Styrene-b-(ethylene-co-butylene)-b-styrene Research Articles

Functionalized Triblock Copolymers with Tapered Design for Anion Exchange Membrane Fuel Cells.

Triblock copolymers such as styrene-b-(ethylene-co-butylene)-b-styrene (SEBS) have been widely used as an anion exchange membrane for fuel cells due to their phase separation properties. However, modifying the polymer architecture for optimized membrane properties is still challenging. This research develops a strategy to control the membrane morphology based on quaternized SEBS (SEBS-Q) by dual-tapering the interfacial block sequences. The structural and transport properties of SEBS-Q with various tapering styles at different hydration levels are systematically investigated by coarse-grained molecular simulations. The results show that the introduction of the tapered regions induces the formation of a bicontinuous water domain and promotes the diffusivity of the mobile components. The interplay between the solvation of the quaternary groups and the tapered fraction determines the conformation of polymer chains among the hydrophobic-hydrophilic subdomains. The strategy presented here provides a new path to fabricating fuel cell membranes with controlled microstructures.

Enhancing thermal energy storage properties of blend phase change materials using beeswax.

This study aims to use beeswax, a readily available and cost-effective organic material, as a novel phase change material (PCM) within blends of low-density polyethylene (LDPE) and styrene-b-(ethylene-co-butylene)-b-styrene (SEBS). LDPE and SEBS act as support materials to prevent beeswax leakage. The physicochemical properties of new blended phase change materials (B-PCM) were determined using an X-ray diffractometer and an infrared spectrometer, confirming the absence of a chemical reaction within the materials. A scanning electron microscope was used for microstructural analysis, indicating that the interconnection of the structure allowed better thermal conductivity. Thermal gravimetric analysis revealed enhanced thermal stability for the B-PCM when combined with SEBS, especially within its operating temperature range. Analysis of phase change temperature and latent heat with differential scanning calorimetry showed no major difference in the melting point of the various PCM blends created. During the melting/solidification process, the B-PCMs possess excellent performance as characterized by W70/P30 (112.45J.g-1) > W70/P20/S10 (94.28J.g-1) > W70/P10/S20 (96.21J.g-1) of latent heat storage. Additionally, the blends tend to reduce supercooling compared to pure beeswax. During heating and cooling cycles, the B-PCM exhibited minimal leakage and degradation, especially in blends containing SEBS. In comparison to the rapid temperature drop observed during the cooling process of W70/P30, the temperature decline of W70/P30 was slower and longer, as demonstrated by infrared thermography. The addition of LDPE to the PCM reduced melting time, indicating an improvement in the thermal energy storage reaction time to the demand. According to the obtained findings, increasing the SEBS concentration in the composite increased the thermal stability of the resulting PCM blends significantly. Despite the challenges mentioned earlier, SEBS proved to be an effective encapsulating material for beeswax, whereas LDPE served well as a supporting material. Leak tests were performed to find the ideal mass ratio, and weight loss was analyzed after multiple cycles of cooling and heating at 70°C. The morphology, thermal characteristics, and chemical composition of the beeswax/LDPE/SEBS composite were all examined. Beeswax proves to be a highly effective phase change material for storing thermal energy within LDPE/SEBS blends.

Magnetorheological response of Permalloy@ styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene elastomers as a function of filler concentration

