Viscometric behavior of disulfonated poly(arylene ether sulfone) random copolymers used as proton exchange membranes

tert-Butylphenyl-terminated disulfonated poly(arylene ether sulfone) random copolymers with a sulfonation degree of 35 mol% (BPS35) and controlled molecular weights (M_n), 20-50 kg mol⁻¹, were successfully prepared by direct copolymerization of the two activated halides, 4,4′-dichlorodiphenyl sulfone (DCDPS) and 3,3′-disulfonate-4,4′-dichlorodiphenyl sulfone (SDCDPS) with 4,4′-biphenol and the endcapper, 4-tert-butylphenol. Dilute viscosity measurements of the BPS35 random copolymers were successfully conducted in NMP containing various concentrations of LiBr from 0.01 to 0.2 M and mostly at 0.05 M according to the measured theory. The effects of salt concentration and molecular weights of the copolymers on the viscometric behavior were studied and compared with published data for sulfonated polystyrene. The charge density parameter (ξ) for the BPS35 copolymers was determined to be smaller than 1, suggesting that no counterion condensation occurs. Studies of the effect of ionic strength (I) on the intrinsic viscosities ([η]) under theta condition were obtained by plotting [η] vs. I^−1/2 and extrapolating to infinite ionic strength. For salt-free BPS35 solutions, the viscometric behavior was shown to fit well with the Liberti-Stivala equation, providing a way to determining intrinsic viscosity when the copolymer charge is fully screened. Intrinsic viscosity and molecular weight characterization of BPS35 copolymers by SEC and static light scattering are also presented. The results are very useful for characterizing polymeric electrolyte membrane (PEM) for fuel cells, reverse osmosis and ionic transducer membranes.     

Synthesis and aqueous solution characterization of amphiphilic diblock copolymers containing carbazole

A series of near-monodisperse diblock copolymers of 2-(N-carbazolyl)ethyl methacrylate and 2-(dimethylamino)ethyl methacrylate (DMAEMA) of relatively low molecular weights (2600-24,000 g mol⁻¹) were synthesized by group transfer polymerization using tetrahydrofuran (THF) as a solvent. The molecular weight distributions and compositions of all the copolymers were obtained using gel permeation chromatography (GPC) in THF and proton nuclear magnetic resonance (¹H NMR) spectroscopy, respectively. Differential scanning calorimetry and thermal gravimetric analysis provided low glass transition temperatures (T_gs) of about 60 °C and decomposition temperatures between 320 and 450 °C for the copolymers, respectively. The three copolymers with the highest DMAEMA content were water-soluble below pH 7. Aqueous GPC at pH 3 showed that the water-soluble block copolymers formed micelles with apparent number average molecular weights above 100,000 g mol⁻¹.     

Poly(arylene ether sulfone) multi-block copolymers bearing perfluoroalkylsulfonic acid groups

Poly(arylene ether sulfone) (PAES) multi-block copolymers bearing perfluoroalkylsulfonic acid moieties were prepared from hydrophilic and hydrophobic prepolymers. The latter were synthesized by reaction of N,N-diisopropylethylammonium 2,2-bis(p-hydroxyphenyl)pentafluoropropanesulfonate (HPPS) with bis-(4-fluorophenyl) sulfone (FPS), and biphenol (BP) with FPS, respectively. Prepolymers and multi-block copolymers were prepared at 180 °C in N,N-dimethylacetamide in the presence of K₂CO₃. The prepolymers were reacted overnight; the multi-block copolymers were reacted only 80 min to minimize transetherification. Prepolymers and multi-block copolymers were characterized using ¹H and ¹³C NMR. ¹⁹F NMR provided molecular weight of hydrophilic prepolymers bearing aryl fluoride end groups. GPC was used to characterize the multi-block copolymers. Copolymer block lengths were determined by quantifying ¹³C NMR peak areas of quaternary carbon atoms adjacent to sulfur in FPS moieties. Hydrophilic and hydrophobic block lengths were in the range 9.4-23.4 and 4.4-11.8 repeating units, respectively. AFM showed phase separation for all block lengths. Conductivity at 80 °C and 100% relative humidity ranged from 6.2 to 34.3 mS/cm, with the best value obtained for hydrophilic/hydrophobic block lengths of 13.3/6.0.     

