pinecone/core-2020-05-10-deduplication huggingface dataset:
Stereospecific Anionic Polymerization of α-(Hydroxymethyl)acrylate with Protective Group

Anionic polymerizations of hydroxyl-protected α-(hydroxymethyl)acrylates were investigated. The methyl ester with methoxymethyl (1-MOM) and allyl (1-allyl) protecting groups were polymerized by isopropyl α-lithioisobutyrate (Li-iPrIB) in toluene at −78 °C, affording highly isotactic polymers. Similarly, the polymerization of ethyl ester (2-MOM) gave an isotactic polymer, while those of t-butyl (3-MOM) and isobutyl (4-MOM) ester did not form any polymeric products. The hydrolysis of poly(2-MOM) in acidic conditions resulted in the deprotection of MOM group, although the acid also catalyzed the ester exchange between the neighboring units to form lactone units, as observed by 1H NMR analysis, IR spectroscopy and thermogravimetric analysis. A film of poly(2-MOM) exposed to HCl vapor for 2 h became insoluble in any organic solvents due to the lactonization in solid state
Activation of a bis-(phenoxyimine) titanium (IV) catalyst using different aluminoxane co-catalysts

This is the peer reviewed version of the following article: ROMANO, D., RONCA, S. and RASTOGI, S., 2015. Activation of a bis-(phenoxyimine) titanium (IV) catalyst using different aluminoxane co-catalysts. Macromolecular Symposia, 356(1), pp.61-69., which has been published in final form at http://dx.doi.org/10.1002/masy.201500047. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.The activation of a bis-phenoxyimine catalyst based on titanium (IV) using different aluminoxanes (MAO, PMAO and MMAO12) has been studied. The effect of a co-catalyst modifier (BHT) used in combination with the MAO has been also tested. In particular, the effect of the activation time between the catalyst and the different aluminoxanes has been taken into consideration. On increasing the activation time between catalyst and the different aluminoxanes and TMA-free MAO, differences in the catalyst activities have been observed. UHMWPEs having a reduced number of entanglements have been synthesized activating the FI catalyst with MAO and TMA-free MAO. The obtained reactor powders can be solid-state processed below the melting temperature in order to obtain high modulus/high tenacity tapes used for body armor and vehicle protection applications
Shear Viscosity of Poly (acrylamide/acrylic acid) Solutions

This is the peer reviewed version of the following article: Riahinezhad, M., McManus, N., & Penlidis, A. (n.d.). Shear Viscosity of Poly (Acrylamide/Acrylic Acid) Solutions. Macromolecular Symposia, 360(1), 179–184, which has been published in final form at https://doi.org/10.1002/masy.201500092 This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.Acrylamide (AAm)/Acrylic acid (AAc) copolymers are being used in a wide spectrum of applications, from which enhanced oil recovery (EOR) is the target application in this research study. The shear viscosity of the copolymer solution is extremely important in determining the performance properties of AAm/AAc copolymers. A series of copolymers with selected properties were prepared to study the effect of polymer concentration, copolymer composition, and salinity on the shear viscosity of the copolymer solutions. The results revealed the considerable effect of solution concentration and salinity on shear viscosity. Moreover, the behavior of the copolymer composition showed a maximum with respect to shear viscosity.Natural Sciences and Engineering Research Council (NSERC) of Canada
Canada Research Chair (CRC) progra
An Overview of the Potential of UV Modification of Polypropylene

