Diffusion of large molecules in polymers: a measuring technique based on microdensitometry in the infra-red

A technique based on infra-red microdensitometry has been developed for studying the centre-of-mass translational diffusion of large additive molecules in polymeric matrices. In this technique the diffusion broadening with time of a known initial concentration profile of the additive within the bulk polymer is monitored. The shape of the concentration profile after diffusion broadening readily yields D, the diffusion constant; it may also yield the concentration dependence of D where this is significant. The technique is found to be reasonably flexible, and applicable to a number of polymer—additive combinations. Values of D in the range 10^?5 to 10^?10 cm²/sec and initial additive concentrations of down to 0.3% may be studied. The technique is viable over a wide range of temperatures and pressures. Some results obtained by this technique are presented, for the case of various linear long-chain amides diffusing in low density polyethylene.     

Synthesis of a side chain liquid crystalline polycarbonate with a chiral backbone

We report the experimental demonstration of a novel and environmentally benign supercritical carbon dioxide (ScCO₂) technique that yields an optically active, side chain liquid crystalline polycarbonate in a single‐step reaction. The obtained polymer is worthwhile, since it is highly stereoregular and can find applications in an enlarged mesomorphic temperature range compared to its acrylic analogues. The synthesized materials were characterized by IR, ¹H‐NMR, and ¹³C‐NMR, while the thermal properties were measured by DSC. Polarized optical micrograph and wide angle X‐ray diffraction were used for the mesogenic property characterization of the copolymer. The transfer chirality from the backbone to the mesophase is demonstrated on the optical microscopy textures. Being consistent with the ¹³C‐NMR, X‐ray implies an ordered polymeric structure. The DSC analysis of the copolymer indicates that the T_i (the clearing point temperature) value does not change dramatically, whereas a pronounced decrease in T_g (the glass transition temperature) value is observed from that of its acrylic analogues. Hence, the obtained polymer exhibits another practical benefit by widening the mesomorphic temperature range. This study is the insightful combination of material processing and chemical design that elucidates the advantages of ScCO₂ application, in terms of liquid crystallinity and the tacticity of the obtained polymer. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1915–1921, 2006     

Silver-doped silica powder with antibacterial properties

In this study a simple and reproducible method was used to develop silver-doped silica powder with antibacterial properties. Silica matrices were synthesized via a sol–gel route which allows one to easily tailor textural and chemical properties. A wide range of silica-materials/products was obtained via the present route. These are: pure silver nanoparticles (Ag⁰), silver in ionic state (Ag⁺), AgCl nanoparticles, and the mixture of Ag⁰ and AgCl. The efficacy of these products were tested against Escherichia coli and the results demonstrate that materials that are suitable for antibacterial applications were obtained by this newly developed technique while utilizing sodium silicate, which is relatively inexpensive, as a silica precursor. This may significantly boost the industrial production of the inexpensive silver-doped silica products for various applications. A project on other innovative industrial applications of our products is in progress.     

Survey of contrasts of polymers under a high-contrast X-ray computerized tomography

Contrasts of the polymer materials under a high contrast X-ray computerized tomography (XCT) are comprehensively investigated. We developed a high contrast XCT, and demonstrated its capabilities to polymer systems, such as polymer blends. Then we got a hypothesis that the pixel values of the cross-sectional image obtained by XCT agree with the X-ray absorption coefficient at 15 keV. This hypothesis is intensively examined by using various polymers. Consequently, we propose an empirical criterion that 0.1 cm^?1 difference in the X-ray absorption coefficients at 15 keV is necessary to distinguish the polymers under XCT. This criterion is also confirmed in the polymer blend systems.     

Observation of single chain motion in a polymer melt

Molecular motion of single polymer chains has been investigated in a melt sample of polytetrahydrofuran and compared with results for the same polymer in dilute solution. Using a high resolution neutron scattering technique motion over distances up to 30 Å has been observed with an energy resolution of 0.01 μeV (～10⁷s^?1). The motion of the chains in the melt is described by the Rouse model and a friction factor per segment has been extracted from the data. This compares well with values obtained from viscosity and bulk relaxation measurements on similar polymers.     

