Polymerization Medium Research Articles

Epoxy Functional Porous POSS Microparticle Synthesis

Epoxy-functional porous polyhedral oligomeric silsesquioxane (POSS) microparticles were synthesized by templated polymerization in two-steps by using monodisperse 2µm poly(GMA) seed latex particles as a template. In the first step, templated polymer latex was swollen in emulsion medium to obtain micron size porous POSS particles. In the second step, the hydrophobic monomers metharcyl-POSS, epoxy-functional monomer glycidyl methacrylate (GMA), the crosslinking agent GDMA and the thermal imitator diffused into the swollen template in emulsion medium for free-radical polymerization. The resultant poly(POSS-co-GDMA-co-GMA) microparticles were obtained in polydisperse form due to the high molecular weight of the silica cage core of POSS created difficulty in the diffusion step. However; monodisperse composite microparticles were obtained around 5.8 ± 0.4µm in size via centrifugal post-separation. The spherical fine porous hybrid structure was fully characterized as morphological, thermal, chemical composition, and crystalline form by SEM, TGA, FTIR, and XRD respectively.

Nanostructuring Polyaniline Using Non-Substituted Imidazolium-Based Ionic liquid as Polymerization Medium Enabling Faster Supercapacitor Operation

Non-substituted imidazolium-based protic ionic liquid, namely imidazolium hydrogen sulfate [Imi][HSO4], has been investigated as a polymerization medium for PANI (designated as PANI/PIL). The resulting material was then investigated as electrode materials for supercapacitors. [Imi][HSO4] was prepared via a one-step acid-base reaction, and its structure was confirmed by 1H NMR. [Imi][HSO4] displayed full miscibility with water owing to the charge density distribution of its ions. Furthermore, the binary mixture [Imi][HSO4]/water is highly acid (e.g. pH ~ 0.1 for [Imi][HSO4]/water in a weight ratio of 70/30). As the polymerization medium for PANI/PIL, [Imi][HSO4] plays the role of a soft template agent and induces nanostructured PANI formation with fibrillar morphology (as shown by SEM images) without affecting the typical structure of PANI (as confirmed by FT-IR analysis). Furthermore, PANI/PIL was obtained in emeraldine salt form without any undesirable byproduct. Moreover, the electrical conductivity was seven times superior to that of the conventional PANI (i.e. PANI/HCl) when measured by the four-probe technique of PANI/PIL (~ 21.8 S/cm). This improvement in the PANI/PIL’s electrical conductivity of as well as the fibrillar morphology of PANI/PIL positively influences its electrochemical performances and highlights the suitability of [Imi][HSO4] as a polymerization medium for PANI material.

Sustainable Synthesis of FITC Chitosan-Capped Gold Nanoparticles for Biomedical Applications

The quest for novel nanoscale materials for different applications necessitates that they are easy to obtain and have excellent physical properties and low toxicity. Moreover, considering the ongoing environmental impact of noxious chemical waste products, it is important to adopt eco-friendly approaches for nanoparticle synthesis. In this work, a natural polymer (medium molecular weight chitosan) derived from chitin was employed as a reducing agent to obtain gold nanoparticles (AuNPs) with a chitosan shell (AuNPs@CS) by a microwave oven. The chitosan is economically viable and cost-competitive in the market showing also nontoxic behavior in the environment and living organisms. The synthesized AuNPs@CS-FITC NPs were fully characterized by spectroscopic and microscopic characterization techniques. The size distribution of NPs was about 15 nm, which is a suitable dimension to use in biomedical applications due to their high tissue penetration, great circulation in blood, and optimal clearance as well as low toxicity. The prepared polymer-capped NPs were further functionalized with a fluorescent molecule, i.e., Fluorescein-5-isothiocyanate (FITC), to perform imaging in the cell. The results highlighted the goodness of the synthesis procedure, as well as the high internalization rate that resulted in an optimal fluorescence intensity. Thus, this work presents a good sustainable/green approach-mediated polymer nanocomposite for various applications in the field of diagnostic imaging.