This is the peer reviewed version of the following article: Amintowlieh, Y., Tzoganakis, C., & Penlidis, A. (2016). An Overview of the Potential of UV Modification of Polypropylene. Macromolecular Symposia, 360(1), 96–107, which has been published in final form at https://doi.org/10.1002/masy.201500110. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.UV radiation with a photoinitiator has been utilized to modify polypropylene (PP). Factors affecting solid state photomodification were studied and the optimal processing conditions for formation of three different structures (degraded, long chain branched and crosslinked) in PP were determined. A long radiation time (more than 5 minutes) is required to form long chain branched PP (LCBPP) and this exposure time is even higher for production of crosslinked PP (XPP). Trimethylolpropane triacrylate (TMPTA) was utilized to decrease UV radiation duration. Optimal concentrations of TMPTA and photoinitiator for formation of long chain branched and crosslinked PP were determined. Finally, a setup was suggested for continuous photomodification of PP using a twin screw extruder. In this design, PP strands are irradiated directly after the die. Optimal photoinitiator (benzophenone) concentration, coagent (TMPTA) concentration and radiation time required to form controlled rheology (CRPP) or long chain branched PP or crosslinked PP were identified.Natural Sciences and Engineering Research Council (NSERC) of Canada
Canada Research Chair (CRC) progra
Synthesis and Characterization of Magnetic Colloids

Magnetic fluids which constitute a suspension of magnetic nanoparticles in a carrier liquid are termed ferrofluids. Ferrofluids are smart fluids exhibiting both magnetic and fluid like characteristics. In the present study, we report on ferrofluidswhich are suspensions of magnetite (Fe3O4) nanoparticles in carrier fluids of varying viscosity. The magnetite nanoparticles have been synthesized by a chemical co-precipitation method.X-Raydiffraction of the as prepared sample revealsa single phase of magnetite.SEM characterisation reveals regular morphology and a narrow size distribution for the synthesized nanoparticles. These are dispersed in pure water and mixtures of water and glycerol using suitable surfactants and ultrasonicated. Our studies reveal that the stability of the ferrofluids have a strong dependence on the viscosity of the carrier fluid as well as the pH, with high viscosity and low pH yielding more stable ferrofluids. While low concentration of the magnetic component renders it impossible to see signatures of its presence in Raman spectroscopy, SQUID magnetometryreveals the presence of the magnetic component suggesting a distribution in size of the nanoparticles with a broad blocking temperature range. Further, a magnetic anomaly is seen at the freezing point of the carrier fluid in the ZFC-FC measurements for the ferrofluid made with 50 v/v aqueous glycerol solution. Â© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei
Effect of Bovine Serum Albumin on Red Blood Cell Optical Anisotropy Probed Through the Optomechanical Response in an Optical Trap

The dynamics of trapped entities in an Optical Trap (OT) can yield information with regards to their viscoelastic response as well as optical anisotropy, if any. Detailed analysis of such dynamics correlated with parameters which affect the response can yield additional clues to the exact effect of these on the trapped entities. In this work, we illustrate this point by showing how the altered behavior of Red Blood Cells (RBC) treated with Bovine Serum Albumin (BSA) yields information about the nature of action of BSA, on which there is no current consensus in literature. We conclude from our studies that BSA treatment leads to a change in the birefringence of the RBCs, a conclusion arrived at from the altered optomechanical response of such cells in a linearly polarized Gaussian beam OT. Furthermore, we argue that the observed changes in cellular optical anisotropy may be thought of as due to changes in the curvature of the RBC membrane. We also note that BSA action could help mimic pathological conditions that result in an altered cell shape. Â© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei
From the Plateau problem to periodic minimal surfaces in lipids,
  surfactants and diblock copolymers

We present the novel method for generation of periodic surfaces based on the
simple Landau-Ginzburg model of microemulsion. We test the method on four
minimal surfaces (P,D,G, and I-WP), find two new surfaces of cubic symmetry,
show how to obtain periodic surfaces of high genus and n-tuply-continuous
phases. We point that the Landau model used here should be generic for all
systems characterized by internal interfaces, including the diblock copolymer
systems.Comment: 15 pages, Plain TeX , figures available on request or at
  http://saka.ichf.edu.pl/WTGRH/surfaces.htm
Prediction of sol fraction and average molecular weights after gelation for non-linear free radical polymerizations using a kinetic approach

