Polymerization Medium Research Articles

The interphase degradation in a nanobiosensor including biopolymers and carbon nanotubes

In this paper, a degradation nanobiosensor comprising two biopolymers as poly (lactic acid) (PLA) and poly (ethylene oxide) (PEO) as well as carbon nanotubes (CNT) is developed. The electrical conductivity of the samples for the period of degradation in phosphate-buffered saline (PBS) solution is analyzed focusing on interphase degradation. Furthermore, a model for the conductivity of examples is advanced by CNT properties, filler wettability by polymer medium, interphase depth, degradation portion and tunneling distance. The model’s calculations are linked to the experimental facts and all parameters’ impacts on the conductivity of the decayed examples are described. The predictions of the suggested model sufficiently follow the empirical data. The interphase thickness dwindles during degradation and a high content of CNT largely eliminates the polymer and interphase region, because CNT accelerate the degradation. Both thick interphase and short tunnels obtain the high conductivity, while either thin interphase or a large tunnel causes an insulated example, since thin interphase or a big tunnel prevents the electron transferring. This study can provide a simple approach to calculate and optimize the conductivity to predict the behavior of a degradation nanobiosensor.

Vapourchromic alkali metal ions complexes based on 2-phenmethylamino-7-methyl-1,8-naphthyridine

A series of 2-phenmethylamino-7-methyl-1,8-naphthyridine/alkali metal ion (Li + and Na + ) complexes have been synthesized using a polymeric medium (poly(acrylic acid)) as the key activating component. Upon exposure to methanol or ethanol vapour at ambient temperature, the emission colour of prepared complexes in solid powder and thin film states changes from red-orange or pink to blue, respectively. These phenomena are reversible and rapid (about 5-10 s), hence, the prepared complexes have potential applications as chemosensor materials for detection of volatile methanol vapour.

Collective Nanoparticle Dynamics Associated with Bridging Network Formation in Model Polymer Nanocomposites.

The addition of nanoparticles (NPs) to polymers is a powerful method to improve the mechanical and other properties of macromolecular materials. Such hybrid polymer-particle systems are also rich in fundamental soft matter physics. Among several factors contributing to mechanical reinforcement, a polymer-mediated NP network is considered to be the most important in polymer nanocomposites (PNCs). Here, we present an integrated experimental-theoretical study of the collective NP dynamics in model PNCs using X-ray photon correlation spectroscopy and microscopic statistical mechanics theory. Silica NPs dispersed in unentangled or entangled poly(2-vinylpyridine) matrices over a range of NP loadings are used. Static collective structure factors of the NP subsystems at temperatures above the bulk glass transition temperature reveal the formation of a network-like microstructure via polymer-mediated bridges at high NP loadings above the percolation threshold. The NP collective relaxation times are up to 3 orders of magnitude longer than the self-diffusion limit of isolated NPs and display a rich dependence with observation wavevector and NP loading. A mode-coupling theory dynamical analysis that incorporates the static polymer-mediated bridging structure and collective motions of NPs is performed. It captures well both the observed scattering wavevector and NP loading dependences of the collective NP dynamics in the unentangled polymer matrix, with modest quantitative deviations emerging for the entangled PNC samples. Additionally, we identify an unusual and weak temperature dependence of collective NP dynamics, in qualitative contrast with the mechanical response. Hence, the present study has revealed key aspects of the collective motions of NPs connected by polymer bridges in contact with a viscous adsorbing polymer medium and identifies some outstanding remaining challenges for the theoretical understanding of these complex soft materials.

Effects of interfacial shear strength on the operative aspects of interphase section and tensile strength of carbon-nanotube-filled system: A modeling study

In this article, the required interfacial shear strength (τc) between a polymer medium and carbon nanotubes (CNTs) is determined to define the operative interphase thickness in nanocomposites. The roles of the operative interphase thickness in the operative CNT loading and percolation onset are determined. Additionally, “τc,” interfacial shear strength (τ), operative filler concentration, CNT curliness, interphase thickness, and percolation onset are used to develop a model for determining the strength of CNT-filled systems. The equations and the suggested model adequately reflect the roles of the parameters in the model’s outputs. In addition, many real values for several examples validate the proposed model. A low “τc” and high “τ” positively control the operative interphase thickness, operative CNT concentration, and percolation onset, thus improving the nanocomposite’s strength. Among the variables considered herein, CNT size is the most important term because it changes the relative strength (nanocomposite’s strength divided by polymer strength) from 1 to 25.