PANI-WO3·2H2O Nanocomposite: Phase Interaction and Evaluation of Electronic Properties by Combined Experimental Techniques and Ab-Initio Calculation.

The development of conjugated polymer-based nanocomposites by adding metallic particles into the polymerization medium allows the proposition of novel materials presenting improved electrical and optical properties. Polyaniline Emeraldine-salt form (ES–PANI) has been extensively studied due to its controllable electrical conductivity and oxidation states. On the other hand, tungsten oxide (WO3) and its di-hydrated phases, such as WO3·2H2O, have been reported as important materials in photocatalysis and sensors. Herein, the WO3·2H2O phase was directly obtained during the in-situ polymerization of aniline hydrochloride from metallic tungsten (W), allowing the formation of hybrid nanocomposites based on its full oxidation into WO3·2H2O. The developed ES–PANI–WO3·2H2O nanocomposites were successfully characterized using experimental techniques combined with Density Functional Theory (DFT). The formation of WO3·2H2O was clearly verified after two hours of synthesis (PW2 nanocomposite), allowing the confirmation of purely physical interaction between matrix and reinforcement. As a result, increased electrical conductivity was verified in the PW2 nanocomposite: the DFT calculations revealed a charge transfer from the p-orbitals of the polymeric phase to the d-orbitals of the oxide phase, resulting in higher conductivity when compared to the pure ES–PANI.

Templating effects in dye-containing polypyrrole-gelatin cryogels

Polypyrrole-gelatin cryogels were prepared by cryopolymerization in the presence of safranin, methyl orange and Acid Blue 25 dyes. The macroporous morphology (pore size <55 μm) of the obtained materials was not affected by the introduction of the dyes. The used dyes are known to form templates and change polypyrrole morphology in similar polymerization conditions without gelatin. However, optical microscopy showed that the anionic dyes (Acid Blue 25 and methyl orange) did not precipitate and form morphology-guiding templates after addition of iron(III) chloride in the presence of gelatin. In contrast, the template-forming behavior of the cationic dye (safranin) was found to be preserved. Starting from 0.5 mol% of safranin (compared to the monomer) in the polymerization medium, the safranin templates were presumably incorporated into pore walls of the cryogels, reinforcing them, and increasing tensile modulus by ≈ 6 times (up to ≈400 kPa) compared to the cryogel without a dye. According to TGA, introduction of the dyes to the polypyrrole-gelatin aerogels resulted in decrease of their thermal stability. Molecular structure of the aerogels was studied by vibrational spectroscopy. The aerogel prepared in the presence of Acid Blue 25 had the highest conductivity (10.4 S cm−1) and specific surface area (37.5 m2 g−1) as well as porosity (95.1%) and pore volume (13 cm3 g−1). In general, incorporation of the dyes resulted in higher specific surface area (up to ≈10 times) of the materials, compared to the cryogels without a dye. Therefore, the preparation of polypyrrole-gelatin cryogels/aerogels in the presence of the dyes can be a promising approach for enhancement of their properties.

Gel Electrophoresis of a Hydrophobic Liquid Droplet with an Equipotential Slip Surface.

A theoretical study has been carried out on the electrophoresis of charged dielectric liquid droplets with an equipotential and hydrodynamically slipping surface moving in a quenched polymeric charged hydrogel medium. The liquid inside the droplet is electrically neutral. The Brinkman-Debye-Bueche model is employed to study the gel electrophoresis of such a hydrophobic and equipotential liquid droplet considering the long-range hydrodynamic interaction between a migrating droplet and the gel skeleton. Within the weak field and Debye-Hückel electrostatic framework, we derive an original closed-form expression for electrophoretic mobility, which further recovers the existing mobility expressions derived under several limiting conditions. The derived expressions for electrophoretic mobility explicitly involve exponential integrals, which are not so convenient for practical applications. Thus, the exact forms of the electrophoretic mobility under various electrohydrodynamic conditions are further approximated to make them free from exponential integrals. The approximate forms are found to be in excellent agreement with the exact results with maximum relative errors of about 1.5%.

