High‐Performance Nanocomposites of Sodium Carboxymethylcellulose and Graphene Oxide

High‐performance nanocomposites of NaCMC with GO are produced by solution casting. FESEM images reveal a good homogeneous dispersion of GO in the NaCMC matrix. The composite formation is facilitated by H‐bonding interaction between GO and NaCMC. T_g of the composites increases with increasing GO concentration. The storage modulus (G′) exhibits a maximum 174% increase over NaCMC at 1 wt% GO. The mechanical properties of the composites exhibit highest increase of tensile stress and Young's modulus of 188 ± 4% and 154 ± 11%, respectively, for 1 wt% GO. Analysis of Young's modulus (E_y) data using the Halpin‐Tsai equation suggests that the E_y data are close to the unidirectional orientation at >0.5 wt% GO, indicating more efficient load transfer at these compositions.

     

Plasticizing and Reinforcing Features of Siloxane Domains in Amine‐Cured Epoxy/Silica Hybrids

Organic/inorganic hybrid materials comprising an amine‐epoxide network and siloxane domains are produced by the sol/gel method. The presence of both plasticizing flexible linear siloxane sequences and reinforcing nanosized silica particles and branched silsesquioxanes (SSQO) structures is confirmed by ²⁹Si NMR and SAXS analysis. The hybrids display simultaneously a monotonical reduction in T_g and an increase in rubbery plateau modulus with increasing siloxane content. At the same time, nanoindentation tests reveal an improved resistance to plastic deformation. The effect of siloxane content on the values of the rubbery plateau modulus is evaluated through the EBM model for blends and composites exhibiting the characteristic co‐continuity of the two constituent phases.

     

Processability,Structure and Mechanical Properties of Poly(ether imide)/Amorphous Copolyester Blends

Blends of PEI with an amorphous copolyester (PCTG) were obtained by melt‐mixing followed by injection molding. The processability of PEI increased several times upon addition of just 10% PCTG, thus expanding the applications of PEI. All the blends showed a single T_g and most of them were transparent. However, they were biphasic as suggested by the widening of the T_g's and proved by SEM. A fine dispersed particle size and good adhesion level were also observed by SEM. The values of the modulus of elasticity and the yield stress appeared close the additivity rule, and were attributed to the combined effects of the density increase and orientation decrease in the blends. These morphological changes had a slightly negative influence on ductility which was nevertheless high.

     

Fabrication of Uniaxially Aligned Poly(propylene) Nanofibers via Handspinning

A straightforward method, which is termed novel handspinning, is reported for producing uniaxially aligned sPP nanofibers. As demonstrated by SEM analysis, the morphologies of handspun sPP nanofibers are strongly dependent upon the processing conditions such as spinning method and solvent system. Compared to the normal electrospun sPP nanofibers, the handspun sPP nanofibers show smoother morphologies. FT‐IR analysis demonstrates a significant difference in polymer chain conformation between the handspun and electrospun sPP nanofibers. Moreover, interestingly, the handspun sPP single nanofibers show higher Young's modulus and tensile strength than electrospun sPP single nanofibers.

     

Synthesis,Characterization, and Properties of Multifunctional Epoxy Maleimide Resins

Summary: Novel multifunctional formaldehyde resins bearing diaminodiphenylmethane groups are synthesized by the polymerization of a mixture of diaminodiphenylmethane (DDM), o‐cresol (o‐Cz), and cyclohexanone (CH_x) with formaldehyde (FA) (at a molar ratio of monomers/formaldehyde, 1/1), in the presence of acid catalyst (HCl). The obtained resins are epoxidated with a large excess of epichlorohydrin and transformed into multifunctional epoxy resins. The multifunctional epoxy maleimide resins are obtained by reaction of the epoxy resins with carboxy phenyl maleimide in the presence of triethylamine as a catalyst. The resultant resins are characterized by IR and NMR spectroscopy, elemental, and thermal analysis. The curing and thermal behavior of these epoxy maleimide resin/DDM systems are investigated using differential scanning calorimetry (DSC) and thermogravimetry (TG) techniques. The activation energies of the curing reactions are situated in the range of 53–90 kJ · mol^?1. The cured products have good thermal properties, and activation energies of degradation reactions have values between 42–74 kJ · mol^?1.