Following principles of green chemistry: Low ppm photo-ATRP of DMAEMA in water/ethanol mixture

Based on the 12 principles of green chemistry, the possibility of the synthesis of cationic PDMAEMA brushes in environmentally favorable aqueous medium, water-alcohol mixture as well as commercially available alcoholic beverages (three types of traditional Polish vodka and spirit) via dually-controlled photo-ATRP was presented. The addition of ethanol to the polymerization medium allowed to obtain a product with narrower molecular weight distribution (Ð = 1.17) than a fully aqueous medium (Ð = 1.29). Moreover, the application of alcoholic beverages of organic origin (e.g. pure grain vodka) increases the synthetic process rate while maintaining a controlled structure of the synthesized product. Furthermore, pH-responsive character of polymer brushes grafted from the silicon wafers (Si-g-PDMAEMA) was confirmed, indicating the application potential for controlled adhesion of proteins or drug release.

The Effect of Using Micro-Clustered Water as a Polymer Medium.

The aim of the study was to investigate the changes within the physicochemical properties of gelatin, carrageenan, and sodium alginate hydrosols prepared on the basis of micro-clustered (MC) water. The rheological parameters, contact angle and antioxidant activity of hydrosols were investigated. Moreover, the pH, oxidation–reduction potential (ORP) and electrical conductivity (EC) were measured. The hydrosols with MC water were characterized by a lower pH, decreased viscosity, a lower contact angle, and only slightly lower antioxidant activity than control samples. The results showed that hydrosol’s properties are significantly changed by MC water, which can lead to enhancement of its applicability but requires further investigation.

Supramolecular cocrystals built through redox-triggered ion intercalation in \u03c0-conjugated polymers

Self-organization in π-conjugated polymers gives rise to a highly ordered lamellar structure, in which inter-chain stacking spontaneously forms two-dimensional conjugated sheets. This multi-layer stacked nature of semicrystalline polymers allows the inclusion of various functional molecules. In particular, redox-triggered ion-intercalation is an ideal system for molecular doping, for which extremely high charge carrier density has been achieved. Here, we conducted a detailed structural analysis and electron density simulation to pinpoint exactly where the guest dopants are located periodically in the void space in a polymer’s lamellae. Our findings are indicative of an intercalation compound of layered polymers and a guest intercalant. We show that a homogeneous cocrystal structure can be realized throughout the host polymer medium, which is proved by the observation of coherent carrier transport. The intercalation cocrystal nature gives the best achievable doping level in semicrystalline polymers and excellent environmental stability. These findings should open up possibilities for tuning the collective dynamics of functional molecules through intercalation phenomena.

Effect of experimental conditions on the binding abilities of ciprofloxacin-imprinted nanoparticles prepared by solid-phase synthesis

Imprinted nanoparticles present several advantages respect to bulk imprinted materials, but, when prepared by traditional methods, their usefulness is limited as the approaches are costly or require complex optimization steps, while the purification from template molecules is challenging. An innovative approach is the solid-phase synthesis. It consists in the covalent immobilization of the template onto a solid support, the polymerization of nanoparticles around the template, the clean-up from unproductive components and the final release of the imprinted nanoparticles, which are free of template and demonstrate high affinity for the target molecule. Here we report the use of ciprofloxacin as immobilized template to evaluate the effect of different experimental conditions in the solid phase polymerization (template scaffolding, polymerization mixtures, polymerization medium) and different rebinding conditions (buffer pH) on the binding properties. The results confirm that the solid phase synthesis approach is a flexible approach, where the experimental conditions are decisive for the binding properties. The results show that this approach is a powerful technique to easily prepare nanoparticles fully compatible with the aqueous environment, with reduced non specific binding (≈104 Mol L−1), high equilibrium binding constants (105–107 Mol L−1) and fast association rate constants (≈106 Mol L−1 min−1), values which are comparable to those of natural antibodies.