Comparison of Calculated and Experimental Depth Distributions of Gamma Radiation Doses in Polymer Media

The paper discusses a comparison of depth distributions of doses in plastics obtained by simulation in the PCLab software and experimentally with a Theratron Equinox–80 gamma–therapy unit. We used items made of ABS, HIPS and PLA plastics suitable for 3D printing and with different fill factors. Our study has demonstrated that the simulation results are consistent with the experimental ones within the uncertainty limits.

Tuning Polymer/TiO2 Nanocomposites Morphology by In Situ Non-Hydrolytic Sol-Gel Syntheses in Viscous Polymer Medium: Influence of the Polymer Nature and Oxygen Donor.

Herein, we reported the synthesis of TiO2 through different non-hydrolytic sol-gel (NHSG) routes in viscous polymer media. For the first time, the influence of the polymer nature (Polystyrene (PS) or Polypropylene (PP)) on the morphology of synthesized inorganic domains was investigated. The non-hydrolytic sol-gel reactions between titanium isopropoxide Ti(OiPr)4 and acetic anhydride in molten polypropylene lead to the formation of microfillers with a mean diameter of about 1 μm, while the same synthesis carried out in viscous polystyrene lead to the formation of nanofillers with diameter lower than 10 nm forming aggregates of approximately 200 nm. We have also investigated the influence of the oxygen donor nature on the morphology of synthesized fillers using aromatic oxygen donors in a polystyrene matrix. The use of benzoic anhydride or acetophenone as oxygen donors with Ti(OiPr)4 in viscous polystyrene lead to respectively platelet-like morphology or aggregated nanofillers. We demonstrated that the affinity between polymer, reactants, and/or by-products had an influence on the morphology and the size of in situ synthesized TiO2 fillers. These results evidenced for the first time the possibility to control and to tune the morphology of in situ grown inorganic objects through the NHSG process by the appropriate choice of solvent, here a viscous polymer medium, and reactants.

A review on magnetically assisted abrasive flow machining and abrasive material type

The development of fine surface finish with no defects is still a significant challenge for the present industry and the finishing operation in the manufacturing of the precision components is the major problem. It is difficult rather impossible to polish/finish the difficult-to-reach surfaces, internal surfaces, and complex geometries by existing finishing methods. Abrasive flow machining (AFM) is a well-established advanced finishing process that can meet the required finishing requirements. However, the main disadvantages of this process are the surface integrity with low surface finish and high machining times. Magnetically Assisted Abrasive flow machining (MAAFM) is one of the non-conventional machining techniques that can successfully handle these problems. This process was developed in the early 2000s as a technique for deburring, polishing, and radiusing tough to reach surfaces like complicated configurations and edges/boundaries by flowing a magnetic abrasive polymeric medium across them. Magnetic flux density (MFD), extrusion pressure, flow volume, abrasive type, grit size, number of process cycles, medium, and workpiece configuration are the principal machining parameters that control the surface finish characteristics. The medium extruded forward and backward between two vertically opposed hydraulic cylinders across transit created by the workpiece and tooling. Abrasion of workpiece takes place wherever the medium proceeds across the highly confining transit. The major elements of the MAAFM process are the machine, tooling, and the magnetic abrasives containing media. MAAFM has a wide scope of uses in industries including automotive, aviation, precision dies, medicinal, electronics. This article represents a review of current advancements in the area of the MAAFM process and the type of magnetic abrasive particles (MAPs) used.

