Styrene-isoprene Block Copolymers Research Articles

Smart-Adhesive, Breathable and Waterproof Fibrous Electronic Skins.

For the need of direct contact with the skin, electronic skins (E-skins)should not only fulfill electric functions, but also ensure comfort during wearing, including permeability, waterproofness, and easy removal. Herein, the study has developed a self-adhesive, detach-on-demand, breathable, and waterproof E-skin (PDSC) for motion sensing and wearable comfort by electrospinning styrene-isoprene block copolymer rubber with carbon black nanosheets as the sensing layer and liner copolymers of N, N-dimethylacrylamide, n-octadecyl acrylate and lauryl methacrylate as the adhesive layer. The high elasticity and microfiber network structure endow the PDSC with good sensitivity and high linearity for strain sensing. The hydrophobic and crystallizable adhesive layer ensures robust, waterproof, and detaching-on-demand skin adhesion. Meanwhile, the fiber structure enables the PDSC good air and water permeability. The integration of electric and wearable functions endows the PDSC with great potential for motion sensing during human activities as both the sensing and wearable performances.

4D Printing of Ultrastretchable Magnetoactive Soft Material Architectures for Soft Actuators.

Magnetoactive soft materials (MSMs) comprising magnetic particles and soft matrices have emerged as smart materials for realizing soft actuators. 4D printing, which involves fabricating 3D architectures that can transform shapes under external magnetic fields, is an effective way to fabricate MSMs-based soft actuators with complex shapes. The printed MSMs must be flexible, stretchable, and adaptable in their magnetization profiles to maximize the degrees of freedom for shape morphing. This study utilizes a facile 4D printing strategy for producing ultrastretchable (stretchability > 1000%) MSM 3D architectures for soft-actuator applications. The strategy involves two sequential steps: (i) direct ink writing (DIW) of the MSM 3D architectures with ink composed of NdFeB and styrene-isoprene block copolymers (SIS) at room temperature and (ii) programming and reconfiguration of the magnetization profiles of the printed architecture using an origami-inspired magnetization method (magnetization field, Hm = 2.7 T). Various differently shaped MSM 3D architectures, which can be transformed into desired shapes under an actuation magnetic field (Ba = 85 mT), are successfully fabricated. In addition, two different soft-actuator applications are demonstrated: a multifinger magnetic soft gripper and a Kirigami-shaped 3D electrical switch with conductive and magnetic functionalities. Our strategy shows potential for realizing multifunctional, shape-morphing, and reprogrammable magnetoactive devices for advanced soft-actuator applications.

Density Fluctuations Inside an Individual Polymer Coil.

More than five hundred images of individual macromolecules of random styrene-butadiene copolymers and styrene-isoprene block copolymers dissolved in a polystyrene matrix were analyzed. The presence of density fluctuations inside the macromolecular coil has been established. Within the framework of the model of harmonic oscillations, the radial distribution of such density fluctuations is estimated.

Effect of SIS block copolymers on damping properties of natural rubber/AO-80 and the performance enhancement mechanism: experimental study and molecular dynamics simulation

Natural rubber/blocked phenol/styrene-isoprene block copolymer (NR/AO-80/SIS) composites were prepared by using hindered phenolic polar small molecules (AO-80) and styrene isoprene block copolymer (SIS) as damping performance-enhancing components and (NR) as rubber substrate to overcome the problems of narrow effective damping temperature range, unsatisfactory damping effect and subpar mechanical properties in NR/AO-80 rubber applications.The effects of SIS and AO-80 on the morphology, structure, mechanical properties, aging resistance, and damping properties of the NR/AO-80/SIS composite were investigated. Molecular dynamics simulations (MD) were employed to investigate the intermolecular forces, and interaction mechanisms of the rubber composites. SIS exhibited compatibility with the NR/AO-80 matrix and can significantly enhanced the mechanical, aging, and damping properties of the NR/AO-80 matrix. The effective damping temperature range can be extended to a maximum of 114.5 °C, demonstrating its notable improvement to the damping performance of NR/AO-80. The primary mechanisms of enhancing damping performance involve the more van der Waals forces, electrostatic interactions in NR/AO-80/SIS composites,which is beneficial for increasing the internal friction of rubber and improving the damping performance of NR/AO-80 /SIS.

Stability Study of the Irradiated Poly(lactic acid)/Styrene Isoprene Styrene Reinforced with Silica Nanoparticles.

