Ionomers for proton exchange membrane fuel cells by sulfonation of novel dendritic multiblock copoly(ether‐sulfone)s

The synthesis and properties of the first examples of dendritic multiblock co PES s, bearing sulfonated dendritic clusters, that form strong membranes are described. End‐capped dendritic multiblock co PES s with various average block lengths (n = 50–80) were synthesized by two‐step reactions. The synthesis of dendritic blocks consisting of difunctional dendritic block and monofunctional dendritic end‐group was accomplished by an aromatic nucleophilic substitution reaction of hexakis(4‐(4‐fluorophenylsulfonyl)phenyl)benzene with varying amounts of 1‐(4‐hydroxyphenyl)‐2,3,4,5,6‐pentaphenylbenzene, which provides a number of pendant phenyl rings as postsulfonation sites. Polycondensation of a controlled molar ratio between 4,4′‐dihydroxybenzophenone and bis(4‐fluorophenyl)sulfone monomers was carried out in the presence of the difunctional and monofunctional dendritic blocks in sulfolane at 215 °C for 3.5 h. Essentially six sulfonic acid groups were introduced into each hexaphenylbenzene moiety on the dendritic blocks by reaction with a large excess of chlorosulfonic acid, followed by hydrolysis with KOH aqueous solution. The introduction of longer average blocks (n = 60–80) into the dendritic PES s improved the mechanical properties of the resulting sulfonated dendritic PES membranes. At a level of IEC (0.92–1.26 meq/g) similar to Nafion (0.91 meq/g), PES membranes showed proton conductivities (58–67 mS/cm) comparable with that of Nafion (99 mS/cm). © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5461–5473, 2009     

An efficient route for the synthesis of hyperbranched polymers and dendritic building blocks based on urea linkages

A highly efficient synthetic route, based on the quantitative reaction between amine and isocyanate functionalities, was used successfully for the synthesis of hyperbranched polymers and dendritic building blocks based on urea linkages. The thermal decomposition of 3,5‐diamino benzoyl azide or 5‐amino isophthaloyl azide generated in situ the corresponding phenyl isocyanates, which were then polymerized to give wholly aromatic hyperbranched polyureas. Hyperbranched polyurea with amine chain ends was soluble in common organic solvents. The degree of branching, as calculated with ¹H NMR, was 0.55. Diethyl 5‐amino isophthalate and Boc‐protected 5‐amino isophthaloyl azide were used for the successful stepwise synthesis of dendritic wedges based on urea linkages. The thermal generation of the isocyanate functionality with gaseous nitrogen as the side product and its quantitative reaction with amine groups were the salient features of this convergent synthesis. This eliminated the use of chromatographic purification, an inherent part of other convergent growth approaches, and made it a very efficient synthetic route for the synthesis of dendritic wedges. The products were characterized by ¹H NMR, ¹³C NMR, and electron spray mass spectroscopy (ESMS) techniques. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1295–1304, 2001     

Synthesis and sulfonation of poly(arylene ether)s containing tetraphenyl methane moieties

Novel poly(arylene ether)s with sulfonic acid containing pendent groups were successfully synthesized by the nucleophilic displacement of aromatic dihalides with bisphenols in an aprotic solvent in the presence of excess potassium carbonate followed by sulfonation with chlorosulfonic acid. The sulfonation took place only at the controlled positions on the phenyl rings due to the novel bisphenol structures designed. The sulfonic acid group containing polymers were very soluble in common organic solvents, such as dimethyl sulfoxide, N,N′‐dimethylacetamide, and dimethylformamide, but swelled only slightly in water. These sulfonic acid group containing polymers were readily cast into tough and smooth films from organic solvents. The synthesized polymers had high glass‐transition temperatures of 171.0–240.7 °C and high molecular weights of 15,600–33,000 Da. These films could potentially be used as proton‐exchange membranes for fuel cells. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1779–1788, 2004     

Selectively sulfonated poly(aryl ether sulfone)‐b‐polybutadiene for proton exchange membrane

