Polystyrene Triblock Copolymer Research Articles

Synthesis and characterization of (star po1ystyrene)- block - (linear polydimethylsi1oxane)- block -(star polystyrene) triblock copolymers

(Star po1ystyrene)-block-(linear polydimethy1siloxane)-block-(Star polystyrene) triblock copolymers were synthesized by making living Star-shaped polystyrenes through a convergent living anionic polymerization procedure, followed by ring-opening polymerization of hexamethylcyclotrisiloxane (D3) then difunctional coupling. The molecular weights of the resulting polymers were characterized by gel permeation chromatography (GPC), multi angle laser light scattering (MALLS) and 1H NMR spectroscopy. Triblock copolymers with relatively narrow molecular weight distributions were obtained.

Synthesis of amphiphilic triblock copolymer of polystyrene and poly(4-vinylbenzyl glucoside) via TEMPO-mediated living radical polymerization

4-Vinylbenzyl glucoside peracetate 1 was polymerized with α,α′-bis(2′,2′,6′,6′-tetramethyl-1′-piperidinyloxy)-1,4-diethylbenzene 2 in chlorobenzene using (1 S)-(+)-10-camphorsulfonic acid anhydrous (CSA) as an accelerator ([ 1]=0.4 M,[ 1]/[ 2]/[CSA]=75/1/1.3) at 125 °C for 5 h. The polymerization afforded poly(4-vinylbenzyl glucoside peracetate) having TEMPO moieties on both sides of the chain ends, 3, with a molecular weight ( M w,SLS) of 8500, a polydispersity index ( M w/ M n) of 1.09, and an average degree of polymerization of the 1 unit ( x) of 17. Styrene (St) was polymerized with 3 in chlorobenzene at 125 °C (St/chlorobenzene=1/2, w/w). The polymerization successfully afforded polystyrene–poly(4-vinyl glucoside peracetate)–polystyrene, 4, when the polymerization time was below about 2 h. Polymer 4 with the M w,SLS of 12,500, 17,900, and 29,400, the compositions ( y– x– y) of 20–17–20, 45–17–45, and 100–17–100, and the M w/ M n of 1.12, 1.14 and 1.17 were modified by deacetylation using sodium methoxide in dry-THF into polystyrene–poly(4-vinyl glucoside peracetate)–polystyrene, 5. The solubility of polymer 5 was examined using a good solvent for polystyrene such as toluene and for the saccharide such as H 2O.

Synthesis and Characterization of Neutral/Ionic Block Copolymers of Various Architectures

Near-monodisperse diblock, triblock, and multiarm star-block copolymers of polystyrene (PS) and poly(4-tert-butylstyrene) (PtBS) were synthesized using anionic polymerization techniques. Selective sulfonation of PS blocks by using the complex of sulfur trioxide (SO3) and triethyl phosphate (TEP) in 1,2-dichloroethane (DCE), followed by neutralization with sodium methoxide, was performed to yield the corresponding well-defined neutral/ionic block copolymers of sodium poly(styrenesulfonate) (NaPSS) and PtBS. A number of techniques including matrix-assisted laser desorption ionization time-of-flight mass spectroscopy (MALDI/TOF/MS), Fourier transform infrared spectroscopy (FT-IR), and nuclear magnetic resonance spectroscopy (NMR) were employed to characterize these materials.

Constrained polymer layers to reduce noise: reality or fiction?—An experimental inquiry into their effectiveness

The frequency and temperature dependent noise radiation properties of constrained polymer layered oil pans are examined through mobility and intensity measurements. Four metal/polymer/metal sandwich composites of varied thermo-plastic elastomer systems of polystyrene–polybutadiene–polystyrene triblock copolymers are investigated within a wide frequency range covering 1000–5000 Hz, and over a wide temperature range covering 20–100 °C, with results compared to those of an ordinary steel oil pan. The mobility and intensity are found to be strongly frequency and temperature dependent, displaying a substantial mobility reduction as compared to that of the ordinary pan, while using the constrained layer damping configurations at their maximum loss factor temperatures. However, the reduction of noise radiation is smaller than that of the mobility at those temperatures, mainly due to the increased radiation efficiency while adding damping materials.

