Aromatic Block Copolymers Research Articles

Aromatic block copolymer ligand sensitized lanthanide nanostructures as ratiometric fluorescence probe for determination of residual K2CO3 in super engineering thermoplastics

• An aromatic amphiphilic block copolymer named of D5S5 was synthesized. • D5S5 was self-assembled with Tb 3+ and Rhodamine B to obtain nanoprobe of Tb-D5S5/RB. • Tb-D5S5/RB exhibits pH dependent fluorescence emission in acid and basic solution. • Tb-D5S5/RB shows ratiometric enhanced fluorescence as the increased K 2 CO 3 content. • Tb-D5S5/RB nanoprobe is able to detect residual K 2 CO 3 in super-engineering polymer. The residual catalyst (K 2 CO 3 ) presented in the super engineering polyarylene ethers exerts side effects onto their processability and electrical properties. However, the sensitive and reliable analytical tools, that are able to detect residual K 2 CO 3 content in these high performance thermoplastics, are rarely reported. Herein, we firstly synthesized an aromatic amphiphilic block copolymer bearing pendent carboxyl and sulfonate groups (named as D5S5). Next, a lanthanide ions mediated solvent-exchange self-assembly was explored to fabricate fluorescent metallopolymeric nanospheres composed of D5S5 and Tb 3+ with strong green emission (named as Tb-D5S5). Then, the rhodamine B (RB) dyes were combined with the Tb-D5S5 to obtain the fluorescent probe of Tb-D5S5/RB, which exhibited a ratiometric fluorescence response to K 2 CO 3 . Specifically, the I 545 /I 585 (intensity ratio of two emission bands at 545 nm and 585 nm) of probe linearly increased with the increasing K + concentration of K 2 CO 3 in the range from 0.05 to 7.41 mM. Furthermore, the sensing mechanism of this probe towards K 2 CO 3 was revealed. Finally, the Tb-D5S5/RB probe was employed to determine the residual K 2 CO 3 in a super engineering polyarylene ether produced by an industrial plant, which showed 85.98 %–89.31 % recoveries of the benchmark results obtained from the inductively coupled plasma optical emission spectrometer (ICP-OES).

Emulsion solvent evaporation induced self-assembly of polyarylene ether nitrile block copolymers into functional metal coordination polymeric microspheres

Self-assembly of block copolymer is a well-known methodology to fabricate soft functional nanostructures. Herein, the block copolymers containing both rigid aromatic moieties and flexible ether groups in the backbone, named of co-polyarylene ether nitriles, have been synthesized and further transformed into metal coordination polymeric microspheres (MCPMS) via the Pb2+ mediated self-assembly occurring in confined emulsion droplet. Based on the systematic characterization of SEM, TEM, SAED, XRD and XPS, it is found that the size, morphology, aggregate structure as well as fluorescent properties of obtained MCPMS can be readily modulated by tuning of block copolymer backbone structures and self-assembly parameters. More interestingly, the obtained MCPMS can be further employed as robust templates for in-situ immobilization of silver nanoparticles. Therefore, the metal ions assisted self-assembly of aromatic block copolymer in emulsion droplets reported in this work basically open a new way for fabrication of functional hybrid nanomaterials.

Correction: Pb2+ coordination-driven self-assembly of amorphous amphiphilic aromatic block copolymer into semi-crystallized nanostructures with enhanced fluorescence emission

Correction for ‘Pb2+ coordination-driven self-assembly of amorphous amphiphilic aromatic block copolymer into semi-crystallized nanostructures with enhanced fluorescence emission’ by Junni Xie et al., J. Mater. Chem. C, 2019, 7, 1057–1064.

Pb2+ coordination-driven self-assembly of amorphous amphiphilic aromatic block copolymer into semi-crystallized nanostructures with enhanced fluorescence emission

Luminescent crystallized soft nanostructures are fabricated via a facile Pb2+ mediated self-assembling of amorphous aromatic non-conjugated copolymer.