AbstractDeveloping advanced magnetorheological elastomers (MREs) with a range of specific characteristics is essential for matching the growing demands from a wide spectrum of applications such as automotive, healthcare, sensors, and actuators. However, the compatibility problems between constituents and the low magnetorheological (MR) effect have limited their performance and integration into actual applications. Here, a novel MRE consisting of styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene (SEBS) and Ni‐rich Permalloy (Ni80Fe17Mo3) has been developed with remarkable functional properties. The correlation between the filler concentration and microstructural, mechanical, thermal, magnetic, and MR properties is reported. The incorporation of Ni‐rich Permalloy has a reinforcement effect in the polymer matrix and leads to an improvement of the thermal stability. Further, the saturation magnetization and remanence of the composites increase with increasing filler content. In particular, the saturation magnetization increases from 14.3 to 41.9 A m2/kg, and the remanence from 1.2 to 4.0 A m2/kg when the concentration increases from 20 to 60 wt%. Finally, the MR effect of composites with 20, 40, and 60 wt% filler content is 8%, 15%, and 35%, respectively. A magnetic dipole interaction model is used to discuss the MR effect and a relation between the MR effect and the main parameters affecting it is proposed. Importantly, the obtained MR values are higher when compared with related composites for the same magnetic content, and for the same or similar polymeric matrices, demonstrating the suitability of the developed materials for the fabrication of high‐response functional MR devices.

Study on the potential of multi-performance enhanced phase change materials in battery thermal management

Lots of research has proved the effectiveness of flexible composite phase change material (CPCM) in thermal management of electronic products. However, the key properties of materials, e.g., flexibility, thermal conductivity and resistance are mutually restricted, further limiting its application in practical thermal management engineering. Unfortunately, the above performance has not been comprehensively considered in the existing research. In this work, a novel shape-stabilized flexible CPCM with considerable comprehensive performance was proposed. Styrene-b-ethylene-co-butylene-b-styrene (SEBS) was used as a flexible matrix to expand the flexible temperature range, and ALN was used to improving the thermal conductivity (0.786 W·m−1·K−1), strengthening the three-dimensional thermal conductivity skeleton of expanded graphite and improving the resistivity to 5.16 × 1010 Ω·m. Meanwhile, the CPCMs showed excellent performance in cycle stability, the melting enthalpy only decreased by 1.29 % after 500 cycles. The result of thermal management exhibited that the maximum temperature (Tmax) and maximum temperature difference (ΔTmax) of the battery at 6C discharge rate were 43.64 °C and 2.39 °C respectively with the help of CPCMs. More importantly, it was also obtained that the thermal conductivity played a major role in the battery temperature control in the long-term operation, the increase of the thermal conductivity reduced ΔTmax by 68.05 %. This work will further provide technical support for the practical engineering application of flexible CPCMs for electronic thermal management.

Bio-based sustainable composites from hazelnut shell and PP/SEBS blends

In this study, waste hazelnut shells (HNS) were powderized and used as the filler for the fabrication of sustainable polymeric composites. HNS based composites can be used for many applications because of their tunable intrinsic brown color for various indoor and outdoor applications including decking applications and furniture that require a natural esthetic appearance. Polypropylene (PP), styrene-b-(ethylene-co-butylene)-b-styrene (SEBS), and 50/50 PP/SEBS blends were used as the polymeric matrixes. HNS concentration was set to 2.5, 5, and 10 wt%. PP/SEBS blend and HNS filled granules were prepared by melt mixing in an extruder. Following that polymeric films were fabricated from the granules by compression molding. The morphological, structural, thermal, mechanical, contact angle, water absorption analyses were performed in order to characterize the composites. Matrix type and filler concentration were found significant for the properties. PP/SEBS blends showed homogeneous morphology. At low concentrations, fillers were well-dispersed. On the other hand, at 10 wt% HNS loading agglomerations were observed and mechanical properties showed a noticeable drop. PP-based composites showed the highest tensile strength and elastic modulus with the lowest tensile strain. SEBS-based composites showed the lowest tensile strength and elastic modulus with the highest tensile strain. PP/SEBS composites showed mechanical properties between PP and SEBS. The incorporation of SEBS into PP increased the flexibility of the composites and resulted in relatively higher strain at break.

