Highly effective organometallic‐mediated radical polymerization of vinyl acetate using alumina‐supported Co(acac)2 catalyst: A case study of adsorption and polymerization

An alumina support system for cobalt^(II) acetylacetonate (Co(acac)₂) catalyst was studied for the cobalt‐mediated radical polymerization (CMRP) of vinyl acetate (VAc). We report a simple but efficient technique to produce this supported catalysts through the adsorption of Co(acac)₂ on the surface of alumina particles. Moreover, kinetic and thermodynamic study of Co(acac)₂ adsorption on the alumina support were conducted and the influence of effective parameters were investigated. It was found that using alumina‐supported Co(acac)₂ for radical polymerization of VAc yields polymers with controlled molecular weight, narrow molecular weight distribution, and high purity. For the alumina‐supported CMRP, changing the polymerization mechanism and domination of termination pathway compared to degenerate transfer pathway resulted in a 2.5 times increase in polymerization rate (k_ap) and a drop in induction time while maintaining a good control of the VAc polymerization. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46057.     

Electrophoretic deposition of titanium nitride coatings

Electrophoretic deposition of the titanium nitride (TiN) coatings from suspensions prepared by dispersion of TiN particles in triethanolamine (TEA) containing butanol medium was studied. Effects of the TiN particles concentration (C_TiN) on the weight of the deposited coatings, triethanolamine concentration (C_TEA=0.25, 0.5, 0.75, and 1 mL/L) on the Zeta potential of the TiN particles, suspension electrical conductivity and pH, as well as effects of the deposition voltage (V_d=60, 90, and 120 V) and time (t_d =1, 2, and 3 minutes) on the microstructure and thickness of the deposited coatings were investigated. Variations in deposition current density, effective deposition voltage, electrical resistance, and deposited coating weight versus deposition time were recorded. The morphology of the as‐dried coatings was studied using Scanning Electron Microscope (SEM). The results indicated that by increasing the C_TiN the weight of deposits increases linearly up to 40 g/L. For suspensions containing C_TiN=40 g/L, the optimum C_TEA is obtained to be 0.5 mL/L leading to Zeta potential of 43.25 mV. Uniform and crack‐free as‐dried coatings obtained at V_d and t_d of 90 V and 2 minutes, respectively.     

Morphological evolution on the surface of hydrothermally synthesized hydroxyapatite microspheres in the presence of EDTMP

Well-ordered and surface engineered hierarchical hydroxyapatite microspheres (HAM) were prepared via a template free hydrothermal process. Ethylene diamine tetra (methylene phosphonic acid) (EDTMP) was used as chelating or regulating agent for the first time in this study. The results indicated the formation of sheet-like particles in the absence of EDTMP. On the other hand, microspheres with radially grown nanorods (HAMNR) or nanosheets (HAMNS) on the surface were obtained (with average diameter of 5?µm) in the presence of EDTMP. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy were used to characterize the crystalline phases in the synthesized samples. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that EDTMP concentration played an important part in regulating the morphology to form well organized microspheres with nanosheets or nanorods on the surface. Brunauer-Emmett-Teller (BET) revealed an increase in the specific surface area with the change in morphology from the HAMNS to HAMNR. Possible mechanisms are proposed to account for the formation of different morphologies based upon thermodynamic and kinetic theories.     

Controlled release of fluorouracil (5-FU) from chitosan-co-poly(ethylene glycol)/ poly(glycerol sebacate)-co-poly(ethylene glycol)-coated iron oxide

A blend of polyglycerol sebacate-poly ethylene glygol/chitosan-poly ethylene glycol-coated iron oxide (PGS-PEG/CS-PEG@Fe₃O₄) nanoparticles for 5FU delivery was prepared by reverse ultrasonic emulsification method. To enhance polymers’ solubility, PEG was grafted. Chemical characterization was performed through Fourier transformed infrared and proton nuclear magnetic resonance spectra. In vitro assay revealed that release profile of 5FU-loaded PGS-PEG/CS-PEG@Fe₃O₄ is sustained. Moreover, cytotoxicity was analyzed on HT29 cell line at the presence of external magnetic field using the lactate dehydrogenase and Alamar Blue. Results illustrate that (PGS-PEG/CS-PEG@Fe₃O₄) is promising to use as a carrier for 5FU anticancer agent with sustained tailored release.     

The pozzolanic reactivity of monodispersed nanosilica hydrosols and their influence on the hydration characteristics of Portland cement

This study reveals that the nanosilica hydrosols with higher specific surface areas had faster pozzolanic reactivity, especially at early ages; moreover, the results are indicative of the accelerating influence of nanosilicas and silica fume on the hydration of cement. Faster initial and final setting times observed for cement pastes containing nanosilicas are consequence of these mechanisms. However, less hydration degree of cement compared to the plain paste was observed at age of 7 days and after. This can be attributed to the entrapment of some of mix water in the aggregates of nanosilicas formed in cement paste environment, making less water available for the progress of cement hydration. The same mechanism is believed to be responsible for the reduction of flowability of cement pastes.     

A new manufacturable filter design approach for spectral reflectance estimation

Selection of the best possible filter set among a set of available filters is the obvious method of increasing dimension of camera signals for spectral reflectance reconstruction. There are also methods that are focusing on the filter design regardless of noticing to the constructability of the designed filters. This study shows that direct optimization of physical variables of filter manufacturing technique is more reliable than indirect approach of designing and then physical manufacturing of the designed filters. Direct optimization of the transmission‐controlling primaries in filter manufacturing process would guarantee having the designed filters in reality. Combination of some solvent dyes was used as the spectral transmission matching system for filter manufacturing. As a conventional technique, filters were designed and best possible dye concentrations that match the desired filters were calculated. As an alternative approach, filters were also designed using direct optimization of dyes concentrations. The results showed that direct optimization of dye concentrations exhibits better performance in comparison with the conventional technique. © 2016 Wiley Periodicals, Inc. Col Res Appl, 42, 316–326, 2017     

High‐performance carboxylate superplasticizers for concretes: Interplay between the polymerization temperature and properties

Polycarboxylate superplasticizers based on acrylic acid (AA) and maleic anhydride (MAn) were synthesized via free‐radical copolymerization with an ethylene glycol monomer and characterized. The copolymerization temperature (ranging from 50 to 90 °C) appeared to be the key operating factor governing the chemical structure of the superplasticizers. The chemical structures of the products were analyzed by gel permeation chromatography, whereas an optimized sample was further analyzed by Fourier transform infrared spectroscopy and ¹H‐NMR. Superplasticizers of the AA and MAn classes were then incorporated into concrete, and their performances were measured by slump and slump loss tests, where a large dependency of the microstructure on the synthesis temperature was recognized. The optimum temperatures were found to be 50 and 80 °C for the AA and MAn modifiers, respectively. At their own optimum temperatures, the AA and MAn superplasticizer revealed slump losses from 23 to 4 cm and 15 to 5 cm, respectively, after 45 min. The chemical structures of the plasticizers were patterned illustratively to speculate the performance of each superplasticizer according to changes that took place in the backbone length and side‐chain density. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44908.