Block Copolymers Of Polystyrene Research Articles

Systematic Alkaline Stability Study of Polymer Backbones for Anion Exchange Membrane Applications

Anion exchange membranes are an important component in alkaline electrochemical energy conversion and storage devices, and their alkaline stability plays a crucial role for the long-term use of these devices. Herein, a systematic study was conducted for the analysis of polymer backbone chemical stability in alkaline media. Nine representative polymer structures including poly(arylene ether)s, poly(biphenyl alkylene)s, and polystyrene block copolymers were investigated for their alkaline stability. Polymers with aryl ether bonds in their repeating unit showed poor chemical stability when treated with KOH and NaOCH3 solutions, whereas polymers without aryl ether bonds [e.g., poly(biphenyl alkylene)s and polystyrene block copolymers] remained stable. Additional NMR studies and density functional theory (DFT) calculations of small molecule model compounds that mimic the chemical structures of poly(arylene ether)s confirmed that electron-withdrawing groups near to the aryl ether bonds in the repeating unit acc...

Viscoelasticity and morphology of polystyrene-block-poly[ethylene-co-(ethylene-propylene)]-block-polystyrene tri-block copolymer/paraffinic oil blends. 1. Effect of oil content

We have investigated the microdomain structure and viscoelastic properties of polystyrene-block-poly(ethylene-co-(ethylene-propylene)-block-polystyrene copolymer (SEEPS-1)/paraffinic oil (Oil-1) blends. The SAXS results revealed that, with increasing oil content, the structures change from a lammelar microdomain for SEEPS-1/Oil-1 = 100/0 to a hexagonally packed cylindrical microdomain for SEEPS-1/Oil-1 = 75/25 blend, and furthermore change to a spherical microdomain packed in a cubic lattice for SEEPS-1/Oil-1 = 50/50 and 25/75 blends. SEEPS-1/Oil-1 = 100/0 and 75/25 blends held each same microdomain structure below 300 °C. In contrast, SEEPS-1/Oil-1 = 50/50 and 25/75 blends, respectively, exhibited order-disorder transition temperature (TODT) at 210–220 °C and 150–160 °C. Below TODT, the microdomain structures did not change. Corresponding to the SAXS observations, the viscoelastic responses showed that the dynamic storage modulus G′, respectively, is proportional to ω1/2, ω1/4∼ω1/3, and ω0 at low frequencies for SEEPS-1/Oil-1 = 100/0, 75/25, and 50/50 and 25/75, indicating lamellar, cylindrical, and spherical microdomains The time-temperature superposition was applicable on the ordered state, and the activation energy obtained from the shift factors was roughly independent of blend composition (in other words, microdomain structure), suggesting that the viscoelastic responses are due to the presence of defects of long range order of microdomain structures.

Multidetector thermal field-flow fractionation as a unique tool for the tacticity-based separation of poly(methyl methacrylate)-polystyrene block copolymer micelles

Poly(methyl methacrylate)-polystyrene (PMMA-PS) micelles with isotactic and syndiotactic coronas are prepared in acetonitrile and subjected to thermal field-flow fractionation (ThFFF) analysis at various conditions of increasing temperature gradients. It is shown for the first time that multidetector ThFFF provides comprehensive information on important micelle characteristics such as size (Dh), shape (Rg/Rh), aggregation number (Z), thermal diffusion (DT) and Soret coefficients (ST) as a function of temperature from a single injection. Moreover, it is found that micelles exhibit a unique decreasing trend in DT as a function of temperature which is independent of the tacticity of the corona and the micelle preparation method used. It is also demonstrated that ThFFF can monitor micelle to vesicle transitions as a function of temperature. In addition to ThFFF, it is found from DLS analysis that the tacticity of the corona influences the critical micelle concentration and the magnitude to which micelles expand/contract with temperature. The tacticity does not, however, influence the critical micelle temperature. Furthermore, the separation of micelles based on the tacticity of the corona highlight the unique capabilities of ThFFF.

