Styrene-butadiene Diblock Copolymer Research Articles

Synthesis of block copolymer with cis-1,4-polybutadiene and isotactic-rich polystyrene using α-diimine nickel catalysts.

A series of styrene-butadiene di-block copolymers with high cis-1,4 unit content (greater than 92%) polybutadiene (PB) and isotactic-rich polystyrene (PS) (mmmm > 65%) was synthesized using α-diimine nickel catalysts (Ni-diimine). Four different Ni-diimine catalysts were synthesized via a complexing reaction between nickel (II) naphthenate and laboratory-made α-diimine ligands L1, L2, L3 and L4, which have different steric volume structures. The results indicate that the Ni-diimine catalyst prepared using the L4 ligand with a higher steric volume can effectively initiate the block polymerization of butadiene and styrene, and the resulting polymer has distinguished cis-1,4 structure unit PB and high isotactic-selective PS block. Differential scanning calorimetry and electrochemical performance tests show that these block copolymers with cis-1,4-regulated and isotactic-selective polymerization have advantages in terms of high-temperature and low-temperature resistance as well as corrosion resistance. Therefore, these copolymers are expected to be widely used in some harsh industrial environments.

A New Synthesis Strategy on Styrene-Butadiene Di-Block Copolymer Containing High cis-1,4 Unit Via Transfer of Anionic to Coordination Polymerization.

A novel synthesis strategy on styrene-butadiene di-block copolymer (PS-b-PB) with high cis-1,4 unit content was developed, based on a transfer technique from anionic to coordination polymerization. Firstly, the styrene monomer was initiated by n-butyllithium (Li) utilizing anionic polymerization at 50 °C, which resulted in a macromolecular alkylating initiator (PSLi). Secondly, PSLi was aged with nickel naphthenate (Ni) and boron trifluoride etherate (B) for obtaining a complex catalyst system (Ni/PSLi/B). Then, Ni/PSLi/B was applied to initiate the butadiene (Bd) polymerization. Following this new strategy, a series of PS-b-PBs were successfully synthesized. The experimental results indicated that under the molar ratio combination of [Li]/[Ni] = 5 and [B]/[Li] = 1, styrene-butadiene di-block copolymers could be easily achieved with high cis-1,4 unit content (>97%) and controlled molecular weight as well as narrow molecular weight distribution (Mw/Mn < 1.5). Furthermore, the copolymer’s block ratio could also be effectively controlled by controlling the two components’ monomer feed ratio.

Formation of bio-based elastomer from styrene-butadiene copolymer and epoxidized soybean oil

Styrene-butadiene copolymers and epoxidized soybean oil (ESO) were used to synthesize bio-elastomers. The reaction occurred via a living anionic polymerization using n-butyllithium as initiator and cyclohexane as solvent. The gel permeation chromatography (GPC), 1HNMR and FTIR spectroscopy analysis of the microstructure of precursor styrene-butadiene copolymers and the final products suggests that the ester group in the triglyceride of ESO was broken and reacted with the living polymer chain to form the bio-elastomer. The effect of the molecular weight of styrene-butadiene copolymer and the molar ratio of precursor copolymer to ESO on the formation of bio-elastomer are studied. The bio-elastomer based on styrene-butadiene diblock copolymer (SB) reveal higher tensile strength and break elongation compared with the precursor copolymer, but the one based on styrene-butadiene triblock copolymer (SBS) shown the opposite result.