(Invited) The Effects of Water Binding and Morphology on Proton Transport in Polymer Membranes

The effects of water binding and morphology will be reported in the context of designing new proton exchange membranes (PEMs). While much has been learned about the function of proton exchange membranes by studying perfluorosulfonic acid and sulfonated aromatic polymers, new generations of proton-conducting polymers for aqueous applications are being developed. Key to these advancements have been block copolymers and random copolymers with new sulfonic-acid bearing headgroups. Sulfonated aromatic block copolymers are a known route to high-performing proton exchange membranes. Compared to their random sulfonated copolymer counterparts, the organization of the sulfonate groups in a concentrated ionic domain has demonstrable benefits to proton conductivity. However, the relative humidity effects on the specific headgroup chemistry still often lead to lower conductivity than desirable at low RH. Using FTIR, we have explored the water binding in aromatic random copolymers with a number of new sulfonate groups. Our data shows that superacid groups on aromatic backbones can give comparable conductivities to perfluorosulfonic acid membranes. The interaction of these headgroups with water is one of the important factors for high proton conductivity – even though their morphologies can be much different than block copolymers or perfluorosulfonic acid materials. This talk will discuss the morphology and water binding factors that influence the proton conductivity of a number of unique aromatic polymer-based proton exchange membranes. Figure 1

Deformation and Strength Characteristics of Fatty Aromatic Block Copolymers Based on Polycarbonate

Polycarbonate—poly(tetramethylene oxide) block copolymers were synthesized using acceptor—catalytic polycondensation. The phase composition and deformation and strength characteristics of the block copolymers were studied using various methods. It was shown that rigid and elastic blocks were partially aligned in block copolymers containing up to 30 mass% of poly(tetramethylene oxide) blocks. Phase separation of microscopic blocks occurred at higher contents. The deformation and strength properties of the block copolymers were studied. Properties of thermoplastics or thermoplastic elastomers appeared depending on the polymer composition.

Effect of Sulfonated Triphenylphosphine Oxide Groups in Aromatic Block Copolymers as Proton-exchange Membranes

The introduction of sulfonated triphenylphosphine oxide moieties improved the oxidative stability of aromatic block copolymer membranes, while other factors such as water affinity also played an im...

Synthesis and properties of butadiene-alpha-methylstyrene thermoplastic elastomer

Butadiene-α-methylstyrene block – copolymer – a thermoplastic elastomer (TPE-R DMST) occupies a special place among the ethylene – vinyl aromatic block copolymers. TPE-R DMST comprising as plastic – poly-α-methylstyrene unit and elastic – polybutadiene block. TPE-R DMST has high heat resistance, flexibility, abrasion resistance compared to butadiene-styrene thermoplastic elastomer (TPE DST). The synthesis of block copolymers of butadiene and α-methylstyrene was carried out. The process of polymerization the α-methylstyrene characterized the high speed of polymerization in polar medium and low reaction speed in hydrocarbon solvents. Anionic catalyst nbutyllithium (n-BuLi) and high concentration – 60–80% α-methylstyrene in the mixture influenced by synthesis of the 1st block of TPE-R DMST, it’s technologically difficult. Found that the low temperature of polymerization α-methylstyrene (+61 o C), the reversibility of these reactions and the high concentration of residual monomer are very importance. It was revealed that a high polymerization rate α-methylstyrene can be achieved by conducting the reaction in a hydrocarbon solvent with polar additives compounds such as tetrahydrofuran (THF) and methyl tert-butyl ether (MTBE). The conditions for the synthesis of P-DMST were developed. The kinetics of polymerization for the first DMST-P unit was obtained. Analysis of physical and mechanical properties DMST-P samples was conducted. The optimum content of bound α-methylstyrene block copolymer provides a good combination of properties in a relatively wide temperature range. The tensile strength at normal and elevated temperatures, the hardness and the stiffness of the polymer increased by increasing the content of bound α-methylstyrene. The elongation and the elasticity reduced by increasing the content of bound α-methylstyrene.

Anion conductive aromatic polymers containing fluorenyl groups: Effect of the position and number of ammonium groups

ABSTRACTSynthesis and properties of anion conductive aromatic block copolymers, QPE‐bl‐3, QPE‐bl‐3 M2, and M4, containing fluorenylidene biphenylene groups as scaffold for ammonium groups are described. These copolymers share the same main chain structure, but the position and the number of ammonium groups on a fluorenyl group differ. High molecular weight quaternized block copolymers were obtained via typical chloromethylation reaction or using preaminated monomers, and were well‐characterized by 1H NMR spectra. Self‐standing bendable membranes were obtained by solution casting. QPE‐bl‐3 M4 membranes containing four ammonium groups per hydrophilic repeat unit (highest ammonium density) in the hydrophilic block exhibited well developed phase‐separated morphology, while QPE‐bl‐3 membranes containing two ammonium groups per hydrophilic repeat unit exhibited high anion conductivity. The highest anion conductivity (104 mS/cm) was obtained with QPE‐bl‐3 membrane (IEC = 2.1 meq/g) at 80 °C in water. An H2/O2 alkaline fuel cell was operable with the membrane to achieve 62 mW/cm2 of the maximum power density at 161 mA/cm2 of the current density. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 935–944

