Block Copolymers Of Polystyrene Research Articles

Synthesis and Self-Assembly of Poly(4-acetoxystyrene) Cubosomes.

Polymer cubosomes (PCs) are a recent class of self-assembled nanostructures with great application potential due to their high porosity and surface area. Currently, most reported PCs consist of polystyrene block copolymers (BCPs), for which self-assembly parameters are rather well understood. Changing the block chemistry would be desirable to introduce more functionality; however, knowledge of adapting the self-assembly process to new chemistries remains limited. This work, reports on synthesizing poly(ethylene oxide)-block-poly(4-acetoxystyrene) and its copolymers with styrene, and provide conditions for their self-assembly into PCs with high yield and high inner order. It is shown that the polarity of the starting solvent toward the corona block allows tuning of the final morphology by controlling the corona volume and packing parameter.

A Straightforward Solvent-Pair-Enabled Multicomponent Coassembly Approach toward Noble-Metal-Nanoparticle-Decorated Mesoporous Tungsten Oxide for Trace Ammonia Sensing.

The straightforward synthesis of noble-metal-nanoparticle-decorated ordered mesoporous transition metal oxides remains a great challenge due to the difficulty of balancing the interactions between precursors and templates. Herein, a solvent-pair-enabled multicomponent coassembly (SPEMC) strategy is developed for straightforward synthesis of noble-metal-nanoparticle-decorated nitrogen-doped ordered mesoporous tungsten oxide (abbreviated as NM/N-mWO3, NM=Pt, Rh, Pd). The amphiphilic poly(ethylene oxide)-block-polystyrene (PEO-b-PS) copolymers coassemble with ammonium metatungstate (AMT) clusters and different kinds of hydrophilic noble metal precursors without phase separation. SPEMC synthesis requires no direct interaction between PEO-b-PS and AMT, thus the assembly equilibriums between noble metal precursors and PEO-b-PS can be readily controlled. The obtained NM/N-mWO3 nanocomposites possess ordered mesopores, abundant oxygen vacancies, and metal-metal oxide interfaces. As a result, the Pt/N-mWO3 sensors exhibit superior ammonia sensing performances with high sensitivity, an ultralow limit of detection (51.2 ppb), good selectivity, and long-term stability. Spectroscopic analysis reveals that ammonia is oxidized stepwise to NO, NO2 -, and NO3 - during the sensing process. Moreover, a portable wireless module based on Pt/N-mWO3 sensor can recognize ppm-level concentration of ammonia, which lays a solid foundation for its application in various fields.

Mass transfer limitation phenomena across the separator in a zero-gap alkaline water electrolysis stack: Anion-selective polymer electrolyte membrane vs. Zirfon™ Perl UTP 500 case study

Endeavours to decrease the KOH concentration in a circulating medium represent an important target of today's research. They are connected with current efforts to increase the flexibility of alkaline water electrolysis and improve its efficiency with regard to renewable energy sources. This study reports on the impact of reduced KOH solution concentration on mass and charge transport in a laboratory alkaline water electrolysis stack with two separator types. The separators used are a homogeneous anion-selective polymer-electrolyte membrane based on chloromethylated polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene copolymer functionalised by 1,4–diazabicyclo[2.2.2]octane and a commercial composite porous Zirfon™ Perl UTP 500 diaphragm. The stack was assembled in zero-gap mode and a bipolar connection of the electrodes was used. Load curves were recorded for different KOH concentrations and operational temperatures to assess the performance of the stack. Surprisingly, mass transfer limiting behaviour of the stack was observed at KOH concentrations below 2 wt% KOH for the Zirfon™ Perl UTP 500 separator. This was not the case for the stack utilising an anion-selective membrane as a separator. A 1-dimensional, single cell, stationary mathematical model was developed and implemented to clarify this phenomenon and to understand the details of the mass transport across the different types of separators in this process. This information is crucial for understanding obstacles faced once the concentration of KOH approaches zero, i.e., the final target of research in this field.