Purity characterization of 3,3′-disulfonated-4,4′-dichlorodiphenyl sulfone (SDCDPS) monomer by UV–vis spectroscopy

The purity of the disulfonated monomer, 3,3′-disulfonated-4,4′-dichlorodiphenyl sulfone (SDCDPS), is very important for obtaining high molecular weight disulfonated poly(arylene ether sulfone) random or block copolymers, which are promising candidates for proton exchange membrane (PEM) fuel cells. For commercialization purposes, direct use of unrecrystallized SDCDPS monomer with known purity in the copolymerization favorably influences its economics relative to the traditional recrystallization purification process. In this paper, a novel method to characterize the purity of the prepared unrecrystallized SDCDPS has been developed using UV–vis spectroscopy. The purity of the comonomer was determined from a Beers Law calibration curve developed using a highly purified SDCDPS sample. High molecular weight poly(arylene ether sulfone) random copolymers, based on this unrecrystallized SDCDPS monomer, 4,4′-dichlorodiphenyl sulfone (DCDPS), and 4,4′-biphenol monomers, were successfully synthesized. The molecular weight obtained from gel permeation chromatography (GPC) (M_n > 45 kg mol^?1) was high enough to allow tough films for PEMs to be solvent cast. This confirmed that the purity characterization method was relatively accurate and applicable. The effect of storage and drying time of SDCDPS were also studied using Beer's Law plots.     

Functional bioengineering copolymers. II. Synthesis and characterization of amphiphilic poly(N-isopropyl acrylamide-co-maleic anhydride) and its macrobranched derivatives

Radical-initiated copolymerization of N-isopropyl acrylamide (NIPA) with maleic anhydride (MA) and macromolecular reactions of synthesized poly(NIPA-co-MA) with polyethyleneglycol (PEG with a methoxy chain end and molecular weight of 2000 g mol⁻¹) and polyethyleneimine (PEI with molecular weight of 2000 g mol⁻¹) have been studied as a way to obtain new reactive amphiphilic water-soluble polymers potentially useful as carriers for gene delivery. Structure, composition and thermal behaviour of synthesized copolymers and their macrobranched architectures are determined by FTIR, ¹H and ¹³C NMR spectroscopy, elemental (N content) and chemical (acid number) analysis and differential scanning calorimetry, differential thermal and thermal gravimetric methods. It is shown that synthesized copolymers with given composition have low critical solution temperature (LCST) in the range of 30.2-46.4 °C at pH values of 4.0-7.4, which suggest the possibility of their biomedical applications.     

Synthesis, characterization and evaluation of amphiphilic diblock copolymer emulsifiers based on methoxy hexa(ethylene glycol) methacrylate and benzyl methacrylate

Linear, amphiphilic diblock copolymers based on the nonionic, hydrophilic monomer methoxy hexa(ethylene glycol) methacrylate (HEGMA) and the hydrophobic monomer benzyl methacrylate (BzMA) of different molecular weights and compositions were synthesized by group transfer polymerization. The molecular weights and comonomer compositions of these copolymers were characterized by gel permeation chromatography and proton nuclear magnetic resonance (¹H NMR) spectroscopy, respectively. Dynamic light scattering on aqueous solutions of the diblock copolymers indicated that all the copolymers formed aggregates whose size increased with the % w/w BzMA composition and with the overall molecular weight of the linear chains. Turbidimetry on 1% w/w aqueous copolymer solutions was used to determine the cloud points, which were found to increase with the composition in hydrophilic units and the linear chain molecular weight. After polymer characterization, xylene/water and diazinon (pesticide)/water emulsions were prepared using the above polymers as stabilizers at 1% w/w polymer concentration and at different overall organic phase/water ratios. At an organic phase/water mass ratio of 4/1, the lower molecular weight (2500 and 5000 g mol⁻¹) diblock copolymers provided stable single-phase o/w emulsions, matching the behavior of commercially available hydrophilic Pluronics.     

