Block Copolymer Composition Research Articles

Aspects of the synthesis of poly(styrene-b-isobutylene-b-styrene) block copolymers using living carbocationic polymerization

The effect of the time of styrene addition on the composition of SBS block copolymers synthesized using a dicumyl chloride/TiCl 4 /pyridine initiating system and the sequential addition of monomers was inveatigated at-80°C. It was found that the addition of styrene at an isobutylene (IB) reaction time significantly exceeding the time necessary for complex IB consumption results in contamination of the material with a substantial amount of homo-PS. Conversely, the addition of styrene to PIB chains formed under conditions of intermediate IB conversion resulted in a very slow buildup in molecular weight after the addition of styrene

IBR Block Copolymers as Compatibilizers in NR/BR Blends

Abstract The effect of the addition of 1,4-polyisoprene-1 ,4-polybutadiene (IBR) block copolymers on polymer compatibility and vulcanizate properties of a natural rubber/cis-1,4-polybutadiene rubber blend is studied. Differential scanning calorimetry and transmission electron microscopy are used to determine the degree of polymer compatibility and vulcamzate properties are measured in a sulfur cured, carbon-black filled rubber compound Block copolymer composition, concentration and molecular weight are found to be critical. Improvements in compatibility and vulcamzate properties are observed at low concentrations of IBR block copolymers.

The mechanical properties of short fiber‐styrenic block copolymer composites

AbstractThe effect of fiber loading, fiber length, matrix type, and interface adhesion on mechanical properties of PET short fiber‐styrenic block copolymer TPEs, SIS, and SBS, was investigated. A strong bonding between PET fiber and TPE was obtained by surface treatment of TPE with isocyanate in toluene solution. The stress of the composites, filled with treated fiber, increased with increasing strain by two steps; the modulus for the first step was higher than the one for the second step, and the composites yielded obviously at about 50% strain, with higher stress than that of matrix TPE. With increasing fiber loading and fiber length, the modulus for the first step and the yield stress increased, but the yield elongation decreased. It seems that the matrix elastomer underwent most of the deformation and that the filled fiber underwent large internal stress with little deformation during extension of the composite, which may be an important phenomenon to influence short fiber reinforcement. The stress softening of composites showed a somewhat larger decreased rate than that of the matrix with repeated stress‐strain cycles, and the stress softening in the first cycle increased linearly with increasing fiber loading and increased in an S shape with increasing fiber length. In comparison with the SIS elastomer, the hysteresis of the SBS elastomer showed a big residual strain after the first elongation of 30%, and its retraction and subsequent re‐extension curves were obviously different from the extension curve, which was considered to be due to the destruction of parts of the styrene hard domai in SBS. The stress softening of the composites was influenced by the matrix elastomer, as well as by the loading fiber. The interface separation around the end of a fiber under large strain, and the breaking and restructuring of hard domain in the matrix, were considered to be important sources of softening of the composite. © 1993 John Wiley & Sons, Inc.

A GPC method to determine the composition of two component copolymers

The overall composition of random and block copolymers comprising two kinds of repeat units can be determined as a function of molecular weight by a new dual (e.g., UV and RI) detector GPC technique, if one of the repeat units can be specifically “seen” by one of the detectors. The method is demonstrated by the use of random copolymers of styrene (St) and isobutylene (IB) as the UV “visible” and “invisible” components, respectively. Novel triblock copolymers comprising two polyacenaphtylene (PAc) outer-segments and a polyisobutylene (PIB) mid-segment are also analyzed.

Rheology, composition, and peel‐mechanism of block copolymer–tackifier‐based pressure sensitive adhesives

AbstractThree samples of styrene–isoprene–styrene (S–I–S) block copolymers were chosen; copolymer A had 25% styrene, and copolymers B and C had 14% styrene. Copolymers A and B contained 20% diblock polymer and copolymer C contained 40% diblock polymer. All copolymers were mixed with a terpene type tackifier to make 56% and 48% weight tackifier concentration. These represent our model samples of pressure sensitive adhesives. The determination of tack, room‐temperature peel‐strength, and failure temperature under static shear were performed. The above results have been interpreted with the basic rheological data. The dynamic viscoelastic measurements and tensile stress–strain measurements were used. The effects of tackifier on the rubbery plateau moduli were treated with the Guth–Gold‐type equation. The implications of the deviation from the equation are discussed in terms of the connectivity between polystyrene domains and the stability of the hard domains affected by inclusion of rubber segments.

Theory of supermolecular structures in polydisperse block copolymers: 5. New double cylindrical structure in binary mixture of cylinder-forming diblock copolymers

Analytical self-consistent field theory of superstructure formation in a binary mixture of cylinder-forming diblock copolymers in the strong segregation limit is developed. It is shown that for the case when both components of the mixture are ‘quasi-isomorphous’, i.e. when the domain-forming blocks of the components are different, several types of supermolecular structure are possible depending on the composition of the mixture. The possible types of structure are: mixed cylindrical structure (C), mixed lamellar structure (L), two cylindrical structures (C + C′) formed by individual components of the mixture, and, finally, a new double cylinder structure (CC′), formed by cylindrical domains of one component coated by cylindrical layers of another component. Stability ranges of these structures are investigated for different compositions of block copolymers and mixture content.