Influence of Thin Film Confinement on Surface Plasticity in Polystyrene and Poly(2-vinylpyridine) Homopolymer and Block Copolymer Films

Thin block copolymer films have attracted considerable academic attention because of their ability to self-assemble into various microstructures, many of which have potential technological applications. Despite the ongoing interest, little effort has focused on the onset of plasticity and failure which are important factors for the eventual adoption of these materials. Here we use delamination to impart a quantifiable local stain on thin films of homopolymer polystyrene and poly(2-vinylpyridine), as well as block copolymers made of styrene and 2-vinylpyridine. Direct observation of the damage caused by bending with atomic force microscopy and laser scanning confocal microscopy, leads to the identification of a critical strain for the onset of plasticity. Moving beyond our initial scaling analysis, the more quantitative analysis presented here shows strain levels for thick films to be comparable to bulk measurements. Monitoring the critical strain leads to several observations: 1.) as-cast PS-P2VP has low critical strain, 2.) annealing slowly increases critical strain as microstructural ordering takes place, and 3.) similar to the homopolymer, both as cast and ordered films both show increasing critical strain under confinement.

A simple route to deuterated polystyrene block copolymers by reverse iodine transfer polymerisation

For the first time, deuterated polystyrene block copolymers were synthesized by RITP and analysed by advanced fractionation and spectroscopic methods.

Ionic liquid-mediated synthesis and self-assembly of poly(ethylene glycol)-block-polystyrene copolymer by ATRP method

Poly(ethylene glycol)-block-polystyrene (PEG-b-PS) was synthesized by the atom transfer radical polymerization of styrene using PEG-Br as the macroinitiator in an ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]). CuBr and 2,2″-bipyridyl were used as the catalyst and ligand, respectively. The structure, composition, and molecular weight of the PEG-b-PS copolymer were characterized by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, and gel permeation chromatography. The PEG-b-PS copolymer with a high molecular weight (Mn = 51,000 g mol−1) and relatively low polydispersity index (PDI = 1.35) was formed at 110 °C for 5 h. Self-assembly of this amphiphilic block copolymer in toluene at different concentrations and in dimethylformamide (DMF)/water systems was also examined. Transmission electron microscopy showed that the block copolymer formed different morphologies spontaneously according to the different solvent systems used.

DC-Driven, Sub-2 V Solid-State Electrochemiluminescent Devices by Incorporating Redox Coreactants into Emissive Ion Gels

We demonstrate a DC-driven solid-state electrochemiluminescent (ECL) device based on a solution-processable ion gel containing luminescent complexes and tetrabutylammonium oxalate (TBAOX) as a coreactant. The ECL gel, comprising a polystyrene-block-poly(methyl methacrylate)-block-polystyrene copolymer, 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl)imide ionic liquid, tris(2,2′-bipyridine)ruthenium(II) hexafluorophosphate (Ru(bpy)3(PF6)2) and TBAOX, was cast as a film on indium tin oxide-coated glass (anode) by spin-coating, and a top electrode (cathode) was prepared by brush-painting Ag paint. Application of 1.6 V DC bias across the device resulted in the onset of light emission. The maximum luminance was achieved at 1:5 mol ratio of Ru(bpy)3(PF6)2 and TBAOX, and the turn-on voltage was independent of the composition. The simplicity of the ECL device and its low voltage operation characteristics make it potentially attractive as a display element for printed electronic circuits.

Highly efficient removal of uranium (VI) from aqueous solutions using poly(acrylic acid)-functionalized microspheres

Abstract Uranium (VI) is highly toxic and radioactive in water, and may pose the great risk to human health and environment. A new adsorbent is reported here for highly efficient removal of uranyl ions from aqueous solution. Specifically, poly(acrylic acid)- block -polystyrene (PAA- b -PSt) block copolymers were synthesized as macromolecular surfactant for the emulsion polymerization of styrene. The obtained PSt microspheres had the controlled density and length of PAA chain on the surface, which lead to a controlled high adsorption capacity. The effects of pH, adsorbent dose, coexisting ions, temperature, contact time, initial concentration were evaluated on the removal of uranyl ions. Adsorption equilibrium could be achieved within 4 h, and the kinetic data could be well described by pseudo-second-order kinetics equation, and the maximum adsorption capacity calculated from Langmuir equation was ∼990 mg/g at 298.15 K and pH 4.5. This work indicates that PAA-functionalized microspheres can be used as a new adsorbent for highly efficient removal of uranium (VI) from aqueous solutions.