Ladder-type aromatic block copolymers containing sulfonated triphenylphosphine oxide moieties as proton conductive membranes

The synthesis and characterization of ladder-type aromatic block copolymers containing sulfonated triphenylphosphine oxide moieties (LadP-SPE) are reported. Through aromatic nucleophilic substitution polycondensation and Pd-catalyzed intrapolymer Heck reaction, the target copolymers LadP-SPE with high molecular weight (Mn = 47–50 kDa, Mw = 289–579 kDa) and different ion exchange capacity (IEC) values (1.04, 1.84 and 2.22 meq g−1, by titration) were prepared. By solution casting method, all the copolymers gave transparent and bendable membranes. The membrane with IEC = 2.22 meq g−1 exhibited high proton conductivity in wide range of relative humidity (RH) at 80 °C (ca. 1.6 mS cm−1 at 20% RH and 351.2 mS cm−1 at 95% RH). Moreover, the stiff ladder structure strengthened the molecular chain which contributed to the membrane with high IEC value and water uptake to have desirable mechanical stability up to 90% RH at 80 °C.

Durability and Degradation Analysis of a Hydrocarbon Membrane in PEFC Accelerated Stress Evaluation

Perfluorosulfonic acid (PFSA) membranes such as Nafion® have been widely used as the electrolyte for polymer electrolyte fuel cells (PEFCs) in automotive applications due to their high proton conductivity and chemical stability. However, high gas permeability and high cost remain issues for the PFSA membranes. In our previous studies,1 we proposed advanced strategies for addressing these problems by developing and applying aromatic block copolymer electrolyte membranes that possess highly hydrophilic/hydrophobic phase separation, high proton conductivity and low gas permeability. In this study, we investigated the durability of an aromatic block copolymer membrane (sulfonated poly ketone block copolymer: SPK-bl-12) and PFSA membrane (Nafion NRE 211), both 25 µm thick, under accelerated operating conditions appropriate for actual fuel cell vehicles. The durability of open circuit voltage (OCV) was evaluated under hydrogen (76% RH) and air (86% RH) at 90 oC and 160 kPaG pressure. In addition, we examined the effects of a practical startup process through a combined durability test (startup and OCV) for the membranes. For the practical startup process, first, air was supplied to the anode and cathode for 90 seconds, and then H2 gas was introduced to the anode for 90 seconds. Finally, N2 gas was supplied to the anode and cathode for 60 seconds. These three steps were defined as one cycle. The durability of the membrane electrode assemblies (MEAs) prepared with SPK-bl-1 and NRE 211 were evaluated for 1000 cycles. After the durability evaluation, the post-test MEAs were analyzed via gel permeation chromatography (GPC), nuclear magnetic resonance (NMR), and cross-sectional scanning electron microscopy (SEM). These results were compared with those of the initial MEAs. Figure 1 shows the OCV evaluation for the cells using SPK-bl-1 and NRE211 membranes. The durability of the MEA using SPK-bl-1 was superior to that using NRE211. This may be attributed to the suppression of the decomposition of the membrane, because the gas permeability of the SPK-bl-1 was one order of magnitude lower than that of NRE 211, which would reduce the production of oxidative radical species from hydrogen peroxide generated on the anode side. However, the cell potentials of both membranes decreased significantly in the OCV evaluation combined with startup cycles, as seen in Figure 1 (open symbols). This indicates that the startup cycles accelerated the degradation of the membranes. The GPC and NMR spectra show that the weight-averaged molecular weight of SPK-bl-1 decreased by ca. 25% during the durability tests, and the hydrophilic blocks of the membrane were partially decomposed. These analyses indicate that the SPK-bl-1 membrane was likely to decompose in the hydrophilic blocks. Figure 2 shows SEM/ electron probe microanalysis (EPMA) images of the MEAs using SPK-bl-1 before and after the durability evaluation. The sulfur content decreased near the anode side in the membrane, and Pt particles were deposited at the interface between the anode catalyst layer and the membrane (faint red line). To investigate the factors involved in accelerated aging in more detail, we used Pd/CB as the anode catalyst instead of Pt/CB and analyzed the distribution of Pt in the MEA. Figure 3 shows the ZC image and energy-dispersive X-ray (EDX) spectrometric analysis of the MEA using SPK-bl-1 after 1000 cycles of startup evaluation. The Pt particles in the cathode were dissolved into the membrane and were re-precipitated along with the Pd particles in the membrane. These analyses may suggest the possibilities that (1) the Pt ions dissolved from the cathode migrated within the membrane toward the anode, (2) even reaching the anode/membrane interface, and (3) then the Pt ions were reduced by permeated hydrogen. In addition, we investigated the distribution of Pt particle size during the durability evaluation (Figure 4). The Pt particle size of the cathode catalyst (Pt/GCB-HT) decreased after the startup evaluation, whereas that of the anode catalyst (Pt/CB) increased. The former result was in accordance with that in our previous research3, but the latter might be ascribed to the Pt deposition from the anode catalyst layer possibly because hydrogen and air supplied to the anode during the startup evaluation caused the anode potential to vary between 0 V and 1.0 V vs. RHE. Acknowledgement This research was supported by funds for the “Research on Nanotechnology for High Performance Fuel Cells” (HiPer-FC) project from the New Energy and Industrial Technology Development Organization (NEDO) of Japan.