Crystallization within Melt Ordered Semicrystalline Block Copolymers: Exploring the Coexistence of Microphase-Separated and Spherulitic Morphologies

The crystalline and microphase-separated morphology of semicrystalline block copolymers are compared in bulk (0.5-1 mm) and thin films (5-0 Im), as characterized by transmission electron microscopy (TEM) and polarized light microscopy (PLM). Bulk films of a triblock copolymer of polystyrene, polybutadiene, and polycaprolactone, (PS)0.35(PB)0.15(PCL)0.5, where the subscripts denote the mass fraction, show a lamellar-cylindrical microphase-separated morphology with a lamellar repeat of =62 nm, as observed by TEM. Bulk films of a diblock copolymer consisting of (PB)0.2(PCL)0.8 show an imperfect cylindrical microphase-separated structure by TEM coexisting with crystalline lamellae of PCL. For both bulk specimens, the PLM shows a speckle pattern of birefringence that confirms the PCL is crystallized within the microphase-separated structure, but no large-scale spherulites are observed by PLM. The microstructure in the as-cast thin films (5-10 Im) by TEM is lamellar-cylindrical for the triblock copolymer and cylindrical for the diblock copolymer, as described above for the bulk specimens. Upon thermal treatment of these thin films, large and well-defined PCL spherulites are observed by PLM for both block copolymers. TEM of the thermally treated triblock copolymer thin films shows that, after the formation of spherulites, the microphase structure is no longer lamellar-cylindrical but entirely dominated by PCL lamellar crystals. In contrast, TEM of the thermally treated diblock copolymer thin films shows that the PCL lamellar crystals coexist with the PB microphase-separated cylinders after the formation of PCL spherulites. Bulk specimens could not be induced to form spherulites under similar thermal treatment conditions.

Structure/property relationships in polystyrene–polyisobutylene–polystyrene block copolymers

Structure/property relationships of polystyrene–polyisobutylene–polystyrene (PS–PIB–PS) triblock copolymer made by different processes were studied using dynamic mechanical analysis (DMA). The PS–PIB–PS films were composed of approximately 30% polystyrene end-blocks. Small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) confirm that a self-assembled, segregated cylindrical morphology forms in the copolymer. DMA was used as a tool to investigate the structure–property relationships in these polymers. Modified PS–PIB–PS copolymers were also characterized. Modifications of the copolymers were carried out by conversion of approximately 20 mol% of the polystyrene end-blocks to styrene sulfonic acid. The modified copolymers exhibited distinctly different thermal characteristics than the unmodified copolymers, which were most notable in the storage modulus and tan δ data. The presence of sulfonic acid groups disrupted the morphology and solvent sorption characteristics of the copolymers. Dynamic mechanical behavior is discussed as it relates to the morphology of the PS–PIB–PS copolymers formed via different processing methods and chemical modification.

Microphase Separation in Normal and Inverse Tapered Block Copolymers of Polystyrene and Polyisoprene. 1. Phase State

We have investigated the influence of composition gradients on the microdomain structure and viscoelastic properties of tapered block copolymers by (i) varying the amount of interfacial material and (ii) the block sequence. Normal tapered and inverse tapered triblock copolymers of polystyrene and polyisoperne with a tapered midblock have been synthesized via anionic polymerization with a nearly symmetric composition and compared with the corresponding diblock copolymers. We found that increasing the amount of tapered material within the interface systematically increases the compatibility. Block sequencing is found to be an important factor controlling compatibility. Inverse tapered block copolymers are much more compatible than the corresponding normal tapered block copolymers. Results presented here could be used as a guideline for preparing copolymers with controlled compatibility at the synthesis level.