Development of Cost-Effective Membranes for Redox-Flow Batteries

Developing long-duration energy storage (LDES) systems is key to promoting the penetration of intermittent energy storage, such as solar and wind into the electric grid. DOE’s Long Duration Storage Shot establishes a target to reduce the cost of grid-scale energy storage by 90% for systems with durations of >10 hours. Non-aqueous RFBs (non-aqueous RFB) using earth-abundant materials are promising to fulfill this target. A key bottleneck to keeping RFB from market penetration is the lack of high-performance and cost-effective membranes. Membranes represent the most critical component in non-aqueous RFB, and they are decisive to the cell stack performance and cost. For example, the ionic conductivity of the membrane determines the power density of the RFBs, while ion selectivity and solvent uptake govern non-aqueous RFB cycle life. Herein, we will present recent progress in our team on the membrane development for the non-aqueous flow batteries.The ionic conductivity - mechanical strength tradeoff is a long-standing challenge for all polymer electrolyte development. In a redox flow battery, solvent uptake promotes membrane ionic conductivity but decreases its storage modulus due to the increased polymer chain relaxation. Two strategies are found effective to alleviate such a tradeoff i) selective plasticization of the ion-conductive block such as poly(ethylene oxide) (PEO) in a polystyrene (PS)− PEO−PS block copolymer (SEO) electroconductivity by glyme-type of solvent, and ii) enhancement of the membrane mechanical strength by creating hydrogen and ionic bonds between the polymer matrix and the inorganic scaffold. Mitigating redox-active species crossover poses another challenge in membrane design. We show that the cation exchanged single ion conducting membrane can effectively decrease the crossover of the polysulfide species in a Na metal – polysulfide hybrid flow battery, which promotes the RFB capacity retention, Columbia efficiency, and cycle life benchmarked to a commercial porous membrane. Acknowledgment This research was conducted at Oak Ridge National Laboratory, managed by UT Battelle, LLC, for the U.S. Department of Energy (DOE) and is sponsored by the U.S. Department of Energy through the Energy Storage Program led by Dr. Imre Gyuk, in the Office of Electricity.

Alkaline Water Electrolysis – Investigation of the Charge Transport Limitations across the Separator Under Low KOH Concentration

Currently, the water electrolysis is employed when high purity hydrogen is required, or excess of cheap electricity is available. With a broader future perspective, an important benefit of this technology represents fact, that it can be powered from renewable energy sources. The hydrogen produced from renewables is, thus, “green” CO2 neutral, playing an important role as energy vector in the so called “hydrogen economy”. Nowadays, the hydrogen economy represents strategy for transition of our economy towards the renewable energy sources, with water electrolysis (denoted as Power-to-X technology) being a crucial part of this scheme.Nowadays, the alkaline water electrolysis technology (AWE) operating at elevated temperatures (70 – 100 °C) with KOH electrolyte (25 – 30 wt.% KOH) dominates in the field of industrial hydrogen production by the water electrolysis. The alkaline environment is advantageous since it does not require platinum-group catalysts. On the other hand, highly concentrated caustic solution at elevated temperatures used as a liquid electrolyte limits the flexibility of the process operation. Currently several alternative technologies offering higher production intensity (proton-exchange membrane water electrolysis) and higher efficiency (high temperature solid-oxides steam-electrolysis) are developed and approach industrial application state. There are also promising innovations of the AWE process developed, e.g. application of an anion-selective membrane (AM) as the separator alternative to the diaphragm used in the conventional AWE. The AMs of interest exhibit improvement, contrary to diaphragm, of anionic conductivity with decreasing KOH concentration and operating temperature. Therefore, application of such AM allows to reduce KOH concentration in a liquid electrolyte (down to 5 – 15 wt.%) and operating temperature, thus, solve the above-mentioned problems of conventional AWE in connection with renewables. Moreover, the AM is dense, therefore might represent more effective barrier for produced gasses than diaphragm. However, one has to keep on mind increasing solubility of gasses with decreasing KOH concentration followed by potentially enhanced H2 cross-over. Another non-negligible benefit of lower KOH concentration and operating temperature is lower electrolyte conductivity in the manifolds contributing to reduced parasitic (bypass) current. However, systematic research aimed at evaluation of real application potential and searching for optimal conditions of the AM at diluted KOH concentrations is so far missing.In the presented contribution, study on a behaviour of two types of the separators in the laboratory scale AWE stack in bipolar zero-gap configuration is presented. The separators used are: a) a homogeneous AM based on chlormethylated polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene copolymer functionalized by 1,4-diazabicyclo-[2.2.2]octane (PSEBS-CM-DABCO) and b) a commercial composite diaphragm Zirfon™ Perl. The load curves were recorded to assess optimal performance of the stack with both separators at KOH concentration range of 1 – 15 wt.% and operating temperature range of 25 – 40 °C. The effect of different electrolyte flow rate through the Ni-foam electrodes was investigated as well. Additionally, 1-dimensional stationary mathematical model of single AWE (both with diaphragm and AM) cell corresponding to the studied laboratory set-up was developed to clarify the differences in the stack load curves recorded for the two studied separators. The Nernst-Planck equation is used to describe migration and diffusion transport in the cell, while convective flow of electrolyte in the porous electrode is considered in material balance. The gas evolution is neglected in the present model. A macrohomogeneous continuum theory is employed for description of the porous electrodes. The AM-solution interface is characterized by Donnan equilibrium. At all studied experimental conditions, the stack with AM outperforms the one with diaphragm. This fact is even more pronounced at KOH concentration below 5 wt.% due to occurring transport limitation, which is more significant in the case of the diaphragm, as demonstrated both by modelling and experimentally. The presented work clearly identifies interval of operating conditions, in which AM represents an important advantage over porous separator and opposite. Thus, it gives important hints for further development of this technology.Project has received funding from the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 862509).