In this paper, the stability improvement of poly(lactic acid) (PLA)/styrene-isoprene block copolymer (SIS) loaded with silica nanoparticles is characterized. The protection efficiency in the material of thermal stability is mainly studied by means of high accurate isothermal and nonisothermal chemiluminescence procedures. The oxidation induction times obtained in the isothermal CL determinations increase from 45 min to 312 min as the polymer is free of silica or the filler loading is about 10%, respectively. The nonisothermal measurements reveal the values of onset oxidation temperatures with about 15% when the concentration of SiO2 particles is enhanced from none to 10%. The curing assay and Charlesby–Pinner representation as well as the modifications that occurred in the FTIR carbonyl band at 1745 cm−1 are appropriate proofs for the delay of oxidation in hybrid samples. The improved efficiency of silica during the accelerated degradation of PLA/SIS 30/n-SiO2 composites is demonstrated by means of the increased values of activation energy in correlation with the augmentation of silica loading. While the pristine material is modified by the addition of 10% silica nanoparticles, the activation energy grows from 55 kJ mol−1 to 74 kJ mol−1 for nonirradiated samples and from 47 kJ mol−1 to 76 kJ mol−1 for γ-processed material at 25 kGy. The stabilizer features are associated with silica nanoparticles due to the protection of fragments generated by the scission of hydrocarbon structure of SIS, the minor component, whose degradation fragments are early converted into hydroperoxides rather than influencing depolymerization in the PLA phase. The reduction of the transmission values concerning the growing reinforcement is evidence of the capacity of SiO2 to minimize the changes in polymers subjected to high energy sterilization. The silica loading of 10 wt% may be considered a proper solution for attaining an extended lifespan under the accelerated degradation caused by the intense transfer of energy, such as radiation processing on the polymer hybrid.

Silk inspired in-situ interlocked superelastic microfibers for permeable stretchable triboelectric nanogenerator

Wearables and on-skin triboelectric nanogenerator (TENG) highly desire intrinsic stretchability, favorable permeability and waterproofness, fibers/textiles as one of the ideal substrates could meet the requirements. However, realizing the versatile integration of hydrophobic elastic fibers with electrodes remains a huge challenge. Herein, inspired by the sericin-bundled silk with outstanding stretchability, we develop a microfibers-membrane with omnidirectional superelasticity, permeability and superhydrophobicity (SPSM) by synchronous electrospinning of styrene-isoprene (SIS) block copolymers and electrospraying of the fluorinated SiO2 nanoparticles. Co-solvent welding effect free of extra binders is proposed for the generation of in-situ anchored junctions between the SIS fibers, as well as achieving the anchoring effect for enhanced integration of SIS fiber-membranes with a variety of conductors such as sputtered gold (Au) layer, vacuum filtrated liquid metal-silver nanowires (LM-AgNWs) network and printed liquid metal-silver flakes-SIS (LM-AgFKs-SIS) ink, creating diverse elastic conductors and triboelectric-active-materials with optional advantages in mechanical stability, electrical robustness, triboelectric output and permeability. A self-cleaning SPSM-based single-electrode stretchable TENG (STENG) is demonstrated adaptive for tapping, stretching, bending and humidity, realizing a breathable self-powered sensor for materials identifying and hand posture monitoring. This work proposes a versatile superelastic fiber material competent for permeable STENGs and wearables with environment adaptivity.

Bi-Phasic Ag-In-Ga-Embedded Elastomer Inks for Digitally Printed, Ultra-Stretchable, Multi-layer Electronics.

A bi-phasic ternary Ag-In-Ga ink that demonstrates high electrical conductivity, extreme stretchability, and low electromechanical gauge factor (GF) is introduced. Unlike popular liquid metal alloys such as eutectic gallium-indium (EGaIn), this ink is easily printable and nonsmearing and bonds strongly to a variety of substrates. Using this ink and a simple extrusion printer, the ability to perform direct writing of ultrathin, multi-layer circuits that are highly stretchable (max. strain >600%), have excellent conductivity (7.02 × 105 S m-1), and exhibit only a modest GF (0.9) related to the ratio of percent increase in trace resistance with mechanical strain is demonstrated. The ink is synthesized by mixing optimized quantities of EGaIn, Ag microflakes, and styrene-isoprene block copolymers, which functions as a hyperelastic binder. When compared to the same composite without EGaIn, the Ag-In-Ga ink shows over 1 order of magnitude larger conductivity, up to ∼27× lower GF, and ∼5× greater maximum stretchability. No significant change over the resistance of the ink was observed after 1000 strain cycles. Microscopic analysis shows that mixing EGaIn and Ag microflakes promotes the formation of AgIn2 microparticles, resulting in a cohesive bi-phasic ink. The ink can be sintered at room temperature, making it compatible with many heat-sensitive substrates. Additionally, utilizing a simple commercial extrusion based printer, the ability to perform stencil-free, digital printing of multi-layer stretchable circuits over various substrates, including medical wound-dressing adhesives, is demonstrated for the first time.