Polyoxometalates/polymer composites for the photodegradation of bisphenol-A

Nowadays water scarcity represents a threat for human and living beings. Therefore, to satisfy the demands of people for clean and safe water, new technologies for wastewater treatment have been developed. Thus, photocatalysis has emerged as a green chemical approach for such treatment. In this context, new polyoxometalate (POM)/polymer composites with relevant photocatalytic properties have been developed via an easy and cheap photopolymerization process upon mild visible light irradiation at 405 nm. This fruitful association between POM and polymer allowed the obtention of shaped materials facile to collect and reuse at the end of the photocatalytic treatment avoiding then the usual time-consuming regeneration methods. The prepared photocomposites displayed excellent photocatalytic performance for the removal of bisphenol-A from water under different sources of irradiation. Hence, 100%, 88%, and 50% of this model compound were decomposed by the phosphomolybdic composite under just 90 min of UV lamp, solar and LED@375 nm irradiations, respectively. The effectiveness of these developed photocatalysts towards the degradation of other organic compounds, as well as the degradation mechanism based on the generation of highly reactive chemicals such as ^•OH radicals promoting the degradation were already reported. Bisphenol-A degradation pathway and the identification of the photoproducts were discussed using mass spectroscopy technique. Therefore, this paper highlighted the photocatalytic efficiency of the new manufactured materials for the photodegradation of the bisphenol-A, thus expanding their application fields, under different sources of irradiation and under pure solar irradiation which make their applications more interesting and less energy consuming.     

Surface functionalized colloidal silica particles from an inverse microemulsion sol gel process

Colloidal silica particles are prepared via a sol gel technique carried out in an inverse microemulsion of water in a toluene solution of tetraethoxysilane (TEOS), stabilized by either an anionic surfactant AOT or isopropanol. Functionalized material was obtained using a functional coupling agent (RO)₃Si(CH₂)₃ X, X being a functional group such as methacryloyl, thiol, vinyl, amino group, or a chlorine atom. Functionalization can be carried out either directly via the direct copolycondensation of TEOS and the coupling agent, or in a two-step process involving a core-shell polycondensation of the coupling agent onto preformed silica particles. Kinetic studies of the copolycondensation are carried out using either²⁹Si NMR analysis or liquid chromatography. They show that the consumption of TEOS is more rapid than that of the coupling agent. The materials are characterized both chemically (elemental analysis, FTIR,¹³C and²⁹Si NMR CPMAS analysis), and by their particle size. The silica functionalized with a polymerizable methacryloyl group is encapsulated by a polymer layer in an inverse emulsion polymerization of acrylic acid. After inversion of the emulsion in water, the resulting material is covered with a layer of hydrophobic polymer in a conventional emulsion polymerization.     

Synthesis and electropolymerization of a multifunctional naphthalimide clicked carbazole derivative

In this study, a multifunctional ‘clicked’ naphthalimide carbazole derivative (CNaP) was synthesized via Huisgen 1,3‐dipolar cycloaddition reaction. Combining carbazole as an electroactive group with naphthalimide as a fluorescence group via click chemistry imparts multifunctional properties to this unique structure. CNaP was characterized via Fourier transform IR, ¹³C and ¹H NMR spectroscopy as well as fluorescence and electrochemical measurements. The electrochemical polymerization of the CNaP monomer was carried out in acetonitrile/boron trifluoride diethyl etherate (2:1) (v/v) by the cyclic voltammetry technique. The resulting polycarbazole‐derived conductive polymer was characterized via optical and electrochemical measurements. PCNaP displayed multi‐electrochromism behaviour with good optical contrast (41% at 693 nm) and switching time (1.92 s at 693 nm). These results demonstrate that the new ‘clicked’ fluorescent, polycarbazole‐derived conductive polymer can be used in various applications such as electrochemical/optical sensors and electrochromic and fluorescence imaging devices. © 2019 Society of Chemical Industry     