Poly(3-hexyl thiophene)-b-Fullerene Functionalized Polystyrene Copolymers (P3HT-b-PSFu) as Compatibilizer in P3HT/Phenyl-C61-butyric Acid Methyl Ester (PCBM) Solar Cells

Poly(3-hexyl thiophene)-fullerene functionalized polystyrene block copolymers (P3HT-b-PSFu) with a variety of block lengths and compositions were synthesized by reacting P3HT macroinitiator with styrene and chloromethyl styrene via an atom transfer radical polymerization. After that, the prepared copolymers were reacted with C60 via an atom transfer radical addition to obtain P3HT-b-PSFu. Chemical structures and molecular weights of the products were characterized by1H-NMR, FTIR, and GPC, respectively. Next, the various P3HT-b-PSFu copolymers were added to P3HT/PCBM bulk heterojunction (BHJ) polymer solar cell. It was found that efficiency increased from 0.52% to the maximum value of 1.23%, after adding the copolymers.

Polyferrocenylsilane homopolymers and diblock copolymers with pendant ruthenocenyl groups by photocontrolled ring-opening polymerisation

The strained, sila[1]ferrocenophane [{Fe(η-C5H4)2}SiMe(η-C5H4)Ru(η-C5H5)] (4) has been prepared by the reaction of Li[(η-C5H4)Ru(η-C5H5)] (8) with [{Fe(η-C5H4)2}SiMeCl] (7). Two different routes for the synthesis of 8 were investigated, which differed predominately in the purity of the product obtained. Although the thermal ring-opening polymerisation (ROP) of 4 failed to yield soluble polymeric material, photocontrolled ROP using Na[C5H5] as the initiator afforded relatively monodisperse, soluble polymers of predetermined molecular weights and the general formula [(η-C5H4)Fe(η-C5H4)SiMe{(η-C5H4)Ru(η-C5H5)}]n (19). This material was stable to both oxygen and moisture. Electrochemical characterisation of 4 revealed unusual, concentration dependent behaviour as a consequence of the oxidation of the ruthenocenyl groups. This phenomenon was not observed upon oxidation of the Ru centres in 19, presumably due to the sterically encumbered structure of the polymer. The photocontrolled ROP protocol was extended to afford the block copolymers polystyrene (PS)n-b-[(η-C5H4)Fe(η-C5H4)SiMe{(η-C5H4)Ru(η-C5H5)}]m (22) by the application of a PS-based macroinitiator. These materials represent rare examples of complex polymer architectures where two different metals are incorporated in the same block.

Lamellar Morphology in Block Copolymers of Polystyrene and Poly[methyl(3,3,3-trifluoropropyl)siloxane

Well-defined polystyrene-block-poly[methyl(3,3,3-trifluoropropyl)siloxane] (PS-b-PMTFPS) diblock copolymers and polystyrene-block-poly[methyl(3,3,3-trifluoropropyl)siloxane]-block-polystyrene (PS-b-PMTFPS-b-PS) triblock copolymers with the volume fraction of PS between 0.46–0.61 were synthesized by anionic polymerization. The phase behavior and morphologies of the block copolymers were investigated via differential scanning calorimetry (DSC), rheological measurements, small-angle X-ray scattering (SAXS), and transmission electron microscopy (TEM). Equilibrium domain orientations of well-ordered lamellar microphase-separated structures were observed in the PS-b-PMTFPS diblock and PS-b-PMTFPS-b-PS triblock copolymer melts. The results showed that the synthesized block copolymers were desirable for achieving long-range order resulting from a high driving force between PS and PMTFPS blocks.

