Polymer-based Matrices Research Articles

Dense and Nanoporous Glasses as Host Matrices to Grow Quantum Dots for Optical and Photonic Applications.

Quantum dots (QDs)grown within inorganic glasses (hereafter referred to as "QD glasses") arepromising candidates for an expanding list of applications such as nonlinear optical (NLO) devices. However, lots of research into NLO properties of QDs still uses polymer-based matrices, whose low laser damage threshold hinders practical applications. This can be explained by the difficulties typically encountered by researchers wishing to grow QDs within glass matrices. Fortunately, much progress has been made, not only as regards dense glass but also in the use of nanoporous (NP) glass which is prepared and explored as a macro-matrix in the growth of QDs. In situ growth techniques for the preparation of QD glasses are more appealing than ex situ methods, as the formercan effectively avoid agglomeration of the QDs and the need for application of prior treatments such as ligand exchange. Here, a review of advances in growth techniques of QDs in both dense and NP glasses is provided, with a discussion on the effect of glasses on the emission nature of the grown QDs, the routes to tune emission, enhancing optical performance and, finally, potential applications of QD glasses. The overview of directions and future challenges of this area are also presented.

Polymeric materials and their applications

Materials obtained from nature are divided into two groups: natural and artificial. Materials fall into four main categories: metals, ceramics, polymers, and composites. Glass is a solid material that is transparent, usually rigid, fragile, and has an inorganic amorphous structure that allows the preservation of liquids. Ceramics, on the other hand, are solid materials containing metal and non-metal inorganic compounds with ionic or covalent bonds. Nontechnical ceramics fall into three general groups: cement and concrete, fired clay, minerals, and stone. Fibers and particles are utilized as strengthening constituents in different types of composite materials. Hybrids can be used as different types of composite materials and thermal insulation parts. Hybrid materials are divided into four groups: composites, foams, honeycombs, and natural materials. Composites and foams can be made from metallic, ceramic, or polymer-based matrices. Metals and their alloys are materials connected by metallic bonds. Metals are divided into two groups: ferrous and non-ferrous. A polymer is a substance comprised of enormous molecules. Polymers have larger molecular masses than small molecule compounds. Polymers are materials connected by covalent bonds and dominant van der Waals bonds. Polymeric materials are divided into two groups: elastomers and plastics. Plastics (polymers) are divided into two main parts: thermoplastics and thermosets. Thermoplastics can be reused when heated due to their weak bonds, meaning they are suitable for recycling. A thermoset is a thermosetting polymer and is a material attained by permanently hardening the resin. Industrial usage areas of polymers include textiles, electronic goods, the automotive industry, healthcare, building materials, and food. In this study, polymeric materials were defined, then classified and their usage areas were criticized.

A review of the role of elevated temperatures on the mechanical properties of fiber-reinforced geopolymer (FRG) composites

In recent years geopolymers (GPs) have emerged as environmentally friendly construction materials and as incombustible mineral matrices for use in fiber-reinforced composites. The incorporation of fibers, either in discrete or continuous form, changes brittle behavior to ductile or quasi-ductile, resulting in high-performance, fiber-reinforced geopolymer (FRG) composites.For a larger-scale use of FRGs in construction and infrastructure industries, the impact of elevated temperatures is an inevitable matter of concern. The results obtained from existing studies on the fire response of GP composites differ significantly due to the differences in adopted geopolymer (GP) matrix designs, fibre types and their dosage, or testing methods. Mechanical properties of FRGs, including flexural and tensile strength, fracture toughness, and compressive strength, are comprehensively reviewed at ambient and elevated temperature levels and then correlated to microstructural changes.The article at hand aims to establish a conceptual and technical novel background for the current understanding of the combined influence of such factors and deliver an in-depth review of their effects on the performance of FRG at elevated temperatures depending on the fiber typology. Significant findings show inherently superior heat resistance for FRG composites as compared to either cement or polymer-based matrices, while it requires careful compositional design for sufficient processability, effectiveness of fibers, low volume changes and strength endurance. Furthermore, pointed out are potential applications and recommendations for heat and fire resistance, all of which still need to be addressed through further experimental and numerical studies.