Studies of the Sulfonated Hydrogenated Styrene-Isoprene-Styrene Block Copolymer and Its Surface Properties, Cytotoxicity, and Platelet-Contacting Characteristics.

Styrenic thermoplastic elastomers (TPEs) consist of styrenic blocks. They are connected with other soft segments by a covalent linkage and are widely used in human life. However, in biomedical applications, TPEs need to be chemically hydrogenated in advance to enhance their properties such as strong UV/ozone resistance and thermal-oxidative stability. In this study, films composed of sulfonated hydrogenated TPEs were evaluated. Hydrogenated tert-butyl styrene–styrene–isoprene block copolymers were synthesized and selectively sulfonated to different degrees by reaction with acetyl sulfate. By controlling the ratio of the hydrogenated tert-butyl styrene–styrene–isoprene block copolymer and acetyl sulfate, sulfonated films were optimized to demonstrate sufficient mechanical integrity in water as well as good biocompatibility. The thermal plastic sulfonated films were found to be free of cytotoxicity and platelet-compatible and could be potential candidates in biomedical film applications such as wound dressings.

Preparation of Magnetorheological Fluid Using Stabilizing Additives

In this study, we examined three kinds of stabilizing additives to prepare stable MRF with good fluidity. We selected three stabilizing additives; a styrene isoprene block copolymer, a hydrophobic fumed silica, and an organogelator (CMOL SB03; PMDA-2C8/oleyl). We measured the rheological properties both for the dissolutions of the stabilizing additives in the base oil and MRFs prepared with the additives by using a rheometer; MCR302 (Anton Paar Corp.). From the experimental results, the viscosity of styrene isoprene block copolymer dissolution increased with concentration showing non-Newtonian properties. We selected a suitable concentration as 5wt% to satisfied good fluidity without forming gel. Since the viscosities of 7wt% fumed silica and 1wt% CMOL SB 03 dissolutions in the base oil consequently showed similar viscosity of the 5wt% copolymer, MRFs using such conditions were prepared. From the results of the stability test, the addition of the copolymer was effective to satisfy the stability of the MRF. We also found that the addition of such stabilizing additives were effective to increase the magnetic property of MRFs.

Sulfonation and Characterization of Tert-Butyl Styrene/Styrene/Isoprene Copolymer and Polypropylene Blends for Blood Compatibility Applications.

Hydrogenated styrenic block copolymers (HSBCs) have been used in medical tubing for many years due to their high clarity, flexibility, kink resistance, and toughness. However, when it comes to blood storage applications, HSBC compounds’ market has been limited because of their high hydrophobicity, which may trigger platelet adhesion when contacting with blood. HSBC needs to be physically or chemically modified in advance to make it blood compatible; however, HSBC has strong UV/ozone resistance, thermooxidative stability, and excellent processing capability, which increases the difficulty of the chemical modification process as unsaturated dienes has been converted to saturated stable midblocks. Moreover, medical HSBC-containing compounds primarily make up with the non-polar, hydrophobic nature and benign characteristics of other common ingredients (U.S. Pharmacopeia (USP) grades of mineral oil and polypropylene), which complicates the realization of using HSBC-containing compounds in blood-contacting applications, and this explains why few studies had disclosed chemical modification for biocompatibility improvement on HSBC-containing compounds. Sulfonation has been reported as an effective way to improve the material’s blood/platelet compatibility. In this study, hydrogenated tert-butyl styrene (tBS)-styrene-isoprene block copolymers were synthesized and its blends with polypropylene and USP grades of mineral oil were selectively sulfonated by reaction with acetyl sulfate. By controlling the ratio of the hydrogenated tBS-styrene-isoprene block copolymer in the blend, sulfonated films were optimized to demonstrate sufficient physical integrity in water as well as thermal stability, hydrophilicity, and platelet compatibility.