Styrene–butadiene block copolymer with high cis‐1,4 microstructure

AbstractThe sequential block copolymerization of styrene (St) and butadiene (Bd) was carried out with an activated rare earth catalyst composed of catalyst neodymium tricarboxylate (Nd), cocatalyst Al(i‐Bu)3 (Al), and chlorinating agent (Cl). The microstructure, composition, and morphology of the copolymer were characterized by FTIR, 1H NMR, 13C NMR, and TEM. The results show that styrene–butadiene diblock copolymer with high cis‐1,4 microstructure of butadiene units (∼ 97 mol %) was synthesized. The cis‐selectivity for Bd units was almost independent on the content of styrene units in the copolymer ranging from 18.1 mol % to 29.8 mol %. The phase‐separated morphology of polystyrene (PS) domains of about 40 nm tethered by the elastomeric polybutadiene (PB) segments is observed. The PS‐b‐cis‐PB copolymer could be used as an effective compatilizer for noncompatilized binary PS/cis‐PB blends. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Effect of composition of added random copolymer on the phase behavior of block copolymer

Blends of styrene–butadiene diblock copolymer (S–B, 52 wt% styrene content) and styrene–butadiene random copolymer (SBR) of various styrene compositions were studied by small-angle X-ray scattering, light scattering, and transmission electron microscopy. The composition of random copolymer plays an important role in the solubilization of SBR in S–B. The order–disorder transition temperature, T ODT, decreases linearly with the addition of SBR. T ODT decreases as the symmetry in SBR composition increases and shows the highest value in the case of homopolymers. Asymmetric butadiene-rich SBR dissolves mostly into PB microdomain of S–B to increase lamella microdomain spacing, D, and its addition makes the overall microdomains of S and B in the mixture more asymmetrical. Symmetric SBR is localized into the interface of S–B microdomain to reduce unfavorable S–B contact at the interface. The phase diagram for S–B containing asymmetric SBR shows a succession of mixed mesophases of different morphologies from lamellae and cylinder to disordered liquid phases, whereas the phase diagram containing symmetric SBR shows two homogeneous phases and one region of two-phase coexistence, where macroscopically separated phases coexist together.

Development of a Stirred Airflow Test Procedure for Short-Term Aging of Asphaltic Materials

Short-term aging procedures, either the thin-film oven test or the rolling thin-film oven test (RTFOT), are used to approximate the aging that occurs by asphalt binders during the hot-mix process. For unmodified binders, both of these procedures do a reasonable job of duplicating this aging not only with respect to physical property changes in the binder but also with respect to oxidation, as measured by changes in the infrared absorption spectrum. For modified binders, however, significant difficulties exist, among them surface skin formation and poor flow in the bottles. A new apparatus specifically designed to age modified binders as well as unmodified binders has been developed. This apparatus consists of a temperature-controlled vessel, a tube for introducing either nitrogen or air, a dispersing impeller for mixing the air and binder, and a condenser for collecting volatiles. Besides temperature, gas flow rate and mixing speed are controlled to desired values. The collection of volatiles allows a direct, rather than indirect, measure of volatiles loss. The required aging time of 30 min is less than the RTFOT’s 85 min. Tests of the process with unmodified binders achieved excellent comparisons with RTFOT aging in both physical properties (dynamic shear rheometer) and oxidative aging (Fourier-transform infrared analysis). Trials with modified binders achieved uniform aging with no complications caused by the rheology of these materials. Modified binders studied included polymer-modified styrene butadiene diblock copolymer and styrene butadiene triblock copolymer materials.

The influence of styrene–butadiene diblock copolymer on styrene–butadiene–styrene triblock copolymer viscoelastic properties and product performance

AbstractThe effects of the styrene–butadiene (SB) diblock copolymer on the viscoelastic properties of styrene–butadiene–styrene (SBS) triblock copolymers were examined in both in the the neat state and within specific product applications. The addition of the SB diblock copolymer into a pure SBS triblock copolymer resulted in a significant decrease in the plateau storage modulus and a quantitative linear rise in tan delta. In a pure triblock, in which all endblocks are anchored in polystyrene domains, all entanglements are physically trapped. The SB diblock embodies untrapped polybutadiene endblocks that are able to relax stress by chain reptation through the rubbery polybutadiene matrix. The SB diblock copolymer quantitatively lowered the microphase separation temperature (MST) of the SBS triblock copolymer. These changes in linear viscoelastic behavior manifest themselves into a reduction in the efficiency and performance of the SBS triblock copolymer in asphalt pavement binders and hot‐melt adhesive blends. Specifically, the SB diblock diminished the complex shear modulus and elasticity of a polymer‐modified asphalt, which translated into lower predicted rutting specification values. The increase in diblock content altered the viscoelastic response of the hot‐melt adhesive blend, translating into a reduction in the shear holding power and shear adhesion failure temperature. The lack of network participation, coupled with the relaxation of the polybutadiene endblocks, accounts for the lower strength and greater temperature susceptibility of the diblock‐containing systems. © 1995 John Wiley &amp; Sons, Inc.