Design of thermo-responsive cell culture dishes using poly(N-isopropylacrylamide)-block-polystyrene copolymers for cell sheet technology

The main objective of this work was to assess the cell sheet fabrication of a newly designed thermo-responsive polymer. Thermo-responsive diblock copolymers of poly(N-isopropylacrylamide)-block-polystyrene (PNIPAM-b-PS) with different block ratios were synthesized via sequential reversible addition-fragmentation chain transfer (RAFT) polymerization. The prepared copolymers were characterized by Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance and gel permeation chromatography techniques in terms of molecular weight and composition. Physical adsorption was employed to prepare thermo-responsive films. Employing atomic force microscopy (AFM) and water contact angle (WCA) measurements, we found that the PNIPAM-b-PS diblock copolymer coatings showed a temperature-triggered phase transition in water through the reversible hydration of PNIPAM segments. Thermo-responsive PNIPAM-b-PS coatings were utilized as functional substrates for human dermal fibroblasts (HDFs) adhesion and detachment. By adjusting PNIPAM to PS segments ratio, HDFs successfully detached from the PNIPAM-b-PS spin-coated tissue culture polystyrene (TCPS) substrates in a temperature-induced manner.

Polyacrylonitrile-b-Polystyrene Block Copolymer-Derived Hierarchical Porous Carbon Materials for Supercapacitor.

The use of block copolymers as a sacrificial template has been demonstrated to be a powerful method for obtaining porous carbons as electrode materials in energy storage devices. In this work, a block copolymer of polystyrene and polyacrylonitrile (PS-b-PAN) has been used as a precursor to produce fibers by electrospinning and powdered carbons, showing high carbon yield (~50%) due to a low sacrificial block content (fPS ≈ 0.16). Both materials have been compared structurally (in addition to comparing their electrochemical behavior). The porous carbon fibers showed superior pore formation capability and exhibited a hierarchical porous structure, with small and large mesopores and a relatively high surface area (~492 m2/g) with a considerable quantity of O/N surface content, which translates into outstanding electrochemical performance with excellent cycle stability (close to 100% capacitance retention after 10,000 cycles) and high capacitance value (254 F/g measured at 1 A/g).

A Novel Magnetoelastic Biosensor With Flexible TbDyFe Film as Sensing Materials for Osteoarthritis Marker MMP-3 Detection

