Study on the polycarboxylate superplasticiser by dual initiator synthesis: performance, polymerisation mechanism and microstructure

Polycarboxylate superplasticizers (PCs) with ether linkages and ester linkages between the main chains and the poly(ethylene glycol) (PEG) branch chains were synthesized, respectively. The effects of the PCs molecule linkage mode on the performance of concrete paste were investigated using the slump loss test and thermogravimetric analysis and analyzing fluidity, absorption, and setting time. Results showed that the linkage between main chains and PEG branch chains in PCs molecules had an important influence on the performance of cement paste and concrete prepared from them. PCs with ester linkages can endow the cement paste with higher fluidity and higher water‐reduction ratio resulting from the higher absorption amount on the cement particles. This is related with the alternating distribution of the carboxyl groups and branch chains of PEG when different macromonomers are involved in the preparation of PCs. PCs containing ester linkages are more vulnerable than PCs with ether linkages in an alkali environment, leading to quicker slump loss and shorter setting times. In contrast, PCs with ether linkages had excellent fluidity and slump flow stability. A slightly different ettringite hydration product was observed during the early period of the hydration of cement paste that employed these two PCs. Copyright © 2012 John Wiley & Sons, Ltd.

Polyion Complex Micelles Composed of All-TranS Retinoic Acid and Poly (Ethylene Glycol)-Grafted-Chitosan

Immunogenicity of murine mPEG-red blood cells and the risk of anti-PEG antibodies in human blood donors.

ABSTRACTStar‐shaped superplasticizers, which incorporated polyol ester with unsaturated bond at their cores and bore comb‐type structures as their arms were synthesized via esterification‐copolymerization in aqueous phase from pentaerythritol, acrylic acid (AA), and isopentenyl oxy poly(ethylene glycol ether) (TPEG). The monomer ratios of AA and TPEG were varied and comonomer sodium methallyl sulfonate (SMAS) bearing short side chains was added to regulate the arm structure of star‐shaped polycarboxylate superplasticizers (SPCEs). The effects of the SPCEs on cement paste were investigated and the cement dispersion as well as early hydration mechanism were explored. As a main result, SPCEs with SMAS and certain molar ratios for anchoring groups and PEO side‐chains in their arm structure exhibited good paste dispersion and fluidity retention, which also delayed the early hydration process and prolonged both the initial and the final setting time. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46312.

Separation of 2H NMR spectra assisted by molecular dynamics in diamagnetic and paramagnetic solids

Novel poly(amino acid)-type superplasticizers with enhanced dispersing performance for Portland cement doped with clay impurities

Through molecular structure design, modified polycarboxylate superplasticizers (PCEs) were synthesized via copolymerization using isoprenyl oxy poly(ethylene glycol) ether (TPEG), acrylic acid, and hydroxyethyl methacrylate phosphate. TPEG-PCEs were selected as potential dispersants for Na/Ca-bentonite containing cement mortar. Other two kinds of commercial PCE that were obtained based on methallyl ether (HPEG) and ethylene-glycol monovinyl polyethylene glycol (EPEG) as macromonomers were also applied in the mortar. The effects of the type of bentonite and its dosage, as well as the monomer structure of PCEs and the type of cement, on the dispersion properties of the bentonite-containing mortar were studied. According to the findings, the initial fluidity of the mortar was reduced by about 20 mm when two kinds of bentonite were used. Applying 3% Ca-bentonite resulted in 40% flow loss in the mortar after 1 h. The fluidity of the mortar with Na-bentonite exhibited lower dispersion ability than that with Ca-bentonite when HPEG-PCE and EPEG-PCE were chosen as dispersants. The TPEG-PCE exhibited superior dispersing performance over HPEG-PCE and EPEG-PCE and exerted a retarding effect on cement, being also weakly sensitive to clay content. Thus, TPEG-PCEs with phosphate groups present a viable alternative to conventional PCEs.

