Transparent conductive polymer composites obtained via electrostatically assembled carbon nanotubes–poly (methyl methacrylate) composite particles

Interest in the controlled formation of advanced carbon-based composite materials with good transparency for lightweight and portable device applications has been increasing. This study reports on the feasible formation of carbon nanotubes (CNT)-incorporated poly (methyl methacrylate) (PMMA) composite pellets, which exhibited good electrical conductivities with high optical transparency. Despite using a low amount of CNT incorporation (0.0068～0.068 vol%), conductive channels were generated through the homogeneous decoration of CNT onto PMMA particles obtained via an electrostatic assembly method. The conductive channels formed at pressed interface of CNT–PMMA pellets were confirmed using a scanning probe microscope with contact current imaging. The findings of this study present a promising prospect for carbon-based composite materials fabrication via powder metallurgy inspired method that can be used for manufacturing of lightweight, transparent and conductive polymers.     

Ionic conductivity and diffusion coefficient of barium-chloride-based polymer electrolyte with poly(vinyl alcohol)–poly(4-styrenesulphonic acid) polymer complex

A composite polymer electrolyte comprising poly(vinyl alcohol)–poly(4-styrenesulphonic acid) with barium chloride dihydrate (\(\hbox {BaCl}_{2}{\cdot } 2\hbox {H}_{2}\hbox {O}\)) salt complex has been synthesized following the usual solution casting. The ionic conductivity of polymer electrolyte was analysed by impedance spectroscopy. The highest room temperature (at 30\({^{\circ }}\)C) conductivity evaluated was 9.38 \(\times \) 10\(^{-6}\) S cm\(^{-1}\) for 20 wt% loading of \(\hbox {BaCl}_{2}\) in the polymer electrolyte. This has been referred to as the optimum conducting composition. The temperature-dependent ionic conductivity of the polymer electrolyte exhibits the Arrhenius relationship, which represents the hopping of ions in polymer composites. Cation and anion diffusion coefficients are evaluated using the Trukhan model. The transference number and enhanced conductivity imply that the charge transportation is due to ions. Therefore this polymer electrolyte can be further studied for the development of electrochemical device applications.     

Three-phase polymer–ceramic–metal composite for embedded capacitor applications

This paper addresses the materials and processes for printed wiring board compatible embedded capacitor using ceramic, polymer and metal. The Ca[(Li_1/3Nb_2/3)_0.8Ti_0.2]O_3?δ (CLNT)–epoxy–silver, three-phase composites were prepared by two step mixing and thermosetting technique. The dielectric properties of the three-phase composites were investigated in terms of volume fraction of silver, temperature and frequency. The dielectric properties of epoxy–CLNT composites were compared with theoretical predictions. The relative permittivity of the three-phase composites increased with silver loading. Addition of 0.28 volume fraction of silver increases the relative permittivity of epoxy–CLNT composites from 8 to 142 at 1 MHz. This composite is flexible and can be fabricated into various shapes with low processing temperature.     

Shape-memory polymer networks from sol–gel cross-linked alkoxysilane-terminated poly(ε-caprolactone)

A novel type of covalently cross-linked semi-crystalline polymer with shape-memory and biocompatibility properties was prepared from alkoxysilane-terminated poly(ε-caprolactone) (PCL) by sol–gel process that allowed the generation of silica-like cross-linking points. A fine tuning of the cross-linking density and thermal properties (melting temperature) of the materials was obtained by controlling the molecular weight of the PCL precursor (and thus the molecular structure of the resulting network) and the curing conditions. The shape-memory behaviour was investigated with bending tests. Recovery times of less than one second were observed in water depending on the temperature, and a linear correlation of the recovery time with cross-linking density and molecular weight of PCL network precursor was observed.     

Mechanical studies on poly(vinyl chloride)–poly(methyl methacrylate)-based polymer electrolytes

The aim of the present work is to study the mechanical properties of poly(vinyl chloride) (PVC)/poly(methyl methacrylate) (PMMA) blends based polymer electrolytes for lithium ion batteries. The introduction of PVC into PMMA is found to increase the Young’s modulus value from 5.19 MPa (in pure PMMA) to 6.05 MPa (in PVC:PMMA = 70:30). The different Young’s modulus values in PVC blends is due to the difference in the cross-linking density provided by PVC with different weight fraction values. The stress–strain analysis reveals that the mechanical strength of the polymer electrolyte system deteriorated with the incorporation of LiCF₃SO₃. The results show that the introduction of salt decreases the Young’s modulus and stress at peak values along with higher elongation at peak value. The addition of low molecular weight plasticizers to PVC–PMMA–LiCF₃SO₃ decreases the modulus and stress at peak of the complexes. To be applicable in practical applications, the mechanical strength of the plasticized films is found to improve with the addition of silica as nanocomposite filler.     