A new design of flexible magnetoelastic (ME) biosensor based on TbDyFe/polystyrene-poly (ethylene-butylene)-polystyrene block copolymer (SEBS) film for the osteoarthritis (OA) marker matrix metalloproteinase 3 (MMP-3) detection is presented. This article studied a novel flexible ME film to replace the traditional rigid substrate for biosensors. The magnetostrictive material of TbDyFe was mixed homogeneously with paraffin solution to fabricate TbDyFe fluid, which was reacted at high temperature with SEBS in a certain ratio to prepare the film. TbDyFe/SEBS films were used as substrates for the immobilization of MMP-3 antibodies. Specific binding of antibodies to MMP-3 antigens generated compressive stress on the substrate surface, which in turn led to changes in magnetic permeability and impedance. To improve the sensitivity of the biosensor, the TbDyFe doping concentration was optimized and the magnetic response performance of the TbDyFe/SEBS composite film was measured. The results show that this assay is capable of detecting concentrations of MMP-3 between 0.76 and 10000 ng <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\cdot $ </tex-math></inline-formula> mL−1 with a detection limit of 0.76 ng <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\cdot $ </tex-math></inline-formula> mL−1, covering the range of clinical tests required for the diagnosis of OA. This novel flexible ME biosensor provides a viable method for the diagnosis and monitoring of OA.

Synthesis and Morphology of High-Molecular-Weight Polyisobutylene-Polystyrene Block Copolymers Containing Dynamic Covalent Bonds.

Incorporating dynamic covalent bonds into block copolymers provides useful molecular level information during mechanical testing, but it is currently unknown how the incorporation of these units affects the resultant polymer morphology. High-molecular-weight polyisobutylene-b-polystyrene block copolymers containing an anthracene/maleimide dynamic covalent bond are synthesized through a combination of postpolymerization modification, reversible addition-fragmentation chain-transfer polymerization, and Diels-Alder coupling. The bulk morphologies with and without dynamic covalent bond are characterized by atomic force microscopy and small-angle X-ray scattering, which reveal a strong dependence on annealing time and casting solvent. Morphology is largely unaffected by the inclusion of the mechanophore. The high-molecular-weight polymers synthesized allow interrogation of a large range of polymer domain sizes.

Robust superhydrophobic coating with hollow SiO2/PAA-b-PS Janus microspheres for self-cleaning and oil–water separation

Superhydrophobic coating can be widely used in many fields because it is not easily wetted by water like lotus leaves. However, most of superhydrophobic coating is difficult to withstand abrasion attack. Herein, hollow SiO2/PAA-b-PS Janus microspheres were synthesized via emulsion interfacial synthesis method using amphiphilic block copolymer of polyacrylic acid block polystyrene (PAA-b-PS) and hollow NH2-SiO2 microspheres as raw materials in this paper. Because the hemisphere grafting organic polymer chain was hydrophobic and the other hemisphere was hydrophilic and contained amino groups, hollow SiO2/PAA-b-PS Janus microspheres exhibited amphiphilic and asymmetrical nature, which was a typical inorganic/polymer Janus microspheres. Robust superhydrophobic coating was facilely achieved using hollow SiO2/PAA-b-PS Janus microspheres on polyurethane pretreated substrate like leather and fabric. Robust superhydrophobic coating after 90 sandpaper abrasion cycles still retained excellent superhydrophobicity. As expected, robust superhydrophobic coating had prominent self-cleaning property against different pollutants and was capable to separate a variety of oil–water mixtures with ultrahigh separation efficiency. The separation efficiency of robust superhydrophobic coating for oil–water mixture was maintained above 98% even after 40 separation cycles. In total, robust superhydrophobic coating constructed by hollow SiO2/PAA-b-PS Janus microspheres possesses distinguished superhydrophobicity, abrasion resistance, self-cleaning, oil–water separation capacity and universality, which shows a promising application in multifunctional coating.

Selective Plasticization of Poly (ethylene oxide) (PEO) Block in Nanostructured Polystyrene− PEO− Polystyrene Triblock Copolymer Electrolytes

The plasticization of a polymer electrolyte usually promotes its ionic conductivity but decreases its storage modulus due to the increased polymer chain flexibility. Herein, we show that such a tradeoff between the ionic conductivity and the mechanical robustness of the polymer electrolyte can be alleviated by selective plasticization of the ion-conductive block, such as poly(ethylene oxide) (PEO) in a polystyrene (PS)− PEO−PS block copolymer (SEO) electrolyte using an ether type plasticizer, tetraethylene glycol dimethyl ether (TEGDME). At maximum plasticizer loading, the room temperature ionic conductivity increases by up to 3 orders, whereas the storage modulus, G′ reduces to half, is still on the order of 102 MPa. At above the melting temperature of the PEO block, the dynamic storage modulus, G′ of the plasticized membrane surpasses its dry PS-PEO-PS counterpart. Such a phenomenon results from that, a) TEGDME co-crystallizes with PEO to promote its crystallinity and hence the storage modulus, b) TEGDME swells the amorphous PEO phase to enhance the polymer chain segmental mobility and hence ionic conductivity, and c) the PS phase remains intact from TEGDME to keep the SEO elastic.