The performances of expanded graphite on the phase change materials composites for thermal energy storage

For the storage of latent thermal energy (LTES), phase change materials (PCM) are the most commonly used. Nonetheless, their low thermal conductivity values and the liquid leakage on the transition phase of process limits their application. Hence, the stabilization-form can be a solution to surmount these two limitations. In this work, the Hexadecane with large latent heat was used as PCM, styrene-b-(ethylene-co-butylene)-b-styrene (SEBS) tri-block copolymer and the low-density polyethylene (LDPE) served as the supporting materials and expanded graphite (EG) was added for improving the thermal conductivity. We focused on the preparation of SEBS/Hexadecane/LDPE Composites and the improvement of the heat transfer using the EG. The Fourier Transformation Infrared spectroscope also demonstrated a good compatibility between SEBS, LDPE, Hexadecane, and EG. The transient Guarded Hot Plate Technique (TGHPT) and a Thermogravimetric analyzer were utilized to assess the thermal properties and thermal stability of the PCM composites respectively. Further, a leakage test proved that the composite has an excellent form-stable property. Thanks to expanded graphite, no hexadecane leakage was depicted at a 75% mass fraction of PCM in composites, which surmounts almost all mass fraction values reported in the literature.

Form-Stable Phase Change Materials Based on SEBS and Paraffin: Influence of Molecular Parameters of Styrene-b-(Ethylene-co-Butylene)-b-Styrene on Shape Stability and Retention Behavior

In this work, the influence of molecular parameters of styrene-b-(ethylene-co-butylene)-b-styrene (SEBS) triblock copolymer as matrix material in form-stable phase change material (FSPCM) on the thermo-mechanical properties and leakage behavior are studied. Various SEBS grades differing in their molecular weight, styrene content, and ethylene/butylene ratio are used as supporting matrix in composites with 90 wt.% paraffin. Thermo-mechanical properties are determined by rheological measurements. The results show phase transitions temperatures from solid to hard gel, hard gel to soft gel, and soft gel to gel fluid. Paraffin leakage in FSPCM is analyzed by mass loss over time in an oven at 60 °C. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) are applied to determine the thermal energy storage capacity. Finally, the molecular weight and the styrene content are combined to the molecular weight of styrene block which is identified as the authoritative parameter for the thermo-mechanical properties of the SEBS/PCM composite.

Thermal properties of shape-stabilized phase change materials based on Low Density Polyethylene, Hexadecane and SEBS for thermal energy storage

In this work, a Shape-stabilized phase change materials were prepared by absorbing hexadecane into the network of styrene-b-(ethylene-co-butylene)-b-styrene (SEBS) tri-block copolymer and coating them with a low-density polyethylene (LDPE). The four composites were prepared at different mass fractions of Hexadecane/SEBS (80/5, 75/10, 65/20, 55/30, w/w %) with 15% of LDPE by the melt-mixing method. Thermal conductivities and diffusivities were evaluated using a Hot Disk Thermal Constants Analyzer (TPS 2500S) and the Transient Guarded Hot Plate Technique (TGHPT) was used to investigate thermal storage and release capacity of the composites. Results were compared to DSC/TGA data. The thermal properties of the composite were improved by the incorporation of the Hexadecane, where the latent heat of composites increased from 106.15 kJ/kg to 179.76 kJ/kg for the composite containing 80% PCM. Interestingly, the mass fraction of Hexadecane could reach approximately 80% with a good form stability, which surmounts almost all mass fraction values reported in the literature.

The effect of compatibilizer SEBS on the mechanical, morphological and thermal properties of the polystyrene/poly (styrene-co-acrylonitrile) copolymer blends