Real‐Time Tunable Red/Near‐Infrared Solid‐State Emitters in the First Biological Window: 9,9‐Diethyl‐2‐diphenylaminofluorene‐Based Push‐Pull Fluorophores for Distributed Feedback and Random Lasing Applications

AbstractIn biological imaging, red‐to‐infrared emissive dyes facilitate direct visualization of molecular interactions, through deep tissue penetration, along with minimal tissue damage. This work uses simple systems based on a single dye‐doped polymeric thin film for distributed feedback and random lasing investigations. As active compounds, novel push‐pull luminescent diphenylaminofluorene derivatives are used, functionalized with different acceptor groups. Integration of such luminescent dyes with a transparent polymeric medium allows fabrication of real‐time lasing tunability in the first biological window (650–950 nm). The observed spectral tuning of 150 nm is a groundbreaking value obtained in a single‐dye system.

Modeling of multiple crack initiation in polymer pipes under oxidative environment

In this study, a novel fundamental model for the multiple crack initiation behavior of polymer pipes transporting fluids with strong oxidizing agents was proposed. Because the oxidant diffuses into the polymer medium with consumption by oxidation, a volumetric sink of the diffused oxidant was considered. The degradation kinetics of the polymer pipes were modeled by diffusion using the reaction equations. To compare the released energy with the crack initiation, Green's function for the stress intensity factor of various crack numbers, sizes, and standard dimension ratios (SDRs) was developed. The number of crack initiations and durations were successfully simulated using potential energy analysis with cracking. At a relatively low internal pressure in an oxidative environment, multiple cracks were estimated with a proper scale of the crack length. Instead, it was predicted that one main crack would be initiated at a higher level of internal pressure. In addition, the knee points representing the slope change of the internal pressure-lifetime plot were shown between these different failure modes, in agreement with previous observations. The experimental results of sustained hydrostatic pressure tests of polymer pipes under chlorinated water can be accurately simulated by the proposed model.

Preparation of colloidal nanoparticles PVA-PHEMA from hydrolysis of copolymers of PVAc-PHEMA as anticancer drug carriers

The novel pH-responsive polymer nanoparticles have been widely used for drug delivery and cancer therapy. The pH-sensitive nanoparticles include chemical structures that can accept or donate protons in response to an environmental pH change. Polybases which mostly contain alkaline groups such as amines and hydroxy, accept protons at low pH and are neutral at higher pH values. This study aimed to prepare pH-sensitive colloidal amphiphilic poly(vinyl alcohol-2-hydroxyethyl methacrylate) (PVA-PHEMA) copolymers in cancer therapy applications. For this purpose, poly(vinyl acetate-2-hydroxyethyl methacrylate) (PVAc-PHEMA) copolymer nanoparticles were synthesized in different polymerization medium fractions from water and methanol and different monomer feed concentration. Then acetate groups were hydrolyzed, and the PHEMA-PVA nanoparticles were synthesized. The nanoparticles were further characterized using dynamic light scattering, Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis to identify the structural and morphological changes. The Methotrexate (MTX) was loaded into the nanoparticles, and drug release kinetics were evaluated. The results confirmed that PHEMA-PVA copolymeric nanoparticles could be favorably used in cancer therapy.

Recent Progress and Potential Biomedical Applications of Electrospun Nanofibers in Regeneration of Tissues and Organs.

Electrospun techniques are promising and flexible technologies to fabricate ultrafine fiber/nanofiber materials from diverse materials with unique characteristics under optimum conditions. These fabricated fibers/nanofibers via electrospinning can be easily assembled into several shapes of three-dimensional (3D) structures and can be combined with other nanomaterials. Therefore, electrospun nanofibers, with their structural and functional advantages, have gained considerable attention from scientific communities as suitable candidates in biomedical fields, such as the regeneration of tissues and organs, where they can mimic the network structure of collagen fiber in its natural extracellular matrix(es). Due to these special features, electrospinning has been revolutionized as a successful technique to fabricate such nanomaterials from polymer media. Therefore, this review reports on recent progress in electrospun nanofibers and their applications in various biomedical fields, such as bone cell proliferation, nerve regeneration, and vascular tissue, and skin tissue, engineering. The functionalization of the fabricated electrospun nanofibers with different materials furnishes them with promising properties to enhance their employment in various fields of biomedical applications. Finally, we highlight the challenges and outlooks to improve and enhance the application of electrospun nanofibers in these applications.