Micromechanics Modeling of Electrical Conductivity for Polymer Nanocomposites by Network Portion, Interphase Depth, Tunneling Properties and Wettability of Filler by Polymer Media

This study presents a micromechanics model for conductivity of polymer nanocomposites comprising carbon nanotubes (CNT) (PCNT) established by expanded Takayanagi equation. The advanced model presumes the roles of CNT nets, interphase, electron tunneling and wettability of particles by polymer media in the conductivity. The effective filler concentration and percolation onset reflect the contribution of interphase to networks. Moreover, the model properly studies the tunneling properties and wettability based on the available equations. The model’s predictions for some samples are linked to the experimental data. Furthermore, the established model estimates the parameters’ impacts on the conductivity. All forecasts fairly agree with the empirical data of specimens approving the recommended model. A thick interphase, poor CNT curliness, thin CNT, high CNT conduction and large networks improve the conductivity. Furthermore, the conductivity expressively increases to 16 S/m at the largest tunneling diameter (d=30 nm) and the smallest tunneling distance (λ=3 nm), but an insulated sample is observed at λ>5 nm. Therefore, the tunneling dimensions largely manipulate the nanocomposite’s conductivity.

Polymer-induced orientation of nanowires under electric fields

The controlled orientation of metallic wires inside a polymeric medium can enhance desired properties of the composites, such as the electrical conductivity or the optical transmittance. In this work, we study silver nanowire orientation in semidilute suspensions of DNA and find an intriguing effect: under the application of low-frequency AC electric fields with moderate amplitude, the DNA coils can provoke the orientation of the wires in solution. The phenomenon is entirely induced by the polymer, when it is deformed by the application of an electric field. This effect is explained using computer simulations based on excluded-volume interactions. Moreover, we experimentally show that such a behaviour is not exclusive of silver nanowire-DNA suspensions, but rather occurs for other particle-polymer systems. This phenomenon can be taken advantage of to achieve strong orientation of particles otherwise insensitive to electric fields.

Modification of Thiol-Ene Ionogels with Octakis(methacryloxypropyl) Silsesquioxane.

The effect of polyhedral oligomeric silsesquioxane (POSS) on the synthesis and properties of hybrid organic–inorganic ionogels was investigated using octakis(methacryloxypropyl) silsesquioxane (methacryl-POSS). Ionogels were prepared in situ by thiol-ene photopolymerization of triallyl isocyanurate with pentaerythritol tetrakis(3-mercaptopropionate) in a mixture of imidazolium ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMImNTf2) and propylene carbonate (PC). Investigations included the kinetics of hybrid materials formation and selected physical and mechanical properties. The disadvantage of ionogels without the methacryl-POSS modifier is leakage and insufficient mechanical properties. Modifying the thiol-ene matrix by the addition of methacryl-POSS made it possible to obtain non-leaking ionogels with improved mechanical and conductive properties. The steric hindrance of POSS cages and high-density network formation played important roles in ionogel synthesis: decrease of polymerization rate (with almost no effect on conversion), as well as dimensions of the formed polymer spheres during dispersion polymerization (highly cross-linked polymer has poorer solubility in polymerizing medium at a similar conversion, and nucleation begins at lower conversion), an increase of glass transition temperature and puncture strength. Hybrid ionogels with high ionic conductivity in the range of 4.0–5.1 mS∙cm−1 with the maximum parameter for 1.5 wt.% addition of the methacryl-POSS were obtained, which can be associated with ion-pair dissociations in ionic liquid clusters caused by methacryl-POSS.

Selected performance indices for assessment of polypropylene susceptibility to dyeing by pigments of different UV resistance

This study presents an assessment of the effects of usage time for polypropylene (PP) experimental samples including those dyed with pigments of different UV resistance. A standard double cavity mold was used to create the samples by injection molding. Selected indices were analyzed in terms of color change (UV resistance of pigments), and UV radiation resistance of a PP polymer medium. The experiment revealed a significant impact of the accepted usage time and the type of dye concentrates on the indices characterizing the sample color change (CIELab) and a change in the structure and state of the PP medium surface.