In this study, the effect of styrene-b-(ethylene-co-butylene)-b-styrene (SEBS) as compatibilizer on polystyrene/poly(styrene-co-acrylonitrile) copolymer (PS/SAN) blends was investigated. For this purpose, blends of various compositions with different content of compatibilizer were prepared by melt blending using a co-rotating twin-screw extruder, and their physical properties, namely the mechanical properties including tensile and impact tests, thermal properties by differential scanning calorimetric (DSC) and thermal stability by thermogravimetric analysis (TGA), studied. Morphological observations using scanning electron microscope (SEM) and viscoelastic properties using dynamic mechanical thermal analysis (DMTA) were also carried out. The results revealed that the mechanical properties were highly improved due to the addition of SEBS which allowed the increase of the blend ductility by enhancing the elongation at break and impact strength. SEM micrographs revealed that the droplet-matrix microstructure was notably refined and the droplets size decreased from 6.7 μm to 2.37 μm in the presence of the compatibilizer. DSC results showed a single glass transition temperature (Tg) for the composition PS/SAN (30/70) compatibilized with 5 and 10% wt of SEBS which confirms the compatibilization of the blend for these compositions.

Piezoresistive performance of polymer-based materials as a function of the matrix and nanofiller content to walking detection application

Thermoplastics and thermoplastic elastomers can be combined with carbon nanotubes (CNT) for the development of piezoresistive composites with varying deformation ranges for sensing applications. This work reports on the influence of the polymer matrix on the mechanical and electromechanical properties of polymer composites prepared by solvent casting. CNT contents up to 5 wt% were dispersed in polymer matrices of different mechanical characteristics, including poly(vinylidene fluoride) (PVDF), styrene-b-(ethylene-co-butylene)-b-styrene (SEBS) and thermoplastic polyurethane (TPU). In all cases, the chemical and thermal properties of the polymers were preserved after the addition of the nanofillers and good nanofiller dispersions were achieved for the polymeric matrices. The electrical properties of the composites are strongly related with the nature of the matrix. Thus, PVDF and SEBS show the lowest and largest percolation threshold, at 0.5 and 2 wt% CNT, respectively, and TPU showed an intermediate value of percolation threshold. The highest electrical conductivity was obtained at 5 wt% CNT composites (0.8 S/m) for the TPU. Piezoresistive sensibility in 4-point-bending and pressure modes shows the largest for the PVDF, for low deformation bending and pressure tests (GF ≈ 2.8 and PS ≈ 12 MPa−1, respectively). Thus, PVDF is the most suitable polymer matrix for low deformation applications, whereas TPU and SEBS are suited for large deformation application due to their stretchability. The different materials have been successfully implemented as pressure sensing materials for human walking detection, with a developed electronic circuit to measure, and compare, different polymer and composites materials. All composites can sense the human walk movement.

Carbonaceous Filler Type and Content Dependence of the Physical-Chemical and Electromechanical Properties of Thermoplastic Elastomer Polymer Composites.

Graphene, carbon nanotubes (CNT), and carbon nanofibers (CNF) are the most studied nanocarbonaceous fillers for polymer-based composite fabrication due to their excellent overall properties. The combination of thermoplastic elastomers with excellent mechanical properties (e.g., styrene-b-(ethylene-co-butylene)-b-styrene (SEBS)) and conductive nanofillers such as those mentioned previously opens the way to the preparation of multifunctional materials for large-strain (up to 10% or even above) sensor applications. This work reports on the influence of different nanofillers (CNT, CNF, and graphene) on the properties of a SEBS matrix. It is shown that the overall properties of the composites depend on filler type and content, with special influence on the electrical properties. CNT/SEBS composites presented a percolation threshold near 1 wt.% filler content, whereas CNF and graphene-based composites showed a percolation threshold above 5 wt.%. Maximum strain remained similar for most filler types and contents, except for the largest filler contents (1 wt.% or more) in graphene (G)/SEBS composites, showing a reduction from 600% for SEBS to 150% for 5G/SEBS. Electromechanical properties of CNT/SEBS composite for strains up to 10% showed a gauge factor (GF) varying from 2 to 2.5 for different applied strains. The electrical conductivity of the G and CNF composites at up to 5 wt.% filler content was not suitable for the development of piezoresistive sensing materials. We performed thermal ageing at 120 °C for 1, 24, and 72 h for SEBS and its composites with 5 wt.% nanofiller content in order to evaluate the stability of the material properties for high-temperature applications. The mechanical, thermal, and chemical properties of SEBS and the composites were identical to those of pristine composites, but the electrical conductivity decreased by near one order of magnitude and the GF decreased to values between 0.5 and 1 in aged CNT/SEBS composites. Thus, the materials can still be used as large-deformation sensors, but the reduction of both electrical and electromechanical response has to be considered.