Effect of Styrene-Diene Block Copolymers and Glass Bubbles on the Post-Consumer Recycled Polypropylene Properties

The recycled polypropylene (rPP) materials that meet technical requirements such as reducing the dimensions and improving the tensile, elongation, impact strength, thermal stability, as well as melt processing, are required for the manufacturing industry. In this paper, we studied the mechanical and thermal properties of post-consumer rPP by adding both synthesized thermoplastic elastomers, and glass bubbles (GB) by a melt allowing process. Styrene-butadiene (SBS) and styrene-isoprene (SIS) block-copolymers that had a styrene content of 30 wt% were synthesized by anionic sequential polymerization. The obtained post-consumer rPP composites were characterized by optical microscopy, scanning electron microscopy (SEM), mechanical analyses (tensile, density, hardness, VICAT softening temperature (VST), heat deflection temperature (HDT), dynamic mechanical analysis (DMA), IZOD strength) and thermal analyses (differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA)). Weight reduction and improvement of the tensile, elongation, impact strength, thermal stability, as well as melt processing of post-consumer recycled polypropylene (rPP) properties compounded with thermoplastic elastomers and glass bubbles, sustain the use of these formulations for engineering applications.

Mechanical and Thermal Properties of Styrene-diene Block Copolymers Films Obtained by Spin Casting from Different Solvents

This paper presents the solvents effect on the mechanical and thermal properties of films of styrene-butadiene and styrene-isoprene block copolymers with the majority diene phase, obtained by spin casting.

Ultrathin film crystallization of poly(ε-caprolactone) in blends containing styrene-isoprene block copolymers: The nano-rose morphology

We report the discovery of a new nanostructured morphology in ultrathin blend films of semi-crystalline poly(ε-caprolactone) (PCL) and various styrene-isoprene block copolymers. The nano-rose morphology is visualized by atomic force microscopy as a monolayer of approximately 500 nm diameter crystalline spirals. Our finding that the nano-rose morphology occurs in a narrow film thickness window commensurate with the crystalline lamellar thickness suggests that this distinctive morphology results from redirection of growing PCL crystalline lamellae due to confinement effects during film casting. The nano-rose morphology was located in blends with several block copolymers of various architecture but was absent in blends with the individual homopolymer components. PCL molecular weight did not affect nano-rose size or film thickness window. However, solvent choice was an important factor, with nano-rose formation favored in non-polar and weakly polar solvents. This work supports theories that unbalanced surface stresses and impurity exclusion cause polymer crystals to grow unconventionally.

Isothermal Microphase Separation Kinetics in Blends of Asymmetric Styrene–Isoprene Block Copolymers

The microphase separation behavior of Kraton D1161, a highly asymmetric styrene–isoprene triblock and diblock copolymer mixture often used as the base polymer in pressure-sensitive adhesives, was studied using time-resolved small-angle X-ray scattering (SAXS) and oscillatory rheological analysis during temperature ramp and temperature quench experiments. The total scattering intensity obtained from SAXS was represented as a sum of the scattering from disordered and ordered polystyrene domains. A modified Percus–Yevick hard-sphere model was used to describe the scattering from disordered spheres, while Gaussian functions were used to model scattering from ordered domains. The temperature- and time-dependent SAXS experiments suggest a sequence of four stages in the development of the copolymer morphology during the isothermal phase separation kinetics experiments. Avrami analysis of the shear modulus evolution following a temperature quench indicates that domain growth is preceded by nucleation process. The ordering of polystyrene domains as observed during rheological and SAXS analysis is dominated by polymer chain mobility, which resulted in slower kinetics at lower temperatures.

Regular Mixing Thermodynamics of Hydrogenated Styrene–Isoprene Block–Random Copolymers

Random copolymerization of A and B monomers represents a versatile method to tune interaction strengths between polymers, as ArB random copolymers will exhibit a smaller effective Flory interaction parameter χ (or interaction energy density X) upon mixing with A or B homopolymers than upon mixing A and B homopolymers with each other, and the ArB composition can be tuned continuously. This approach can also be used to tune the segregation strength in A–ArB “block–random” copolymers. Simple models of polymer mixing thermodynamics suggest that the effective interaction energy density in such block–random copolymers should follow XA–ArB = fB2XA–B, but this prediction has not been tested quantitatively. The present work systematically assesses the validity of this rule for thermally stable hydrogenated derivatives of styrene–isoprene block copolymers, through measurements of the order–disorder transition (ODT) temperature on near-symmetric diblock and diblock–random copolymers of varying composition and suitab...