Macrocycles 25. Cyclic poly(ether sulfone)s derived from 4-tert-butylcatechol

Poly(ether sulfone)s were prepared by polycondensation of silylated 4-tert-butylcatechol and 4,4′-difluorodiphenylsulfone in N-methylpyrrolidone. The feed ratio and the reaction time were varied to study the influence of stoichiometry and conversion on molecular weight and extent of cyclization. Molecular weights and molecular weight distributions (MWD)s were characterized by SEC measurements calibrated with polystyrene. Light scattering confirmed that calibration with polystyrene gives reasonable results and revealed a tendency towards a bimodal MWD for the samples rich in cycles. The MALDI-TOF mass spectrometry indicated that the extent of cyclization increased with higher conversion and with optimization of the stoichiometry. This interpretation was confirmed by ¹H NMR endgroup analyses. For the samples with the highest molar masses only mass peaks of cycles were found, which were detectable up to 20 000 Da before and up to 27 000 Da after fractionation. Via the pseudo-high dilution method low molar mass poly(ether sulfone) containing more than 95 mol% of cycles were prepared, and even these low molar mass samples had broad MWDs. DSC measurements indicated that the glass transition temperatures depend on the structure of the endgroups and increase with higher fractions of cycles.     

Synthesis of novel random and block copolymers of tert-butyldimethylsilyl methacrylate and methyl methacrylate by RAFT polymerization

Hydrophobic-hydrolysable copolymers consisting of methyl methacrylate (MMA) and tert-butyldimethylsilyl methacrylate (TBDMSMA) have been synthesized for the first time by Reversible Addition-Fragmentation chain Transfer (RAFT) polymerization technique using cumyl dithiobenzoate (CDB) and cyanoisopropyl dithiobenzoate (CPDB) as chain transfer agents (CTAs). The monomer reactivity ratios for TBDMSMA (r₁ = 1.40 ± 0.03) and MMA (r₂ = 1.08 ± 0.03) have been determined using a non-linear least-squares fitting method. Well-defined random copolymers PMMA-co-PTBDMSMA have been prepared. Then, the versatility of the RAFT process to synthesize silylated block copolymers with controlled molecular weights and low polydispersities has been demonstrated using two strategies: the synthesis of PMMA-SC(S)Ph or PTBDMSMA-SC(S)Ph as macro-chain transfer agent (macro-CTA) for use in a two step method or an one-pot method which consists in the successive addition of the two monomers. Diblock copolymers with narrow molecular weight distributions (PDI < 1.2) were obtained from the one-pot method with number-average molecular weight values within the range 10,000-22,000 g mol⁻¹.     

Honeycomb structured porous films from amphiphilic block copolymers prepared via RAFT polymerization

The synthesis of polystyrene-block-poly(N,N-dimethylacrylamide) (PS-b-PDMA) via RAFT polymerization was investigated in detail. Two different RAFT agents - benzyl dithiobenzoate and 3-(benzylsulfanylthiocarbonylsufanyl) propionic acid, were employed to prepare polystyrene macroRAFT agents with molecular weights varying between 3000 g mol⁻¹ and 62,000 g mol⁻¹ and polydispersities between 1.1 and 1.4. Chain extensions with N,N-dimethylacrylamide (DMA) were carried out using a constant monomer to RAFT agent concentration ([DMA]/[RAFT] = 500), to compare the rate of polymerization in dependency of the polystyrene chain length. A decreasing rate of polymerization with increasing block length was observed. Depending on the sizes of the first block and type of RAFT agents used, chain extension polymerization with DMA was found to be incomplete, leading to significant low molecular weight tailing in the GPC analyses. Block copolymers prepared using 3-(benzylsulfanylthiocarbonylsufanyl) propionic acid, followed the expected molecular weight evolutions with polydispersity indices of 1.2-1.4. In contrast, block copolymers using benzyl dithiobenzoate clearly showed bimodal molecular weight distributions, especially when the longest PS macroRAFT agent with a molecular weight of 38,000 g mol⁻¹ was employed. These amphiphilic block copolymers were used to fabricate honeycomb structured porous films using the breath figure technique. The regularity of the film was considerably influenced by the humidity of the environment, which could be controlled by the rate of the airflow or the humidity in the casting chamber. The interaction between the hydrophilic block copolymer and the humidity was found responsible for the delicate equilibrium during the casting process, which prevented high pores regularity at very low (below 50%) and at elevated (above 80%) humidity. The interactions of the hydrophilic block with the humidity were observed to superimpose an additional nano-scaled order onto the hexagonal micron-sized porous array. Pores, which are created by encapsulation of water droplets, were found to be more hydrophilic than the surface. Confocal microscopy studies were employed to locate hydrophilic blocks within the film using a fluorescence labeled PDMA polymer.     