A series of selectively sulfonated poly(arylene ether sulfone)‐b‐polybutadiene copolymers (SPAES‐b‐PB) were prepared based on carboxyl terminated polybutadiene (CTPB) and sulfonated poly(arylene ether sulfone) (SPAES) that was directly prepared by polycondensation of 4,4′‐isopropylidenediphenol with different molar ratios of disodium 3,3′‐disulfonate‐4,4′‐dichlorodiphenyl sulfone (SDCDPS) to 4,4′‐dichlorodiphenylsulfone (DCDPS), and subsequent selective postsulfonation of flexible PB block was carried out. Epoxidized modification of membranes was conducted by an in situ‐generated peracid method. The content of sulfonic acid groups attaching to aromatic rings in SPAES was determined by ¹H NMR and was in good aggrement with the controlled ratios. The effect of sulfonated rigid blocks on the postsulfonation of PB blocks was studied by Fourier transform infrared spectroscopy. The glass transition temperature (T_g) and the temperature of the melting peak (T) of membranes in acid form were studied by differential scanning calorimetry. Fenton's reagent test revealed that the selectively sulfonated SPAES‐b‐PB membranes had good stability to oxidation. The microstructure of rod‐like rigid SPAES blocks and interpenetrating network of ions were observed by transmission electron microscopy. Complex impedance measurement showed that an epoxidized membrane with SPAES‐40 exhibited the highest proton conductivity (1.08 × 10^?1 S/cm, 90 °C), which was due to the formation of obvious ionic networks. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 665–672, 2006     

Synthesis and solution properties of anionic linear–dendritic block amphiphiles

The design and synthesis of novel linear–dendritic diblock amphiphiles with linear poly(acrylic acid) (PAA) as the hydrophilic block and dendritic poly(benzyl ether) as the hydrophobic block are described. The synthetic process consisted of two steps: a poly(methyl acrylate) (PMA)–poly(benzyl ether) dendrimer series were synthesized with atom transfer radical polymerization, and through the hydrolysis of linear PMA block into PAA, amphiphilic block copolymers, the PAA–poly(benzyl ether) dendrimer series, were obtained. The copolymers were characterized by ¹H NMR, Fourier transform infrared, and size exclusion chromatography and exhibited well‐defined architectures and low polydispersities. When the generation number of the dendritic block (G_i) less or equal to 3 and the degree of polymerization of the linear chain (n) was greater than 10, the amphiphiles were water‐soluble. The solution intrinsic viscosity increased with both the length of linear chain and the generation number of the dendritic block. The results obtained demonstrate that dendritic blocks play an unusual role in aqueous solutions of amphiphiles. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4282–4288, 2000     

Synthesis of partially fluorinated poly(arylene ether sulfone) multiblock copolymers bearing perfluorosulfonic functions

Partially fluorinated poly(arylene ether sulfone) multiblock copolymers bearing perfluorosulfonic functions (ps‐PES‐FPES), with ionic exchange capacity (IEC) ranging between 0.9 and 1.5 meq H⁺/g, are synthesized by regioselective bromination of partially fluorinated poly(arylene ether sulfone) multiblock copolymers (PES‐FPES), followed by Ullman coupling reaction with lithium 1,1,2,2‐tetrafluoro‐2‐(1,1,2,2‐tetrafluoro‐2‐iodoethoxy)ethanesulfonate. The PES‐FPES are prepared by aromatic nucleophilic substitution reaction by an original approach, that is, “one pot two reactions synthesis.” The chemical structures of polymers are analyzed by ¹H and ¹⁹F NMR spectroscopy. The resulted ionomers present two distinct glass transitions and α relaxations revealing phase separation between the hydrophilic and the hydrophobic domains. The phase separation is observed at much lower block lengths of ps‐PES‐FPES as compared with the literature. AFM and SANS observations supported the phase separation, the hydrophilic domains are well dispersed but the connectivity to each other depends on the ps‐PES block lengths. The thermomechanical behavior, the water up‐take, and the conductivity of the ps‐PES‐FPES membranes are compared with those of Nafion 117^® and randomly functionalized polysulfone (ps‐PES). Conductivities close or higher to those of Nafion 117^® are obtained. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1941–1956     

