Synthesis and property of helical poly(phenylacetylene)s bearing chiral ruthenium complexes and real space imaging of meso- and nanoscopic structures by atomic force microscopy

Novel sets of helical poly(phenylacetylene)s bearing a chiral ruthenium (Ru) complex with opposite chirality (Δ and Λ forms) as a bulky pendant (poly- 1 and poly- 2 ) were synthesized through the polymerization of the corresponding optically pure phenylacetylenes with a rhodium catalyst, and their structures in solution and morphology on solid substrates were investigated with NMR, ultraviolet–visible, and circular dichroism (CD) spectroscopies and with atomic force microscopy (AFM), respectively. The obtained cis–transoidal polymers (poly- 1 and poly- 2 ) showed characteristic Cotton effects in the region of metal-to-ligand charge transfer of the chiral Ru pendants. Poly- 1 and poly- 2 were thought to have a predominantly one-handed helical conformation induced by the chiral pendants. However, the apparent Cotton effects derived from the helically twisted π-conjugated polymer backbone could not be observed, probably because of the strong chiral chromophoric pendants. However, in the AFM images, the helical polymers adsorbed on mica could be easily discerned as isolated strands, and the visualization and discrimination of the right- and left-handed helical structures of the chiral polymers were achieved by high-resolution AFM imaging. On the basis of the AFM observations together with the CD measurements and computational calculation results, possible structures of poly- 1 and poly- 2 were examined. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4621–4640, 2004     

Long‐range effects of chirality in aromatic poly(isocyanide)s

The preparation of optically active atropoisomeric polymers which present chiral backbones, thanks to induction during their synthesis from stereogenic centers, located far away from the skeleton is possible, thanks principally to semirigid conformations of the promesogenic spacers between them. The result is that chiral “information” can be passed as far as 21 Å from the asymmetric center to the carbon atom that forms the polymeric chain in poly(isocyanide)s. The sense of chiral induction in these conformationally rigid polymers parallels the helical sense of the cholesteric phases, as well as to the helical senses of chiral smectic C phases, induced by the monomers in nematic and smectic C phases, respectively. All these phenomena obey the odd–even rules proposed for chiral sense changes in these liquid crystalline phases. Noncovalent interactions play an important part in the induction process, in which steric arguments can be used to justify the inductions observed. The methodology can be used to prepare macromolecules, which display switching behavior upon thermal or electrochemical stimulus. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3161–3174, 2006     

Two modes of asymmetric polymerization of phenylacetylenes having an L‐amino alcohol residue and two hydroxy groups

Four novel chiral phenylacetylenes having an L ‐amino alcohol residue and two hydroxymethyl groups were synthesized and polymerized by an achiral catalyst ((nbd)Rh⁺[η⁶‐(C₆H₅)B^?(C₆H₅)₃]) or a chiral catalytic system ([Rh(nbd)Cl]₂/(S)‐ or (R)‐phenylethylamine ((S)‐ or (R)‐PEA)). The two resulting polymers having an L ‐valinol or L ‐phenylalaninol residue showed Cotton effects at wavelengths around 430 nm. This observation indicated that they had an excess of one‐handed helical backbones. Positive and negative Cotton effects were observed only for the polymers having an L ‐valinol residue produced by using (R)‐ and (S)‐PEA as a cocatalyst, respectively, although the monomer had the same chirality. Even when the achiral catalyst was used, the two resulting polymers having an L ‐valinol or L ‐phenylalaninol residue showed Cotton effects despite the long distance between the chiral groups and the main chain. We have found the first example of a new type of chiral monomer, that is, a chiral phenylacetylene monomer having an L ‐amino alcohol residue and two hydroxy groups that was suitable for both modes of asymmetric polymerization, that is, the helix‐sense‐selective polymerization ( HSSP ) with the chiral catalytic system and the asymmetric‐induced polymerization ( AIP ) with the achiral catalyst. The other two monomers having L ‐alaninol and L ‐tyrosinol were found to be unsuitable to neither HSSP nor AIP because of their polymers' low solubility. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Effects of cosolvents on helical substituted polyacetylene particles prepared through suspension polymerization

Acetylenic monomers undergo aqueous suspension polymerization providing particles constructed by helical substituted polyacetylene. Different from suspension polymerization of vinyl monomers, a cosolvent is indispensable to dissolve Rh catalyst and solid acetylenic monomers. The cosolvent is found to play essential roles in monomers' polymerization and the particles' formation. To systemically explore the effects of cosolvents, three monomers, M1 (achiral, liquid), M2 (achiral, solid), and M3 (chiral, solid), and six cosolvents (divided into two groups by their miscibility with water) are used for performing suspension polymerization in aqueous media at 30 °C, with Rh⁺B^– (C₆H₅)₄ as catalyst and polyvinylpyrrolidone as stabilizer. FTIR spectra and gel permeation chromatography confirm the occurrence of polymerization. Raman spectra demonstrate the high cis contents of the polymer chains. Scanning electron microscope images show that the polymer particles obtained under optimal conditions are in spherical morphology. Circular dichroism and UV‐vis spectroscopy demonstrate the helical structures of the polymer chains forming the chiral particles. Dynamic light scattering characterization is carried out to characterize the nanoparticles. The type and amount of the cosolvent affect the polymerization remarkably. Cosolvents with higher polarity lead to smaller polymer particles, while lower polar cosolvents provide larger ones. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2670–2678     