Synthesis and Characterization of Crystalline Styrene‐b‐(Ethylene‐co‐Butylene)‐b‐Styrene Triblock Copolymers

ABSTRACTBy merit of dual catalysis of the cationic rare‐earth complex [(η5‐Flu‐CH2‐Py)Ho(CH2SiMe3)2(THF) (Flu = fluorenyl, Py = pyridyl) for the living polymerizations of butadiene (BD) and styrene (St), the crystalline styrene‐butadiene‐styrene (SBS) triblock copolymers consisting of elastic polybutadiene (PBD) sequences with suitable 1,4 regularity (about 70%) and crystalline syndiotactic polystyrene (sPS, [rrrr] > 99%) sequences were successfully synthesized through sequential addition of St, BD, and St monomers. The catalytic system showed high polymerization activities for St and BD in a controlled manner. The crystalline styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene (SEBS) triblock copolymers were obtained by hydrogenation of the above SBS copolymers. The observation of a strong endothermic peak at 266 °C in their differential scanning calorimetry (DSC) curves confirmed the existence of the sPS blocks in the crystalline SEBS different from the industrial product Kraton SEBS‐1652. Thermal degradation temperature of the crystalline SEBS (418 ± 2 °C) indicated the well thermostability and process window of this polymer. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 55, 1243–1249

Regulation of Physical Networks and Mechanical Properties of Triblock Thermoplastic Elastomer through Introduction of Midblock Similar Crystalline Polymer with Multiblock Architecture

The physical network structure and mechanical properties of styrene-b-(ethylene-co-butylene)-b-styrene (SEBS) were regulated through rational introduction of crystalline olefin multiblock copolymer (OBC). This copolymer comprised alternated crystallizable and amorphous blocks, both of which had similar composition with ethylene-co-butylene (EB) blocks of SEBS. Polarized optical microscope and atom force microscope observations revealed that OBC exhibited distinct crystalline morphologies in blends. On one hand, major OBC chains were macrophase separated with SEBS, generating bulk crystals. On the other hand, small OBC particle crystals with diameter around 10 nm could be distinguished in the SEBS matrix as well. Considering the unique multiblock architecture of OBC, particle crystals could be regarded as additional physical netpoints to SEBS networks as the corresponding amorphous blocks entangled with continuous EB blocks. Because of the interesting crystalline behaviors of OBC in the SEBS matrix, the bl...

A Facile Strategy to Fabricate Multishape Memory Polymers with Controllable Mechanical Properties.

A facile blending strategy to fabricate multishape memory polymers (SMPs) with only one sort of phase transition material has been reported. In this work, olefin block copolymer (OBC) and styrene-b-(ethylene-co-butylene)-b-styrene (SEBS), which are both physically crosslinked, are blended with crystalline paraffin together. Due to the different interactions between polymer matrices and paraffin, the paraffin penetrated in OBC and SEBS exhibit separated melting transitions. It is quite interesting that merely paraffin distributed in OBC also shows two distinct melting transitions with enough OBC content in composites. Therefore, excellent quadruple shape memory effect can be achieved with a maximum of three melting transitions. Furthermore, through adjusting the polymer species and content, the mechanical and rheological properties can be conveniently tuned to a great extent. Compared with the reported strategies, this simple and controllable method sheds light on rapid design of multi-SMPs using inexpensive raw materials, which greatly paves the way for multi-SMPs from laboratory to factory.