Combining microwave and ultraviolet energy for sample preparation of polymer-based materials for further halogen determination

In this work, a microwave-assisted ultraviolet wet digestion (MAWD-UV) protocol was used to digest polymer-based materials (e-waste, food packing, medical-care materials, and individual protection equipment) for further halogen determination. Digests were suitable for Cl, Br, and I determination by inductively coupled plasma mass spectrometry (ICP-MS) or inductively coupled plasma optical emission spectrometry (ICP-OES). Fluorine determination was performed with ion selective electrode (ISE). The power radiation and the digestion solution were evaluated. The accuracy was evaluated by comparing the results with those obtained after neutron activation analysis (NAA) for Cl and Br or using microwave-induced combustion (MIC) as sample preparation for F and I. Two certified reference materials (CRM) of low-density polyethylene (ERM EC680k and EC681k) were evaluated, and no differences were observed (t-test, 95% confidence level) between the results and the certified values. Quantitative recoveries for Cl, Br, and I were obtained using 200 mg of the sample using diluted acid solution (15 mL of 0.5 mol L−1 HNO3 plus 10.6 mol L−1 of H2O2), with a 40 min radiation program (700 W, 25 min ramp). No statistical differences (ANOVA, 95% confidence level) were observed between the MAWD-UV and ICP-MS results and the reference values for Cl, Br, and I for several samples. However, results were lower than the reference values for fluorine, indicating that digestion efficiency was poor for this analyte, which was probably as an organic molecule (likely polytetrafluoroethylene). The limit of quantification (LOQ) was 0.216 mg g−1 for Cl, 3.33 µg g−1 for Br, and 0.036 µg g−1 for I using ICP-MS. The main advantage of MAWD-UV is that it enables decomposing several polymer-based matrices using diluted acid without halogen losses. The developed method represents an important contribution to the digestion of these hard-to-digest matrices and in compliance with green analytical chemistry, thereby being an advance in sample preparation.

Hydration Patterns in Sodium Alginate Polymeric Matrix Tablets-The Result of Drug Substance Incorporation.

The purpose was to show, using destructive/nondestructive methods, that the interplay between water, tablet structure, and composition determine the unique spatiotemporal hydration pattern of polymer-based matrices. The tablets containing a 1:1 w/w mixture of sodium alginate with salicylic acid (ALG/SA) or sodium salicylate (ALG/SNA) were studied using Karl Fischer titration, differential scanning calorimetry, X-ray microtomography, and magnetic resonance imaging. As the principal results, matrix specific features were detected, e.g., “locking” of the internal part of the matrix (ALG/SA); existence of lamellar region associated with detection of free/freezing water (ALG/SA); existence of water penetrating the matrix forming specific region preceding infiltration layer (ALG/SNA); switch in the onset temperature of endothermic water peak associated with an increase in the fraction of non-freezing water weight per dry matrix weight in the infiltration layer (ALG/SNA). The existence of complicated spatiotemporal hydration patterns influenced by matrix composition and molecular properties of constituents has been demonstrated.

О влиянии углеродных нанотрубок на физико-механические свойства полипропилена

One of the most interesting and promising materials of our time is carbon nanotubes. Most applications of nanotubes are associated with the possibility of combining them with other materials in the form of alloys, mixtures, composites or hybrid materials. In particular, the idea of including carbon nanotubes as a filler in various polymer-based matrices (for example, traditional polymers such as thermoplastics, thermosetting materials or elastomers, as well as conjugated polymers) for the formation of polymer/carbon nanotube nanocomposites has revolutionized materials science and engineering. The introduction of carbon nanotubes into the composite structure affects the structure and properties of the polymer binder, as well as the composite material as a whole. Currently, there are no experimental developments on the basis of which the introduction, distribution and stabilization of the dispersion of carbon nanotubes in polymer composites would be implemented in industrial technology. The development of the most effective methods for introducing carbon nanotubes into polymer materials and determining their effect on the physical and mechanical properties of polymers is an urgent and priority task. It is possible that these methods will be able to find application in the industrial production of polymer composite materials intended for use and operation in various extreme conditions (whether it is high temperatures, erosion, high force exposure or highly acidic/highly alkaline environments). The main physical and mechanical properties of polypropylene samples saturated with carbon nanotubes taken at different concentrations (0; 0.01; 0.05 and 0.1 wt. %), who found that the addition of CNT in large quantities negatively affects the tensile and bending strength limits, which may be associated with an increase in the degree of heterogeneity of the structure and the appearance of large agglomerates, which will be points of stress concentration. With an increase in the mass fraction of carbon nanotubes in the polymer nanocomposite, the tangent of the dielectric loss angle increases, which leads to better conductivity of the sample containing a larger number of nanotubes. This may be due to the fact that nanotubes become conductors of electric current in the volume of the polymer matrix.