Synthesis,characterization, and properties of linear poly(ether sulfone)s with dendritic terminal groups

Hybrid linear‐dendritic ABA polymers, where A and B are dendritic and linear polymers, respectively, were synthesized in a single step via step‐growth polymerization of 4,4′‐difluorodiphenylsulfone and bisphenol A using arylether ketone dendrons of first and second generations (G1‐OH and G2‐OH) as monofunctional end‐cappers. These G1 and G2‐terminated poly(ether sulfone)s (G1‐PESs and G2‐PESs) were characterized by ¹H NMR, SEC, DSC, TGA, melt rheology, and tensile tests. The comparison of the glass transition temperatures (T_gs) of these polymers with those of t‐butylphenoxy‐terminated polysulfones reveal that the G1‐ and G2‐PESs have lower T_gs at all molecular weights investigated. However, a plot of T_g versus 1/M_n shows that the difference between the three series becomes negligible at infinite molecular weight and agrees to the chain end free volume theory. The melt viscosities of G1‐PES and G2‐PES with high molecular weights do not show a Newtonian region and, in the high frequency region, their viscosities are lower than that of the control while the stress–strain properties are comparable to those of the control, suggesting that it is possible to reduce the high shear melt viscosity of a PES without affecting the stress–strain properties by introducing bulky dendritic terminal groups. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 958–969, 2008     

Synthesis and characterization of novel fluoride‐releasing monomers. II. Dimethacrylates containing bis(aminodiacetic acid) and their ternary zirconium fluoride complexes

Novel dimethacrylate monomers containing bis(aminodiacetic acid) chelating ligands with or without additional hydroxyl groups were synthesized, starting from 2,2‐bis(4‐hydroxy‐3‐methylphenyl)propane. The structures of the monomers were characterized by electrospray mass spectrometry (ESMS), ¹H NMR, and ¹³C NMR. The structures and relative stability of fluoride‐releasing monomers containing one or more ternary zirconium fluoride complex moieties were studied by ESMS. The most stable ternary zirconium fluoride complex was in the form of [LZrF]^?, where H₄L is the monomer containing bis(aminodiacetic acid) without additional hydroxyl groups. The synthesized monomer was photopolymerized with camphorquinone and 1‐phenyl‐1,2‐propane‐dione as initiators and N,N‐dimethylaminoethyl methacrylate as the accelerator. The fluoride release, fluoride recharge, compressive strength, and flexure strength were tested on the experimental dental composite containing 13.7 wt % synthesized monomer and three commercial flowable dental composites. The results showed that the experimental composite has significantly higher fluoride release and recharge capabilities than the commercial flowable composites. The compressive strength was comparable to that of the commercial materials. The water sorption and solubility met the requirement of the ISO Specification 4049. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3153–3166, 2005     

Synthesis and surface properties of fluorinated block copolymers containing sulfonic groups

A series of fluorinated block copolymers with different fluorinated block lengths and compositions were synthesized by atom transfer radical polymerization (ATRP), and then the block copolymers containing sulfonic groups with various sulfonation levels were successfully prepared further via a sulfonation reaction. These well‐defined block copolymers were characterized by means of Fourier transform infrared (FTIR), ¹H‐nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC). The surface activities of the fluorinated block copolymers containing sulfonic groups in N‐methyl pyrrolidone solution and the surface properties of the films prepared from such a solution were examined, and the experimental results showed that the fluorinated block copolymers exhibited a high surface activity in solution and quite a low solid surface energy of films, even though they contain hydrophilic sulfonic groups. The critical surface tensions of these copolymers were estimated and were comparable to that of polytetrafluoroethylene. Even more interestingly, the surface activities of the block copolymers containing sulfonic groups or sodium sulfonate groups in aqueous solution were also measured. It was found that the surface activity in aqueous solution was weaker than that in N‐methyl pyrrolidone solution and depended on both the length of the fluorinated block and the sulfonation level of the block copolymers. The surface properties of the films prepared from the block copolymers in aqueous solution were tested, and most of these films exhibited a hydrophilic surface property. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4809–4819, 2004     