Mass balance equations in terms of the moment generating function of the distribution of mole concentrations of polymer species for free radical copolymerizations of mono/divinyl monomers could be numerically solved after gel point using open source code ACDC, needed for extremely stiff two-point boundary value problems. For the first time, it became possible to compare the error of earlier well-known approximated estimation methods for the weight fraction of sol and average molecular weights to this accurate mathematical solution. It turns out that predictions by the pseudo-kinetic method are reasonable only when equal reactivity of double bonds prevails, causing early gelation in the batch reactor. Otherwise the discrepancies between the exact and approximate solutions are quite important
Signatures of a Concentration Dependent Flory chi Parameter: Swelling
  and Collapse of Coils and Brushes

The quality of solvents of polymers is often described in terms of the Flory
chi parameter typically assumed to depend only on the temperature, T. In
certain polymer-solvent systems fitting the experimental data enforces the
replacement of chi(T) by a concentration dependent chieff. In turn, this
modifies the swelling and collapse behavior. These effects are studied, in the
framework of a mean-field theory, for isolated coils and for planar brushes.
The phi dependence of chieff gives rise to three main consequences: (i) Shift
in the cross-over between Gaussian and self-avoidance regimes; (ii) A
possibility of first-order collapse transition for isolated flexible coils;
(iii) The possibility of a first-order phase transition leading to a vertical
phase separation within the brush. The discussion relates these effects
directly to thermodynamic measurements and does not involve a specific
microscopic model. The implementation for the case of
Poly(N-isopropylacrylamide) (PNIPAM) is discussed.Comment: 12 pages, 9 figure
Efficient simulations of charged colloidal dispersions: A density
  functional approach

A numerical method is presented for first-principle simulations of charged
colloidal dispersions in electrolyte solutions. Utilizing a smoothed profile
for colloid-solvent boundaries, efficient mesoscopic simulations are enabled
for modeling dispersions of many colloidal particles exhibiting many-body
electrostatic interactions. The validity of the method was examined for simple
colloid geometries, and the efficiency was demonstrated by calculating stable
structures of two-dimensional dispersions, which resulted in the formation of
colloidal crystals.Comment: 6 pages, 4 figure
Transient behavior and gelation of free radical polymerizations in continuous stirred tank reactors

Using the authors' previously developed method for the general kinetic analysis of non-linear irreversible polymerizations, the simulation of free radical homogeneous polymerization systems with terminal branching and chain transfer to polymer has been carried out for continuous stirred tank reactors. Its improved accuracy on the numerical evaluation of generating functions has been exploited in order to perform their numerical inversion and chain length distributions could also be estimated with or without the presence of gel. A comparison with alternative techniques emphasizing the effect of their simplifying assumptions on the accuracy of calculations is also presented
A Simple Relation for the Concentration Dependence of Osmotic Pressure and Depletion Thickness in Polymer Solutions

We propose simple expressions II/IIo = 1 + and (omega/omega(ex))(3 alpha-1) and (delta(0)/delta)(2) = 1 + (omega/omega(ex))(2 alpha) for the osmotic pressure II and the depletion thickness 6 as a function of the polymer concentration omega. Here, IIo and delta 0 correspond to the dilute limit, and omega(ex) is an extrapolation concentration which is of the order of the overlap concentration omega(ov). The De Gennes exponent a describes the concentration dependence of the semidilute correlation length xi similar to omega(-alpha) it is related to the Flory exponent nu through alpha = nu/(3 nu - 1.). The quantity omega(ex) is experimentally accessible by extrapolating the semidilute limit towards II = IIo or delta = delta(o). These expressions are exact in mean field, where the ratio omega(ex)/omega(ov) (0.49 for II, 0.41 for delta) follows from established models. For excluded-volume chains they describe simulation data excellently: in this case omega(ex)/omega(ov) is 0.69 for II and again 0.41 for delta. We find also very good agreement with experimental data
Crosslink Density Changes during the Hydrolysis of Tridimensional Polyesters