連続多孔質性エラストマーシートの製造

Continuous open cell elastomer sheets were prepared by immersing continuous open cell polymer compounds in hot water, which are obtained by the extrusion and injection of thermoplastic elastomers, pentaerythritol (PETH), polypropylene (PP) and polytetrafluoroethylene (A-PTFE) modified by methyl methacrylate. A styrene-isoprene block copolymer (PSt-E), thermoplastic elastomer, was used as a main polymer in the compounds, giving strength, shock absorptivity and water resistance to the sheets. PETH was added as an open cell forming agent in the compounds, giving continuous open cell to the sheets obtained by immersing the compounds in hot water. The addition of 10phr of PP was effective for decreasing the linear shrinkage of the sheets in the process of the extraction of PETH from the compounds. The addition of 5phr of A-PTFE was also effective for improving the melting tension of the compounds at a molding temperature and the sheeting properties such as roughness, checking, crack, end tear. Molding temperature range of 180 to 230°C was very effective for giving good sheet properties and air flow rate, at which PSt-E and PETH are blended smoothly and continuous open cells were obtained. An extrusion molding gave better continuous open cell elastomer sheets in the point of air flow rate and open cell diameter than an injection molding.

Electrospun Polymer Nanofibers with Internal Periodic Structure Obtained by Microphase Separation of Cylindrically Confined Block Copolymers

Continuous fibers are described having concentric layer or aligned sphere microphase-separated, styrene-isoprene block copolymer morphologies. The fibers are obtained by a two-fluid coaxial electrospinning technique in which the desired block copolymer is encapsulated as the core component within a polymer shell having a high glass transition temperature (Tg). The fibers range in diameter from 300 to 800 nm, and the block copolymer core ranges from 50 to 500 nm. Subsequent annealing of the fibers above the upper Tg of the block copolymer but below the Tg of the shell polymer results in microphase separation of the block copolymer under cylindrical confinement. The resulting fibers exhibit improved long-range order. This two-step strategy creates the opportunity to fabricate continuous nanofibers with periodic internal structure.

Sorption and swelling of block copolymers in the presence of supercritical fluid carbon dioxide

The sorption and swelling of polystyrene, poly(methyl methacrylate), poly(vinyl pyridine) and polyisoprene, and of styrene-methyl methacrylate, styrene-vinyl pyridine and styrene-isoprene block copolymers, in the presence of carbon dioxide, is examined at 35°C and at pressures to 1500 psia. Sorption data were obtained using a quartz spring technique and swelling data were obtained by direct measurement of the dimensions of a separate sample using a cathetometer. Sorption in the glassy polymers increases linearly at low pressures before leveling off at higher pressures, while sorption in the rubber polyisoprene is linear over the entire range of pressures investigated. Sorption in the block copolymers shows a continuous transition from the behavior of one homopolymer to the behavior of the other. The Sanchez-Lacombe equation of state is used to model the homopolymer data using the concept of order parameters to extend the model to the glassy polymers. A simple linear model based on the homopolymer sorption is adequate to describe the copolymer results.

Bromination of some styrene-diene block copolymers

The bromine addition at the polydiene block double bonds of a radial styrene-butadiene (SBS) and a linear styrene-isoprene (SIS) block copolymer (thermoplastic elastomers), in tetrahydrofurane solution at 0 °C, has been investigated by IR spectroscopy. In both cases the bromine reacts exclusively with the polydiene middle block double bonds; the polystyrene blocks are unaffected. The bromine reacts preferentially with the 1,4-type ( cis and trans) double bonds of the polybutadiene block of SBS. At low bromination level (below 5%) the bromine reacts mainly with the 1,4- cis type double bonds of polyisoprene block of SIS, while at higher bromination level the bromine presents the same reactivity towards the 1,4-type ( cis and trans) and vinylic (3,4-type) double bonds.

Effects of the molecular structure of styrene-isoprene block copolymers on the interfacial characteristics of polystyrene/polyisoprene blends

The effects of the molecular structure of the styrene-isoprene block copolymer on the interfacial tension, the morphology and the interfacial adhesion of polystyrene/polyisoprene were investigated. A reduction in interfacial tension is observed with the addition of a small amount of copolymer, followed by a leveling off as the copolymer concentration exceeds the critical micelle concentration. The reduction in interfacial tension between polystyrene and polyisoprene is more significant when the isoprene-rich diblock copolymer is added than the cases when the symmetric or styrene-rich diblock copolymer is added. The interfacial tension data seem to be consistent with the phase morphology and the interfacial adhesion: the lower the interfacial tension, the smaller the domain size of dispersed phase and the better the interfacial adhesion. © 1996 John Wiley & Sons, Inc.