A Proton Conductive Aromatic Block Copolymer Containing Dibenzofuran Moieties

Abstract A rigid, planar dibenzofuran in the hydrophobic parts provided sulfonated aromatic block copolymer with improved membrane properties, i.e., well-developed phase separation, effective water uptake, high proton conductivity, and moderate mechanical strength at wide range of humidity.

Anion conductive aromatic block copolymers containing diphenyl ether or sulfide groups for application to alkaline fuel cells.

A novel series of aromatic block copolymers composed of fluorinated phenylene and biphenylene groups and diphenyl ether (QPE-bl-5) or diphenyl sulfide (QPE-bl-6) groups as a scaffold for quaternized ammonium groups is reported. The block copolymers were synthesized via aromatic nucleophilic substitution polycondensation, chloromethylation, quaternization, and ion exchange reactions. The block copolymers were soluble in organic solvents and provided thin and bendable membranes by solution casting. The membranes exhibited well-developed phase-separated morphology based on the hydrophilic/hydrophobic block copolymer structure. The membranes exhibited mechanical stability as confirmed by DMA (dynamic mechanical analyses) and low gas and hydrazine permeability. The QPE-bl-5 membrane with the highest ion exchange capacity (IEC = 2.1 mequiv g(-1)) exhibited high hydroxide ion conductivity (62 mS cm(-1)) in water at 80 °C. A noble metal-free fuel cell was fabricated with the QPE-bl-5 as the membrane and electrode binder. The fuel cell operated with hydrazine as a fuel exhibited a maximum power density of 176 mW cm(-2) at a current density of 451 mA cm(-2).

Double-layer ionomer membrane for improving fuel cell performance.

A double-layer ionomer membrane, thin-layer Nafion (perfluorinated sulfonic acid polymer) on a sulfonated aromatic block copolymer (SPK-bl-1), was prepared for improving fuel cell performance. Each component of the double-layer membrane showed similar phase-separated morphologies to those of the original membranes. A fuel cell with the double-layer membrane exhibited lower ohmic resistance and higher cathode performance than those with the original SPK-bl-1 membrane despite their comparable water uptake and proton conductivity. Detailed electrochemical analyses of fuel cell data suggested that the thin Nafion interlayer contributed to improving the interfacial contact between the SPK-bl-1 membrane and the cathode catalyst layer and to mitigating excessive drying of the membrane. The results provide new insight on designing high-performance fuel cells with nonfluorinated ionomer membranes such as sulfonated aromatic polymers.

Temperature‐ and Humidity‐Controlled SAXS Analysis of Proton‐Conductive Ionomer Membranes for Fuel Cells

We report herein temperature- and humidity-controlled small-angle X-ray scattering (SAXS) analyses of proton-conductive ionomer membranes. The morphological changes of perfluorosulfonic acid polymers (Nafion and Aquivion) and sulfonated aromatic block copolymers (SPE-bl-1 and SPK-bl-1) were investigated and compared under conditions relevant to fuel cell operation. For the perfluorinated ionomer membranes, water molecules were preferentially incorporated into ionic clusters, resulting in phase separation and formation of ion channels. In contrast, for the aromatic ionomer membranes, wetting led to randomization of the ionic clusters. The results describe the differences in the proton-conducting behavior between the fluorinated and nonfluorinated ionomer membranes, and their dependence on the humidity.