Research Progress on Polyaniline-Ionic liquids for Long Cycle-Stable Supercapacitors with High Capacitance

Ionic liquids have been used either as polymerization medium or as electrolytes for polyaniline (PANI) electrodes to produce long cycle-stable supercapacitors with high capacitance. As a polymerization medium, ionic liquids play the role of a soft template agent and induce the formation of nanostructured PANI morphology. Nanorod, nanowire, or spherical PANI morphology has been obtained in ionic liquids instead of agglomerated particles resulted in the conventional media. The well-defined one-dimensional PANI morphology ensures a short charge transfer distance in the PANI materials and low contact resistance between PANI and electrolyte interfaces. The efficiency of ionic liquids as a soft template agent is related to their structure as well as to their proportion in the reaction medium. As electrolytes, “neat” ionic liquids provide low but stable specific capacitance of PANI over more than hundreds of cycles. Binary mixtures of ionic liquids and solvents (e.g. acetonitrile, water) have increased both the specific capacitance and the capacitance retention of PANI compared with the performances resulting in the conventional aqueous acid electrolytes. Using ionic liquids to carry out both the synthesis and the electrochemical characterization of PANI is an effective approach to improve PANI cycle life. The key parameter is to choose the convenient ionic liquids. This review covers the most significant studies conducted on PANI/ionic liquids for supercapacitor applications.

A simple model for gas barrier performance of polymer nanocomposites considering filler alignment angle and diffusion direction

The available models for predicting the barrier properties of nanocomposite films cannot present the accurate results fitting to experimental data. In this paper, we develop a new model to forecast the barrier performance of polymer nanocomposites by filler orientation angle and changes in diffusion direction after collision of gas molecules to nanoplatelets. The developed model presents the barrier properties by the length, thickness, volume fraction and orientation angle of nanoplatelets as well as the lateral distance between adjacent nanoparticles. To gain a better understanding of the accuracy of new model, the predictions of permeability by previous models are compared to the experimental data of various samples containing nanoclay and graphene. The developed model offers the highest exactness among the models. The orientation of nanofiller in the polymer medium, degree of filler dispersion in addition to the aspect ratio and volume fraction of nanofiller are the most important factors affecting the barrier performance.

Advanced Kolarik model for the modulus of a nanocomposite system reinforced by halloysite nanotubes and interphase zone

AbstractIn the current article, Kolarik model is progressed for the tensile modulus of a polymeric system containing dispersed halloysite nanotubes (HNT) and adjacent interphase section. The progressive model correlates the nanocomposite's modulus to HNT concentration (volume fraction and weight percentage), the extents of HNT and nearby interphase section in addition to the densities of polymer medium and HNT. The productions of the progressive model are linked to the tentative results and the influences of all variables on the modulus of system are justified. The modulus of system reduces as HNT radius increases, but HNT weight percentage directly controls the nanocomposite's modulus. The modulus of samples maximizes by 47% by the deepest interphase section of 20 nm establishing a straight link among nanocomposite's modulus and interphase thickness. The increment of polymer matrix density improves the modulus of samples, but there is an opposite relation between the modulus of system and HNT density. Furthermore, the calculations exactly match to the experimental facts of numerous examples representing the accurateness of the progressed model.

Lyapunov instability of stationary flows of a polymeric fluid in a channel with perforated walls

Abstract The rheological Pokrovskii-Vinogradov model for flows of solutions or melts of an incompressible viscoelastic polymeric medium is studied in the case of flows in an infinite planar channel with perforated walls. The linear Lyapunov instability is proved for the base solution with constant flow rate in the class of perturbations periodic in the variable varying along the channel wall. Bibliography: 14 titles.