Background: Tuberculosis (TB), a disease caused by the bacillus bacteria Mycobacterium tuberculosis is one of the major contributors of ill health in the world. TB is ranked in the top 10 causes of death globally and it is the leading killer associated with a single infectious agent. According to the World Health Organization (WHO), global number of deaths associated with TB have been slowly declining with 1.3 million in reported 2016 and 2017, and 1.2 million reported in 2018 and 2019. Objective: The synthesis, characterisation, biological evaluations, and the prediction of ADMET properties of the novel benzylamine derivatives. Methods: Commercially available reagents and solvents were purchased from Sigma Aldrich and Merck (South Africa). All chemicals were used as received, unless otherwise stated. The synthesised crude compounds were purified by flash silica gel column chromatography (5 – 30% ethyl acetate in hexane). The successful formation and purity of the synthesised compounds was confirmed by NMR, HRMS and melting point. Results: The respective organic compounds were synthesised by treating 3-ethoxysalcyladehyde, 5-bromo-3-ethoxysalcyladehyde, 5-chloro-3-ethoxysalcyladehyde with various aromatic amines and the products were obtained in good to excellent yields. The 1H and 13C NMR spectra of all the products showed the appearance of the methylene signals ranging from 3.88 – 4.68 ppm and 42.25 – 52.57 ppm respectively. Additionally, most compounds showed anti-Mycobacterium tuberculosis activity that ranged between 20 and 28 µM. Conclusion: A total of 36 compounds were synthesised and successfully biologically evaluated against Mycobacterium tuberculosis (Mtb) H37RV strain. All compounds showed activity against Mtb at concentrations of > 20 µM < 28 µM with the exception of compound one that was active against Mtb at higher concentration (MIC90 > 125 µM).

Properties of interstitial liquid phase in cement paste, including the species and concentrations of polymers and ion etc., play an important role for the rheological properties of cementitious materials. In order to better understand their effect, an inert model substance, spherical silica beads (SBs) with defined surface and granulometry were used in the presence of electrolytes (CaCl2) and/or different polymers, including polycarboxylate superplasticizer (PCE) and polyethylene glycol (PEG). It was found the presence of Ca2+ greatly increases the viscosity and yield stress of silica beads paste (SBP), which is proportional to the [Ca2+]. For the effect of PCE, the addition of PCE is beneficial to the flowability of SBP, but a high dosage of PCE leads to a reversal effect. Furthermore, the yield stress firstly increases and then decreases with increasing [Ca2+] under the same dosage of PCE. The addition of PEG always increases the yield stress of SBP, regardless of the ion concentration and the presence or not of PCE.

A new water‐soluble, hydrolyzable polyethylene glycol di‐mercaptoacetate (PGM) was synthesized as a chain transfer agent. Subsequently, an early‐strength polycarboxylate superplasticizer (ESPC) was successfully prepared by using PGM as a chain transfer agent, along with acrylic acid, sodium methylallyl sulfonate (SMAS), and isoprene oxy poly(ethylene glycol) as comonomers. The effect of the ESPC on cement particles was systematically investigated. The fluidity, setting time, and compressive strength were measured to evaluate the performance of the ESPC and compared with those of a conventional polycarboxylate superplasticizer (PCE). The setting time of the ESPC can be shortened by 40 min in comparison with the PCE, and the compressive strength at 24 hr of setting time is increased by 5 MPa. In addition, X‐ray diffraction, thermogravimetric analysis, and scanning electron microscopy characterization were performed to investigate the effect of the ESPC on cement hydration from a microscopic level. Furthermore, the hydration heat was determined to investigate the interactions between the ESPC with the cement particles. It was found that if ester groups were introduced into the backbone chain of the ESPC and subsequently hydrolyzed, the ESPC was readily adsorbed onto cement particles. This enhanced adsorption improved the microstructure of the cement hydrate and accelerated the cement hydration process.

In this paper, a novel chitosan-g-(-O-methyl poly (ethylene glycol))-g-(-N-Tat peptide) (CS-mPEG-Tat) copolymer was synthesized. The synthesized intermediates and final products were characterized and confirmed by Fourier transform infrared spectrum, 1H nuclear magnetic resonance spectrum, and X-ray diffraction, respectively. The particle sizes, size distributions, and zeta potentials can also be determined by dynamic light scattering. Agarose gel electrophoresis study showed effective DNA-binding ability of CS-mPEG-Tat. In vitro cytotoxicity assay indicated that CS-mPEG-Tat copolymers were low toxic and cell compatible as the polymer concentration was smaller than 5 mg/ml. This work provides a facile approach to prepare biocompatible PEG-peptide-chitosan copolymer nanoparticles with controllable performances. In conclusion, the obtained CS-mPEG-Tat copolymer might be attractive cationic polymers for nonviral gene therapy.