Synthesis, isothermal crystallization and micellization of mPEG-PCL diblock copolymers catalyzed by yttrium complex

Amphiphilic biodegradable mPEG-PCL diblock copolymers have been synthesized using rare earth catalyst: yttrium tris(2,6-di-tert-butyl-4-methylphenolate) [Y(DBMP)₃] in the presence of monomethoxy poly(ethylene glycol) (mPEG, M_n = 5000) as macro-initiator. The diblock architecture of the copolymers was thoroughly characterized by ¹H NMR, ¹³C NMR and SEC. The molecular weights of mPEG-PCLs can be well controlled by adjusting the feeding molar ratio of ?-CL to mPEG. Thermal and crystallization behaviors of the diblock copolymers were investigated by DSC and POM (polarized optical microscope). The crystallization property of mPEG-PCL block copolymers depends on the length of PCL blocks. As the molecular weight of PCL block increased, the crystallization ability of mPEG block was visibly restrained. Aqueous micelles were prepared by dialysis method. The critical micelle concentration of the copolymers, which was determined to be 0.9-6.9 mg/L by fluorescence technique, increased with the decreasing of PCL block length. The particle sizes determined by DLS were 30-80 nm increasing with the PCL block length. TEM images showed that these micelles were regularly spherical in shape.     

Processing induced morphological development in hydrated sulfonated poly(arylene ether sulfone) copolymer membranes

The development of morphological solid-state structures in sulfonated poly(arylene ether sulfone) copolymers (acid form) by hydrothermal treatment was investigated by water uptake, dynamic mechanical analysis (DMA), and tapping mode atomic force microscopy (TM-AFM). The water uptake and DMA studies suggested that the materials have three irreversible morphological regimes, whose intervals are controlled by copolymer composition and hydrothermal treatment temperature. Ambient temperature treatment of the membranes afforded a structure denoted as Regime1. When the copolymer membranes were exposed to a higher temperature, AFM revealed a morphology (Regime2) where the phase contrast and domain connectivity of the hydrophilic phase of the copolymers were greatly increased. A yet higher treatment temperature was defined which yielded a third regime, likely related to viscoelastic relaxations associated with the hydrated glass transition temperature (hydrated T_g). The required temperatures needed to produce transitions from Regime1 to Regime2 or Regime3 decreased with increasing degree of disulfonation. These temperatures correspond to the percolation and hydrogel temperatures, respectively. Poly(arylene ether sulfone) copolymer membranes with a 40% disulfonation in Regime2 under fully hydrated conditions showed similar proton conductivity (∼0.1 S/cm) to the well-known perfluorinated copolymer Nafion^® 1135 but exhibited higher modulus and water uptake. The proton conductivity and storage modulus are discussed in terms of each of the morphological regimes and compared with Nafion 1135. The results are of particular interest for either hydrogen or direct methanol fuel cells where conductivity and membrane permeability are critical issues.     

Synthesis and characterization of novel random copolyesters from trans-4-hydroxy-l-proline and functional cyclic esters