Free surface morphology of block copolymers: 1. Styrene-butadiene diblock copolymers

The topology and morphology of the free surface of styrene-butadiene diblock copolymers were investigated by transmission electron microscopy as functions of molecular weight, composition, diene configuration, casting solvent and solvent evaporation rate. It was found that in solvent-cast thick films the formation of equilibrium free surface depends on a delicate balance of kinetic and thermodynamic parameters. Fast evaporation rates induce orientation of lamellar and cylindrical microdomains perpendicular to the free surface, while slow rates produce equilibrium-like domain orientation, parallel to the free surface. Molecular mechanisms of such arrangements are discussed, and it is concluded that to rapidly obtain an equilibrium free surface, the difference between critical surface tensions of polystyrene (PS) and polybutadiene blocks must be the greater the higher the affinity between the casting solvent and the block (PS) with the higher critical surface tension.

Micelle growth and clustering in blends of polystyrene and styrene-butadiene diblock copolymer

Abstract This paper presents an investigation of the morphology of blends containing 5 wt% styrene-butadiene diblock copolymer in a high-molecular-weight polystyrene matrix. Different samples of these blends were prepared by melt compounding in an extruder and by solvent casting. Transmission electron microscopy was used to determine their morphology. The extruded blend contained well dispersed, disc-shaped micelles of the diblock. The morphology of the solvent-cast blend was strikingly different, with onion-skinned structures of diblock copolymer that spanned up to several micrometres. However, upon annealing at 200°C, the morphology of the extruded blend and of the solvent-cast blend evolved towards the same relaxed state. The micelles became more spherical, grew in size and slowly agglomerated into cluster formations. The kinetics of this evolution were observed for the extruded blend. Micelle growth and clustering rates at 200°C and also at 180°C were determined by characterizing their size, shape and spatial distribution. The micelles became more spherical quickly and formed clusters over a longer time period. The changes in micelle shape became apparent in blends annealed at 180°C for as little as 5 min. The micelle clustering, however, was only evident in the blends annealed at 200°C. The rate of clustering was quantified by plots of nearest-neighbour distributions at different times. Analysis of these plots indicates a diffusion mechanism for the clustering. The results seem to support theoretical assertions of Semenov on dynamics of block-copolymer micelles in a high-molecular-weight polymer matrix.

Catenoid-lamellar phase in blends of styrene-butadiene diblock copolymer and homopolymer

A new morphology is observed in a blend of a symmetrical (lamellar) styrene-butadiene diblock copolymer and a styrene homopolymer, in which the two blocks and the homopolymer all have approximately the same molecular weight of 25000. This morphology is associated to the catenoid-lamellar (CL) structure recently discussed in the literature. The CL phase contains lamellae where the layers of component A are penetrated by channels of component B, and the shape of the interphase dividing-surface resembles a minimal surface based on revolution of a catenary about the central axis of the channel