A two-step technique established by simple models to estimate the tensile strength of halloysite nanotubes-filled nanocomposites

The limited quantity of modeling papers on halloysite nanotubes (HNT)-reinforced nanocomposites restricts the optimization of properties for multifunctional applications. In this paper, we develop a two-step technique to approximate the tensile strength for this category of materials. At the first stage, HNT and surrounding interphase are assumed as pseudoparticles and their strength is estimated by Kelly-Tyson approach. At the second step, a developed model predicts the strength of polymer nanocomposites containing polymer medium and pseusoparticles. Many experimental records of several examples and examinations of whole parameters evaluate the advanced technique. The experimental results and parametric checks demonstrate the desirable proofs approving the current methodology. Both interfacial shear strength and interphase strength straightly handle the strength of nanocomposites. The calculations reveal that the dimensions of HNT and interphase section can change the strength of HNT-reinforced samples by 280%. Nevertheless, the variations of HNT aspect ratio and polymer medium strength may improve the nanocomposite's strength by 470%. Additionally, high aspect ratio of HNT and poor polymer host are desirable for the strength of nanocomposites, while thick and short HNT (low aspect ratio < 33) cannot strengthen the polymer medium.

Optimization and Pharmacokinetic Study of Boswellic Acid–Loaded Chitosan-Guggul Gum Nanoparticles Using Box-Behnken Experimental Design

Macromolecules are important in polymer-based drug delivery systems as they help in specific targeting. This study explores the use of guggul gum (GG) and chitosan (Ch) in encapsulating boswellic acid (BA) which has high first-pass metabolism and low aqueous solubility for possible uses in inflammatory conditions. Ionic complexation was used for nanoparticle formulation. The contents of guggul gum, chitosan, and boswellic acid were taken as independent variables, and their influence on encapsulation, particle size, and polydispersity were optimized by using Box-Behnken design. The developed formulation was assessed for drug release (in vitro) and release kinetics, stability, and preclinical pharmacokinetics. The formulation was also evaluated for inhibition of carrageenan-induced hind paw inflammation in rats. The nanoparticles were successfully prepared by ionic complexation method. The runs suggested by the design yielded a quadratic model for predicting the relationship between independent variables and responses. The optimum condition suggested by point prediction tool yielded spherical nanoparticles with 81.7% encapsulation, drug loading 21.2%, 377.19 nm size, and 0.201 PDI. The nanoparticles showed zero-order kinetics demonstrating an amalgamation of drug diffusion through matrix and erosion of polymeric medium. Ionic complexation is a suitable method for nanopartile formulation. GG-Ch nanoparticles are beneficial for specific delivery and anti-inflammation of boswellic acid. The bioavailability of boswellic acid was increased by 11.38 times when given as a GG-Ch nanoparticle. The nanoparticles were stable at 25 °C for 6 months.

Фотолюминесценция композитов полиметилметакрилат / [(Zn,Cd)S : Mn,Cu,Eu

Nanoscale structures based on zinc and cadmium sulfides doped with Mn, Cu, and Eu ions were synthesized by the method of emerging reagents in a polymerizing medium of methyl methacrylate. The broadband photoluminescence of the compositions is associated with recombination processes at the defect levels of semiconductor structures. Narrow photoluminescence bands occur during electron transitions between the energy levels of Eu3+ ions. The excitation of photoluminescence occurs as a result of the interband transition and electron transitions to the levels of structural defects, as well as during self-absorption and energy transfer to the levels of Eu3+ ions.