Diode-array detection with spectral suppression in size exclusion and adsorption chromatography for rapid evaluation of chemical composition in block copolymers of styrene and methyl methacrylate

Diode-array detection has been applied to evaluate the chemical composition of block copolymers from chromatographic data. Two different modes of chromatography have been used for separation: size exclusion chromatography and adsorption chromatography, based on tertiary mixed eluents, comprising tetrahydrofuran, acetonitrile and dichloromethane on a microcolumn, packed with 5 μm wide-pore silica gel (mean pore size 300 Å). U.v. spectral data acquired on-line were manipulated to generate spectral suppression chromatograms in order to selectively detect each component of a block copolymer chromatographed under both size exclusion and critical thermodynamic conditions. The content of polystyrene and poly(methyl methacrylate) residues in a series of model block copolymers of nominally constant composition (∼ 1:1, w/w), but differing in molecular weight, could be rapidly determined by this novel combination of chromatographic selectivity enhanced by digital discrimination. Thus, diode-array detection has significant potential for fast on-line monitoring of polymer processing.

Compatibilizing effect of block copolymers in heterogeneous polystyrene/poly(methyl methacrylate) blends

The morphology of heterogeneous polystyrene/poly(methyl methacrylate) (PS/PMMA) blends has been modified by the addition of diblock copolymers of PS and PMMA and investigated as a function of block copolymer composition, molecular weight and concentration by optical and electron microscopies. A sharp decrease in dispersed phase dimension is observed with the addition of a few per cent of block copolymers having equal segmental mass (50/50 PS/PMMA), followed by a levelling off as the copolymer content is increased above the critical micelle concentration. For concentrations below the critical value, the particle size reduction is linear with copolymer volume fraction and agrees well with the predictions of Noolandi and Hong. The compatibilizing efficiency of the copolymer is strongly dependent on its composition and molecular weight. The effects of processing conditions, such as casting solvents and compression moulding, on the phase morphology have also been studied. Finally, the conformation of the copolymer at the interface is discussed with the help of models: calculations based on the experimental results indicate that the compatibilizer is neither located entirely at the interface, nor penetrates completely into the corresponding homopolymer phases.

Synthesis of block copolymers by heterogeneously initiated emulsion polymerization

The contribution refers to the possibility of using emulsion polymerization of styrene, initiated by a heterogeneous initiator Chydroperoxide of isotactic powdered polypropylene) in the presence of a complex type activator, for the synthesis of block copolymers. Vinylmonomers with various water-solutibility, i.e. methyl methacrylate (MMA), acrylonitrile (AN) and maleic anhydride (MA), were utilized as comonomers of styrene. It was found that at the used conditions, the composition of block copolymers PS-b-P(S/AN) and PS-b-PCS/MA) can be varied by the time of polymerization of the first or second comonomer. The block copolymers were characterized by their molecular weight, and their thermal stability was also investigated.

Microphase Separation in Triblock Copolymer Melts

AbstractPhase diagrams of the microphase morphologies for triblock copolymer melts are calculated for the weak segregation limit. The diagrams are found to be highly asymmetric with block copolymer composition.

Emulsifying effects of block copolymers in incompatible polymer blends

AbstractWe discuss some theoretical aspects of interfacial and emulsifying activity of block copolymers A‐B in incompatible blends of homopolymers A and B. We predict the reduction in interfacial tension due to equilibrium adsorption of copolymers at the interface. It is shown that for an appropriate choice of block copolymer composition and molecular weight a very low interfacial tension can be achieved. This suggests a possible existence of a thermodynamically controlled stable droplet phase in which minority homopolymer particles protected by an interfacial film are suspended in a majority homopolymer matrix. The size distribution of the droplets depends on the rigidity and spontaneous radius of curvature of the interfacial film which, as we show, can be controlled by molecular parameters of copolymers.

Effect of sample history on phase separation and crystallization in block-copolymers with two crystallizing components

Phase composition and crystallization of polyamide-polyethyleneoxide block copolymers were studied by the calorimetric method. The components of these heterogeneous systems are mutually insoluble in the composition and temperature ranges studied. In crystallization studies, strong mutual effects of the components were observed. The largest changes occurred in PEO, as manifested by atypical low-temperature crystallization, as well as by a pronounced dependence of block-copolymer properties on sample history.

Characterization of ABA block copolymers polystyrene-poly(γ-benzyl- l-glutamate) by Fourier transform infrared spectroscopy

The composition of ABA block copolymers polystyrene-poly(γ-benzyl- l-glutamate) was determined by Fourier transform infrared spectroscopy. This could be achieved by establishing a calibration curve of the integrated intensity of the NH stretching band of α-helical poly(γ-benzyl- l-glutamate) between 3137 and 3550 cm −1 as a function of concentration. There is a fairly good agreement between the composition values obtained by FTIR and those obtained by elemental nitrogen analysis.

