Current Applied Polymer Science - Volume 4, Issue 2, 2021

Background: Aiming at in situ regenerative therapy, the tailored design of cytokine-releasing scaffolds is still one of the crucial issues to be studied. A core-shell fibermat is one of the attractive platforms for this purpose. But, very few detail the importance of choosing the right material for the shell units that can endow efficient release properties.

Objective: In this study, we characterized the effectiveness of core-shell fibermats that possess cross-linked gelatin (CLG) as the shell layer of constituent nanofibers, as a protein-releasing cell-incubation scaffold.

Methods: For the core nanofibers in the core-shell fibermats, we utilized a crosslinked copolymer of poly(acrylamide)-co-poly(diacetone acrylamide) (poly(AM/DAAM)) and adipic acid dihydrazide (ADH), poly(AM/DAAM)/ADH. By coaxial electrospinning and the subsequent crosslinking of the gelatin layer, we successfully constructed core-shell fibermats consisting of double-layered nanofibers of poly(AM/DAAM)/ADH and CLG. Using fluorescein isothiocyanate-labeled lysozyme (FITC-Lys) as a dummy guest protein, we characterized the release behavior of the core-shell fibermats containing a CLG layer. Upon loading basic fibroblast growth factor (bFGF) as cargo in our fibermats, we also characterized impacts of the released bFGF on proliferation of the incubated cells thereon.

Results: Although the single-layered poly(AM/DAAM)/ADH nanofiber fibermats did not adhere to the mammalian cells, the core-shell fibermat with the CLG shell layer exhibited good adherence and subsequent proliferation. A sustained release of the preloaded FITC-Lys over 24 days without any burst release was observed, and the cumulative amount of released protein reached over 65% after 24 days. Upon loading bFGF in our fibermats, we succeeded in promoting cell proliferation, and highlighting its potential for use in therapeutic applications.

Conclusion: We successfully confirmed that core-shell fibermats with a CLG shell layer around the constituent nanofibers, were effective as protein-releasing cell-incubation scaffolds.

Polysarcosine (psar) is a non-ionic hydrophilic polypeptoid with numerous biologically relevant properties. Polysarcosine is poly (n-methylated glycine) and has been reported first by Weslay and co-workers in the 1920s. Polysarcosine was first synthesized via ring-opening polymerization (rop) of sarcosine n-carboxyanhydride, using high-vacuum techniques. Overall, findings highlight the potential of poly(sarcosine) as an alternative corona-forming polymer to poly (ethylene glycol)-based analogues of (polymerization-induced self-assembly) pisa assemblies for use in various pharmaceutical and biomedical applications. Numerous studies suggested that such polypeptoids hold enormous potential for many biomedical applications, including protein delivery, colloidal stabilization, and nanomedicine.

Background: In the last decades, the prevalence of obesity showed a significant increase in several countries. This fact is very worrying since there is an association between obesity and metabolic alterations, such as type II diabetes, hypertension, cardiovascular diseases, some types of cancer, and glucose intolerance. Knowledge of causes, preventive strategies, and treatment have been objects of studies by researchers in several centers.

Objective: The present paper aims to review some studies addressing the increase in the prevalence and incidence of obesity, diseases related to overweight, and procedures to reduce body fat. The primary focus of the presented work is the use of polymer systems as an alternative to the conventional pharmacological treatment of obesity, exploiting the natural and synthetic polymer systems that have excellent efficiency and can promote improvement to the existing therapies.

Results: The use of polymers presents the growing relevance as a new therapy and to the improvement of existing treatments. Among the polymers studied in the treatment of obesity, natural polymers such as chitosan and alginate have gained prominence. Synthetic polymer systems such as poly (ε-caprolactone) and poly (lactide-co-glycolide) were also studied for the treatment of obesity.