Intrapolymer Heck reaction for proton conductive ladder-type aromatic block copolymers

A novel polymer synthetic method, intrapolymer Heck reaction, provided ladder-type ionomer membranes with excellent proton conductivity (221 mS cm−1at 80 °C and 90% relative humidity) and mechanical strength over a wide range of humidity (ca.0–90% relative humidity) at 80 °C.

Atomic force microscopy studies of conductive nanostructures in solid polymer electrolytes

The conductivity of three different sulfonated polymer electrolyte membranes (PEM), two perfluorinated membranes, Nafion® and Aquivion®, and JST, a non-perfluorinated aromatic block copolymer, were compared using advanced material-sensitive and conductive atomic force microscopy (AFM). All of the membranes required activation by a current flow to reach significant conductivity for the AFM analysis, indicating the existence of a highly resistive surface skin layer. The two perfluorinated sulfonic acid membranes, a membrane with long side-chains (Nafion®) and a membrane with short side-chains (Aquivion®), exhibited similar properties. A lamellar surface structure, with polymer bundles or micelles in a parallel orientation, was also found for the Aquivion® membrane. AFM high-resolution current images, performed under a continuous current flow, were used to distinguish between the conducting network and the subsurface phase distribution at the membrane surface. The connected subnets of the JST membrane were approximately 100–200nm in size, whereas those for the perfluorinated membrane surfaces were 200–300nm in size. The conductive areas of the Aquivion® and JST membranes exhibited larger homogeneous conducting areas, corresponding to the smaller correlation lengths of ionic phase separation. Membrane cross sections were analyzed to elucidate the structure of the bulk ionic network of the Nafion® membrane, before and after operation. The existence of extended water layers in the bulk, even before operation, was confirmed.

Synthesis and Properties of Partially Fluorinated Poly(arylene ether) Block Copolymers Containing Ammonium Groups as Anion Conductive Membranes

Abstract Synthesis and properties of aromatic block copolymers containing fluorinated phenylene and biphenylene groups and ammonium-substituted fluorene groups are reported. High-molecular-weight poly(arylene ether) block copolymers were prepared from the corresponding telechelic oligomers and were chloromethylated. Quaternization reaction of the chloromethylated precursors with trimethylamine provided the title ammonium-substituted block copolymers (QPE-bl-4). The QPE-bl-4 membrane with the highest ion-exchange capacity (IEC = 1.3 mequiv g−1) showed high hydroxide ion conductivity (45 mS cm−1) at 80 °C due to its phase-separated morphology with interconnected ion-transporting pathway. The accelerated stability test in aqueous KOH solution containing hydrazine revealed that the ammonium groups decomposed to certain extent while the polymer main chains were rather robust to maintain the self-supporting membranes.

Anion Conductive Aromatic Block Copolymer Membranes Containing Diphenyl Ether or Diphenyl Sulfide Moieties

not Available.

Block selective grafting of poly(vinylphosphonic acid) from aromatic multiblock copolymers for nanostructured electrolyte membranes

Alternating aromatic multiblock copolymers have been structurally designed to enable selective lithiation and subsequent anionic graft polymerization from only one of the two block types. The multiblock copolymers were prepared by coupling polyfluoroether (PFE) and polysulfone (PSU) precursor blocks under mild conditions. The judicious combination of blocks allowed for block selective lithiation of the PSU blocks to obtain a macroinitiator for anionic polymerization of diethyl vinylphosphonate. The block selective grafting was confirmed by 1H and 19F NMR spectroscopy. After hydrolysis to obtain poly(vinylphosphonic acid) (PVPA) side chains, mechanically stable transparent electrolyte membranes were cast from 1-methyl-2-pyrrolidinone solutions. Analysis by atom force microscopy showed that the copolymers self-assembled to form nanostructured membranes with continuous proton conducting PVPA phase domains. Calorimetry showed separate glass transition temperatures from the PFE and PVPA phases, with the latter increasing with increasing annealing temperatures as a result of anhydride formation. Fully hydrated multiblock copolymer membranes reached proton conductivities above 80 mS cm−1 at 120 °C. The approach of block selective lithiation and modification of aromatic block copolymers can be used as a general strategy to prepare durable and functional nanostructured polymer membranes and materials.