Degradation of poly(p-phenylene benzobisthiazole) (PBT) rigid rod,poly(ether ether ketone ether ketone) (PEEKEK) semi-flexible coil,and a grafted “hairy rod” polymer containing PBT and PEEKEK

Thermal degradation pathways of the rigid-rod polymer, poly (p-phenylene benzobisthiazole, PBT) have been elucidated by thermal volatilization analysis and related techniques. Processes are characterized by the expulsion of hydrogen sulphide, acetylene, and some carbon disulphide. Evidence is presented for the production and subsequent polymerization of aromatic nitriles and for the existence of thermal rearrangements to produce quinoline derivatives. A similar analysis of the semi-flexible coil polymer, poly (ether ether ketone ether ketone, PEEKEK) revealed the importance of directed chain-scission processes to form oligomers, carbon monoxide expulsion with radical recombination to produce biphenyl linkages, and aromatic fusions to produce fluorenone-type derivatives. Examination of a hairy rod comb-type graft copolymer of PBT and PEEKEK revealed some instability introduced by the grafting process and determined that the graft site thermally isomerized through oxygen migration to yield xanthone-based heterocyclic intermediates of degradation.     

Tissue engineering scaffolds of mesoporous magnesium silicate and poly(ε-caprolactone)–poly(ethylene glycol)–poly(ε-caprolactone) composite

Mesoporous magnesium silicate (m-MS) and poly(ε-caprolactone)–poly(ethylene glycol)–poly(ε-caprolactone) (PCL–PEG–PCL) composite scaffolds were fabricated by solvent-casting and particulate leaching method. The results suggested that the incorporation of m-MS into PCL–PEG–PCL could significantly improve the water adsorption of the m-MS/PCL–PEG–PCL composite (m-MPC) scaffolds. The in vitro degradation behavior of m-MPC scaffolds were determined by testing weight loss of the scaffolds after soaking into phosphate buffered saline (PBS), and the result showed that the degradation of m-MPC scaffolds was obviously enhanced by addition of m-MS into PCL–PEG–PCL after soaking for 10 weeks. Proliferation of MG63 cells on m-MPC was significantly higher than MPC scaffolds at 4 and 7 days. ALP activity on the m-MPC was obviously higher than MPC scaffolds at 7 days, revealing that m-MPC could promote cell differentiation. Histological evaluation showed that the introduction of m-MS into PCL–PEG–PCL enhanced the efficiency of new bone formation when the m-MPC scaffolds implanted into bone defect of rabbits. The results suggested that the inorganic/organic composite of m-MS and PCL–PEG–PCL scaffolds exhibited good biocompatibility, degradability and osteogenesis.     

Superior toughness obtained via tuning the compatibility of poly(ethylene terephthalate)/poly(ethylene–octene) blends

As a partial of the systematic investigation of the preparation and characterization of poly(ethylene terephthalate) (PET) blending/compounding materials with excellent comprehensive mechanics in the authors’ group, this study deals with the compatibilization modification of PET/elastomer blends to obtain superior toughness. Poly(ethylene–octene) (POE) was employed as elastomer toughener, while maleic anhydride grafted POE (mPOE) was selected as compatibilizer. To highlight the effect of compatibility on toughening, the sum amount of elastomer component, POE and mPOE, was fixed at 20 wt%, but the mass ratio of mPOE/POE was changeable. It is interesting to find that an optimization of toughening can be attained at 3 wt% mPOE, at which the notched impact strength is about 15 folds for that of neat PET. The toughening behavior observed is due to a combination of good dispersion of elastomer phase particles and, particularly, appropriate interfacial adhesion condition. Microscopic fractured morphology reveals that a moderate level of interfacial adhesion is important for good dispersion of elastomer phase and debonding between PET matrix and elastomer particles, which initiate matrix shear yielding to dissipate more energy than other interfacial adhesion conditions.     