Conclusion: This mini-review reflects exclusive strategies that point out to polymers that can be an alternative to conventional pharmacological treatments or even as occupants in the treatment of obesity. Besides, we do believe that the most profound union between Polymers and Medical Science will allow us to mitigate this disease and all associated conditions, improving the quality of life, mainly of the poor populations from emerging countries.

Background: The mixing of the formation water present in oil and gas reservoirs and the injected water (often seawater) can form inorganic incrustations, during enhanced oil recovery operations. In this case, the cations (calcium, barium, strontium, iron, magnesium, etc.) of the injected water react with the anions (mainly sulfate and carbonate) of the formation water and produce inorganic salts that can precipitate in the reservoir rock, damaging the oil production by clogging the pipes and production lines. One of the ways to prevent this problem is to remove the cations from the injected water, but this is a challenging procedure.

Objective: In this study, the Sulfonated polymer(divinylbenzene) (DVBS) and the copolymer sulfonated poly(methyl methacrylate-co-divinylbenzene (MMA-DVB) were compared in their efficiencies in reducing, to a very low level, the concentration of removing, chemically modified with sulfonic (S) groups to ascertain their performance, the calcium and magnesium ions present in water.

Methods: The resins were modified with sulfonic groups and characterized. We used central composition planning with batch tests to evaluate the adsorption, which occurred significantly for both ions using both resins with a contact time of 10 minutes.

Results: For both resins, calcium was preferentially adsorbed in relation to magnesium.

Conclusion: Taking into account the cost-benefit, the copolymer MMA-DVBS (a less expensive adsorbent than the polymer DVBS) presented a satisfactory behavior, making it a potential material for the treatment of water.

Background: Sandwich structures are progressively being used in various engineering applications due to the superior bending-stiffness-to-weight ratio of these structures. We adapted a novel technique to incorporate carbon nanotubes (CNTs) and polyhedral oligomeric silsesquioxanes (POSS) into a sandwich composite structure utilizing a sonochemical and high temperature vacuum assisted resin transfer molding technique.

Objective: The objective of this work was to create a sandwich composite structure comprising of a nanophased foam core and reinforced nanophased face sheets, and to examine the thermal and mechanical properties of the structure. To prepare the sandwich structure, POSS nanoparticles were sonochemically attached to CNTs and dispersed in a high temperature resin system to make the face sheet materials and also coated on expandable thermoplastic microspheres for the fabrication of foam core materials.

Methods: The nanophased foam core was fabricated with POSS infused thermoplastic microspheres (Expancel) using a Tetrahedron MTP-14 programmable compression molder. The reinforced nanophased face sheet was fabricated by infusing POSS coated CNT in epoxy resin and then curing into a compression stainless steel mold.

Results: Thermal analysis of POSS-infused thermoplastic microspheres foam (TMF) showed an increase in thermal stability in both nitrogen and oxygen atmospheres, 19% increase in thermal residue were observed for 4 wt% GI-POSS TMF compared to neat TMF. Quasi-static compression results indicated significant increases (73%) in compressive modulus, and an increase (5%) in compressive strength for the 1 wt% EC-POSS/CNTs resin system. The nanophased sandwich structure constructed from the above resin system and the foam core system displayed an increase (9%) in modulus over the neat sandwich structure.

Conclusion: The incorporation of POSS-nanofillier in the foam core and POSS-coated nanotubes in the face sheet significantly improved the thermal and mechanical properties of sandwich structure. Furthermore, the sandwich structure that was constructed from nanophased resin system showed an increase in modulus, with buckling in the foam core but no visible cracking.

Background: Eucalyptus bark and scraps are generated in the production of medium- density fiberboard (MDF). An approach aiming to add value to such wastes was studied, following the concepts of circular economy and biomass cascade strategy. Bio-oil and phenolic resin were produced by pyrolysis from two types of biomass, Eucalyptus bark and MDF waste. As is well known, conventional phenolic resins are normally obtained from fossil resources. These products were obtained from the pyrolysis of two types of biomass to reduce environmental waste and dependence on petroleum-based products

Objective: The main objective of the present study was to produce phenolic resin from Eucalyptus wastes, aiming to reduce the fossil dependence on conventional resins used in the production line of MDF.