Rheological properties of copolymer modified polyethylene/polystyrene blends

In this study, the effect of hydrogenated styrene butadiene diblock copolymers on the rheological properties of high‐density polyethylene (HDPE)/high impact polystyrene (HIPS) blends is investigated. The blends were prepared in the melt state at 180 °C for 5 min in a batch mixer. The results show that the rheological properties of the blends were very sensitive to the copolymer concentration present in the blend mainly in the low frequency region. At low copolymer content (e.g., 1 wt. %), an important decrease of the zero‐shear viscosity (η0) was observed in the case of HIPS rich blends. For the HDPE rich blends, this decrease was not observed when modified with the pure diblock copolymer. As the copolymer content increases, and depending on the copolymer structure, an increase or a further decrease of η0 was obtained. This behavior was interpreted as due to the change in the copolymer state in the blend, i.e., saturation of the interface and micelles formation. Predictions of an emulsion model of two viscoelastic liquids including an interfacial tension (σ) contribution to the elastic properties were close to the experiments for the 90/10 and 20/80 HDPE/HIPS unmodified blends, but unsatisfactory in the other cases. According to the general features of polymer suspensions and to the predictions of this model, it is concluded that phase interactions as produced by the addition of the copolymer are very important. This aspect must be included in any rheological model for copolymer modified immiscible blends.

Diffusion motions and microphase separation of styrene-butadiene diblock copolymer in solution. 2. Behavior in n-decane in the dilute solution region

Diffusion motions and microphase separation of styrene-butadiene diblock copolymer in solution. 2. Behavior in n-decane in the dilute solution region

Geometrical constraints on microstructural development in block copolymer ultrathin films

The fact that microstructures form in microphase-separated block copolymers, endowing the materials with unique thermo-mechanical properties, is well-established. However, no thermodynamic theories directly address the problem of microstructural development in ultrathin films, which might be useful as adhesives or resists. To predict the microstructural dimensions in such films, a model based on unit-cell geometries and material/volume balances is developed. Predictions of the ratio of the characteristic length of the domain core to domain repeat distance are obtained for poly (styrene-butadiene) diblock (SB) copolymers at 298 K. The finite interphase region is included in the volume balances with the parameterf, the volume fraction of interphase material, obtained from a modified version of the Leary-Henderson-Williams thermodynamic theory and shown here not to be a strong function of composition. An approach, implementingf, for accurately estimating the critical molecular weight of microphase separation in the strong-segregation limit (Mc), as a function of bulk composition for monodisperse SB copolymers at 298 K, is also presented.

Effect of molecular weight of added polystyrene on the order-disorder transition of styrene-butadiene diblock copolymer

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEffect of molecular weight of added polystyrene on the order-disorder transition of styrene-butadiene diblock copolymerShuichi Nojima and Ryong Joon RoeCite this: Macromolecules 1987, 20, 8, 1866–1876Publication Date (Print):August 1, 1987Publication History Published online1 May 2002Published inissue 1 August 1987https://doi.org/10.1021/ma00174a029RIGHTS & PERMISSIONSArticle Views242Altmetric-Citations48LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts Get e-Alerts

Small-angle x-ray scattering study of micelle formation in mixtures of butadiene homopolymer and styrene-butadiene block copolymer. 2. Effects of block lengths

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSmall-angle x-ray scattering study of micelle formation in mixtures of butadiene homopolymer and styrene-butadiene block copolymer. 2. Effects of block lengthsDavid Rigby and Ryong Joon RoeCite this: Macromolecules 1986, 19, 3, 721–728Publication Date (Print):March 1, 1986Publication History Published online1 May 2002Published inissue 1 March 1986https://doi.org/10.1021/ma00157a040RIGHTS & PERMISSIONSArticle Views283Altmetric-Citations41LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts Get e-Alerts

Small-Angle X-Ray Scattering Study of Microand Macro-Phase Separations in Blends of Block Copolymer with Homopolymer

AbstractThe order-disorder phase transition behavior exhibited by blends of a styrene-butadiene diblock copolymer (76% styrene) with a polystyrene of various molecular weight (from 2,200 to 50,000) is studied by means of small-angle X-ray scattering. With a polystyrene of a relatively short chain length the blend, on lowering the temperature, undergoes a microphase separation, and the scattering curve shows a peak at a finite scattering angle. With a polystyrene of relatively long chain length, the scattered intensity curve shows additional low angle component with intensity increasing rapidly as q→0, and this is interpreted in terms of the macrophase separation accompanying the transition from the disordered to ordered phase.