Copolymers of styrene with a quaternary europium complex

A complex of Eu³⁺, benzoate (BA), acrylate (AA), and 1,10‐phenanthroline (Phen) was synthesized in this work. The structure of Eu(BA)₂(AA)(Phen) was characterized with elemental analysis, FTIR, and UV spectroscopy. Copolymers containing rare earth complex were prepared via the copolymerization of Eu³⁺(BA)₂(AA)(Phen) with styrene. Semitransparent, luminescent polymer materials with high fluorescent intensity were obtained. The as‐synthesized materials were further characterized by means of IR and UV spectra, which indicated that they were copolymers instead of blends. The fluorescence spectra of the copolymers revealed the intense UV absorption characteristics of the rare earth complex present in the materials, as long as only a small portion of the complex was incorporated into the copolymers. Moreover, thermal analysis showed that the copolymer had excellent heat stability. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1506–1510, 2006     

Transient plane source (TPS) technique for measuring thermal transport properties of building materials

The electrical circuit for the recently developed transient plane source (TPS) technique for fast and precise measurements of thermal transport properties of solids has been modified for more convenient and more automated measurements. The technique has been tested for measurements of thermal conductivity and thermal diffusivity for a series of building materials ranging from thermally insulating materials (extruded polystyrene and PMMA) to good thermal conductors (stainless steel and aluminium). The results obtained in this work agree well with other techniques and international standard materials. This agreement indicates that the TPS method is accurate to within ±5% over a thermal conductivity range of four orders of magnitude (0.02 W m^?1 K^?1 to 200 W m^?1 k^?1).     

Fabrication of Ti3SiC2-based ceramic matrix composites by a powder-free SHS technique

A powder-free technique for fabrication of Ti₃SiC₂-based composite ceramics via self-propagating high-temperature synthesis (SHS) is developed. The essence of the method is that the SHS-compaction of a multilayer stack comprised alternating layers of titanium foils and polymer films filled with either microsized silicon carbide particles or microsized silicon carbide particles mixed with charcoal particles. It is shown that SHS-compaction of non-powder materials can be used to synthesize dense particulate-reinforced ceramic matrix composites of Ti₃SiC₂TiSi₂SiC_p. Effects of the initial reactant composition and the synthesis conditions on the microstructure of the prepared materials are discussed.     

Preparation and characterization of the structure of PSt‐b‐PAA/Co composite material

The polystyrene‐block‐polyacrylic acid (PSt‐b‐PAA) copolymer is obtained through the reversible addition‐fragmentation chain transfer polymerization (RAFT). Then the cobalt (Co) nano‐particles are synthesized by loading the Co²⁺ salt into the polymer and reducing them. Polymer–matrix composites with an average particle size of 10 nm have been formed by a simple technique. The technique exploits the dispersed phase of the polymer to form numerous identical nanoreactors. In this approach, nanoparticles are rigidly attached to the support surface to prevent their agglomeration. FT‐IR and TEM analysis of these polymer–matrix composites revealed that nano‐structures are formed and the shape can be controlled. Vibrating sample magnetometer is also used to study the magnetic property of the materials at room temperature. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Dispersion of aqueous polymer solutions injected from a point source into turbulent water flows

The dispersion of water and aqueous polymer, when injected from a point source along the flow centre line into two-dimensional, fully developed and uniform turbulent flows with flow Reynolds numbers of the order of 4.6 × 10⁵, have been studied experimentally. Concentration profiles at five locations were obtained for injection concentrations and velocities in the ranges 0 to 1000 w.p.p.m. and equal to or less than the local flow velocity. The concentrations were assessed using a fluorescing dye technique. Empirical equations describing the radial and longitudinal concentration field as a function of the injection and flow parameter are given. A universal concentration profile, independent of the injection flow rate and concentration and length of injection source tube, and valid for water and for polymer solution, under both fully developed and uniform flow, is also presented. The results indicate that the turbulent dispersion of polymer solution is suppressed compared to that of water.     