Dihydrophilic block copolymers with ionic and nonionic blocks. I. Poly(ethylene oxide)‐b‐polyglycidol with OP(O)(OH)2, COOH,or SO3H functions: Synthesis and influence for CaCO3 crystallization

Dihydrophilic block copolymers of poly(ethylene oxide)‐b‐polyglycidol were prepared and polyglycidol blocks converted into ionic blocks containing  OP(O)(OH)₂,  COOH, or  SO₃H groups. Although phosphorylation of polyhydroxy compounds with POCl₃ usually leads to insoluble products, phosphorylation of poly(ethylene oxide)‐b‐polyglycidol using a POCl₃/ OH ratio equal to 1/1 gave soluble products, predominantly monoester of phosphoric acid (after hydrolysis) (provided that the reaction was conducted in triethyl phosphate as solvent). All copolymers were characterized by ¹H NMR, ¹³C NMR, and/or ³¹P NMR spectra for confirming their structure. The degree of substitution was determined from quantitative ¹³C NMR spectroscopy (inverted‐gate decoupling‐acquisition mode). Preliminary results indicate that from these three groups of block copolymers the phosphoric acid esters are the most effective ones at least in controlling the growth of CaCO₃ crystals in aqueous solution. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 955–963, 2001     

Hydroxyl‐terminated hyperbranched aromatic poly(ether‐ester)s: Synthesis,characterization, end‐group modification,and optical properties

Novel AB₂‐type monomers such as 3,5‐bis(4‐methylolphenoxy)benzoic acid ( monomer 1 ), methyl 3,5‐bis(4‐methylolphenoxy) benzoate ( monomer 2 ), and 3,5‐bis(4‐methylolphenoxy)benzoyl chloride ( monomer 3 ) were synthesized. Solution polymerization and melt self‐polycondensation of these monomers yielded hydroxyl‐terminated hyperbranched aromatic poly(ether‐ester)s. The structure of these polymers was established using FTIR and ¹H NMR spectroscopy. The molecular weights (M_w) of the polymers were found to vary from 2.0 × 10³ to 1.49 × 10⁴ depending on the polymerization techniques and the experimental conditions used. Suitable model compounds that mimic exactly the dendritic, linear, and terminal units present in the hyperbranched polymer were synthesized for the calculation of degree of branching (DB) and the values ranged from 52 to 93%. The thermal stability of the polymers was evaluated by thermogravimetric analysis, which showed no virtual weight loss up to 200 °C. The inherent viscosities of the polymers in DMF ranged from 0.010 to 0.120 dL/g. End‐group modification of the hyperbranched polymer was carried out with phenyl isocyanate, 4‐(decyloxy)benzoic acid and methyl red dye. The end‐capping groups were found to change the thermal properties of the polymers such as T_g. The optical properties of hyperbranched polymer and the dye‐capped hyperbranched polymer were investigated using ultraviolet‐absorption and fluorescence spectroscopy. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5414–5430, 2008     

Fluorinated block copolymers containing poly(vinylidene fluoride) or poly(vinylidene fluoride‐co‐hexafluoropropylene) blocks from perfluoropolyethers: Synthesis and thermal properties