The melt polycondensation reaction of trans-4-hydroxy-N-benzyloxycarbonyl-l-proline (N-CBz-Hpr) and functional cyclic esters containing protected functional groups (carboxyl, and amino) at a wide range of molar fractions in the feed produced new degradable poly(N-CBz-Hpr-co-functional-ε-CL)s with stannous 2-ethylhexanoate (Sn(Oct)₂) as a catalyst. The optimal reaction conditions for the synthesis of the copolymers were obtained with 1.5 wt% Sn(Oct)₂ at 140 °C for 24 h. The copolymers obtained were characterized by Fourier transform infrared spectroscopy (FT-IR), ¹H NMR, differential scanning calorimetry, gel permeation chromatography, and Ubbelohde viscometry. The copolymers synthesized exhibited oligomeric molecular weights (3000-5000 g mol⁻¹) with modestly narrow molecular weight distributions (1.11-1.37). The values of the glass-transition temperature (T_g) of the copolymers depend on the compositions, and the molar fractions of cyclic lactone. For the poly(N-CBz-Hpr-co-4-EtC-ε-CL) system, with a decrease in 4-EtC-ε-CL contents from 79 to 3 mol%, the T_g increased from −34 to 67 °C In vitro degradation of these copolymers was evaluated from weight-loss measurements.     

Synthesis and characterization of two shape-memory polymers containing short aramid hard segments and poly(ε-caprolactone) soft segments

A number of segmented copolymers were synthesized by reacting 4-aminobenzoyl end-functionalized poly(ε-caprolactone)s of M_n 2000, 3000 and 4000 g mol⁻¹ with three aromatic diacid dichlorides in the presence of chlorotrimethylsilane. Polymer purity, molar mass, thermal and mechanical properties were characterized by NMR, MALDI-TOF mass spectrometry, GPC, DSC, and DMTA. Promising shape-memory properties were observed for two polymers that contained comparatively short, semicrystalline poly(ε-caprolactone) soft segments of molecular weight 3000 g mol⁻¹ and either terephthalamide or 2,6-naphthalenedicarboxyamide hard segments. Cast films of these polymers were soft and elastomer-like at room temperature. Loading could be conveniently achieved by cold-drawing at room temperature and strain recovery took place upon heating above the melting temperature of the soft segment (35 °C). Cast films reached uniform deformation properties with strain recovery rates as high as 99% and strain fixity values of 78% after passing through only one or two training cycles.     

Synthesis, characterization and evaluation of amphiphilic star copolymeric emulsifiers based on methoxy hexa(ethylene glycol) methacrylate and benzyl methacrylate

Amphiphilic star copolymers were synthesized by sequential monomer and cross-linker additions using group transfer polymerization (GTP). Benzyl methacrylate (BzMA) and methoxy hexa(ethylene glycol) methacrylate (HEGMA) served as the hydrophobic and hydrophilic monomers, respectively, whereas the also hydrophobic ethylene glycol dimethacrylate (EGDMA) was used as the cross-linker. In total, twelve star copolymers were prepared, covering three different overall hydrophobic compositions, 39, 53 and 70% w/w, and four different architectures, AB star-block, BA star-block, heteroarm star and random star. The theoretical molecular weight of each arm was kept constant at 5000 g mol⁻¹. The molecular weights and molecular weight distributions of the linear precursors and of all the star copolymers were characterized by gel permeation chromatography (GPC) in tetrahydrofuran (THF), while their compositions were confirmed by proton nuclear magnetic resonance (¹H NMR) spectroscopy. Moreover, all the star copolymers were characterized by static light scattering (SLS) in THF to determine the absolute weight-average molecular weight, M_w, and the weight-average number of arms. After polymer characterization, xylene-water and diazinon (pesticide)-water emulsions were prepared using these star copolymers as stabilizers at 1% w/w copolymer concentration and at different overall organic phase/water ratios. The most important factor in determining the emulsion type was the star copolymer composition in hydrophobic units. The four most hydrophilic star copolymers (39% w/w hydrophobic composition) always formed o/w emulsions, while the four most hydrophobic star copolymers (70% w/w hydrophobic composition) always formed w/o emulsions. The type of the emulsion in the case of the star copolymers with the more balanced composition, 53% w/w hydrophobic units, also depended on the emulsion content in the organic solvent, similar to particulate-stabilized emulsions. Considering that the best o/w emulsifier is that star copolymer which can emulsify the largest quantity of organic phase in water resulting in low viscosity, o/w emulsions without excess oil or water phase, it appeared that the most hydrophilic random copolymer star is the optimal emulsifier. Moreover, this star copolymer presented the smallest droplet size in its emulsions. It is also noteworthy that the resulting emulsions almost never had high viscosity, a feature attributable to the compact nature of star polymers.     