Effect of planar extension on the structure and mechanical properties of polystyrene–poly(ethylene-co-butylene)–polystyrene triblock copolymers

Two thermoplastic poly(styrene)–poly(ethylene-co-butylene)–poly(styrene) triblock copolymers containing either spherical or cylindrical poly(styrene) microdomains were pre-oriented through extensional flow. Small angle neutron scattering (SANS) measurements revealed that the pre-oriented triblock with a spherical microstructure adopts a body-centred cubic (bcc) structure with a [111] orientation along the flow direction. For the pre-oriented triblock with a cylindrical microstructure, the cylinder axis is aligned along the extensional flow direction. Investigation of the mechanical properties showed that Young's moduli of the pre-oriented copolymers are highly anisotropic. Specimens were then subject to uniaxial deformation along the extensional flow direction and at the same time microstructural changes induced by the deformation were investigated by SANS. It was found that the deformation of the bcc lattice is affine, and that the deformation of the microstructure is reversible. For the triblock copolymer with a cylindrical microdomain structure the deformation of the lattice was found to be non-affine. In this case, SANS patterns suggest a “micronecking” and a breaking of the cylindrical domains without any change in the domain spacing.

An Associative Polyelectrolyte End-Capped with Short Polystyrene Chains. Synthesis and Rheological Behavior

Polystyrene (PS) end-capped polyelectrolytes were prepared by modification of polystyrene−poly(tert-butyl acrylate)−polystyrene triblock copolymers synthesized via anionic polymerization. These amphiphilic polymers are associated in dilute aqueous solutions forming loose multimicellar clusters. At higher polymer concentrations an extensive intermicellar bridging occurs, leading to the formation of a transient network as revealed by the viscoelastic response of the system. The so-formed gel is characterized by low gel concentration, i.e., 0.2 wt %, yield stress, complex steady-shear viscosity profile, high plateau modules, and long relaxation times. These characteristics can be attributed to the highly hydrophobic character of the PS junctions and the stretched conformation of the polyelectrolyte bridges.

Thermoreversible Physical Gelation of Block Copolymers in a Selective Solvent

Solidlike and liquidlike linear viscoelastic responses were observed at low and high temperatures (T) for polystyrene−polyisoprene−polystyrene (SIS) triblock copolymers dissolved in an I-selective ...

Preparation of Telechelic Polysilylenes: A General Methodology for the Synthesis of Polysilylene-Based Triblock Copolymers

Telechelic polysilylenes have been developed involving the chemical degradation of poly(di-n-hexylsilylene) with bromine. The molecular weight of the newly formed telechelic PDHS depends on the ratio of bromine to the starting PDHS. The percentage of end groups increases as the molecular weight of the telechelic PDHS is lowered, reaching a maximum of 99% difunctionality. Polystyrene−PDHS−polystyrene triblock copolymers have been prepared by coupling polystyryllithium to the telechelic PDHS in the presence of cryptand [2.1.1]. The effect of molecular weight on the disordering transition of PDHS into a columnar mesophase has been studied, and temperature and enthalpy have been shown to decrease by the presence of the PS end groups and eventually became unobservable at high fractions of PS. The morphologies of the triblock copolymers were studied by atomic force microscopy.

Microstructure of Ionomers Based on Sulfonated Block Copolymers of Polystyrene and Poly(ethylene-alt-propylene)

Block copolymer ionomers were prepared by lightly sulfonating the polystyrene (PS) blocks of diblock and triblock copolymers of PS and poly(ethylene-alt-propylene) (PEP), followed by neutralization of the sulfonic acid groups with either sodium or zinc. The block copolymers contained between 10 and 50 wt % PS, and as the PS content increased, the mesophase texture varied from PS spheres to hexagonal-close-packed (hcp) PS cylinders to alternating PS and PEP lamellae. The sulfonation level was varied from 1 to 17 mol % of the styrene repeat units, which provided a range of functionalization (NS) of between 2 and 9 sulfonate groups per molecule. The microstructure was analyzed by small-angle X-ray scattering (SAXS) and dynamic mechanical thermal analysis (DMTA). An ion-rich microphase formed within the PS microdomains, and that hindered the development of a well-ordered block texture. Sulfonation of a diblock copolymer containing ca. 20 wt % PS resulted in a transition of the block microphase texture from a hcp to lamellar. The order-to-disorder transition temperature, TODT, of the block copolymer was relatively insensitive to the choice of the cation, and TODT increased as NS increased.

