Nano‐ and Microfibrillar Single‐Polymer Composites: A Review

A new class of polymer materials is reviewed, the SPCs, in which the matrix and the reinforcement share the same chemical composition. In addition to their milder environmental impact as compared to traditional polymer composites, they show superior mechanical performance mainly due to the improved adhesion between matrix and reinforcement. Another advantage of SPCs is the missing dispersion step in their production, thus contrasting the common polymer nanocomposites. Definition, manufacturing, classification, and the application opportunities of SPCs are described. Special attention is paid on the very new members of the SPC family, the micro‐ and nanofibrillar SPCs, including the techniques for preparation of their starting neat micro‐ and nanofibrils using bulk polymers.

     

Blends of a Main Chain Liquid‐Crystalline Polyester with a Diepoxide and with a Diepoxide/Amine Mixture Prepared in a Twin‐Screw Extruder

Summary: Blending of the commercial LC‐polyester Rodrun LC‐3000 with the bisphenol‐A‐diglycidyl ether based diepoxide DOW D.E.R.330 alone and with the mixture of the diamine (MCDEA) and D.E.R.330 by means of a twin‐screw extruder has been investigated. Conditions to suppress curing of epoxide and amine during blending have been established. Due to the very low solubility of Rodrun in the diepoxide only LCP‐rich blends with a minimum content of 60 wt.‐% Rodrun could be obtained. The blends were investigated by SEM and thermal analysis (DSC, DMTA). Binary blends are immiscible while ternary blends appear miscible from DMTA up to 30 wt.‐% of epoxy/amine.

SEM micrograph of Rodrun moulded at 230 °C.     

Near Infrared Reflection Spectroscopy: A Versatile Tool for Rapid Characterization of Olefin Copolymers and High‐Throughput Experiments

Near infrared (NIR) spectroscopy was developed as a rapid analytical method for the determination of the composition of olefin copolymers obtained in high‐throughput screening. NIR spectra of ethene/propene and ethene/1‐hexene copolymers, also characterized by means of ¹³C NMR spectroscopy, were recorded and used to design multivariate calibration models. Different methods for the preprocessing of the spectra, including the linearization by non‐linear transformations, were compared. Optimal methods and error estimates were established using crossvalidation. This technique is of particular interest for the rapid on‐line analysis of high‐throughput experiments in the field of polymer and catalyst design employing methods from combinatorial chemistry.

Predicted versus true value of the propene incorporation and standard deviation for ethene/propene copolymers.     

Preparation and Characterization of Organic/Inorganic Polymer Composites Based on Mg‐Silicates

Summary: An organic‐inorganic hybrid material consisting of a 3‐(methacryloxy)propyl functionalized SiO₂/MgO framework was synthesized. This hybrid was successfully reacted with styrene, butyl acrylate and butyl methacrylate via a free radical emulsion polymerization to form polymer composites. The polymer composites were investigated by means of FT‐IR spectroscopy, TGA, DSC and rheometry. It is shown that the polymer is linked covalently to the organic/inorganic hybrid. Although the polymer content is rather low, the composites exhibit a polymer‐like character and enhanced mechanical properties compared to the corresponding homopolymers.

     

Coaxial Electrospinning with Triton X‐100 Solutions as Sheath Fluids for Preparing PAN Nanofibers

Coaxial electrospinning using surfactants as sheath fluid for preparing high‐quality polymer nanofibers is studied. PAN nanofibers are fabricated using this process with Triton X‐100 solutions in DMF. FESEM demonstrates that the Triton X‐100 solution has a significant influence on the quality of the nanofibers. The nanofiber diameters can be controlled by adjusting the concentration of Triton X‐100 in the sheath fluids with a scaling law D = 640 C^?0.32. The mechanism of the influence of Triton X‐100 solutions on the formation of PAN fibers is discussed and it is demonstrated that coaxial electrospinning with surfactant solution is a facile method for achieving high‐quality polymer nanofibers.