Valorization of Arnica montana Wastes after Extraction of the Ethanol Tincture: Application in Polymer-Based Matrices.

The waste solids remaining after the ethanolic extraction of arnica were proposed as raw material for the recovery of the remaining phenolic fraction. Greener processes based on intensification extraction, with microwave (MHG) and ultrasound (UAE) assistance and pressurized hot water extraction under subcritical conditions (AH), were studied. The entire process provided approximately 28% of phenolics for the sequence when MHG was used, 22% in the sequence where AH was employed, and the extracts showed up to 60% the ABTS radical scavenging capacity of Trolox. However, the cytotoxic effects on the cell growth of tumoral cells were only moderate. Therefore, considering a possible external topical application, extracts containing selected arnica extracts were further used to develop polymer-based gelled matrices formulated with either chitosan or polyvinyl alcohol. Rheological testing indicated that all proposed matrices exhibited relatively high mechanical features, even better than those determined with matrices prepared with their counterpart commercial arnica tinctures. Overall, the shear-thinning behavior of gelled matrices loaded with arnica extracts obtained by MHG or AH stages was enhanced compared to those containing ethanolic extracts, whereas the viscoelastic features became smoother for polymeric matrices incorporated with arnica extracts recovered at the highest MHG irradiation powers or at the highest set point temperatures of AH treatments.

DISSOLUTION KINETIC OF MELOXICAM FROM HYDROPHILIC MATRIX-TYPE FILMS FOR TRANSDERMAL THERAPY

Taking into consideration the fact the transdermal administration of the active pharmaceutical ingredients can represent a therapeutic approach that increases the patient’s compliance, this study aims to evaluate the release of meloxicam (MX), a potent non-steroidal anti-inflammatory drug, incorporated in hydrophilic polymer-based matrices for transdermal therapeutic systems was studied. Three different formulations were realized by solvent casting method containing two types of hydroxypropyl methylcellulose (HPMCE5 with low viscosity and HPMC15000 with high viscosity) whose concentration was also varied. The drug release test was performed by Franz diffusion cell and the dissolution curves were analysed from a kinetical point of view by model dependent and model independent methods. Linearization by simple regression allowed the flux calculations of values that varied between 0.183 and 32.270 g/(cm2h). Based on the results obtained with the mathematical analysis, we can conclude that the MX release is influenced by the pH of the dissolution media and by the type and concentration of the matrix forming agent. Discrimination of model dependent mathematical models was done by the Akaike index with values between 49 and -62. The kinetic analysis of the MX releasing curves from the proposed formulations showed that Korsmeyer-Peppas was more suitable for the release characterisation of the active pharmaceutical ingredient from the transdermal therapeutic systems analysed.