Solubility of Poly (phenylene ether) to Polystyrene-<i>block</i>-polyethylenebutylene-<i>block</i>-polystyrene Triblock Copolymers

Polystyrene-block-polyethylenebutylene-block-polystyrene (SEBS) triblock copolymers are widely utilized as thermoplastic elastomers. In this study, solubilization of poly (phenylene ether) (PPE) into polystyrene (PS) microdomains was examined in order to improve the heat resistance of the SEBS triblock copolymers, where the PPE homopolymer has a higher glass transition temperature than PS and is generally known to be totally miscible with PS homopolymers with any composition. An ordinary solvent-cast method was employed for the sample preparation. As a result, macroscopic phase separation took place, although a small quantity of PPE was blended. The macroscopically phase-separated structures and microphase-separated structures were analyzed by the small-angle X-ray scattering technique and complementarily by the transmission electron microscopic observation. An appreciably broad interface between the macroscopically phase-separated domains was observed in SEBS/PPE solvent-cast samples. Based on the assumption that the cast solvent is more or less accumulated in the interface, the mechanism of forming such a broad interface is presented.

Impact and tensile properties of SEBS copolymer compatibilized PS/HDPE blends

In this study, polystyrene–hydrogenated polybutadiene–polystyrene (SEBS) triblock copolymer was used as a compatibilizer for the blends of polystyrene (PS) and high-density polyethylene (HDPE). The morphology and static mechanical and impact properties of the blends were investigated by means of scanning electron microscopy, uniaxial tension, and instrumented falling-weight impact measurements. Tensile tests showed that the yield strength of the PS/HDPE/SEBS blends decreases considerably with increasing HDPE content. However, the elongation at break of the blends tended to increase significantly with increasing HDPE content. The excellent tensile ductility of the HDPE-rich blends resulted from shield yielding of the matrix. Charpy impact measurements indicated that the impact strength of the blends increases slowly with HDPE content up to 50 wt %; thereafter, it increases sharply with increasing HDPE content. The impact energy of the HDPE-rich blends exceeded that of pure HDPE, implying that the HDPE polymer can be further toughened by the incorporation of brittle PS minor phase in the presence of SEBS compatibilizer. The correlation between the impact property and morphology of the blends is discussed. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1099–1108, 1998

Impact and tensile properties of SEBS copolymer compatibilized PS/HDPE blends

In this study, polystyrene–hydrogenated polybutadiene–polystyrene (SEBS) triblock copolymer was used as a compatibilizer for the blends of polystyrene (PS) and high-density polyethylene (HDPE). The morphology and static mechanical and impact properties of the blends were investigated by means of scanning electron microscopy, uniaxial tension, and instrumented falling-weight impact measurements. Tensile tests showed that the yield strength of the PS/HDPE/SEBS blends decreases considerably with increasing HDPE content. However, the elongation at break of the blends tended to increase significantly with increasing HDPE content. The excellent tensile ductility of the HDPE-rich blends resulted from shield yielding of the matrix. Charpy impact measurements indicated that the impact strength of the blends increases slowly with HDPE content up to 50 wt %; thereafter, it increases sharply with increasing HDPE content. The impact energy of the HDPE-rich blends exceeded that of pure HDPE, implying that the HDPE polymer can be further toughened by the incorporation of brittle PS minor phase in the presence of SEBS compatibilizer. The correlation between the impact property and morphology of the blends is discussed. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1099–1108, 1998

Microstructure of block copolymers of polystyrene and poly(ethylene- alt-propylene)