FORC analysis of nanopatterned vs unpatterned films: Coercivity and switching mechanisms

We have studied the use of self-assembled block copolymers to pattern multilayers of Co and Pd on silicon wafers. Stacks ranging from four to twelve bilayers of Co (0.3 nm)/Pd (0.8 nm) were sputtered onto Ta/Pd seed layers and capped with 3 nm of Ta and were found to have perpendicular magnetic anisotropy as-deposited. The block copolymer polystyrene-block-poly(ferrocenyl dimethylsilane) (PS-b-PFS) was dissolved in toluene and spun onto the wafers. The polymers were phase-separated by heat treatment, leaving self-assembled PFS spheres embedded in PS, which was removed by oxygen-plasma ashing. The PFS spheres were then used as masks to ion-mill the Co/Pd multilayers into nanopillars. To study the effect of etch time and etch angle on the coercivity distribution, we synthesized samples in a Design of Experiments-(DoE)- in these two factors. Scanning electron micrographs showed nanopillars ranging from 15 to 30 nm in diameter, depending primarily on etch time. M-H loops measured on both patterned and unpatterned wafers showed an increase of up to 130% in overall coercivity upon patterning. First Order Reversal Curves (FORC) were measured, and the resulting FORC distributions displayed using a smoothing program (FORCinel) and one that can display the raw data without smoothing (FORC+). We find that FORC+ reveals information about fine-scale structure and switching mechanism that cannot be seen in the smoothed display.

DEPOSITION OF SILVER PARTICLES ON THE SOLID SURFACES WITH THE PARTICIPATION OF BLOCK COPOLYMER OF POLYSTYRENE AND POLYETHYLENE GLYCOL

Earlier the ability of obtaining of stabilized organosols in such systems as «toluene-water», «toluene-methanol» in presence of block copolymer of polystyrene and polyethylene glycol has been shown. In present investigation these disperse systems have been used in a mixture with precursor of silver nanoparticles (silver salt) and reducing agent (sodium citrate or hydrazine hydrate). Thus obtained silver sols have been put on a glass or graphite surfaces with subsequent removal of block copolymer by heating of samples in air to 500 °C. The dimension of obtained silver sols particles has been determined by means of sedimental turbidimetry (ST) and dynamic light scattering (DLS) methods. It has been shown that in silver sols obtained in the system «toluene-water-citrate» with the copolymer content of 0.25 and 1 g/100 ml have particle diameters of 800 and 1100 nm correspondingly. According to scanning electron microscopy (SEM) data the silver particles have spheric form. Their size does not depend much on the concentration of silver, but with an increase in the concentration of the copolymer, their size heterogeneity increases. The formation of spatial ordered structures of silver particles on the glass surface is noted, while the particles on the graphite surface are distributed more evenly. Using the system "toluene-methanol-block copolymer-silver salt-hydrazine hydrate" on the basis of thermally expanded graphite (TEG), a composite with a silver content of 130 mg/g was obtained and its effect on the activity of yeast fungi was evaluated. In comparison with the control samples (TEG and TEG treated with a similar dispersed system without the participation of a block copolymer), a decrease in foam formed in the column during fermentation of sucrose at 35 °C was found. Thus, it is shown that the block copolymer of polystyrene and polyethylene glycol promotes a more uniform deposition of silver particles from sols on the surface of graphite and can be used, in particular, to create materials with potential biological activity.

Graphoepitaxy of Symmetric Six‐Arm Star‐Shaped Poly(methyl methacrylate)‐block‐Polystyrene Copolymer Thin Film

Front Cover: By utilizing directed self-assembly of a lamellar forming six-arm star-shaped poly(methyl methacrylate)-block-polystyrene copolymer [(PMMA-b-PS)6] thin film confined within trenches, Jaeup U. Kim, Jin Kon Kim, and co-workers successfully fabricate two or more different nanopatterns including nanotubes and straight lines on a single substrate by carefully controlling the trench width and the affinity between the blocks and the trench wall. This work can be found in article number 2100411.