Influence of fibre loading and surface treatment on the impact strength of coir polyester composites

Purpose: In this work, coir fibre with varying fibre content was selected as reinforcements to prepare polymer-based matrices and the problem of reduced fibre-matrix interfacial bond strength has been diluted by chemical treatment of coir fibres with alkali solution. Design/methodology/approach: The effect of fibre loading, solution concentration and soaking time on the impact strength of the composites were analyzed using statistical techniques. Response Surface Methodology (RSM) approach was used to model and optimize the impact properties of coir-polyester composites. Findings: The impact strength of coir fibre reinforced polyester composite depends mainly on the fabrication parameters such as fibre-polyester content, soaking time, concentration of soaking agent and adhesive interaction between the fibre and reinforcement. Research limitations/implications: The mechanical properties of any coir polyester composite depend on the nature bonding between the fibre and reinforcement. The presence of cellulose, lignin on the periphery of any natural fibre reduces the bonding strength of the composite. This limitation is overcome by fibre treatment over sodium hydroxide to have better impact properties. Practical implications: Now days, natural fibre reinforced composites are capable of replacing automotive parts, subjected to static loads such as engine Guard, light doom, name plate, tool box and front panels etc. These materials can withstand any static load due to its higher strength to weight ratios. Originality/value: The effect of fibre loading, solution concentration and soaking time on the impact strength of the composites were analyzed using statistical techniques. Response Surface Methodology (RSM) approach was used to model and optimize the impact properties of coir-polyester composites. The impact strength of NaOH impregnated coir fibre reinforced polyester composites was evaluated.

Characterization and determination of thermal and radioluminescence properties of low-density polyethylene (LDPE)-(nanozeolite + Y2O3) composite

Nanotechnology has become one of the most popular areas of interdisciplinary research. In the vast majority of nanotechnology applications, polymer-based matrices were used as the dispersing medium of nanoparticles. The combination of polymer–zeolite nanocomposite has the potential to come out with the advantages of polymers and zeolites while coping with the deficiencies of both materials. In this study, the synthesis and properties of low-density polyethylene (LDPE) composites with nanozeolite + Y2O3 are investigated. Polyethylene nanocomposite fibers containing nanozeolite + Y2O3 at 5% by mass using a melt extrusion method were composed in a laboratory type twin screw extruder. The thermal properties of the composite fibers were determined by analysis of both thermal gravimetric and differential thermal spectra. Their structural properties were enlightened by scanning electron microscopy, Fourier transform infrared, and ultraviolet absorption. According to the results of X-ray diffraction tests, the samples contain crystals in semicrystalline and α form. The mechanical properties of LDPE matrices increased with the addition of nanoparticles. In addition, radioluminescence properties of the polymer were also improved after composing with nanozeolite and Y2O3.

Biomaterials in Tendon and Skeletal Muscle Tissue Engineering: Current Trends and Challenges.

Tissue engineering is a promising approach to repair tendon and muscle when natural healing fails. Biohybrid constructs obtained after cells’ seeding and culture in dedicated scaffolds have indeed been considered as relevant tools for mimicking native tissue, leading to a better integration in vivo. They can also be employed to perform advanced in vitro studies to model the cell differentiation or regeneration processes. In this review, we report and analyze the different solutions proposed in literature, for the reconstruction of tendon, muscle, and the myotendinous junction. They classically rely on the three pillars of tissue engineering, i.e., cells, biomaterials and environment (both chemical and physical stimuli). We have chosen to present biomimetic or bioinspired strategies based on understanding of the native tissue structure/functions/properties of the tissue of interest. For each tissue, we sorted the relevant publications according to an increasing degree of complexity in the materials’ shape or manufacture. We present their biological and mechanical performances, observed in vitro and in vivo when available. Although there is no consensus for a gold standard technique to reconstruct these musculo-skeletal tissues, the reader can find different ways to progress in the field and to understand the recent history in the choice of materials, from collagen to polymer-based matrices.

Glucose - Responsive Smart Insulin

ABSTRACTThe discovery of insulin in 1920s revolutionized the management of Type 1 Diabetes Mellitus. The evolution of insulin over the last nine decades has seen three phases, namely discovery and understanding of the molecule, advances in synthesis of the molecule and advancements in the optimization of insulin structure and delivery. These advances aim to minimize hypoglycemia while simultaneously improving anti-hyperglycemic efficacy. Glucose-responsive insulin (GRI) systems were first conceptualized in 1979. These are novel insulin formulations that provide anti hyperglycemic activity appropriate to circulating glucose levels but with a mechanism to avoid hypoglycemia, that often accompanies stringent glycemic control. GRIs are of three major typesalgorithm-based mechanical, polymer-based, molecular GRI analog systems. They differ in the mechanisms of achieving glucose responsiveness. Algorithm-based systems are closed loop insulin pumps that adjust insulin delivery commensurate with blood glucose levels on the basis of predetermined algorithms, that terminate or increase insulin delivery according to blood glucose trends. The second category of GRI includes glucose-responsive polymer-based matrices that house insulin, releasing insulin as needed based on ambient glucose levels. The third approach is to incorporate glucose sensitive motifs in the insulin molecule itself that would decrease or increase insulin availability based on blood glucose levels. The mechanisms behind these novel approaches to insulin delivery and action will be the focus of this review article.