The microstructure and microphase behaviour of diblock ( M a ≈ 27 and 50 kg mol −1) and triblock ( M a ≈ 50kg mol −1) copolymers of polystyrene (PS) and poly(ethylene- alt-propylene) (PEP) were studied by small angle X-ray scattering (SAXS), transmission electron microscopy (TEM) and dynamic mechanical thermal analysis (DMTA). The composition was varied from 10 wt.% to 50 wt.% PS. The morphology of solution-cast and compression-moulded samples was compared. The common packing arrangements of body-centred-cubic (BCC) spheres, hexagonal-close-packed (HCP) cylinders and alternating lamellae were observed for the PS microdomains using SAXS and TEM. A microphase texture of PS spheres with a liquid-like packing (LLP) was obtained at lower molecular weight and PS content. Coexisting textures of LLP spheres and HCP cylinders of PS were observed in a triblock copolymer with low PS content. An order—order transition between conventional lamellar and perforated lamellar textures was detected in a nearly-symmetric triblock copolymer. Conventional order—disorder transitions were identified for most of the other polymers using DMTA and temperature-resolved SAXS.

Morphological Development in Solvent-Cast Polystyrene−Polybutadiene−Polystyrene (SBS) Triblock Copolymer Thin Films

This paper describes morphological development in solvent-cast polystyrene (PS)−polybutadiene (PB)−polystyrene (SBS) triblock copolymer thin films (30 wt % PS) as a function of solvent evaporation ...

Nanoscale Patterning of BaTiO3 on Block Copolymers

Nanoscale pattering of inorganics can be facilitated by using complex fluids as templates. One such approach is to use block copolymeric nanodomains in solid films (< 50 nm) as the template for patterning ceramic clusters with desired shapes and orientations. For instance, we use a triblock copolymer of polystyrene (PS) -polybutadiene (PB) - polystyrene (PS) - Kraton Dl 102® (MW = 71,000 and PS/PB = 28%/78%) as a template material to pattern barium titanate for energy storage applications. The important features of our approach are that (i) the interdomains of PBs in the preformed solid thin films are chemically OH-functionalized in situ, and (ii) the barium titanate precursors are solely localized within and reacted to the interdomains of PBs in solid thin films by condensation.Thin films were prepared by spin casting a 1% w/w Kraton D1102®/toluene solution on a coverglass. Thin films were transferred to gold TEM specimen grids by the water lift off method.

Junction Point Fluctuations in Microphase Separated Polystyrene−Polyisoprene−Polystyrene Triblock Copolymer Melts. A Dielectric and Rheological Investigation

Dielectric spectroscopy is employed in two polystyrene−polyisoprene−polystyrene (SIS) triblock copolymers well below the order-to-disorder transition temperature and in the frequency range from 10-2 to 106 Hz. Small angle X-ray scattering has shown the formation of lamellar structures with a long period of about 25 nm. Besides the polyisoprene and polystyrene segmental relaxations and a slower process associated with the reorientation of the interface, we provide evidence for a new type of chain dynamics associated with the mobility of the junction points at the interface. From the relaxation strength of this processwhich is very much reduced as compared to the chain relaxation in bulk polyisoprenewe extract a characteristic length of the end-to-end vector fluctuations in the interface in the range 4−6 nm. This value compares well with an independent estimate of the interfacial thickness based on thermodynamics. Dielectric spectroscopy can therefore be used as a dynamic probe of the interface in ordered triblock copolymers. Over the same temperature range rheology is influenced by a broad spectrum of modes related to the dynamics of tethered polyisoprene chains.

Nanoscale Patterning of Barium Titanate on Block Copolymers

A triblock copolymer of polystyrene−polybutadiene−polystyrene (Kraton D1102) has been used to pattern barium titanate precursor with nanoscale modulations. The copolymer self-assembles to yield cylindrical polystyrene nanodomains in a polybutadiene matrix. The preorganized thin films of polymer are then selectively OH-functionalized in situ on the unsaturated carbon bonds in the polybutadiene matrix with antistereochemistry. Anchoring the barium titanate precursor onto the hydroxylated polymer thin films is possible only in the trans-1,2 polybutadiol matrix through the condensation between the barium titanium double alkoxides and the hydroxyl groups. The regioselective deposition of the barium titanium double alkoxides on the original polybutadiene matrix of the Kraton thin films was verified by transmission electron microscopy and electron energy loss spectroscopy. The spacing of the coordinated barium titanium double alkoxide pattern was ∼23 nm, equivalent to the interdomain spacing of the original poly...