The curing reaction of multifunctional epoxy maleimide resins with DDM.     

A Conducting Polymer/Protein Composite with Bactericidal and Electroactive Properties

Lysozyme, an enzyme with bactericidal activity over Gram‐positive bacteria cells, is incorporated into PEDOT to prepare films with high biological and electrochemical activity. Two different strategies are used: (1) PEDOT films are coated with a layer of enzyme, which was adsorbed on the surface; and (2) the lysozyme is added to the polymerization medium used for the preparation of the conducting polymer. The enzyme adsorbed at the surface of the polymer produces a biphasic system that retains the electrochemical properties of the conducting polymer but is not able to protect against bacterial growth. In contrast, the addition of lysozyme to the polymerization medium results in a homogeneous composite with high bactericidal and electrochemical activities.

     

Hybrid Organic‐Inorganic Membranes on Porous Supports by Size Exclusion and Thermal Sintering of Fluorescent Polyphenylsilsesquioxane Nanoparticles

Hybrid organic–inorganic membranes were prepared by size‐exclusion deposition and thermal sintering of fluorescent polyphenylsilsesquioxane nanoparticles on a ceramic support. Fluorescent polyphenylsilsesquioxane particles were prepared by a two‐step co‐polymerization of phenyltriethoxysilane with 0.1 mol‐% N‐(triethoxysilylpropyl)dansylamide. Because they were larger than the pores in the support, the particles formed a layer on top of the ceramic support that was sintered at 300 °C into a homogeneous, non‐porous membrane. Fluorescence of the modified polyphenylsilsesquioxane provided a valuable tool to monitor particle deposition and assist in characterization of the membranes.

     

Efficient Synthesis of Highly Active Phospha‐Isosteres of the Influenza Neuraminidase Inhibitor Oseltamivir

With a Hunsdiecker–Barton iododecarboxylation strategy, we converted the carboxylate group of the oseltamivir precursor into exemplary phosphonate monoesters. In all cases, K_i values towards influenza virus sialidase remained in the sub‐nanomolar range. We have thus made valuable structural space available for the design of novel oseltamivir‐based tools for influenza virus research.

     

Well‐Controlled Microcellular Biodegradable PLA/Silk Composite Foams Using Supercritical CO2

PLA biodegradable composites reinforced with various silk fibroin powder contents (0, 1, 3, 5 and 7 wt.‐%) were prepared by solution processing technique using CH₂Cl₂ as solvent. After that the composites and virgin PLA were foamed by using supercritical CO₂. The influence of silk contents on PLA/silk fibroin powder composite foams were investigated by using SEM, XRD and DSC. Compared with PLA foam, the composite foams exhibited a reduction in cell size and increase in cell density at high silk content. With an increase in saturation temperature and pressure, the cell size was increasing and both the cell density and foam density were decreased simultaneously.

     

Single Radiation‐Induced Grafting Method for the Preparation of Two Proton‐ and Lithium Ion‐Conducting Membranes

Summary: Two distinct types of polymer electrolyte membranes for conducting protons and lithium ions have been prepared by a radiation‐induced grafting method. The polymer electrolyte precursor (PVDF‐g‐PS) is obtained by the simultaneous grafting of styrene onto poly(vinylidene fluoride) (PVDF) followed by one of two specific treatments. This includes sulfonation with a chlorosulfonic acid/dichloromethane mixture to obtain proton (H⁺)‐conducting membranes, or activation with LiPF₆/EC/DC liquid electrolyte to obtain lithium ion (Li⁺)‐conducting membranes. The chemical structure of the obtained electrolyte membranes is verified by FT‐IR spectroscopy. Differential scanning calorimetry is used to examine the changes in the crystallinity and the thermal properties of both electrolyte membranes during the preparation process. The thermal stability of both electrolyte membranes is also evaluated using thermal gravimetrical analysis. The obtained polymer electrolyte membranes achieve superior conductivity values: 1.61 × 10^?3 S · cm^?1 for Li⁺ and 5.95 × 10^?2 S · cm^?1 for H⁺ at room temperature at a polystyrene content of 50%. The results of this work suggest that high quality H⁺‐ and Li⁺‐conducting membranes can be obtained using a single radiation‐induced grafting method.

Schematic representation of the single root for preparation of Li⁺‐ and H⁺‐conducting membranes started by radiation‐induced grafting of styrene onto a PVDF film followed by chemical treatment.     

