escherichia coli ribosomes have not so far yielded crystallizable RNA, but it has been obtained from rabbit reticulocyte ribosomes. Implications of the results for ribosome and transfer RNA structure are discussed.