Chemoselective functionalization of nanogels for microglia treatment

The development of nanogels as nanoscale multifunctional polymer-based matrices for controlled drug and gene delivery purposes has been the subject of intense research during the last decades. Indeed, polymeric nanoparticles are capable to interact with cells to different extents, depending on their size, shape, surface properties and ligands tagged to the surface. Moreover, coating these devices using appropriate functionalization strategies can greatly improve or not their adhesion and uptake by cells. In this work, we proposed different coatings and then we studied their ability to improve or reduce microglia internalization. Nanogels (NGs) were composed by polyethylene glycol (PEG) and polyethyleneimine (PEI) conjugated with rhodamine through click chemistry reaction. Coatings were prepared using PEG monomethyl ether (mPEG), modifying its terminal hydroxyl groups with different linkers to evaluate the amount of mPEG layer chemically bond to the nanogel and its effect over microglia internalization. Nanogels were also investigated to identify which procedure is able to form networks with adequate dimensions and stability, according to the physicochemical parameters for the microglia applications in vitro. The biological experimental results showed that NGs were efficiently internalized by cells and the coating-microglia interactions allowed different cellular uptake. This outcome could be considered a promising perspective of nanogels use as carriers for drugs or genes delivery within microglia environment, improving their therapeutic effect through polymer surface modifications.

Comparison between two different click strategies to synthesize fluorescent nanogels for therapeutic applications

The development of nanogels as nanoscale multifunctional polymer-based matrices for controlled drug and gene delivery purposes has been the subject of intense research during the last decades. Their use in biomedical field is related to the effect of their size on the interactions with living cells: only within a defined range nanoparticles could be subjected to active or passive cellular uptake. In this work we propose two methods to synthetize Rhodamine modified nanogels in order to produce nanostructures that could be traced during the cellular interactions and internalization and suitable as carrier for drugs or genes. We compared the obtained sizes and charges of both nanogels, underlining which one could be more useful for biological and therapeutic applications referring to the morphological and physico-chemical properties requested in accordance with medical needs. We also tested their cytocompatibility and their characteristic behavior as drug delivery vehicles.

Synthesis and characterization of CaO-loaded electrospun matrices for bone tissue engineering.

This study aims to synthesize and characterize biodegradable polymer-based matrices loaded with CaO nanoparticles for osteomyelitis treatment and bone tissue engineering. Poly(ε-caprolactone) (PCL) and PCL/gelatin (1:1, w/w) solutions containing CaO nanoparticles were electrospun into fibrous matrices. Scanning (SEM) and transmission (TEM) electron microscopy, Fourier transformed infrared (FTIR), energy dispersive X-ray spectroscopy (EDS), contact angle (CA), tensile testing, and antibacterial activity (agar diffusion assay) against Staphylococcus aureus were performed. Osteoprecursor cell (MC3T3-E1) response (i.e., viability and alkaline phosphatase expression/ALP) and infiltration into the matrices were evaluated. CaO nanoparticles were successfully incorporated into the fibers, with the median fiber diameter decreasing after CaO incorporation. The CA decreased with the addition of CaO, and the presence of gelatin made the matrix very hydrophilic (CA=0°). Increasing CaO concentrations progressively reduced the mechanical properties (p≤0.030). CaO-loaded matrices did not display consistent antibacterial activity. MC3T3-E1 cell viability demonstrated the highest levels for CaO-loaded matrices containing gelatin after 7days in culture. An increased ALP expression was consistently seen for PCL/CaO matrices when compared to PCL and gelatin-containing counterparts. Despite inconsistent antibacterial activity, CaO nanoparticles can be effectively loaded into PCL or PCL/gelatin fibers without negatively affecting the overall performance of the matrices. More importantly, CaO incorporation enhanced cell viability as well as differentiation capacity, as demonstrated by an increased ALP expression. CaO-loaded electrospun matrices show potential for applications in bone tissue engineering.