The hydrolysis of almost ideal networks based on macrodiols of average molar mass about 2 kg mol 1, with L¼18 ester groups per chain is studied. Tensile testing is used to evaluate the crosslink density through the statistical theory of rubber elasticity at two temperatures and three values of relative humidity. A kinetic model for ester consumption including an autocatalysis term is proposed and combined with two original approaches for modeling the crosslink density changes. This allows kinetic parameters of hydrolysis to be determined, and very good predictions are obtained for the variations of crosslink density (or elastic modulus) in the three aging conditions
considered. The initial curvature of elastic modulus versus time is predicted positive for weak autocatalysis and negative for strong autocatalysis. The obtained conversion ratio at degelation is found to decrease sharply with the number of esters per elastically active chaincontrat de recherche SAFRAN - ART
Equilibrium morphologies and force extension behavior for polymers with hydrophobic patches : role of quenched disorder.

Equilibrium morphologies and mechanical properties of copolymers with hydrophobic segments are explored using Langevin dynamics simulations. The interplay between different length scales, namely, persistence length ℓp, and disorder correlation length p, in addition to the fraction of hydrophobic patches f, determines the equilibrium morphology and in turn their mechanical response. Globular and coil phases for flexible chains and core-shell and looped morphologies for semi-flexible ones are reported. Consequently, a force induced globule-coil transition for flexible chains is observed for all disorder realizations, with p dictating the force vs. extension curves. Semi-flexible chains with same ℓp and f but different p, show different sequences of force-induced conformational transitions on account of their differing equilibrium conformations
Spherically symmetric solvent is sufficient to explain lower critical
  solution temperature in polymer solutions

We study the lower critical solution temperature (LCST) in thermoresponsive
polymer solutions by means of a coarse grained single polymer chain simulation
and a theoretical approach. The simulation model includes solvent explicitly
and thus accounts for solvent interactions and entropy directly. The
theoretical model consists of a single chain polymer in an implicit solvent
where the effect of solvent is included through the intra-polymer solvophobic
potential proposed by Kolomeisky and Widom. Our results indicate that the LCST
behavior is determined by the competition between the mean energy difference
between the bulk and bound solvent, and the entropy loss due to the bound
solvent. At low temperatures, solvent molecules are bound to the polymer and
the solvophobicity of the polymer is screened, resulting in a coiled state. At
high temperatures the entropy loss due to bound solvent offsets the energy gain
due to binding which causes the solvent molecules to unbind, leading to the
collapse of the polymer chain to a globular state. Furthermore, the coarse
grained nature of these models indicates that mean interaction energies are
sufficient to explain LCST in comparison to specific solvent structural
arrangements
Comparison between RVE and full mesh approaches for the simulation of compression tests on cellular metals

Metal foams are materials of recent development and application that show interesting combinations of physical and mechanical properties. Many applications are envisaged for such materials, particularly in equipments of passive safety, because of their high capacity of energy absorption under impact conditions. The damage analysis in metallic foams is a complex problem and must be performed in a finite strain context. Considering that compression is the dominant loading in impact situations, a finite deformation simulation including damage effects of a compression test on a cellular metal sample is shown in this work. The main objective of the paper is to compare simulations considering periodic boundary conditions, by means of a representative volume element (RVE) approach, with results obtained using full meshes. It is shown that, when the imposed deformation is high, the use of RVE does not describe in a proper manner the deformation that occurs at the walls of cells. This characteristic of RVE approach results in a too stiff behavior when considering load-displacement relations. A comparison with experimental results is also presented
Substituting conventional steel alloys by carbon fibre composites in structural parts of an existing laser cutting equipment