Cobalt hexacyanoferrate–poly(methyl methacrylate) composite: Synthesis and characterization

The preparation of cobalt hexacyanoferrate nanoparticles–poly(methyl methacrylate) (CoHCF–PMMA) composites are described together with their characterization and thermochromic properties. CoHCF nanoparticles – investigated by dynamic light scattering – were prepared by optimizing solvent composition and temperature to obtain nanoparticles with a reduced degree of aggregation. The nanoparticles were embedded in a PMMA matrix to obtain a transparent coloured composite which was studied by transmission electron microscopy. The nanoparticle chromic features, enhanced by their reduced sizes, were investigated by UV–vis and FT-IR spectroscopy.     

Crosslinked poly(acrylonitrile–glycidyl methacrylate) as a novel gel polymer electrolyte

Novel gel polymer electrolytes (GPEs) based on poly(acrylonitrile–glycidyl methacrylate) (P(AN–GMA)) crosslinked with α,ω-diamino poly(propylene oxide) (Jeffamine) of various weight ratios and molecular weights have been prepared, and the crosslinked polymers were characterized by FT-IR and thermal analysis. It is revealed that the crosslinked polymers were amorphous in pristine state and became crystallized when doped with lithium electrolyte. Their swelling properties and mechanical behaviors were investigated and found to be heavily affected by the weight ratio and molecular weight of Jeffamine. The effect of weight ratios and molecular weights of Jeffamine on the ionic conductivity of the GPEs based on the crosslinked polymers were determined by AC impedance spectroscopy. GPEs consisting of Jeffamine of higher molecular weights and increased weight ratios showed higher ionic conductivity. The GPE based on P(AN–GMA) crosslinked with Jeffamine D2000 at a weight ratio of 1.5 exhibited the highest ionic conductivity of 8.23 × 10^?4 S cm^?1 at 25 °C, and preserved a moderate mechanical strength. The crosslinked polymers can be potential candidates for the construction of rechargeable lithium batteries.     

Local delamination on heavily deformed polymer–metal interfaces: evidence from microscopy

In this work the microstructure of interfaces present in heavily bi-axially deformed polymer-coated metal is studied. Cross sections of deformed polymer-coated steel are prepared using several polishing strategies, including the use of focused ion beam, and are imaged using optical microscopy and scanning electron microscopy. We find that the interfaces show significant details right down to the smallest scale observable with the preparation techniques used of about ~10 nm. Local delamination events at these deformed interfaces are observed and are found to be preferentially associated with overhanging parts on the interface. Overhanging parts are frequently observed, but only below a certain length-scale on the interfaces that are otherwise found to be self-affine up to a certain correlation length. The smallest detail includes the tail of the size distribution of the overhanging features. Together this suggests that the physical mechanisms determining the formation of critical features for adhesion operate at sub-grain level as well as at grain level.     

Microstructure and mechanical properties of an Al–TiC metal matrix composite obtained by reactive synthesis

A metal matrix composite has been obtained by a novel synthesis route, reacting Al₃Ti and graphite at 1000 °C for about 1 min after ball-milling and compaction. The resulting composite is made of an aluminium matrix reinforced by nanometer sized TiC particles (average diameter 70 nm). The average TiC/Al ratio is 34.6 wt.% (22.3 vol.%). The microstructure consists of an intimate mixture of two domains, an unreinforced domain made of the Al solid solution with a low TiC reinforcement content, and a reinforced domain. This composite exhibits uncommon mechanical properties with regard to previous micrometer sized Al–TiC composites and to its high reinforcement volume fraction, with a Young’s modulus of ∼110 GPa, an ultimate tensile strength of about 500 MPa and a maximum elongation of 6%.     

Encapsulation and controlled release of lysozyme from electrospun poly(ε-caprolactone)/poly(ethylene glycol) non-woven membranes by formation of lysozyme–oleate complexes

In this study, the concept of hydrophobic ion pairing was adopted for incorporating lysozyme into electrospun poly(ε-caprolactone) (PCL)/poly(ethylene glycol) (PEG) non-woven membranes. The solubility of lysozyme in organic solvent was enhanced through the formation of lysozyme–oleate complexes, which could be directly loaded into PCL/PEG membranes using electrospinning technique. The resultant PCL/PEG nanofibers have a compact structure with an average diameter ranged from about 0.4 μm to 0.9 μm. The addition of PEG into the PCL nanofibers not only improved the hydrophilicity of the membrane, but also played an important role on in vitro lysozyme release rate. It was found that the release rate of lysozyme was enhanced with the increase of PEG content. In addition, the increase of salt concentration in the release medium accelerated lysozyme release. It has also been shown that the released lysozyme retained most of its enzymatic activity.     