     

Novel Poly(N‐isopropylacrylamide)‐graft‐poly(vinylidene fluoride) Copolymers for Temperature‐Sensitive Microfiltration Membranes

In the present work, we report on the synthesis and characterization of poly(vinylidene fluoride) (PVDF) with N‐isopropylacrylamide (NIPAAM) polymer side chains from molecular graft copolymerization in solution. The copolymer can be readily cast into temperature‐sensitive microfiltration (MF) membranes by the phase inversion technique. The copolymer approach to membrane fabrication allows a much better control of the physicochemical nature of the membrane pores through the variation in graft concentration, membrane casting temperature and concentration of the membrane casting solution.

     

Influence of Stabilizer Concentration on Transport Behavior and Thermopower of CNT‐Filled Latex‐Based Composites

The influence of the stabilizer/SWNT ratio on the transport behavior of latex‐based polymer nanocomposites is examined in an effort to improve electrical conductivity while maintaining or improving the Seebeck coefficient (i.e., thermopower). Results show that phonon and electron transport are significantly affected by tube/tube junctions, and the carrier transport across the junctions can be manipulated by altering the stabilizer concentration. Electrical conductivity of composites containing 10 wt.‐% SWNT nearly doubles, becoming greater than 900 S · m^?1, by changing the SWNT:GA ratio from 1:3 to 10:1, while thermal conductivity and Seebeck coefficient remain relatively constant (near 0.25 W · m‐K^?1 and 40 µV · K^?1, respectively).

     

Preparation of Ultrafine Ethylene/Propylene/Diene Terpolymer Rubber Fibers by Coaxial Electrospinning

Elastomeric EPDM fibers with diameters of 200–400 nm are prepared by coaxial electrospinning of PVP/EPDM fibers, subsequent vulcanization of the polymers and finally removal of the outer PVP layer using ethanol. The initially applied PVP layer restricts the elastic recovery of the EPDM fibers. The crosslinking density of the EPDM fibers reaches 8.44 × 10^?5 mol · cm^?3. The original morphology of EPDM is preserved after removing the PVP layer. The ultrafine EPDM fibers are expected to be useful in many fields, such as brittle plastics toughening, as well as applications in extremely high or low temperatures.

     

Crystalline and Conductive Poly(3‐hexylthiophene) Fibers

Intrinsically conducting polymer fibers are prepared from P3HT by melt spinning. High crystallinity is achieved by drawing the fibers after the spinning process, applying a draw ratio of 1:2. DSC and XRD measurements confirm the continuous increase of crystalline phases with drawing. For comparison, poly(ethylene terephthalate) fibers are coated with P3HT and drawn as well. Again, the drawing of the coated fiber results in a significant increase in crystallinity of the P3HT coating. The high amount of crystalline phases is associated with a dramatic increase in conductivity (350 S · cm^?1) after doping with FeCl₃ in nitromethane.

     

Matrimid Aerogels by Temperature‐Controlled,Solution‐Based Crosslinking

This paper reports on a temperature‐controlled, solution‐based method to prepare diamine crosslinked Matrimid aerogels. Addition of a diamine to a preheated polymer solution resulted in a well‐dispersed solution, allowing formation of a homogeneous gel upon cooling. The gels (studied by FTIR and AFM) were dried by solvent extraction with supercritical CO₂. The resulting aerogels showed surface areas of approximately 150 m² · g^?1 and porosities of 0.66–0.69 mL · g^?1 with polymer domains and pore sizes of tens of nanometers. A room temperature‐prepared, inhomogeneous aerogel gave approximately 250 m² · g^?1 and 0.31 mL · g^?1 with meso‐ and micropores. SEM images of the aerogels show similar surface features as AFM images of the Matrimid solvent gels.

     

Fabrication of Polylactide‐Based Biodegradable Thermoset Scaffolds for Tissue Engineering Applications

The fabrication of tissue engineering scaffolds based on the polymerization of crosslinked polylactide using leaching and batch foaming to generate well‐controlled and interconnected biodegradable polymer scaffolds is reported. The scaffold fabrication parameters are studied in relation to the interpore connectivity, pore morphology, and structural stability of the crosslinked PLA scaffold. In vitro cell culture and in vitro degradation are used to analyze the biocompatibility and biodegradability of the scaffolds. The new crosslinked PLA thermoset scaffolds are highly suitable for bone tissue engineering applications due to their complex internal architecture, thermal stability, and biocompatibility.