In the present work, a finite element (FE) analysis was employed to validate the use of advanced carbon fibre composites as replacement of traditional low-alloy steel in the construction of the main runway frame structure of a laser cutting equipment currently available in the market. This new composite solution was adopted to increase the current laser equipment precision and cutting speed. The main objective was to enhance the machine cutting performance by using much stiffer and lighter main structural runway frames to support the machine cutting head and all major laser beam mirrors and lens, which allows decreasing dramatically the inertial and vibration efforts developed in service through the use of carbon fibre composites.
The paper presents, compares and discusses the mechanical and dynamical behaviour obtained in the FE simulations made by using both solutions, the current one based on a steel frame and the new innovative composite adopted structure. The processing method to be used in the production of the innovative composite structure is also proposed. Finally, as production costs may also have an important impact on final equipment commercial price and acceptation, an economical study considering both manufacturing situations (currently used and new one) are discussed
Effects of thermal creep of prestressed steel on post-tensioned concrete slabs in and after fire

The effects of thermal creep of prestressing steel on post-tensioned concrete slabs in and after fire were investigated based on existing thermal creep model and calibrated parameters in this paper. A nonlinear finite element model was built up employing ABAQUS package, taking into account frictionless contact behaviour between prestressing steel tendons and surrounding concrete. The nonlinear material behaviour of concrete and prestressing steel at elevated temperatures was taken into account, where three material models for prestressing steel were adopted with or without considering thermal creep, and based on the model from EN 1992-1-2. The finite element model developed was verified against experimental results from the literature, showing that the model considering thermal creep was more accurate. Then the fire resistance period and responses of post-tensioned concrete slabs in and after fire were investigated based on the verified model. Ignoring thermal creep underestimated the fire resistance period but overestimated the residual tendon stresses. The model from EN 1992-1-2 achieved nearly the same effects as the model considering thermal creep in fire but might yield inaccurate evaluation of residual tendon stresses. The model considering thermal creep worked well under fire and in the post-fire conditions yielding reasonable predictions.postprin
Position dependent surface quality in selective laser melting

Additive manufacturing receives nowadays opulent attention in both media and ongoing research. In particular, the techniques involving full melting of the raw material, enabling the fabrication of directly deployable components, are of high interest. To date, there are still secondary influences which are yet to be considered, leading to substantial, mainly directional dependent, deviations. The study at hand investigated the surface roughness dependencies in plane, focusing on the interaction of the unidirectional inert gas stream with the irradiation sequence; more precisely the weld splashes emerging from the melt pool, and the resulting in plane pattern. The surface roughness of the upwards orientated faces revealed clear fluctuations, being lowest close to the gas-inlet and also in the back area of the machine. Perpendicular to the fabrication plane aligned surfaces did not reveal any volatility regarding the inert gas stream. Increasing the energy density of the irradiation led to an increase in the surface roughness of all side faces, but to an improved roughness of the upwards facing surfaces coupled with a significant reduction in evident weld splashes.An Unassigned Group, An Unassigned DepartmentFull Tex
Combination of finite element method and Drucker-Prager Cap material model for simulation of pharmaceutical tableting process

Density-dependent Drucker-Prager Cap (DPC) model is widely used for assessing the compaction behaviour of powders due to its capability of capturing the various phenomena associated with the powder compaction process such as work hardening, nonlinear densification, and frictional and compressible behaviour of the powder. This paper presents a full description of the Drucker-Prager Cap model for the compaction behaviour of microcrystalline cellulose (MCC) Avicel PH101 pharmaceutical powder. The experimental calibration process of Drucker-Prager Cap is detailed and all model parameters are calculated as a function of powder relative density. Also, the calibrated parameters are implemented in finite element code to perform a numerical simulation of a typical pharmaceutical tablet. The results showed that the finite element model (FEM) was able to accurately predict the compaction behaviour of the microcrystalline cellulose powder. Furthermore, the finite element predictions of stress and density distributions of the powders during the compaction were used to analyse the failure mechanisms associated with tableting