The Influence of Compatibilizer Addition and Gamma Irradiation on Mechanical and Rheological Properties of a Recycled WEEE Plastics Blend

Waste electrical and electronic equipment (WEEE) is growing rapidly, and the plastics within WEEE have an important role in fulfilling the recovery and recycling targets defined in the European WEEE Directive. This study considers recycling of WEEE plastics by making a blend of the different plastics instead of separating them. The mechanical and thermal properties can be enhanced by adding a compatibilizer. It was found that one compatibilizer, a styrene-b(ethylene-co-butylene)-b-styrene (SEBS) copolymer named Kraton® G1652 E, had a large impact on the ductility of the recycled WEEE plastics blend. By adding 2.5 weight % (wt%) of this copolymer, the elongation at break increased by more than five times compared with the non-compatibilized samples, with only a small decrease in stiffness and strength. The storage modulus (G’) decreased slightly with increasing compatibilizer amounts while the impact strength increased with increasing amounts of compatibilizer, from 2.1 kJ/m2 (reference material) to 3.6 kJ/m2 (5 weight % (wt%) compatibilizer). It was found that Kraton® FG1901 E (styrene-b(ethylene-co-butylene)-b-styrene (SEBS) grafted with maleic anhydride (MAH)), Royaltuf® 372P20 (styrene acrylonitrile (SAN) modified with ethylene-propylene-diene elastomers (EPDM)) and Fusabond® P353 (polypropylene (PP) with a high degree of grafted MAH) were ineffective as compatibilizers to the blend. Gamma irradiation (50 kGy) did not improve the mechanical properties however: the impact strength of the gamma-irradiated samples was lower than that of the non-irradiated samples.

Metal foam embedded in SEBS/paraffin/HDPE form-stable PCMs for thermal energy storage

The objective of this study is to overcome the leakage and low thermal conductivity problems of paraffin as PCMs (phase change materials) for thermal energy storage by impregnating SEBS/paraffin/HDPE FSPCMs (form-stable phase change materials) into metal foam. The form-stable composites were prepared by absorbing paraffin into the network of powder-like styrene-b-(ethylene-co-butylene)-b-styrene (SEBS) triblock copolymer and covering high-density polyethylene (HDPE) on pre-prepared SEBS/paraffin mixture. The composites were characterized by using differential scanning calorimetry (DSC), Scanning electron microscope (SEM), Fourier Transform Infrared Spectrometer (FT-IR), X-Ray Diffraction (XRD) and Hot disk. Paraffin leakage was investigated by accelerated degradation test at 80°C. The melting temperature and latent heat of the composites were determined as 50.56°C and 151.6J/g, respectively. FT-IR results revealed good chemical compatibility among paraffin, SEBS and HDPE. SEM images and XRD test results demonstrated that the paraffin had uniformly dispersed into SEBS. This composite was testified able to keep paraffin from seepage with only 2.39wt% of paraffin loss after 50 thermal cycles test (150h). In addition, the thermal conductivity of SEBS/paraffin/HDPE was 0.272W/mK, which was increased up to 2.142W/mK when copper foam was embedded in the composite.

Construction of d-α-tocopheryl polyethylene glycol succinate/PEO core-shell nanofibers on a blood-contacting surface to reduce the hemolysis of preserved erythrocytes.