Synthesis and gelation properties of HPMC-g-poly(AM/AA/APEG2400) quaternary copolymer

To improve the stability of the polymers applied to profile control in high-temperature and high-salinity reservoirs, a water-soluble graft-copolymer HPMC-g-poly(AM/AA/APEG2400) was synthesized from hydroxypropylmethylcellulose (HPMC), acrylamide (AM), acrylic acid (AA), and allyl polyoxyethylene ether (APEG2400) via free-radical copolymerization using potassium persulfate (KPS) as the initiator. The molecular weight (Mw) of HPMC-g-poly(AM/AA/APEG2400) was controlled by the addition of the chain-transfer agent, sodium formate (SF), to the polymerization medium and was measured by capillary viscometry. Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), proton nuclear magnetic resonance (1H NMR), and scanning electron microscopy (SEM) were performed to characterize the graft-copolymer. The rheological properties of the graft-copolymer were investigated at different salinities and temperatures. The graft-copolymer solution showed better salt resistance, temperature tolerance, and long-term thermal stability than partially hydrolyzed polyacrylamide (HPAM). In addition, hydrogels were prepared using the graft-copolymer with varying Mw (346 × 104–1319 × 104), a crosslinker (hexamethylenetetramine–resorcinol, (HMTA–RC)), and additives (citric acid, (CA), and ammonium phosphate monobasic, (MAP)), and the hydrogels exhibited adequate strength and tunable gelation time. The hydrogels prepared using the graft-copolymer with high Mw possessed excellent long-term stabilities with negligible syneresis at 45 °C after 130 d, for the same conditions, the syneresis of conventional hydrogels prepared by HPAM reached approximately 90%.

Development of a model for modulus of polymer halloysite nanotube nanocomposites by the interphase zones around dispersed and networked nanotubes

Theoretical studies on the mechanical properties of halloysite nanotube (HNT)-based nanocomposites have neglected the HNT network and interphase section, despite the fact that the network and interphase have significant stiffening efficiencies. In the present study, the advanced Takayanagi equation for determining the modulus of nanocomposites is further developed by considering the interphase zones around the dispersed and networked HNTs above percolation onset. Furthermore, simple equations are provided to determine the percolation onset of HNTs and the volume portions of HNTs and interphase section in the network. The experimental values obtained for many samples and the assessments of all relevant factors validate the proposed model. The high ranges of HNT concentration, interphase depth, HNT modulus, HNT length, network modulus, interphase modulus, interphase concentration, and network fraction enhance the system modulus. However, the low levels of HNT radius, percolation onset, and matrix modulus can intensify the reinforcing effect. Notably, the moduli of the dispersed HNTs and the surrounding interphase negligibly affect the modulus of the samples. Moreover, HNTs cannot reinforce the polymer medium when the HNT volume fraction is lower than 0.01 and the interphase depth is less than 5 nm.

Influence of polymer initiators in light guiding in a cyanobacterium incorporated (poly)-methyl methacrylate matrix

This letter investigates the luminescence property of a cyanobacterium, Arthospira platensis (spirulina) in an acrylic polymer medium. We fabricated 5 mm thick rectangular sheets by incorporating this photosynthetic organism in (Poly)-Methyl Meth Acrylate (PMMA) for waveguide applications in Luminescent Solar Concentrators (LSCs). Meanwhile, during polymerization, the use of the benzoyl peroxide initiator had a notable effect on the optical property of the pigment-protein. We recorded an enhanced fluorescence emission of the sheet fabricated in the peroxide environment. Emission efficiency is 4.09% more than that in an azo- environment. This is due to the anti-oxidant property of spirulina’s pigment-protein, which absorbs the oxygen radicals produced by the peroxide initiator.