Effects of preparation conditions on the morphology and gas permeation properties of polyethylene (PE) and ethylene vinyl acetate (EVA) films

In this study, the effect of film preparation conditions on the gas permeation properties of polyethylene (PE) and ethylene vinyl acetate (EVA) films (containing 18 and 28 wt% vinyl acetate) was investigated. Film blowing and phase inversion methods were applied in the production of PE and EVA films, respectively. The permeation of pure oxygen and carbon dioxide gases was measured at room temperature. The results indicated that with the increase of PE film thickness, permeability and solubility of O₂ and CO₂ in these films decreased; but the diffusivities of gases through PE films increased. In addition, in the case of EVA copolymers, by increasing the content of vinyl acetate, the permeability of CO₂ increased. The rate of increase in CO₂ permeability was different for samples having different preparation conditions. For example, the samples prepared using chloroform as the solvent instead of THF, showed lower CO₂ permeability. Also, the morphological studying of film structure indicated that the higher CO₂ permeability for the samples made from THF solvent is due to the existing of higher porosity in the under layer polymer area. Also scanning electron microscopy (SEM) micrographs showed that with the usage of phase inversion method, there will be a thin dense layer near to the glass substrate.     

High surface area benzimidazole based porous covalent organic framework for removal of methylene blue from aqueous solutions

In this study, a highly thermally stable benzimidazole based covalent organic framework (bCOF) was synthesized by the reaction of perlin‐tetracarboxylic anhydride, 5‐aminoisophthalic acid and diaminobenzidine in polyphosphoric acid medium. The synthesized porous bCOF was identified by different techniques. From CO₂ adsorption, the micropore surface area of the bCOF was found to be 856 m² g^?1; this synthesized bCOF has a widespread netting construction, and it has various porosity. The TGA results displayed the high thermal strength of the synthesized bCOF. After characterization, the bCOF was used for the removal of methylene blue from aqueous solution, and the essential parameters such as pH of the solution, contact time and initial concentration were assessed. The maximum adsorption capacity of the bCOF for removal of methylene blue was 63.29 mg g^?1 after only 40 min contact time at a pH of 6. Two kinetics and adsorption models were used for interpretation, and the outcomes showed that the pseudo‐second‐order and Langmuir models respectively were better fitted to the results. According to the results, the novel bCOF can be applied to remove methylene blue from aqueous solution. © 2020 Society of Chemical Industry     

Poly(lactic-co-glycolic acid): The most ardent and flexible candidate in biomedicine!

Among all polymers, without doubt, poly(lactic-co-glycolic acid) (PLGA) is the most popular one in biology and biomedicine fields. Having a tunable structure, a controllable and desired release profile, huge capacity of functionalization with various agents besides an incredible biosafety and biocompatibility, which led to its food and drug administration (FDA) approval, is among some outstanding features of this polymer. Cancer treatment using PLGA-based vehicles carrying anticancer agents, delivery of various active compounds from drugs to peptides and vaccines, tissue regeneration, and treatment of central nervous system disorders, all shows the potential of this polymer in this area. Nowadays, the focus of most investigations is on designing the most efficient PLGA formulation and improving its effectiveness with various synthesis and postsynthesis modifications. The aim of this review is to mention some recent investigations directed to improve PLGA efficiency in biomedical area.