The hemolysis of erythrocytes is a big obstacle to the development of new non-plasticizer polymer containers for erythrocyte preservation. To construct a long-term anti-hemolytic surface of a plasticizer-free polymer, we coaxially electrospin core-shell structured d-α-tocopheryl polyethylene glycol 1000 succinate (TPGS)/poly(ethylene oxide) nanofibers on the surface of a styrene-b-(ethylene-co-butylene)-b-styrene (SEBS) elastomer that is covered with grafted poly(ethylene glycol) (PEG) chains. Our strategy is based on the fact that the grafted layers of PEG reduce mechanical damage to red blood cells (RBCs) while the TPGS released from the nanofibers on a blood-contacting surface can act as an antioxidant to protect RBCs from oxidative damage. We demonstrate that TPGS/PEO core-shell structured nanofibers have been well prepared on the surface of PEG modified SEBS; the controlled release of TPGS in distilled water is obtained and the release can last for almost 4 days at 4 °C; during RBC preservation, TPGS acts as the antioxidant to decrease the membrane oxidation and hemolysis of RBCs. Our work paves a new way for the development of non-plasticizer polymers for RBC preservation, which may be helpful for the fabrication of long-term anti-hemolytic biomaterials in vivo.

Validation of the Use of SEBS Blends as a Substitute for Liquid Silicone Rubber in Injection Processes

Liquid silicone rubber is an interesting material at an industrial level, but there are great difficulties in the design and machining of molds, and in addition, it cannot be processed using conventional equipment. Therefore, new lines of research have focused on the search for new materials capable of providing final properties similar to liquid silicone rubber, that can also be engineered using simple, conventional processes and machinery. In this investigation, a range of compatible blends, based on two commercial grades of styrene-b-ethylene-co-butylene-b-styrene (SEBS) thermoplastic elastomer, was studied in order to obtain a range of different Shore A hardness blends for industrial applications where liquid silicone rubber (different hardness) is currently used. The two blended elastomers used had widely differing Shore A hardness values (5 and 90). Once the blended materials had been characterized, the Cross and Williams et al. [20] (Cross-WLF) mathematical model was applied in order to obtain theoretical performance curves for the viscosity of each of the blends. After this, a model was developed using the Computer Aided Engineering (CAE) software package Autodesk Moldflow 2012™. This computer modeling validated the results obtained from the mathematical models, thus making available to process engineers the full range of hardnesses necessary for industrial products (where liquid silicone rubber is used), while still providing the advantages of thermoplastic injection molding.

A temperature sensor based on a MWCNT/SEBS nanocomposite

The fabrication of a temperature sensor based on multi-walled carbon nanotubes (MWCNTs)/styrene-b-(ethylene-co-butylene)-b-styrene (SEBS) triblock copolymer composite is reported. The device was realized by drop casting 10μl of a MWCNTs dispersion in a toluene solution of SEBS onto gold electrodes fabricated onto a polyimide support. Thermogravimetric and electrical resistance measurements highlighted a good reproducibility of film composition and sensing properties. A negative temperature coefficient with an absolute value comparable to the highest values in metals was measured when a substantial amount of MWCNTs was incorporated into the nanocomposite (40% by weight), and a five-fold increase was observed close to the percolation threshold. Though such sensitivity seems to be partly lost after the first heating, the results allowed us to be optimistic about the feasibility of realizing nanocomposite films with temperature sensitivities comparable to that of common thermistors in the range 20–60°C.

Improving hemocompatibility of styrene-b-(ethylene-co-butylene)-b-styrene elastomer via N-vinyl pyrrolidone-assisted grafting of poly(ethylene glycol) methacrylate

In this work, in order to enhance the grafting degree, N-vinyl pyrrolidone (NVP) was used to assist the melt grafting of the macromonomer-poly(ethylene glycol) methyl ether methacrylate (PEGM)-which has good hemocompatible property, onto styrene-b-(ethylene-co-butylene)-b-styrene (SEBS) elastomer with free radical initiator. The grafting degree of PEGM with NVP assistance was increased by at least 4-fold to those without NVP. In addition, side reactions such as homopolyerization of the PEGM monomer during the melt grafting process could be largely reduced in the NVP-assisted system. Both the hydrophilicity and hemocompatibility of the PEGM modified SEBS were highly improved. Comparing to virgin SEBS, the amount of fibrinogen adsorption was reduced by up to 75% in the NVP-assisted grafting samples.