PFPE‐b‐PVDF and PFPE‐b‐poly(VDF‐co‐HFP) block copolymers [where PFPE, PVDF, VDF, and HFP represent perfluoropolyether, poly(vinylidene fluoride), vinylidene fluoride (or 1,1‐difluoroethylene), and hexafluoropropylene] were synthesized by radical (co)telomerizations of VDF (or VDF and HFP) with an iodine‐terminated perfluoropolyether (PFPE‐I). Di‐tert‐butyl peroxide (DTBP) was used and was shown to act as an efficient thermal initiator. The numbers of VDF and VDF/HFP base units in the block copolymers were assessed with ¹⁹F NMR spectroscopy. According to the initial [PFPE‐I]₀/[fluoroalkenes]₀ and [DTBP]₀/[fluoroalkenes]₀ molar ratios, fluorinated block copolymers of various molecular weights (1500–30,300) were obtained. The states and thermal properties of these fluorocopolymers were investigated. The compounds containing PVDF blocks with more than 30 VDF units were crystalline, whereas all those containing poly(VDF‐co‐HFP) blocks exhibited amorphous states, whatever the numbers were of the fluorinated base units. All the samples showed negative glass‐transition temperatures higher than that of the starting PFPE. Interestingly, these PFPE‐b‐PVDF and PFPE‐b‐poly(VDF‐co‐HFP) block copolymers exhibited good thermostability. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 160–171, 2003     

Fluorinated,crosslinkable terpolymers based on vinylidene fluoride and bearing sulfonic acid side groups for fuel‐cell membranes

The radical terpolymerization of 8‐bromo‐1H,1H,2H‐perfluorooct‐1‐ene with vinylidene fluoride (VDF) and perfluoro(4‐methyl‐3,6‐dioxaoct‐7‐ene) sulfonyl fluoride is presented. Changing the feed compositions of these three fluorinated comonomers enabled us to obtain different random‐type poly[vinylidene fluoride‐ter‐perfluoro(4‐methyl‐3,6‐dioxaoct‐7‐ene) sulfonyl fluoride‐ter‐8‐bromo‐1H,1H,2H‐perfluorooct‐1‐ene] terpolymers containing various sulfonyl fluoride and brominated side groups. Yields higher than 70% were reached in all cases. The hydrolysis of the sulfonyl fluoride group into the ? SO₃Li function in the presence of lithium carbonate was quantitatively achieved without the content of VDF being affected, and so dehydrofluorination of the VDF base unit was avoided. These original terpolymers were then crosslinked via dangling bromine atoms in the presence of a peroxide/triallyl isocyanurate system, which produced films insoluble in organic solvents such as acetone and dimethylformamide (which totally dissolved uncured terpolymers). The acidification of ? SO₃Li into the ? SO₃H function enabled protonic membranes to be obtained. The thermal stabilities of the crosslinked materials were higher than those of the uncured terpolymers, and their electrochemical performances were investigated. According to the contents of the sulfonic acid side functions, the ion‐exchange capacities ranged from 0.6 to 1.5 mequiv of H⁺/g, whereas the water uptake and conductivities ranged from 5–26% (±11%) and from 0.5 to 6.0 mS/cm, respectively. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4566–4578, 2006     

Synthesis and properties of poly(arylene ether)s bearing sulfonic acid groups on pendant phenyl rings

Two kinds of new aromatic poly(arylene ether)s containing sulfonic acid groups were synthesized. Polymer 1 composed of tetraphenylphenylene ether and perfluorobiphenylene units was sulfonated with chlorosulfonic acid. Sulfonation took place only at the para position of the pendant phenyl rings. The average degree of sulfonation per repeating unit (m) was controlled from 1 to 4. Sulfonated polymer 2 with m = 3 was soluble in methanol and dimethyl sulfoxide and swelled in water. Incorporating bis(3,5‐dimethylphenyl)sulfone moieties into the sulfonated polymer imparts less methanol affinity. Polymers 4 with 30–65 mol % tetrakis(sulfophenyl)phenylene ether units has high decomposition temperatures above 300 °C, hydrophilicity, and good hydrolytic stability. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3211–3217, 2001     

Synthesis and photophysical characterization of amphiphilic dendritic–linear–dendritic block copolymers

