Synthesis and characterization of side-chain maleimide-styrene copolymers with new pendant azobenzene moieties

Four side-chain maleimide-styrene polymers have been synthesized from maleimide-alt-styrene copolymer (MASt) and some original azo-moieties using polymer analogous reactions. The structures have been obtained with good yields; remarkably, they showed a high chromophore load, up to ~100%. The polymers were characterized by means of SEC, FT-IR, ¹H-NMR, DSC-TGA, and elemental analysis. The side-chain polymers exhibited improved solubility and enhanced thermal stability up to 320oC, while their glass transition temperatures have been found to be as high as 210oC. The third-order NLO refraction (n₂) and susceptibility χ⁽³⁾ coefficients were measured by Z-scan technique. The results of Z-scan measurements showed that the polymers have only nonlinear refraction, the nonlinear absorption being negligible.     

Silsesquioxane-based hybrid nanocomposites with methacrylate units containing titania and/or silver nanoparticles as antibacterial/antifungal coatings for monumental stones

The present paper reports on the evaluation of two silsesquioxane-based hybrid nanocomposites with methacrylate units containing titania and/or silver nanoparticles aimed as antibacterial coatings for monumental stones. Sol–gel reaction of titanium isopropoxide and/or 3-(trimethoxysilyl)propyl methacrylate, in the presence of silver nitrate and a primary amine surfactant, yielded new types of hybrid nanocomposites with high antibacterial/antifungal efficacy. Different polymer behaviours regarding a frequently used monumental stone originating from Romania were evidenced through Fourier-transform infrared (FTIR) spectroscopy and powder X-ray diffraction (PXRD) technique. Conclusions regarding the stones acid-resistant character and lower influence of salt weathering on its durability, as well as a better protective coating containing titania units were revealed.     

Factorial design optimization of polystyrene microspheres obtained by aqueous dispersion polymerization in the presence of poly(2‐ethyl‐2‐oxazoline) reactive stabilizer

The present study highlights the use of statistical design to establish an effective model for the synthesis of polystyrene microspheres by aqueous dispersion polymerization using poly(2‐ethyl‐2‐oxazoline) reactive stabilizer. The significant parameters (e.g. solvent polarity, stabilizer and initiator concentration) influencing the characteristic responses of the process such as yield, particle size and size distribution, as well as the interactions between the variables, were identified. The macromonomer concentration and solvent polarity influence both particle size and size distribution, whereas initiator concentration influences the yield. Analysis of the variance of process variables indicates that the models can be successfully used to describe the dispersion polymerization process. Moreover, the factorial design allows the development of microspheres with optimal properties with respect to size and size distribution. The experimental data regarding yield, particle size and size distribution of the optimized dispersion polymerization shows less than 7% difference compared with the predicted responses. In view of these results, the implementation of statistical design models represents an efficient solution for optimizing microparticle synthesis while aiming for industrial applications. © 2020 Society of Chemical Industry     

Heat treatment influence on the structural properties of supported Ni nanoclusters

Ni nanoclusters supported on Al₂O₃ were prepared using a coprecipitation method. A heat treatment at different temperatures was applied. The obtained samples were analyzed by X-ray diffraction (XRD), X-ray absorption spectroscopy and X-ray photoelectron spectroscopy in order to determine their global, local and electronic structures. The average particle size, the mean squares of the microstrain, the particle size and microstrain distribution functions of the supported Ni nanoclusters were determined by the XRD method using a generalized Fermi function for the approximation of the X-ray line. The recrystallization induced during the heat treatment process was analyzed. The present study indicated strong deformation of the local structure of the active metal in all of the samples investigated due to the metal-support interaction and the effects of the small particle size. Electronic structural investigations showed the presence of Ni in a metallic state as well as Ni²⁺ on the cluster surfaces.     

Green Blends Based on Ionic Liquids with Improved Performance for Membrane Technology: Perspectives for Environmental Applications

Present research was directed towards the development of new high-performance and cost-effective polysulfone membranes (PSFQ) by introducing ionic liquids (ILs—Cyphos 101 IL and Aliquat 336) into their matrix. Variation of ILs was performed with the aim to find the one that brings new properties and improves the functionality and selectivity of PSFQ membranes in ultrafiltration processes. Based on the obtained results of the rheological study, we established the compatibility of compounds and optimal content of the used ILs, namely 3 wt% and 15 wt% Cyphos 101 IL and compositions varying between 3 and 15 wt % Aliquat 336. Results indicated that the ILs acted as plasticizers when they were added to the system, a helpful aspect in processing membranes used in water decontamination. The efficiency and performance of the membranes were evaluated by their use in the treatment of diclofenac (DCF)-containing waters. Membranes obtained from PSFQ/Aliquat 336 solution containing 15 wt% IL exhibited a 97% removal degree of DCF in the treatment process of 50 mL solution containing 3 mg/L DCF. The separation efficiency was kept constant for four filtration/cleaning cycles. The results indicated an improvement in membrane performance as the amount of IL in their structure increased, which confirms the potential for application in water treatment processes.     

Materials Based on Quaternized Polysulfones with Potential Applications in Biomedical Field: Structure–Properties Relationship

Starting from the bactericidal properties of functionalized polysulfone (PSFQ) and due to its excellent biocompatibility, biodegradability, and performance in various field, cellulose acetate phthalate (CAP) and polyvinyl alcohol (PVA), as well as their blends (PSFQ/CAP and PSFQ/PVA), have been tested to evaluate their applicative potential in the biomedical field. In this context, because the polymer processing starts from the solution phase, in the first step, the rheological properties were followed in order to assess and control the structural parameters. The surface chemistry analysis, surface properties, and antimicrobial activity of the obtained materials were investigated in order to understand the relationship between the polymers’ structure–surface properties and organization form of materials (fibers and/or films), as important indicators for their future applications. Using the appropriate organization form of the polymers, the surface morphology and performance, including wettability and water permeation, were improved and controlled—these being the desired and needed properties for applications in the biomedical field. Additionally, after antimicrobial activity testing against different bacteria strains, the control of the inhibition mechanism for the analyzed microorganisms was highlighted, making it possible to choose the most efficient polymers/blends and, consequently, the efficiency as biomaterials in targeted applications.