Effects and mechanism of Lactococcus lactis thermo-sensitive hydrogel on the wound healing of full-thickness skin defects in diabetic mice

Effects and mechanism of Lactococcus lactis thermo-sensitive hydrogel on the wound healing of full-thickness skin defects in diabetic mice

Polymeric proton exchange media with ionic bonds in the main chain of the polymer

This paper proposes a method of obtaining the first representative of a polymeric proton-conducting medium with protic ionic groups in the main chain of a polymer by the mutual neutralization of linear telechelic oligomers with end groups of the basic and acidic nature. Oligoethylene oxide containing 1-(3-aminopropyl) imidazole fragments with two types of basic centers (aliphatic secondary amine groups and imidazole fragments) at the ends of the chain was used as the oligomer with basic properties. Sulfonic acid-terminated oligoethylene oxide was used as the acid oligomer. Protonation of aliphatic secondary amino groups in the composition of the oligomer of the basic type with the formation of an ion-elongated polymer chain is more probable at the equimolar ratio of the starting compounds according to the analysis of ΔKa values. It is shown that the synthesized polymer contains two types of crystalline formations with melting points of 37.6 °C and 46.2 °C and turns into a liquid state, when heated to higher temperature values. The proton conductivity of the polymer under anhydrous conditions is close to the conductivity of the initial sulfonic acid-terminated oligomer in the temperature inter val of 40-100 °C and reaches 2.3 · 10–4 S/cm at 100 °C, despite a much lower content of proton charge carriers.

Advancement of a model for electrical conductivity of polymer nanocomposites reinforced with carbon nanotubes by a known model for thermal conductivity

The models for thermal conductivity of polymer nanocomposites reinforced by carbon nanotubes (CNT) (PCNT) can express the electrical conductivity, because both electrical and thermal conductivities consistently depend on the CNT properties. In this study, a known model for thermal conductivity of PCNT is simplified and developed for electrical conductivity assuming CNT aspect ratio, network fraction, interphase districts, tunneling area between near CNT and CNT wettability by polymer medium. Simple equations express the volume fraction of networked CNT by CNT loading, CNT size and interphase depth. In addition, applicable equations suggest the total conduction of CNT and tunnels. The satisfactory matching among measured records and forecasts in addition to the rational effects of whole factors on the conductivity confirm the advanced model. Lengthy CNT and dense interphase usefully manipulate the conductivity, but short CNT or thin interphase cannot increase the conductivity of insulated medium. Additionally, only the high level of polymer tunneling resistivity prevents the conducting efficiency of CNT in PCNT. Also, wide tunnels and short tunneling distance highly progress the conductivity, but very small tunneling width causes an insulated specimen.

A review on abrasive flow finishing of metal matrix composites

Metal matrix composites are widely used in the area of aerospace, automobile, defence/military industries due to their advantages over conventional alloys. This group of materials is heterogeneous as they are fabricated by mixing particulate reinforcement in the metallic matrix material. Conventional grinding and advanced finishing processes like electrochemical grinding finds less use to finish these novel materials because of the geometrical limitations posed by these processes. On the other hand, abrasive flow finishing is a novel way of finishing the components, by extruding a laden viscoelastic polymer medium through intricate shapes of the components. This process gives predictable, repeatable, and uniform surface roughness on the components being finished. This article reviews the extensive works carried out on the finishing of metal matrix composites with the abrasive flow finishing process and reports the results and challenges faced in the process of finishing. Some of the advanced finishing processes that arepotential to finish metal matrix composites are also listed at the end.

Electrical conductivity of interphase zone in polymer nanocomposites by carbon nanotubes properties and interphase depth

AbstractIn this work, carbon nanotubes (CNT) properties and interphase depth define the interphase conductivity in polymer CNT nanocomposites (PCNT). In addition, the operative CNT length and volume portion are linked to the conductivity transportation between CNT and insulated polymer medium to propose a simple model for conductivity. The significances of various terms on the interphase conductivity and conductivity of PCNT are justified and the model's predictions are examined using the experimental outputs of certain examples. Thin CNT and dense interphase obtain the extraordinary conductivity transportation, while CNT length and conductivity are ineffective. Moreover, thin, small, and high‐conductive CNT as well as dense interphase introduce the high interphase conductivity. The estimations of conductivity appropriately follow the experimental data authorizing the established model. This model is capable to substitute the conventional models owing to the assumption of innovative nanocomposite's terms.