Amphiphilic dendritic–linear–dendritic triblock copolymers based on hydrophilic linear poly(ethylene oxide) (PEO) and hydrophobic dendritic carbosilane were synthesized with a divergent approach at the allyl end groups of diallyl‐terminated PEO. Their micellar characteristics in an aqueous phase were investigated with dynamic light scattering, fluorescence techniques, and transmission electron microscopy. The block copolymer with the dendritic moiety of a third generation could not be dispersed in water. The block copolymers with the first (PEO–D ‐Si‐1G) and second (PEO–D ‐Si‐2G) generations of dendritic carbosilane blocks formed micelles in an aqueous phase. The critical micelle concentrations of PEO–D ‐Si‐1G and PEO–D ‐Si‐2G, determined by a fluorescence technique, were 27 and 16 mg/L, respectively. The mean diameters of the micelles of PEO–D ‐Si‐1G and PEO–D ‐Si‐2G, measured by dynamic light scattering, were 170 and 190 nm, respectively, which suggests that the micelles had a multicore‐type structure. The partition equilibrium constants of pyrene in the micellar solution increased with the increasing size of the dendritic block (e.g., 7.68 × 10⁴ for PEO–D ‐Si‐1G and 9.57 × 10⁴ for PEO–D ‐Si‐2G). The steady‐state fluorescence anisotropy values (r) of 1,6‐diphenyl‐1,3,5‐hexatriene were 0.06 for PEO–D ‐Si‐1G and 0.09 for PEO–D ‐Si‐2G. The r values were lower than those of the linear polymeric amphiphiles, suggesting that the microviscosity of the dendritic micellar core was lower than that of the linear polymeric analogues. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 918–926, 2001     

Synthesis,characterization, and self‐assembly of comb‐dendronized amphiphilic block copolymers

Novel amphiphilic comb‐dendronized diblock copolymers composed of hydrophobic Percec‐type dendronized polystyrene block and hydrophilic comb‐like poly(ethylene oxide) grafted polymethacrylate P(PEOMA) block were designed and synthesized via two steps of atom transfer radical polymerization (ATRP). The comb‐like P(PEOMA) prepared by ATRP of macromonomers (PEOMA) with two different molecular weights (M_n = 300 and 475) were used to initiate the sequent ATRP of dendritic styrene macromonomer (DS). The molecular weights and compositions of the obtained block copolymers were determined by ¹H NMR analysis. The copolymers with relatively narrow polydispersities (1.27–1.38) were thus obtained. The bulk properties of comb‐dendronized block copolymers were studied by using differential scanning calorimetry, polarized optical microscopy and wide‐angle X‐ray diffraction (WAXD). Similar to dendronized homopolymers, the block copolymers exhibited hexagonal columnar liquid‐crystalline phase structure. By using such amphiphilic comb‐dendronized block copolymers as building blocks, the rich self‐assembly morphologies, such as twisted string, vesicle, and large compound micelle (LCM), were obtained in a mixture of CH₃OH and THF. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4205–4217, 2008     

Synthesis of proton‐conducting block copolymer membranes composed of a fluorinated segment and a sulfonic acid segment

Diblock copolymer membranes having a fluorinated segment and a sulfonic acid segment were prepared by living radical polymerization, solution casting, and crosslinking, followed by heat treatment. Diblock copolymers of 2,3,4,5,6‐pentafluorostyrene (PFS)/4‐(1‐methylsilacyclobutyl)styrene (SBS) and neopentyl styrenesulfonate (SSPen) (poly(PFS‐co‐SBS)‐b‐polySSPen)s were synthesized by nitoroxy‐mediated living radical polymerization. Self‐standing crosslinked membranes were obtained by casting a THF solution of the block copolymer with Pt catalyst. Heat treatment of the membrane at 230 °C induced decomposition of the neopentyl sulfonate esters to provide block copolymer membranes having a fluorinated segment and a free sulfonic acid segment. It was confirmed that the block copolymer with a high sulfonic acid content exhibited high ion exchange capacity and high proton conductivity as well as high thermal stability. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4479–4485, 2008     

Synthesis of hybrid dendritic‐linear block copolymers with dendritic initiators prepared by convergent living anionic polymerization