Monte Carlo simulation study of the polymerization of polyurethane block copolymers: 3. Modelling of premature phase separation during reaction and differing reactivities of the chain extender and polyol using the simple sinking pool model

Because of the complexities involved in polyurethane reaction chemistry and the difficulties encountered in making experimental measurements, relatively little attention has been paid to determining the precise molecular weight, composition and hard-segment length distributions of polyurethane block copolymers. Yet, the available evidence suggests that variations in these distributions can markedly influence structure-property relationships in these materials. Therefore, computer models have been developed using Monte Carlo methods that allow for simulation of the polymerization process under various conditions and subsequent calculation of the various distributions. The model developed in this contribution is based on a sinking pool of monomers and is thus termed the simple sinking pool model. This model offers several advantages over previous models; in particular it can simulate effects due to differing reactivity of the chain extender and the polyol, and effects due to phase separation occurring at varying points in the reaction. The model and rationale behind the inclusion of the various parameters are described, and the effects of varying the model parameters on the simulated composition, molecular weight and hard-segment length distributions are determined and discussed.

The synthesis, structure and properties of triblock methylthiirane-arylene imide block-copolymers

Oligomethylthiirane with M = 1000 and a terminal amino group participates in poly-condensation with dianhydrides and diaminodiphenyl ether, forming triblock oligomethylthiirane-imide-oligomethylthiirane block-copolymers. The stages of oligomethylthiirane production have been studied as well as the influence of its recovery and storage conditions on block copolymer yield and composition. That block-copolymers are formed is proved by turbidimetric titration. A solvent mixture was suggested for the separation of the homopolyamide acid. The molecular characteristics of one sample have been determined. The methylthiirane block was shown to stabilize the polyamic acid during storage of the block-copolymer in solution.

Study of surface composition and morphology of block copolymers of bisphenol A polycarbonate and poly(dimethylsiloxane) by x-ray photoelectron spectroscopy and ion scattering spectroscopy

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStudy of surface composition and morphology of block copolymers of bisphenol A polycarbonate and poly(dimethylsiloxane) by x-ray photoelectron spectroscopy and ion scattering spectroscopyRobert L. Schmitt, Joseph A. Gardella Jr., Joseph H. Magill, Lawrence Salvati Jr., and Roland L. ChinCite this: Macromolecules 1985, 18, 12, 2675–2679Publication Date (Print):December 1, 1985Publication History Published online1 May 2002Published inissue 1 December 1985https://doi.org/10.1021/ma00154a051RIGHTS & PERMISSIONSArticle Views279Altmetric-Citations102LEARN 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 (666 KB) Get e-Alerts Get e-Alerts

Determination of the composition of polycarbonate dimethylsiloxane block copolymers

A method based on IR spectroscopy has been developed for determination of the composition of block copolymers containing dimethylsiloxane and polycarbonate oligomers. Discrepancies between the IR and the NMR data do not exceed 6%. By comparing the data obtained with the ratio of degrees of polycondensation of the initial copolymers deductions may be made regarding the character of the end blocks, and sometimes in regard to the MW of the block copolymers.

Permeability of silane-siloxane block-copolymers to hydrocarbons

The coefficients of diffusion, D, and permeability, P, of saturated and unsaturated C 1–C 4 hydrocarbons have been measured in type AB and type BAB block-copolymers of vinyltrimethylsilane and hexamethylcyclotrisiloxane. The values of D and P rise rapidly as the siloxane concentration in the block-copolymer is increased. The curves for P and D as a function of composition are compared with the predictions of various morphological models of the block-copolymer. Features of the dependence of P and D on the block-copolymer's composition enable it to be postulated that the transfer of the various hydrocarbon molecules in a heterophase block-copolymer occurs by diverse diffusion paths.

Precipitation fractionation of block copolymers

Possibilities offered by classical precipitation fractionation in the preparative separation of polymer admixtures from block copolymers and in an estimate of the polydispersity in molar mass and of the heterogeneity in chemical composition of block copolymers have been examined. A mixture of a two-block copolymer, polystyrene-block-polyisoprene, with polystyrene was separated in the systems cyclohexane/1-propanol and 1,4-dioxan/1-propanol, and a mixture of three two-block styrene-isoprene copolymers having different chemical composition was fractionated in the system benzene/methanol. In the cyclohexane/1-propanol system, two commercial samples of three-block copolymers polystyrene-block-poly(ethene-co-butene)-block-polystyrene and their mixture were fractionated. The results showed that the polydispersity and chemical heterogeneity thus estimated are much lower than the real ones, especially due to the colloid properties of block copolymers.

The crystallization kinetics of polyblock polyarylene sulphonoxide-polyethylene oxide block copolymers

The crystallization of polyblock polyarylene sulphonoxide-polyethylene oxide block copolymers has been studied and the strong influence of the block copolymer composition on PEO crystallization established. For both block copolymers with PEO ( M=40,000) and PEO homopolymers, no change in crystallization regime is noted, whilst for low molecular weight PEOs, transitions from regime II to regime I (for small degrees of supercooling) and to regime III (for large degrees of supercooling) were observed. The transition from regime II to regime III for PEO in block copolymers possesses certain features, explained by the presence of chemical bonding of the ends of the crystallizing molecules with the amorphous component.