Methods: Fast pyrolysis and slow pyrolysis were employed for bio-oil and phenolic resin production. The bio-oil and resins were characterized with standard lab analyses for their physicochemical properties, while their thermal properties were studied via thermogravimetric analysis (TGA).

Results: The shear strength of the lap internal bonding of the phenolic resin binders with 19.8% of bio-oil was 2.09, 1.34, and 1.63 MPa under dry, boiler, and soaked conditions, respectively, which was acceptable for panel fabrication and can represent a significant saving in terms of fossil resins and cost reduction.

Discussion: According to the results, 1 g medium fraction of bio-oils was equivalent to 1.35 g of conventional phenols, indicating those bio-oils as phenolic structures that could be used as binders. The bio-oil yields for bark and MDF were 40.9 and 25.1, respectively, which indicate a potential for replacing the conventional fossil-based phenolic resin.

Conclusion: The results revealed the possibility of replacing conventional fossil-based chemicals with phenolic resin from renewable resources with similar overall properties, replacing about 1/3 of the conventional resin.

Background: This work presents the preparation and characterization of the polymeric nanocomposites based on methyl methacrylate (MMA), ethyl acrylate (EA), and natural and modified clays. The clays used to prepare the composite were natural green bentonite (GBC-N) and organophilic clays modified with ammonium quaternary salts: Praepagen (GCB-P), Dodigen (GCB-D) and Praepagen/Dodigen mixture 1:1 in weight (GCB-P/D).

Objective: The experimental studies focused on the evaluation of the effect of clays (in nature and chemically modified) on the final quality of the polymeric nanocomposites containing around 3 wt%. of clay nanocharges in association with MMA to produce poly(methyl methacrylate)/clays, and MMA/EA to form poly(methyl methacrylate-co-ethyl acrylate)/clays.

Materials and Methods: The poly(methyl methacrylate)/clay and poly(methyl methacrylate-co-ethyl acrylate)/clay materials were synthesized through mass-suspension polymerization process. The natural and modified green bentonite clays were characterized by X-ray powder diffraction (XRD), infrared spectroscopy (IR), Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) analyses to understand its effect on the basal spacing, d001 (compared to the pure clay), as a result of cation exchange step, which also improved the thermal efficiency of the final nanocomposites.

Results: The proper incorporation of MMA and MMA/AE monomers between the layers of natural and modified clays occurred through in situ mass-suspension polymerization, leading to a successful exfoliation of clay layers during the growth of the polymer chains.

Conclusion: The IR, SEM, TGA and DSC analyses confirmed the improvement in the thermal property of the composites compared to polymers formed in the absence of clays. The experimental results are very promising, indicating that the experimental protocol based on the in situ formation of polymer nanocomposites by using sequential mass-suspension polymerization consisting of an interesting tool.

Objective: The objective of this work is to study the artificial ageing of semi-rigid and plasticized polyvinyl chloride (PVC) stabilized with epoxidized sunflower oil (ESO) as a biobased derivative in combination with zinc and calcium stearates.

Methods: For comparison, a formulation of PVC plasticized and stabilized with epoxidized soya bean oil (ESBO) was considered. Artificial ageing was carried out during the 304 hours. Samples were taken off after: 48, 146, 234 and 304 hours and then characterized. The evolution of density, glass transition temperature and morphology, was followed as a function of the time. The structural modifications of polymer were analyzed by Fourier transform infrared spectroscopy in attenuated total reflectance and transmission modes.

Results: The results showed a little decrease of density, a considerable increase of the glass transition temperatures values and a change of morphology. All changes in the properties of PVC relate to formation of new chemical structures.

Conclusion: Globally, it was found that ESO exhibited similar performances to those of ESBO.