Hybrid dendritic‐linear block copolymers were made in one‐pot by convergent living anionic polymerization. Dendritic polystyrene macroinitiators were synthesized by slowly adding a mixture of either vinylbenzyl chloride (VBC) or 4‐(chlorodimethylsilyl)styrene (CDMSS) and styrene (1 : 10 molar ratio of coupling agent to styrene) to a solution of living polystyryllithium. The addition was ceased prior to the addition of a stoichiometric amount of coupling agent to retain a living chain end. To the living dendritically branched polystyrene was then added either styrene or isoprene to polymerize a linear block from the dendritic polystyrene. The resulting copolymers were characterized by gel permeation chromatography coupled with multiangle laser light scattering (GPC‐MALLS), which clearly demonstrated the formation of diblock copolymers. The diblock copolymers were further characterized by ¹H NMR, which showed the presence of the two blocks in the case of dendritic polystyrene‐block‐linear polyisoprene. The measurement of intrinsic viscosity showed that the dilute solution properties of the block copolymers are greatly influenced by the dendritic portion. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 152–161, 2001     

Novel sulfonated block copolymer containing pendant alkylsulfonic acids: Syntheses,unique morphologies,and applications in proton exchange membrane

In this article, we report the syntheses and characterizations of a series of novel block polyelectrolytes, poly(styrene‐block‐sulfonated hydroxystyrene) (PS‐b‐sPHS), containing pendant sulfonic acid groups attached to the backbone via propyl spacers in the sPHS domain. PS‐b‐sPHS with various compositions were synthesized via anionic polymerization and the following analogous chemistry to achieve accurate control of molecular weight (M_w), narrow polydispersity and high degree of sulfonation. Proton exchange membranes (PEMs) were prepared from PS‐b‐sPHS with sulfonic acids in either potassium salts or tetra‐alkylammonium salts via solvent casting and following treatments. Some unique morphologies, such as hallow channels and lamellar arrangement of strings of beads, were observed as a consequence of equilibrium between microphase separation and columbic interactions between polyelectrolytes. The transportation properties were found to closely relate to the morphologies of the PEMs. The combination of microphase separation of block polyelectrolytes and freedom of movement of pendent alkylsulfonic acids was demonstrated to effectively enhance the proton transport and suppress the methanol crossover for the PEMs, leading to the selectivity higher than Nafion 117 by five times at most. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis and characterization of novel phosphonated and sulfonated poly(styrene–isobutylene–styrene) for fuel cell and protective clothing applications

A novel aromatic block–graft copolymer of sulfonated poly(styrene–isobutylene–styrene)‐graft‐poly(vinyl phosphonic acid) (SIBS‐g‐PVPA SO₃H) was synthetized for direct methanol fuel cell (DMFC) and chemical and biological protective clothing (CBPC) applications. The polystyrene (PS) blocks of SIBS were chloromethylated via a Friedel–Crafts reaction to obtain the macroinitiator SIBS‐CH₂Cl. Atom transfer radical polymerization (ATRP) was performed to graft VPA to the chloromethylated groups of the macroinitiator and yield SIBS‐g‐PVPA, which was subsequently sulfonated using acetyl sulfate as the sulfonating agent. After each functionalization step, a membrane was prepared by using the solvent casting technique. The final membrane was composed of triblock SIBS as the backbone, PVPA grafts attached to the chloromethylated PS end blocks and sulfonic groups in the non‐chloromethylated PS units. A comprehensive materials characterization study (e.g., GPC, FTIR, TGA, EA) was performed to confirm proper functionalization of each material. Unique ionic interactions (i.e., crosslinking via formation of sulfonate–phosphonium complexes) arose between the phosphonic and sulfonic groups (i.e., PO₃H₂ and SO₃H, respectively) that enhanced the water absorption capabilities, thermal and oxidative stability, and the transport properties of SIBS. The SIBS‐g‐PVPA SO₃H membrane presented high Nafion ® normalized selectivity and separation efficiency, indicating that this ionomer adequately functions for both applications. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1424–1435