Graphoepitaxy of Symmetric Six-Arm Star-Shaped Poly(methyl methacrylate)-block-Polystyrene Copolymer Thin Film.

The authors perform directed self-assembly based on graphoepitaxy of symmetric six-arm star-shaped poly(methyl methacrylate)-block-polystyrene copolymer [(PMMA-b-PS)6 ] thin film. The affinity between each block and the trench wall is adjusted by using polymer brushes or selective gold (Au) deposition. When the surface of the trench is strongly selective for the PMMA block, (n+0.75)L0 thick (n is the number of the lamellae, L0 is lamellar domain spacing) lamellae parallel to the trench wall are formed at each side, while nanotubes are formed away from the trench wall. However, for a trench grafted with PS brushes, nanotubes are formed beside (n+0.25)L0 thick lamellar layers. By adjusting the trench width (W) and the affinity between the block and the wall, various dual nanopatterns consisting of lines and nanotubes are fabricated. Moreover, when the trench wall is selectively deposited by Au, asymmetric dual nanopattern is formed, where different numbers of lines exist on each side wall, while nanotubes are formed in the middle of the trench. The observed morphologies depending on the commensurability condition between W and L0 are consistent with predictions by self-consistent field theory.

Effect of Surface Silanol Density on the Proton Conductivity of Polymer-Surface-Functionalized Silica Nanoparticles

We have developed a polymer electrolyte membrane (PEM) material using polymer-coated silica nanoparticles (NPs) by the reversible addition-fragmentation chain-transfer polymerization with particles (RAFT PwP) method. In this paper, we controlled the number density of surface silanol groups on the silica NPs that not only maintain the structure of the surface adsorbed polymers by RAFT PwP but also form fast proton-conducting interface to study the silanol density effect on proton conductivity. The number of surface silanol groups was successfully increased by NaOH surface treatment and decreased by heat treatment. Then, we clarified that silanol-rich silica NPs with a polyacrylic acid and polystyrene block copolymer (PAA-b-PS) applied by RAFT PwP exhibit larger proton conductivity. This result implies that hydrophilicity of the filler is one of the important factors in the design of filler-functionalized PEM with high proton conductivity.

Synthesis of poly (n-butyl acrylate) with tempo by nitroxide mediated polymerization method

It has been observed that acrylate monomers are very difficult to polymerize with the low cost nitroxide catalyst 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO). Therefore, costly acyclic nitroxides such as N-tert-butyl-N-(1-diethylphosphono-2,2-dimethyl)-N-oxyl, (SG1), 2,2,5-Trimethyl-4-phenyl-3-azahexane-3-nitroxide (TIPNO) and TIPNO derivatives have to be used for the polymerization of the acrylic acid derivatives. There are very few reports on the use of TEMPO-derivatives toward the polymerization of n-butyl acrylate. Generally different reducing agents viz. glucose, ascorbic acid, hydroxyacetone etc. have been used to destroy excess TEMPO during the polymerization reaction. The acrylate polymerizations fail in the presence of TEMPO due to the strong C–O bond formed between the acrylate chain end and nitroxide. To the best of our knowledge, no literature report is available on the use of TEMPO without reducing agent or high temperature initiators, toward the polymerization of n-butyl acrylate. The present study has been carried out with a view to re-examine the application of low cost nitroxide TEMPO, so that it can be utilized towards the polymerization of acrylate monomers (e.g. n-butyl acrylate). We have been able to polymerize n-butyl acrylate using the nitroxide TEMPO as initiator (via a macroinitiator). In this synthesis, a polystyrene macroinitiator was synthesized in the first step from TEMPO, after this TEMPO end-capped styrene macroinitiator (PSt-TEMPO) is used to polymerize n-butyl acrylate monomer. The amount of macroinitiator taken was varied from 0.05% to 50% by weight of n-butyl acrylate monomer. The polymerization was carried out at 120°C by bulk polymerization method. The experimental findings showed a gradual increase in molecular weight of the polymer formed and decrease in the polydispersity index (PDI) with increase in amount of PSt-TEMPO macroinitiator taken. In all experiments conversion was more than 80%. These results indicate that the polymerization takes place through controlled polymerization process. Effect of different solvents on polymerization has also been investigated. In the following experiments TEMPO capped styrene has been used as macroinitiator leading to the successful synthesis of poly n-Butyl acrylate. It has been found that styrene macroinitiator is highly efficient for the nitroxide mediated polymerization, even in very small concentration for the synthesis of poly n-butyl acrylate. High concentration of macroinitiator results in the formation of block copolymers of polystyrene and poly ( n-butyl acrylate) viz. polystyrene-block-poly-( n-butyl acrylate). The use of TEMPO toward controlled polymerization is of much importance, because it is the nitroxide commercially available at the lowest cost.