Synthesis, association and surface morphology of poly (ethylene oxide)-polystyrene block copolymer

Synthesis of block copolymers is of great interest due to their abilities to self-assemble into a variety of struc- tured, ordered, or partially ordered morphologies, and be- cause they have number of applications. Three samples of poly(styrene)-block-poly(ethylene oxide) (PS-b-PEO) were synthesized by employed atom transfer radical polymeriza- tion (ATRP) technique and using monofunctional PEO- macroinitiator (mPEO-F) as starting material. The composition of the copolymer was obtained through NMR spectroscopy, whereas the molecular mass and degree of dispersity from light scattering and GPC/SEC. The CMC was obtained from the dependence of hydrodynamic radius (RH) over the concentra- tion and found that it was decreased with contents of polysty- rene and temperature. The RH dependence also indicated that shape of micelles change after certain concentration of copol- ymer. The reduced viscosity data plotted against concentration did not show a simple straight line as expected in case of polymers; rather, its slope was changed at a particular concen- tration, indicating sudden variation in the self-assembling behav- ior of the copolymers. The transmission electron microscopic (TEM) results of the material indicated the morphology pattern of two-dimensional arrays of hexagons with holes.

Surface Modification of Sulfonated Polystyrene Ethylene Butylene Polystyrene Membranes by Layer-by-layer Assembly of Polysulfone for Application in Direct Methanol Fuel Cell

Methanol permeability is a major drawback for application of sulfonated polystyrene ethylene butylenes polystyrene block copolymers (SPSEBS) in direct methanol fuel cells (DMFC). Modification of SPSEBS by layer-by-layer (LBL) assembly of aminated (APSU) and sulfonated polysulfone (SPSU) was attempted to reduce its methanol permeability. The LBL deposition of APSU and SPSU on SBSEBS was carried out by dipping in their solutions alternatively for 10 min. The LBL assembly was confirmed by SEM analysis. The methanol permeability was lower than SPSEBS and Nafion 117. The proton conductivity, ion exchange capacity, and water absorption were lower than SBSEBS but higher than Nafion 117. Its selectivity ratio (0.70 × 105) was higher than both SBSEBS (0.54 × 105) and Nafion 117 (0.06 × 105). The maximum power density of LBL (62 mW/cm2) was about five times higher than SBSEBS. These features of LBL confirm the LBL assembly method as a very simple procedure to modify SBSEBS for application in DMFC.

Hairy fluorescent nanoparticles from one‐pot click chemistry and atom transfer radical emulsion polymerization

AbstractWell‐defined hairy and crosslinked fluorescent nanoparticles with diameters in the range 70–220 nm were obtained from simultaneous copper‐catalyzed alkyne–azide cycloaddition (CuAAC) and atom transfer radical emulsion polymerization (ATREP) of a mixture of styrene, divinylbenzene, 4‐vinylbenzylazide and 7‐propinyloxycoumarin (Cr), using bromide‐terminated poly(ethylene glycol) (PEG) as macroinitiator, Tween‐20 as emulsifier, copper(I) bromide as catalyst and pentamethyldiethylenetriamine as ligand. The generation of biocompatible PEG brushes and the introduction of fluorescent functionalities as well as crosslinking of nanoparticles were realized in one step. In order to verify that functionalization and propagation of polymer chains could be realized in a controlled manner by one‐pot simultaneous ATREP and CuAAC, linear block copolymers of PEG and polystyrene (PS) with partially clicked pendent Cr groups (PEG‐b‐(PS‐c‐Cr)) were synthesized. All prepared PEG‐b‐(PS‐c‐Cr) copolymers had a controlled molecular weight and defined molecular structure. The hairy fluorescent nanoparticles exhibit a low cytotoxicity and could find applications in cell labeling. © 2013 Society of Chemical Industry

Thermoresponsive behavior of amphiphilic diblock co-oligomers of ethylene glycol and styrene in aqueous solution