Entanglement in polymer blends: A manifestation of polymer effects

Viscoelastic behavior of binary blends of narrow molecular-weight-distribution (MWD) polystyrenes (PS) of low and high molecular weights (coded as 1- and 2-chains, respectively) and of styrene-butadiene diblock copolymers (SB) and polybutadienes (hB) is analyzed in terms of the tube theory to elucidate the effects of entanglement by examining the relaxation modes exhibited by these blends. The results suggest that PS/PS blends exhibit the reptation, tube renewal and Rouse modes, and SB/hB blends the path breathing the tube renewal modes, depending on the molecular weights, the molecular weight ratios, and the composition of the blends. The onset of entanglement in monodisperse (flexible-linear) polymers may be interpreted as a change in the relaxation mode from Rouse to reptation occuring as a result of competition between the Rouse, reptation and tube renewal modes.

Thermal degradation of styrene-butadiene diblock copolymer: Part 2—Characteristics and mechanism of degradation of the copolymer

The degradation behaviour of the copolymer has been studied under programmed heating conditions and isothermally at 380°C and compared with the characteristics of the degradation of polystyrene (PS), polybutadiene (PB) and a 1:1 by weight blend of the homopolymers, under the same conditions. The degradation shows many similarities to that of the blend. Evolution of styrene from the PS sections is at first inhibited by early volatile products from the PB parts of the chains and is subsequently retarded by other products. The extent of these stabilisation effects is greater in the copolymer than in the blend. In consequence, greater amounts of PS and PB chain structures can persist to higher degradation temperatures than in the case of homopolymer or blend: this explains the considerably higher proportion of toluene in the volatile products and the greater extent of aromatisation of the PB chain fragments.

Small-angle x-ray scattering study of micelle formation in mixtures of butadiene homopolymer and styrene-butadiene block copolymer

Abstract : The small-angle X-ray scattering technique is utilized to study the formation of micelles in mixtures containing polybutadiene homopolymer (Mn = 2350) with much smaller amounts (0.5 to 8 wt%) of styrene-butadiene diblock copolymer (Mn = 25000, 52.2 wt% styrene). The following quantities, characterizing the structure of the micelle core consisting of styrene blocks swollen with polybutadiene, have been evaluated as a function of temperature and the copolymer concentration: the radius of gyration of the core, the degree of swelling of the core, the number of block copolymer molecules forming a micelle, and the volume of a core. In addition, the critical micelle concentration (i.e., the minimum copolymer concentration necessary for micelle formation) and the number density of micelles as a function of the concentration were also determined. The degree of swelling of micelle cores by polybutadiene increases steadily with increasing temperature. The micelle core size is fairly independent of the concentration and, as the temperature is raised, at first remains unchanged but then increases rapidly before it finally dissolves completely. The temperature of dissolution increases with concentration of the copolymer. The micelle core volumes, determined by two independent methods (one by the Guinier analysis and the other from the ratio I(O)/Q), agree well with each other.

Statistical mechanical theory of deformation of liquid crystalline structure in styrene-butadiene diblock copolymers in n-tetradecane

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStatistical mechanical theory of deformation of liquid crystalline structure in styrene-butadiene diblock copolymers in n-tetradecaneHiroshi Watanabe and Tadao KotakaCite this: Macromolecules 1983, 16, 11, 1783–1789Publication Date (Print):November 1, 1983Publication History Published online1 May 2002Published inissue 1 November 1983https://doi.org/10.1021/ma00245a018RIGHTS & PERMISSIONSArticle Views53Altmetric-Citations9LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (867 KB) Get e-Alerts Get e-Alerts