Considerations of polymerization method and molecular weight for proton-conducting poly(p-phenylene) derivatives

Ni(0)-catalyzed coupling polymerization of 2,5-dichloro-4′-phenoxybenzophenone was investigated by varying the ligand and coligand, temperature, reaction time, and solvent. The weight-average molecular weight (M_w) of poly(4-phenoxybenzoyl-1,4-phenylene)s (PPBPs) could be controlled by the polymerization conditions and reached a maximum of 4.4 × 10⁵ g mol⁻¹. Sulfonated PPBPs (S-PPBPs) with various M_ws were prepared with sulfuric acid to study the effect of molecular weight on the chemical and electrical properties of PPBP-based electrolytes. The strong molecular interactions in S-PPBP provided an ion exchange capacity of 2.9 meq g⁻¹ without loss of high mechanical properties. High molecular weight S-PPBPs had more desirable properties for fuel cell applications. While the swelling ratios and hydration numbers of S-PPBPs decreased with increasing molecular weight, the mechanical strength, proton conductivity, and fuel cell performance increased. S-PPBP also showed anisotropic behavior in the swelling and proton conductivity; such behavior is caused by the rigid-rod nature and the liquid-crystal structure.     

Hydrophilic-hydrophobic multiblock copolymers based on poly(arylene ether sulfone) via low-temperature coupling reactions for proton exchange membrane fuel cells

Two series of multiblock copolymers based on poly(arylene ether sulfone)s were developed and evaluated for use as proton exchange membranes (PEMs). The multiblock copolymers were synthesized by a coupling reaction between phenoxide terminated fully disulfonated poly(arylene ether sulfone) (BPSH100) and decafluorobiphenyl (DFBP) or hexafluorobenzene (HFB) end-capped unsulfonated poly(arylene ether sulfone) (BPS0) as hydrophilic and hydrophobic blocks, respectively. The highly reactive nature of DFBP and HFB allowed the coupling reactions to be accomplished under mild reaction conditions (e.g., <105 °C). The low coupling temperatures prevented possible ether-ether exchange reactions which can cause a loss of order due to randomization of the hydrophilic-hydrophobic sequences. The multiblock copolymers produced tough and ductile membranes and their fundamental properties as PEMs were explored. They showed enhanced conductivities under fully hydrated conditions when compared with a random BPSH copolymer with a similar IEC. These copolymers also showed anisotropic swelling behavior, whereas the random copolymers were isotropic. The synthesis and fundamental properties of the multiblock copolymers are reported here and the systematic fuel cell properties and more detailed morphology characterization will be provided elsewhere.     

RAFT polymerization of hydrophobic acrylamide derivatives

Several hydrophobic acrylamide derivatives: the N-tert-butylacrylamide (TBAm), the N-octadecylacrylamide (ODAm) and the N-diphenylmethylacrylamide (DPMAm) have been polymerized by reversible addition-fragmentation chain transfer (RAFT) process in the presence of azobis(isobutyronitrile) (AIBN) and tert-butyl dithiobenzoate (tBDB) as initiator and reversible chain transfer agent (CTA), respectively. Homopolymerizations were compared as regards to kinetics and molecular weight (MW) control, and the results were discussed according to the monomer structure and to the influence of several experimental parameters, such as the [CTA]/[AIBN] ratio and the [Monomer]/[CTA] ratio. TBAm and ODAm monomers exhibited a well controlled polymerization (polydispersity index (PDI) below 1.3 for number average molecular weight (M_n) until 30,000 g mol⁻¹) over a wide range of conversion (until 70%), whereas DPMAm conversion remained below 20% partly due to steric hindrance. The molecular weights of several poly(TBAm) samples determined by four independent analytical techniques, size exclusion chromatography/on-line light scattering detector (SEC/LSD), ¹H NMR, ¹³C NMR and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS), were in agreement, close to the theoretical ones. Moreover, the MALDI-TOF MS analyses suggested the presence of parasite chains resulting from irreversible termination onto RAFT intermediate radicals.     