Chemically decomposable imine-based thermoset using oxidized sugar

Increasing environmental concerns have driven the pursuit of sustainable alternatives to petrochemical-based plastics in polymer chemistry. In this study, we demonstrated a method by which sugar, the most chemically produced biomass, can be used as a thermosetting resin. The sucrose was successfully oxidized, synthesized, and then incorporated into a resin. Sodium periodate (NaIO₄) was used to convert sucrose into chemical raw materials. The resulting polymer, prepared via the imine reaction, exhibited a glass transition temperature T_g of 96°C, as determined by differential scanning calorimetry. Additionally, the thermosetting resin exhibited a tensile strength of 7 MPa, a modulus of 515 MPa, and a T_g of 100°C. We obtained reaction rate constants of 0.7 × 10⁻³ h⁻¹ and 3.2 × 10⁻¹ h⁻¹ using THF and citric acid solutions, respectively. Furthermore, we reused the resin from the decomposed organic matter and confirmed that the resynthesized overall, our findings suggest the potential for green recycling by converting commonly used sugars into nature-derived raw materials, leading to the development of eco-friendly polymer synthesis.     

Polymeric materials as anion-exchange membranes for alkaline fuel cells

After summarizing the different fuel cells systems, including advantages and drawbacks, this review focuses on the preparation of copolymers and polymeric materials as starting materials for solid alkaline fuel cells membranes. The requirements for such membranes are also summarized. Then, different strategies are given to synthesize anion-exchange polymeric materials containing cationic (especially ammonium) groups. The first pathway focuses on heterogeneous membranes that consist in: (i) polymer blends and composites based on poly(alkene oxide)s and hydroxide salts or polybenzimidazole doped with potassium hydroxide, (ii) organic–inorganic hybrid membranes especially those synthesized via a sol–gel process, and (iii) (semi)interpenetrated networks based on poly(epichlorhydrine), poly(acrylonitrile) and polyvinyl alcohol for example, that have led to new polymeric materials for anion-exchange membranes. The second and main part concerns the homogeneous membranes divided into three categories. The first one consists in materials synthesized from (co)polymers obtained via direct (co)polymerization, for example membranes based on poly(diallyldimethylammonium chloride). The second pathway concerns the modification of polymeric materials via radiografting or chemical reactions. These polymeric materials can be hydrogenated or halogenated. The radiografting of membranes means the irradiation via various sources – electron beam, X and γ rays, ⁶⁰Co and ¹³⁷Cs that lead to trapped radicals or macromolecular peroxides or hydroperoxides, followed by the radical graft polymerization of specific monomers such as chloromethyl styrene. The third route deals with the chemical modifications of commercially available hydrogenated aliphatic and aromatic (co)polymers, and the syntheses of fluorinated (co)polymers such as carboxylic and sulfonic perfluoropolymers. In addition, several approaches for the crosslinking of above-mentioned polymeric materials are also reported as this process enhances the properties of the resulting membranes. Moreover, electrochemical and thermal properties of various above ionomers are given and discussed.     

Virus removal from aqueous environments with polyelectrolyte coatings on a polypropylene fleece

The adsorption of viruses from aqueous solution is frequently performed to detect viruses. Charged filtration materials capture viruses via electrostatic interactions, but lack the specificity of biological virus-binding substances like heparin. Herein, we present three methods to immobilize heparin-mimicking, virus-binding polymers to a filter material. Two mussel-inspired approaches are used, based on dopamine or mussel-inspired dendritic polyglycerol, and post-functionalized with a block-copolymer consisting of linear polyglycerol sulfate and amino groups as anchor (lPGS-b-NH₂). As third method, a polymer coating based on lPGS with benzophenone anchor groups is tested (lPGS-b-BPh). All three methods yield dense and stable coatings. A positively charged dye serves as a tool to quantitatively analyze the sulfate content on coated fleece. Especially lPGS-b-BPh is shown to be a dense polymer brush coating with about 0.1 polymer chains per nm². Proteins adsorb to the lPGS coated materials depending on their charge, as shown for lysozyme and human serum albumin. Finally, herpes simplex virus type 1 (HSV-1) and severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) can be removed from solution upon incubation with coated fleece materials by about 90% and 45%, respectively. In summary, the presented techniques may be a useful tool to collect viruses from aqueous environments.     