Synthesis, structural modelling and luminescence of a novel erbium(III) complex with 2,4-nonanedione and 2,2′-bipyridine ligands for chitosan matrices doping

We report the synthesis, the Sparkle/PM7 semi-empirical quantum model for the ground state geometry and the absorption/luminescent properties of the Er3+ ternary complex [Er(nd)3(bipy)] (where Hnd is 2,4-nonanedione and bipy is 2,2′-bipyridine). The solid-state electronic absorption spectra and the photoluminescent spectra show long-wavelength 4f–4f transitions which provide a potential use of the compound as a NIR-emitting material for the doping of polymer-based matrices for waveguides or for bio-analytical applications. The dispersion of the novel complex in a biocompatible chitosan film has been assessed.

Mathematical Modeling and Optimization of Mechanical Properties of Short Coir Fiber-Reinforced Vinyl Ester Composite Using Genetic Algorithm Method

The tensile, flexural, and impact properties of coir-fiber reinforced vinyl ester composites were evaluated. The short coir fibers with different proportions in fiber length and fiber content were used as reinforcements in polymer-based matrices. The mathematical models of tensile, flexural, and impact properties were developed using statistical packages and optimized using the genetic algorithm method to find the optimum fiber parameters for maximum value of mechanical properties.

Mechanical behaviours of calcium carbonate-impregnated short coir fibre-reinforced polyester composites

The tensile, flexural, and impact behaviours of calcium carbonate-impregnated coir fibre-reinforced polyester composites were evaluated. The short untreated coir fibres with different proportions of length, diameter, and filler content were used as reinforcements in polymer-based matrices. The fabricated composites with different levels of fibre parameters were tested as per ASTM standards. The mathematical models of mechanical behaviours were developed using statistical package. The effects of calcium carbonate on the mechanical properties of coir–polyester composites and prediction of mechanical properties using regression models were investigated.

Influence of fiber parameters on tensile, flexural, and impact properties of nonwoven coir–polyester composites

The tensile, flexural, and impact properties of coir fiber/polyester composites were evaluated. The untreated green husk coir fibers with different proportion in length and content were used as reinforcements in polyester polymer-based matrices. The mathematical models of tensile, flexural, and impact properties were developed and optimized using statistical package to find the optimum fiber parameters for maximum mechanical properties. The results are shown that the fiber content in weight percentage is playing major role than the fiber length on the improvement of tensile, flexural, and impact strength properties.

Long-term human pluripotent stem cell self-renewal on synthetic polymer surfaces

Realization of the full potential of human pluripotent stem cells (hPSCs) in regenerative medicine requires the development of well-defined culture conditions for their long-term growth and directed differentiation. Current practices for maintaining hPSCs generally utilize empirically determined combinations of feeder cells and other animal-based products, which are expensive, difficult to isolate, subject to batch-to-batch variations, and unsuitable for cell-based therapies. Using a high-throughput screening approach, we identified several polymers that can support self-renewal of hPSCs. While most of these polymers provide support for only a short period of time, we identified a synthetic polymer poly(methyl vinyl ether-alt-maleic anhydride) (PMVE-alt-MA) that supported the long-term attachment, proliferation and self-renewal of HUES1, HUES9, and iPSCs. The hPSCs cultured on PMVE-alt-MA maintained their characteristic morphology, expressed high levels of markers of pluripotency, and retained a normal karyotype. Such cost-effective, polymer-based matrices that support long-term self-renewal and proliferation of hPSCs will not only help to accelerate the translational perspectives of hPSCs, but also provide a platform to elucidate the underlying molecular mechanisms that regulate stem cell proliferation and differentiation.