We report the thermoresponsive behavior in aqueous solution of amphiphilic diblock co-oligomers of ethylene glycol (EG) and styrene (S) obtained by reversible addition fragmentation chain transfer (RAFT) polymerization (mPEG16-b-PS2, mPEG16-b-PS4 and mPEG16-b-PS6). The block co-oligomers were obtained from the polymerization of styrene mediated by a PEG macro-RAFT agent, mPEG-PBTC. The precise control offered by RAFT polymerization over the length of the short hydrophobic chain permits tuning of the thermoresponsive behavior for all the studied methoxy poly(ethylene glycol)-block-polystyrene copolymers. mPEG16-b-PS2 was shown to self-assemble into micelles at temperatures below the lower critical solution temperature (LCST) of the block co-oligomer, whilst no such critical temperature was observed for solutions of self-assembled mPEG16-b-PS4 and mPEG16-b-PS6. mPEG16-b-PS4 self-assembles into relatively mobile spherical particles which evolve into prolate spheroids with increasing temperature, whilst mPEG16-b-PS6 forms particle clusters, which have lower mobility than the mPEG16-b-PS4 particles. This work is the first study on the aggregation behavior of such short chain lengths of mPEG-b-PS as a function of temperature, and shows how tuning the PS oligomer length permits control of the thermoresponsive behavior of mPEG-b-PS assemblies in water.

Nanoscale organization of proteins via block copolymer lithography and non-covalent bioconjugation

Thin films of cylinder-forming biotinylated poly(ethylene glycol)-polystyrene (PEG-b-PS) block copolymers were studied as a means to produce protein patterns. The orientation of the PEG cylinders depended on the end group functionality as well as on the preparation conditions. In the case of perpendicular cylinders, immobilization of single streptavidin molecules could be achieved. This immobilization was controlled by varying the amount of biotin in the films by mixing with non-functional PEG-b-PS.

Direct monitoring of self-assembly of copolymeric micelles by a luminescent molecular rotor

The detailed analysis of the time resolved luminescence of a specifically designed fluorescent molecular rotor enables the direct monitoring of the self-assembly of a poly(N,N-dimethylacrylamide)-block-polystyrene (PDMA-b-PS) copolymer into core-corona nanoparticles. Comparison with bulk PS indicates hard confinement of the micelle core, due to the solvation of the hydrophilic PDMA corona.

Characterization of Poly(paraphenylene vinylene)-Polystyrene Block Copolymers in Solution

The influence of the solvent temperature and the solvent quality on the chain conformation and the aggregation of semiconducting block copolymers is described in this paper. In selective solvents for the polystyrene block, aggregation is detected by means of optical spectroscopy. The author thinks that the research is useful for the development of material engineering.

Macromol. Biosci. 9/2012

Back Cover: HepG2 hepatocarcinoma cells take up water soluble homo-glycopolymers as well as nanoparticles of polystyrene block copolymers in a sugar-type dependent manner. Preferential internalization of green-fluorescent, galactosylated homopolymers and nanoparticles (20 nm in diameter) could be observed by confocal laser scanning microscopy. Further details can be found in the article by K. Babiuch, D. Pretzel, T. Tolstik, A. Vollrath, S. Stanca, F. Foertsch, C. R. Becer, M. Gottschaldt, C. Biskup, U. S. Schubert* on page 1190.

Characterization of Functional Poly(ethylene oxide)s and Their Corresponding Polystyrene Block Copolymers by Liquid Chromatography under Critical Conditions in Organic Solvents

Separation of functional poly(ethylene oxide) PEO and PEO block copolymers was investigated using liquid chromatography under critical conditions (LCCC) with a mixture of organic solvents as eluent. The optimum eluent is a mixture of 58.05% chloroform, 6.45% methanol, and 35.50% n-heptane (v/v/v) using a reverse phase (C8) column. Unlike what was expected, the elution mechanism is governed by the interaction of a polar end-group with the column. In these conditions, poly(ethylene oxide) (PEO) functionalized with either an acrylate or alkoxyamine moieties were separated. This allows us to investigate the efficiency of the synthesis of poly(ethylene oxide)-b-polystyrene (PEO-b-PS) and polystyrene-b-poly(ethylene oxide) b-polystyrene (PS-b-PEO-b-PS) block copolymers prepared via the combination of 1,2 radical intermolecular addition followed by the nitroxide-mediated polymerization NMP of styrene. Amphiphilic diblock PEO-b-PS and triblock PS-b-PEO-b-PS copolymers were also separated from PEO homopolymers usi...