     

Polyolefins with Long Chain Branches Made with Single‐Site Coordination Catalysts: A Review of Mathematical Modeling Techniques for Polymer Microstructure

Summary: Single‐site coordination polymerization catalysts are considered one of the most important developments on the technology of olefin polymerization during the last two decades. Among the several new capabilities of these catalysts is the ability to produce polymer molecules having narrow molecular weight distribution and long chain branches. These advances in polymer synthesis have stimulated the development of mathematical models to describe and predict several features of their molecular architectures. Many modeling techniques have been used for this purpose, including instantaneous distributions, population balances, the method of moments, and Monte Carlo simulations. This article reviews the mathematical models developed over the last decade to quantify the microstructure of polymers made with single‐site catalysts with special emphasis on the mechanism of long chain branch formation by terminal branching.

     

Improvement of Chromatic Aberration of the Plastic Rod‐Lens Array, 2

Summary: We propose in this paper a new plastic rod‐lens with low chromatic aberration. Since a plastic rod‐lens has a parabolic refractive index distribution, it usually also shows a distribution of Abbe number. This Abbe number distribution is thought to cause the chromatic aberration of the plastic rod‐lens array. We have studied novel materials for a new plastic rod‐lens with low chromatic aberration and have provided new transparent polymer blends consisting of two polymers with different refractive indices and with almost equal Abbe numbers by using a fabrication process based on photopolymerization of methacrylate monomer(s) in the presence of other methacrylic polymers. The process can give new transparent polymer blends which cannot be formed using conventional techniques for polymer blend formation. In this work, tricyclo[5,2,1,0^2,6]deca‐8‐yl methacrylate is used as a high refractive index monomer and tert‐butyl methacrylate is used as a low refractive index one. By using polymer blends including these monomer units, we have created a plastic rod‐lens with lower chromatic aberration.

Molecular structures of comonomers in the study.     

An Application of Silica‐Based Monolithic Membrane Emulsification Technique for Easy and Efficient Preparation of Uniformly Sized Polymer Particles

Summary: Uniformly sized polymer particles were prepared by an emulsification and polymerization technique utilizing a silica monolithic membrane, namely the “silica monolithic membrane emulsification technique”. In this paper, we utilized silica monolithic membrane as a device for the preparation of uniformly sized polymer particles. A mixture of monomers, diluents and oil‐soluble initiator was emulsified into a continuous medium through the silica monolithic membrane and polymerized. The particles obtained had a higher size uniformity than that of particles prepared by previously reported membrane emulsification techniques, such as the Shirasu Porous Glass (SPG) emulsification technique. Through the silica monolithic membrane emulsification technique, we could prepare particles having availability as a possible packing material for solid‐phase extraction (SPE) and high performance liquid chromatography (HPLC).

SEM photograph of silica particles prepared through capillary plate membrane.     

A Novel Inorganic Polymer as Cathode Material for Secondary Lithium Batteries

Summary: This paper introduces a new inorganic poly(phosphazene disulfide) material. With unique element composition and molecular structure, the polymer has noncombustible safety and preferable conductivity. When used as cathode material for rechargeable lithium batteries, the polymer's first discharge capacity is as high as 467.9 mAh · g^?1, which can be retained at 409.9 mAh · g^?1 after 60 repeated cycles. Therefore, it has a great application potential in the field of lithium batteries.

Replacement of the Cl atoms by S? S groups by refluxing Na₂S₂ and linear poly(dichloro‐phosphazene).     