Optimal periodic control of a continuous “living” anionic polymerization II. New theoretical results

In a previous publication¹, a suboptimal technique was developed to solve the problem of producing polymers with prespecified values of the number-average chain length and the polydispersity, through “living” anionic polymerizations carried out in continuous stirred-tank reactors. The solution of that problem involved the periodic operation of the monomer solution feed and of the initiator solution feed, as well as readjustments in their feedstock concentrations. The present work solves the problem directly, without resorting to laborious “optimization-rescaling” procedures. The objective functional considers not only the polymer quality, but also the required polymer production. Compared with the previous results¹, the present solutions are better and obtained with less computational effort. The proposed technique may be applicable to other optimal periodic control problems with nonconventional objective functionals.     

Fabrication and Characterization of PZT/Thermoplastic Polymer Composites for High-Frequency Phased Linear Arrays

A new method of fabricating PZT/potymer composites with 2-2 connectivity is described. This fabrication technique offers significant advantages over conventional dice-and-fill fabrication methods, and the composites exhibit the high electromechanical coupling expected from conventional PZT/polymer composites. In this method, thin (≤20μm) sintered PZT plates and sheets of a thermoplastic polymer film (≤6 μm) are bonded together via thermal processing. A technique for sintering thin, flat PZT plates from tape cast materials was developed to provide the necessary PZT plates. The resulting composite blocks were cut to required dimensions, electroded, and poled. Electromechanical properties were measured to evaluate the composites.     

Macroporous Bioglass-derived scaffolds for bone tissue regeneration

Since it was introduced at the end of the ‘60s, the 45S5 Bioglass^® has played a fundamental role among the materials for orthopedic applications because of its ability to build a stable bond with the surrounding bone. The recent development of bone tissue engineering has led the interest of many scientists in the design of Bioglass^®-based scaffolds, i.e. porous systems able to drive and foster the bone tissue regrowth. Among the available techniques to realize scaffolds, the polymer burning out method, which employs organic particles as pore generating agents in a ceramic matrix, combines versatility and low cost. In spite of the advantages of the polymer burning out method, this technique has been rarely applied to 45S5 Bioglass^® and a systematic feasibility study has not been carried out on this issue yet. In order to fill this gap, in the present contribution the polymer burning out method was employed to design macroporous scaffolds based on 45S5 Bioglass^®. Different amounts of organic phase were used to obtain samples with different porosity. The samples were characterized from a microstructural point of view, in order to evaluate the pore morphology, dimension and degree of interconnectivity. Such findings proved that a proper setting of the processing parameters made it possible to achieve very high porosity values, among the best ones obtained in the literature with the same technique, together with an appreciable mechanical behaviour, according to compression tests. Finally, the scaffolds bioactivity was assessed by means of in vitro tests in a simulated body fluid (SBF) solution. Moreover, in the view of a potential application for bone tissue engineering, a preliminary biological evaluation of the obtained scaffolds to sustain cell proliferation was carried out.     

High-sensitivity chemical derivatization NMR analysis for condition monitoring of aged elastomers

An aged polybutadiene-based elastomer was reacted with trifluoroacetic anhydride (TFAA) and subsequently analyzed via ¹⁹F NMR spectroscopy. Derivatization between the TFAA and hydroxyl functionalities produced during thermo-oxidative aging was achieved, resulting in the formation of trifluoroester groups on the polymer. Primary and secondary alcohols were confirmed to be the main oxidation products of this material, and the total percent oxidation correlated with data obtained from oxidation rate measurements. The chemical derivatization appears to be highly sensitive and can be used to establish the presence and identity of oxidation products in aged polymeric materials. This methodology represents a novel condition monitoring approach for the detection of chemical changes that are otherwise difficult to analyze.