ABSTRACTAcrylate‐containing polycarboxylate superplasticizers were synthesized by copolymerizing acrylic acid, α‐methallyl‐ω‐methoxy poly(ethylene glycol) ether, and acrylic esters [hydroxyethyl acrylate (HEA) or hydroxypropyl acrylate (HPA)]. Their dispersing effects and fluidity‐retaining capabilities were evaluated by spread tests of cement pastes. The temperature sensitivity of the performance was especially focused upon. It was found by Fourier transform infrared spectroscopy and specific anionic charge density measurements that the ester groups in the acrylate‐containing copolymers hydrolyze in alkaline conditions, and thus additional RCOO− groups are continuously produced. The gradual production of RCOO− leads to increasing charge density and hence increasing adsorption of the polymer on the cement surface. The hydrolysis of HEA units is slightly faster than of HPA units in the corresponding copolymers. By this mechanism, a post‐acting, or delayed, dispersing effect is realized. Such post‐acting polymers alone or formulated with normal polycarboxylate superplasticizer can be used achieve a long fluidity retention of fresh concrete, especially under elevated temperatures. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45753.

A novel polycarboxylate superplasticizer (PCE) with energy saving preparation was elaborately designed and synthesized by using acrylic acid (AA), hydroxypropyl acrylate (HPA) and isopentenyl polyethylene glycol (IPEG) as monomers. To investigate the effects of the preparation method on the effectiveness of PCE, the PCEs were prepared from energy-saving method and common method respectively, and the hydration heat evolutions of the cement pastes containing these PCEs were comparatively probed. Furthermore, the working mechanisms of the PCEs by different preparations were identified via adsorption behavior, adsorption kinetic and Zeta potential of the PCE on cement surfaces. The results showed that, this novel PCE prepared in an energy saving manner can significantly prolong the hydration process and present a stronger adsorption capacity. In addition, the adsorption of this PCE on cement surface exhibited a characteristic of pseudo first order kinetic equation model. The evaluation in energy conservation showed that, this energy saving preparation can save 1.548×104 kJ per 10 ton production. The aim of this study is to provide a new avenue to synthesize a PCE with economical method which achieves energy-saving preparation. Due to the indispensable application in construction industry, the innovations from this study contribute to the low energy-consumption production and high eco-effectiveness of the novel PCE, which has potential applications in low-emission building materials.

Polycarboxylate superplasticizer (PCE) was synthesized in non-aqueous system to achieve the rapid transportation and convenient preparation. The results showed that, PCE using isopentenyl polyethylene glycol (TPEG) or isobutenyl polyethylene glycol (IPEG) as macromonomer exhibited excellent paste fluidities and retaining properties at 80°C and 75°C, respectively. Fourier Transform infrared spectroscopy (FTIR) measurement confirmed the polymerization between monomers. The synthesized PCE as solid state was dissolved into water to prepare the PCE solution, and its cement application performances were studied systematically. The results showed that PCEs with good paste fluidity retentions exhibited the longest final setting time and the shortest setting time interval. The hydration heat results showed that PCEs with good fluidity properties can significantly delay the hydration process and lower the hydration heat.

2H nuclear magnetic resonance (NMR) spectra were obtained at 30.87 MHz for 8% (w/v) aqueous dispersions of mixtures of bile salts (MBS), mixed intestinal lipids (MIL; myristic acid, monomyristoylglycerol, dimyristoylphosphatidylcholine = 5:1:1), and cholesterol, in which a single lipid component is selectively 2H-labeled. Using the observation that the time-averaged quadrupole splitting of a C2H3 group varies according to whether it exists in a micellar, multilamellar or solid phase, one-, two-, and three-phase regions in the equilibrium phase diagram have been identified. From the intensities of the singlets and powder patterns in the wide-line 2H NMR spectra, the relative amounts of these organized molecular assemblies were determined. With different C2H3-labeled components in samples of identical total composition, the chemical composition of each phase was calculated for one point (20 mol % cholesterol; 50 mol % MIL, and 30 mol % MBS) in a two-phase region of the phase diagram where the 2H NMR spectrum displayed both a sharp spectral component and a broad uniaxial powder pattern. X-ray diffraction measurements on this sample confirmed that the uniaxial powder pattern in the NMR spectra can be assigned to multilamellar vesicles. At this same point in the phase diagram with the 2H label on the alpha-methylene site of myristic acid, both narrow and broad (delta v = 37 kHz) spectral components were again observed. Relaxation time (T1 and T2) measurements of the sharp spectral component indicate that this peak arises from rapidly tumbling aggregates which, at a total lipid concentration of 8% (w/v), are micellar particles and not unilamellar vesicles. These experiments demonstrate the feasibility of structural investigations of model digestive mixtures by 2H NMR.