Artificial Opals as Effect Pigments in Clear‐Coatings

Summary: In this paper, we describe the use of artificial opals from polymer beads as effect pigments in transparent industrial and automotive coatings. For this purpose, we synthesized monodisperse colloids from fluorinated methacrylates by surfactant‐free emulsion polymerization. The fluorinated monomers, in combination with crosslinking, lead to a refractive index contrast, thermal stability, and solvent resistivity necessary for use as effect pigments. After crystallization of the monodisperse polymer beads, crystal flakes with iridescent colors can be obtained. The crystal flakes can act as effect pigments in various transparent industrial and automotive coatings. Due to photonic crystal behavior of effect pigments, color flops up to 100 nm are observed.

Crystal flakes of CS ‐7 as effect pigments in a transparent coating. The diameter of the tube is 5 mm.     

Functionalized Graphene–PVDF Foam Composites for EMI Shielding

Novel foam composites comprising functionalized graphene (f‐G) and polyvinylidene fluoride (PVDF) were prepared and electrical conductivity and electromagnetic interference (EMI) shielding efficiency of the composites with different mass fractions of f‐G have been investigated. The electrical conductivity increases with the increase in concentration of f‐G in insulating PVDF matrix. A dramatic change in the conductivity is observed from 10^?16 S · m^?1 for insulating PVDF to 10^?4 S · m^?1 for 0.5 wt.% f‐G reinforced PVDF composite, which can be attributed to high‐aspect‐ratio and highly conducting nature of f‐G nanofiller, which forms a conductive network in the polymer. An EMI shielding effectiveness of ≈20 dB is obtained in X‐band (8–12 GHz) region and 18 dB in broadband (1–8 GHz) region for 5 wt.% of f‐G in foam composite. The application of conductive graphene foam composites as lightweight EMI shielding materials for X‐band and broadband shielding has been demonstrated and the mechanism of EMI shielding in f‐G/PVDF foam composites has been discussed.

     

Polyolefin/Lignosulfonate Blends, 9

Summary: In the present study, the compatibility, properties and degradability of polyolefin/lignin blends have been studied. Blends of three maleic anhydride grafted copolymers of ethylene‐propylene rubbers containing various content of functional groups with epoxy‐modified lignosulfonate have been investigated by microscopy, X‐ray diffraction, surface and mechanical indices determination, electron spin resonance, IR spectroscopy, differential scanning calorimetry and thermogravimetry. To assess the environmental degradation characteristics, the behavior of the blends during soil burial test has been investigated. The influence of the buried polymer blends on the physiological vegetative processes of the Vicia X Hybrida hort plant has been monitored.

Optical microscopy images of blend EP‐g‐MA 0.3/5 LER, undegraded (left) and degraded (right).     

Surface Structures in Thin Polymer Layers Caused by Coupling of Diffusion‐Controlled Marangoni Instability and Local Horizontal Temperature Gradient

Summary: Surface tension‐driven Marangoni convection causes the formation of regular surface structures in drying polymer layers. The shape of the surface structures formed during solvent evaporation depends on layer and interfacial dynamic parameters as well as external factors. The influence of a horizontal radial temperature gradient produced by a point heat source below the polymer layer on the diffusion‐controlled Marangoni instability has been studied. In the region of the lateral temperature gradient, radial surface flow coupled with the interfacial instability leads to stripe, ladder, chevron and/or labyrinthine surface structures.

Stepped ladder structures in a poly(vinyl butyral) layer produced by interfacial instability and heating with an ultrasonic sonotrode below the layer substrate.     

Polybenzimidazolium‐Based Solid Electrolytes

A series of methyl, benzyl, and mixed polybenzimidazolium halides was synthesised and characterised by NMR spectroscopy. Membranes were formed and ion exchanged with hydroxides. These membranes are of interest for use in potentially platinum‐free anionic exchange membrane fuel cells. Crosslinked membranes were obtained by the addition of α,α′‐dibromo‐p‐xylene to the casting solution. The ion conductivity of membranes was determined by impedance spectroscopy. A hydroxide conductivity of 29 mS · cm^?1 at 26 °C and 58 mS · cm^?1 at 60 °C was obtained. The thermal and hydrolytic stability was investigated and a pathway for hydrolytic degradation proposed. Hydroxide ions react at the 2 position, the intermediate carbinol opens to the amine–amide, and further degrades under chain scission to diamine and carboxylic acid.