Cation-exchange membranes with sulfonylimide groups showing a high ionic conductivity in water/organic amide mixed systems

Cation-exchange membranes based on polystyrene block copolymer with phenylsulfonylimide ionogenic groups in the Na+-form show conductivities up to 0.2 mS cm−1 in organic amides such as N-methylpyrrolidone and N,N-dimemylacetamide. These values are 2–2.5 orders of magnitude higher compared to those of conventional sulfonated cation-exchange membranes. A strong dependence of solvation degree and ionic conductivity on dielectric permittivity, chemical structure, and composition of the solvent, as well as on the nature of the membrane functional group, was noted and discussed. Further, based on the dependence of membrane’s solvation on the dimethylacetamide or acetonitrile content in the water/organic solvent mixtures and thermodynamic properties of these solvent mixtures, the reasons for the difference in ionic conductivity with a variation in the composition of the solvent and the functional groups of membranes are described. It was shown that conductivity of the cation-exchange membranes can increase dramatically even at low water concentration in the acetonitrile solution. It was demonstrated that the membranes with phenylsulfonylimide groups have high ionic conductivity in water/dimethylacetamide mixtures of any concentrations, which opens new prospects for their applications in electrochemical desalination and metal-ion batteries.

Supramolecular Triblock Copolymers Through the Formation of Hydrogen Bonds: Synthesis, Characterization, Association Effects in Solvents of Different Polarity.

Anionic polymerization techniques were employed for the synthesis of linear polystyrene (PS) and block copolymer of PS and polyisoprene (PI) PS-b-PI bearing end hydroxyl groups. Following suitable organic chemistry transformation, the –OH end groups were converted to moieties able to form complementary hydrogen bonds including 2,6-diaminopurine, Dap, thymine, Thy, and the so-called Hamilton receptor, Ham. The formation of hydrogen bonds was examined between the polymers PS-Dap and PS-b-PI-Thy, along with the polymers PS-Ham and PS-b-PI-Thy. The conditions under which supramolecular triblock copolymers are formed and the possibility to form aggregates were examined both in solution and in the solid state using a variety of techniques such as 1H-NMR spectroscopy, size exclusion chromatography (SEC), dilute solution viscometry, dynamic light scattering (DLS), thermogravimetric analysis (TGA), differential thermogravimetry (DTG), and differential scanning calorimetry (DSC).

Fully Atomistic Molecular Dynamics Computation of Physico-Mechanical Properties of PB, PS, and SBS

The physical properties—including density, glass transition temperature (Tg), and tensile properties—of polybutadiene (PB), polystyrene (PS) and poly (styrene-butadiene-styrene: SBS) block copolymer were predicted by using atomistic molecular dynamics (MD) simulation. At 100 K, for PB and SBS under uniaxial tension with strain rate = 1010 s−1 and 109 s−1, their stress–strain curves had four features, i.e., elastic, yield, softening, and strain hardening. At 300 K, the tensile curves of the three polymers with strain rates between 108 s−1 and 1010 s−1 exhibited strain hardening following elastic regime. The values of Young’s moduli of the copolymers were independent of strain rate. The plastic modulus of PS was independent of strain rate, but the Young’s moduli of PB and SBS depended on strain rate under the same conditions. After extrapolating the Young’s moduli of PB and SBS at strain rates of 0.01–1 s−1 by the linearized Eyring-like model, the predicted results by MD simulations were in accordance well with experimental results, which demonstrate that MD results are feasible for design of new materials.