Designed Monomers and Polymers最新文献

A new class of biologically active polyazomethine/pyrazole and their related nanocomposites, polyazomethine/pyrazole/zinc oxide nanoparticles, have been successfully synthesized through the polycondensation technique in the form of polyazomethine pyrazole (PAZm/Py_4-6) and polyazomethine/pyrazole/zinc oxide nanoparticles (PAZm/Py/ZnO_a-c). The polymeric nanocomposites were prepared with a 5% loading of zinc oxide nanofiller using the same preparation technique, in addition to the help of ultrasonic radiation. The characteristics of the new polymers, such as solubility, viscometry, and molecular weight, were examined. All the polymers were completely soluble in the following solvents: concentrated sulfuric acid, formic acid, dimethylformamide, dimethyl sulfoxide, and tetrahydrofuran. Furthermore, the weight loss of the polyazomethine pyrazole (4, 5, and 6) at 800 °C was 67%, 95%, and 86%, respectively, which indicates the thermal stability of these polymers. At 800 °C, the polyazomethine/pyrazole/zinc oxide nanoparticles (a, b, and c) lost 74%, 68%, and 75% of their weight, respectively. This shows that adding zinc oxide nanoparticles made these compounds more stable at high temperatures. The X-Ray diffraction pattern of the polyazomethine pyrazole (PAZm/Py_4-6) shows a number of sharp peaks with varying intensities. The polymers that were studied had straight crystal structures. Furthermore, the measurements of polyazomethine/pyrazole/zinc oxide nanoparticles (PAZm/Py/ZnO_a-c) indicate a good merging of zinc oxide nanoparticles into the matrix of polymers. The antimicrobial activity of polymers and polymer nanocomposites was tested against some selected bacteria and fungi. The synthesized polymer (c) shows the highest activity against the two types of gram-negative bacteria selected. Most tested compounds were found to be effective against gram-positive bacteria except polyazomethine pyrazole (PAZm/Py₅) and polyazomethine pyrazole (PAZm/Py₆), which do not exhibit any activity. The synthesized polymers and their related nanocomposites were tested for their ability to kill the chosen fungi. All of them were effective against Aspergillus flavus, but only polyazomethine pyrazole (PAZm/Py₄) and polyazomethine/pyrazole/zinc oxide (PAZm/Py/ZnO_c) were effective against Candida albicans.

Alginate fibers have excellent flame-retardant properties and make up for other material defects by blending. To investigate the influence of the blending ratio of alginate fibers on the flame-retardant properties of waterproof and breathable layers for firefighting suits, this paper utilizes the needle-punching and hot-pressing nonwoven reinforcement processes to prepare waterproof and breathable layers based on alginate/aramid base cloths and conducts a series of performance tests on them. The results show that the char residue content of alginate blended base cloth is significantly improved relative to pure aramid, and the addition of alginate fibers to the base cloth of the waterproof and breathable layer improves its flame retardancy and thermal stability. The overall performance of the alginate/aramid blended base fabric waterproof and breathable layer was better than that of the aramid-based waterproof and breathable layer. Moreover, in the flame-retardant multilayer fabric system for firefighting apparel, the multilayer fabric system containing the alginate/aramid-based waterproof and breathable layer showed higher thermal protection performance. Therefore, the alginate/aramid-based waterproof and breathable layer can enhance the overall flame-retardant performance of firefighting clothing to a certain extent.

The thermoresponsive properties of poloxamine (tetra-branch PEO-PPO block copolymer) hydrogels are related to several variables. Of particular interest to this study were the molecular weight of the polymer, the molar ratio between PEO and PPO blocks, and the concentration of the aqueous solution. Accurately controlling the thermoresponsive behaviors of the polymer is critical to the application of such materials; therefore, the structure-property relationship of tetra-branch PEO-PPO block copolymer was studied by synthesis via anionic ring-opening polymerization (AROP). The structure-property relationships were studied by measuring the thermoresponsive behavior via differential scanning calorimetry (DSC) and developing an empirical model which statistically fit the collected data. This empirical model was then used for designing poloxamines that have critical micellization temperatures (CMT) between room temperature and physiological temperature. The model was validated with three polymers that targeted a CMT of 308 K (35°C). The empirical model showed great success in guiding the synthesis of poloxamines showing a temperature difference of less than 3 K between the predicted and the observed CMTs. This study showed a great potential of using an empirical model to set synthesis parameters to control the properties of the polymer products.