Use of Nitrogen as a Blowing Agent for the Production of Fine‐Celled High‐Density Polyethylene Foams

Summary: While many experiments have been performed to examine the effects of administering CO₂ as a blowing agent in the foaming process, very few studies have investigated the use of N₂ for this purpose. In this study, foaming experiments were conducted in extrusion using HDPE as a polymeric material and N₂ as a blowing agent. Talc was used as a nucleating agent, and three different pressure‐drop rates were applied to study the effects of pressure‐drop rates on HDPE foams. The experimental results revealed that the void fraction of high‐density foams blown with N₂ was not affected by the die temperature, contrasting the situation in low‐density foams. Surprisingly, it was the cell density which determined the void fraction of high‐density foams. It was also found that the use of talc significantly increased the cell density and the void fraction of the foams and minimized the role played by the pressure‐drop rate in cell nucleation.

Effect of N₂ content on the cell density of HDPE foams.     

Free‐Standing,Thermostable, Micrometer‐Scale Honeycomb Polymer Films and their Properties

A method of manufacturing free‐standing, micrometer‐scale honeycomb polyetherimide films is reported for the first time. Films are manufactured with a dip‐coating technique under water‐assisted self‐assembly. It is shown that the addition of poly(organosilane/siloxane)s and poly(ethylene glycol) allows the formation of regular honeycomb patterns. The films demonstrated the high thermal stability inherent for polyetherimide. The wetting properties of films are reported. The presence of nanopores was revealed with SEM imaging of the films. The makeup of the films allows their use as asymmetric membranes for reverse osmosis and ultrafiltration.

     

Simple and Rapid Fabrication of Large‐Scale Polymer‐Immobilized Colloidal Crystals by Spray Coating

Polymer‐immobilized colloidal crystal films have been fabricated by conventional spray coating and UV curing of silica–acrylic monomer suspensions. Controlling both the viscosity of the suspensions and the wettability of substrates enabled colloidal crystal films with smooth surfaces and brilliant structural colors due to Bragg diffraction. The structural colors could be controlled by particle concentrations in addition to particle diameter. The wettability influenced the thickness of the coated film and it consequently affected the Bragg reflection intensity of the film. Silhouette figures were textured on a substrate having regions with different wettabilities by single spray coating.

     

Control of Bubble Size and Location in Nano‐/Microscale Cellular Poly(propylene)/Rubber Blend Foams

Plastic foam with nano‐/micro‐scale cellular structures was prepared from a poly(propylene) (PP)/propylene‐ethylene copolymer (PER) blend by controlling bubble nucleation sites and bubble growth in disperse PER domains. Batch foaming experiments using a CO₂ pressure quench method were conducted at room temperature. The bubble size and location were highly controlled in disperse PER domains by exploiting the differences in CO₂ solubility and viscoelasticity between the PER domains and the PP matrix. The average cell diameter of PP/PER blend foams can be controlled within 0.5–2 µm by the PP/PER ratio, depressurization rate, and foaming temperature.

     

Intercalated Polycarbonate/Clay Nanocomposites: Nanostructure Control and Foam Processing

Intercalated polycarbonate (PC)/clay nanocomposites (PCCN)s have been prepared successfully through the melt intercalation method in the presence of a compatibilizer. The internal structure and morphology of the PCCNs has been established by using wide‐angle X‐ray diffraction (WAXD) analyses and transmission electron microscopic (TEM) observations. The morphology of these nanocomposites and degradation of the PC matrix after nanocomposites preparation can be controlled by varying surfactants used for the modification of clay and compatibilizer. The intercalated PCCNs exhibited remarkable improvements of mechanical properties when compared with PC without clay. We also discuss foam processing of one representative PCCN using supercritical CO₂ as a foaming agent.

TEM bright field image of intercalated polycarbonate/synthetic fluorohectorite nanocomposite.     