Preparation and characterization of poly(3,4-ethylenedioxythiophene)–poly(styrene sulfonate) composite thin films highly loaded with platinum nanoparticles

In this work, we propose a simple and efficient, low-temperature (∼120 °C) process to prepare transparent thin films of poly(3,4-ethylenedioxythiophene)–poly(styrenesulfonate) (PEDOT:PSS) loaded with high concentration (up to 22.5 wt%) of platinum (Pt) nanoparticles. Firstly, an improved polyol method was modified to synthesize nano-sized (∼5 nm) and mono-dispersed Pt particles. These nanoparticles were incorporated into the matrix of PEDOT:PSS thin films via a spin coating/drying procedure. The electrochemical activities of the PEDOT:PSS thin film modified electrodes with respect to the I⁻/I₃⁻ redox reactions were investigated. It was found that the modified electrode of PEDOT:PSS thin film containing 22.5 wt% Pt exhibited the electrochemical activity comparable to the conventional Pt thin film electrode, suggesting that this electrode has good potential to serve as a counter electrode in dye-sensitized solar cells.     

Electrochemical behaviour of graphene–poly (3,4-ethylenedioxythiophene) (PEDOT) composite electrodes for supercapacitor applications

In this paper, we report on the electrochemical characteristics of graphene–PEDOT composite electrodes. The electrodes were made of indium tin oxide (ITO) substrates by simple processes of electrophoretic deposition of graphene followed by electropolymerization of EDOT monomer. The composite electrode was obtained by electrochemical measurements, a median specific capacitance of 1410 F/g and a median area capacitance of 199 mF cm ^?2 at a scan rate of 40 mVs ^?1. The composite showed good stability characteristics after repeated scans in cyclic voltammmetry and fared much better than a thin film of PEDOT. The thermal stability of the composite is also much superior when compared to the polymer with a weight loss temperature of 350 °C for the composite and 250 °C for the polymer, respectively. The above electrochemical and thermal behaviours of the composite are correlated to the unique morphology of electrodeposited graphene that provides a conductive and high surface area template for electropolymerization.     

Efficient removal of U(VI) from solution using a MoS42− ion-exchange functionalized polypyrrole composite material

Journal of Materials Science - MoS4–Ppy was synthesized by a simple oxidative polymerization method and functionalized with the MoS42? ions. Because of the good stability and excellent...     

Bioactive glass–poly (ε-caprolactone) composite scaffolds with 3 dimensionally hierarchical pore networks

Hierarchically mesoporous–macroporous–giant-porous bioactive glass/poly ε-caprolactone (PCL) composite scaffolds were prepared using a combination of the sol–gel method, evaporation-induced self-assembly process in the presence of nonionic triblock copolymer, EO₁₀₀PO₆₅EO₁₀₀ (F127), as template, salt leaching method, and rapid prototyping techniques. F127 acts as a template, inducing the formation of mesopores, NaCl with sizes between 25 and 33 μm provides macro-pores after leaching, and rapid prototyping produces giant-pores. The structure and morphology of the scaffolds were characterized by the field emission scanning electron microscopy, transmission electron microscopy, and Hg porosimetry. The mechanical properties of the scaffolds were examined by the dynamic mechanical analysis. Their in vitro bioactivities were confirmed by immersing the scaffolds in simulated body fluid. Their biocompatibilities were also evaluated by culturing human bone marrow stromal cells on the scaffolds. The scaffolds show good molding capabilities, mechanical properties, 3 dimensionally well-interconnected pore structures, bioactivities, and biocompatibilities in vitro. Depending on the amount of NaCl, the scaffolds also show unique sponge-like properties, but still retain better mechanical properties than general salt leaching derived PCL scaffolds. All of the data provide good evidence that the obtained scaffolds possess excellent potential for applications in the fields of tissue engineering and drug storage.