Synthesis of amphiphilic ethyl cellulose grafting poly(acrylic acid) copolymers and their self-assembly morphologies in water

Amphiphilic ethyl cellulose (EC)-g-poly(acrylic acid) (PAA) copolymers were synthesized by atom transfer radical polymerization (ATRP). Firstly, ethyl cellulose macro-initiators with the degree of the 2-bromoisobutyryl substitution of 0.04 and 0.25 synthesized by the esterification of the hydroxyl groups remained in EC macromolecular chains and the 2-bromoisobutyryl bromides. Secondly, tert-butyl acrylate was polymerized by ATRP with the ethyl cellulose macro-initiator and EC-g-PtBA copolymers were prepared. Finally, the EC-g-PAA copolymers were prepared by hydrolyzing tert-butyl group of the EC-g-PtBA copolymers. The grafting copolymers were characterized by means of GPC, ¹H NMR and FTIR spectroscopies. The molecular weight of graft copolymers increased during the polymerization and the polydispersity was low. A kinetic study showed that the polymerization was first-order. Meanwhile, EC-g-PAA copolymers were self-assembled to micelles or particles with diameters of 5 nm and 100 nm in water (pH = 10) when the concentration was 1.0 mg/ml.     

Pendant crosslinked poly(aryl ether sulfone) copolymers sulfonated on backbone for proton exchange membranes

A series of sulfonated poly(aryl ether sulfone) copolymers containing phenyl pendant groups with sulfonic acid groups on the backbone were synthesized through condensation polymerization. The degree of sulfonation (DS) of the copolymers was controlled by changing the feed ratios of sulfonated to unsulfonated monomers. Post‐crosslink reactions are carried out with 4,4′‐thiodibenzoic acid (TDA) as a crosslinker and the carboxylic acid groups in TDA can undergo Friedel–Craft acylation with the phenyls pendent rings in sulfonated poly(arylene ether sulfone)s copolymers to prepare polymer electrolyte membranes for fuel cell applications. The chemical structures of crosslinked and uncrosslinked sulfonated poly(arylene ether sulfone)s copolymers (SPSFs and CSPSFs) were characterized by FTIR, ¹H NMR spectra. The thermal and mechanical properties of the membranes were characterized by thermogravimetric analysis and stress–strain test. The dependence of water uptake, methanol permeability, proton conductivity, and selectivity on DS was studied. Transmission electron microscopic observations revealed that SPSFs and CSPSFs membranes form well‐defined microphase separated structures. POLYM. ENG. SCI., 54:2013–2022, 2014. © 2013 Society of Plastics Engineers     

Synthesis and characterization of soluble copoly(arylene ether sulfone phenyl-s-triazine)s containing phthalazinone moieties in the main chain

A series of new poly(arylene ether sulfone phenyl-s-triazine) copolymers containing phthalazinone moieties in the main chain (PPESPs) were prepared by a direct solution polycondensation of 4-(4-hydroxylphenyl)(2H)-phthalazin-1-one (HPPZ) with 2-phenyl-4,6-bi(4-fluorophenyl)-1,3,5-triazine (BFPT) and 4,4′-dichlorodiphenyl sulfone (DCS). Model reactions monitored by HPLC indicated that BFPT had slightly higher reactivity than DCS in nucleophilic displacement reactions. The obtained random copolymers were characterized by FTIR, NMR, elemental analysis and GPC. The presence of sulfone and phthalazinone in the polymer chain results in an improvement in the solubility of poly(arylene ether phenyl-s-triazine)s in common organic solvents, such as N-methylpyrrolidone, N,N-dimethyl acetamide (DMAc), chloroform, sulfolane and pyridine. Thermal analysis reveal that the copolymers exhibit high glass transition temperatures (T_gs) ranging from 271–300 °C, and excellent thermal stability associated with decomposition temperatures for 5% mass-loss exceeding 503 °C. All copolymers are amorphous except PPESP28 as evidenced by WAXD. Their T_gs and solubility increase with an increase in sulfone content in the polymer backbone, while the crystallinity and overall thermal stability appear to decrease. This kind of phthalazinone-based copoly(arylene ether sulfone phenyl-s-triazine)s may be considered a good candidate for using as high-performance structural materials.