Nanoscale Cellular Foams from a Poly(propylene)‐Rubber Blend

Plastic foams with nano/micro‐scale cellular structures were prepared from poly(propylene)/thermoplastic polystyrene elastomer (PP/TPS) systems, specifically the copolymer blends PP/hydrogenated polystyrene‐block‐polybutadiene‐block‐polystyrene rubber and PP/hydrogenated polystyrene‐block‐polyisoprene‐block‐polystyrene. These PP/TPS systems have the unique characteristic that the elastomer domain can be highly dispersed and oriented in the machine direction by changing the draw‐down ratio in the extrusion process. A temperature‐quench batch physical foaming method was used to foam these two systems with CO₂. The cell size and location were highly controlled in the dispersed elastomer domains by exploiting the differences in CO₂ solubility, diffusivity, and viscoelasticity between the elastomer domains and the PP matrix. The average cell diameter of the PP/TPS blend foams was controlled to be 200–400 nm on the finest level by manipulating the PP/rubber ratio, the draw‐down ratio of extrusion and the foaming temperature. Furthermore, the cellular structure could be highly oriented in one direction by using the highly‐oriented elastomer domains in the polymer blend morphology as a template for foaming.

     

Biocomposites of Cellulose Acetate Butyrate with Modified Hemp Cellulose Fibres

Cellulose acetate butyrate biocomposites, plasticized with tributyl citrate at volume fraction V_f = 0.1–0.3, were prepared with modified hemp. Inclusion of modified hemp fibres at V_f = 0.4 enhanced the modulus and strength of the flexible plasticized cellulose acetate butyrate. Composites containing pectate lyase enzyme treated fibres showed a modulus greater than untreated or alkali treated fibres, when compared at a similar fibre length of 100 µm. Composites containing the shortest alkali treated fibres of 45 µm gave the greatest property improvement, while 500 µm fibres showed worsened properties. Ball‐milled fibres provided reduced values of properties due to cellulose structural disruption, while compression moulding gave better compaction by removing voids.

     

Compatibilization of Immiscible Polymer Blends by Organoclay: Effect of Nanofiller or Organo‐Modifier?

PET/PE blends are prepared with and without different types of organo‐modified montmorillonites (OMMT) using a extrusion process. The droplet size of PE dispersed phase decreases upon organoclays addition, however without any direct dependence on the organoclay initial surface tension. To assess the effect of the organomodifier without MMT, PET/PE blends are then compounded adding solely the surfactants (similar to those used to modify the various organoclays). Whatever the chemical nature of the surfactant, a refinement of the PE droplets is observed, interestingly similar to those previously observed in presence of clay. This shows unambiguously that the key factor for organoclay compatibilization efficiency, in the case of PET/PE blends, is the surfactant modifier itself and not the MMT platelets.

     

Morphology and Crystalline Structure of Poly(ε‐Caprolactone) Nanofiber via Porous Aluminium Oxide Template

Summary: Poly(ε‐caprolactone) (PCL) nanofibers with a dimension of about 150 nm were successfully fabricated by using a process of extruding PCL solution via a porous aluminium oxide template and then solidifying in methanol. The morphology, melting behavior and crystalline structure of the nanofibers were investigated by using scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and X‐ray diffraction (XRD). The results revealed that the weight‐average molecular weight ( ) of PCL hardly influenced the morphology of the nanofibers. However, the melting temperature (T_m) of the PCL crystalline increased slightly from 55.4 to 57.5 °C with an increase in . The accessional pressure and the presence of the porous template played an important role in the improvement of the orientation and crystallization structures of the polymer chains when they were passing through the nano‐scale porous channel, leading to the conglomeration of the fiber and the much larger diameter than those from the pressure‐induced extrusion process. Furthermore, comparing the processes with and without accessional pressure, the crystallinity of the nanofibers obtained under 0.2 MPa pressure increased, and the diffraction for the (001) lattice plane occurred.

SEM image of PCL nanofibers extruded via a porous aluminium oxide template with the aid of pressure.     

Hybrid Polymer/Clay Nanocomposites: Effect of Clay Size on the Structure of Multilayered Films

The influence of size and surface area of two different types of clay on the structure and characteristics of PEO/clay nanocomposites in the form of multilayered films is discussed. To search for new synergistic properties and/or improve the properties of nanocomposite films already known, we study polymer nanocomposites that have laponite as well as montmorillonite incorporated. While DSC measurements showed that higher laponite amounts gradually suppress the crystallinity of PEO in the nanocomposite, XRD measurements provided evidence that higher montmorillonite amounts ensure an improved final orientation of the clay platelets, parallel to the plane of the multilayered film.