Asymmetric anionic polymerizations of 7‐cyano‐7‐alkoxycarbonyl‐1,4‐benzoquinone methides

Asymmetric anionic polymerizations of 7‐cyano‐7‐alkoxycarbonyl‐1,4‐benzoquinone methides ( 1 ) with various alkoxy groups were performed using chiral initiators such as lithium isopropylphenoxide (ⁱPrPhOLi)/(S)‐(–)‐2,2′‐isopropylidene‐bis(4‐phenyl‐2‐oxazoline) ((–)‐PhBox) and lithium isopropylphenoxide (ⁱPrPhOLi)/(–)‐sparteine ((–)‐Sp) to investigate the effect of the alkoxy groups of alkoxycarbonyl substituent in the monomers 1 and chiral ligands of chiral initiators on the control of chiral center in the formation of polymers. Molar optical rotation values of the polymers were significantly dependent upon alkoxy groups, and the polymers with higher molar optical rotation were obtained in monomers with primary alkoxy groups. The asymmetric anionic oligomerizations of the quinone methides having methoxy( 1a ), ethoxy( 1b ), and n‐propoxy( 1c ) groups with chiral initiators were carried out. Both 1‐mers and 2‐mers were isolated and their optical resolutions were performed to determine the extent of stereocontrol. High stereoselectivity was observed at the propagation reaction, but not at the initiation reaction. The effect of the counterion on the control of chiral center in the formation of the polymer was investigated in the asymmetric anionic polymerizations of 1b with ⁱPrPhOM(M = Li, Na, K)/(–)‐Sp and ⁱPrPhOM(M = Li, Na, K)/(–)‐PhBox initiators and discussed. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Chiral Amplification during Asymmetric‐Induced Copolymerization of Phenylacetylenes with Tight Cis‐Cisoidal Main Chains

A novel phenylacetylene ( 1 ) having two hydroxyl groups and a chiral pinanyl group together with the other three related phenylacetylenes has been synthesized and (co)polymerized by using an achiral catalytic system. Among the four monomers, only 1 is suitable to the asymmetric‐induced polymerization ( AIP ). Chiral amplification phenomenon is only observed in the copolymerization of 1 with an achiral phenylacetylene having two hydroxyl groups ( 3 ). The tight helical cis‐cisoidal main chain formed by making intramolecular hydrogen bonds between the hydroxyl groups in the copoly( 1 / 3 ) enhances the efficiency of chiral induction and as a result chiral amplification phenomenon is observed during the copolymerization.

     

Helix formation of poly(phenylacetylene) derivatives bearing amino groups at the meta position induced by optically active carboxylic acids

Two novel phenylacetylene derivatives bearing diethylaminomethyl groups at the meta position on phenyl groups [3‐(N,N‐diethylaminomethyl)phenyl]acetylene ( 1 ) and [3,5‐bis(N,N‐diethylaminomethyl)phenyl]acetylene ( 2 ) were synthesized and polymerized with [Rh(nbd)Cl]₂ (nbd: norbornadiene). Both monomers gave highly cis–transoidal stereoregular polymers that exhibited an induced circular dichroism (ICD) in the UV–visible region, probably because of a prevailing one‐handed helical conformation upon complexation with optically active carboxylic acids such as mandelic acid and lactic acid. The sign of the Cotton effects reflected the absolute configuration of the chiral acids. Therefore, these polymers can be used as a novel probe for determining the configuration of chiral acids. The polymers were stable in the presence of chiral acids in solution. The poly‐ 1 complexed with chiral acids exhibited a split‐type ICD, whereas the poly‐ 2 complexed with chiral acids showed a different, non‐split‐type ICD. The ICD pattern of the poly‐ 1 /chiral acids complexes dramatically changed with an increase in the concentration of the chiral acids, thus showing a non‐split‐type ICD similar to those of the poly‐ 2 /chiral acid complexes. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3180–3189, 2001     

Synthesis of helical poly(phenylacetylene)s bearing cinchona alkaloid pendants and their application to asymmetric organocatalysis

Four novel dynamic helical poly(phenylacetylene)s bearing cinchona alkaloids as pendant groups were synthesized starting from the commercially available cinchona alkaloids, cinchonidine, cinchonine, quinine, and quinidine, by the polymerization of the corresponding phenylacetylene monomers with a rhodium catalyst. These polymers exhibited an induced circular dichroism (ICD) in the UV–visible region of the polymer backbones in solution, resulting from the preferred‐handed helical conformation induced by the optically active cinchona alkaloid pendants. In response to the solvent used, their Cotton effect patterns and intensities were significantly changed accompanied by the changes in their absorption spectra probably due to the changes in their helical conformations, such as the inversion of the helical sense or helical pitch of the polymers. When these helical polymers were used as polymeric organocatalysts for the asymmetric conjugated addition and Henry reactions, the optically active products with a modest enantiomeric excess were obtained whose enantioselectivities were comparable to those obtained with the corresponding cinchona alkaloid‐bound monomers as the catalysts. However, we observed a unique enhancement of the enantioselectivity and a reversal of the stereoselectivity for some helical polymers, suggesting the important role of the helical chirality during the asymmetric organocatalysis. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Ionic conducting membranes based on new sulfonated poly(arylene ether ketone)s for fuel cell applications

The synthesis and characterization of new di‐ and tetra‐sulfonated ether diketone monomers are described. From these monomers, a wide series of sulfonated poly(arylene ether ketone)s (SPAEK) are synthesized by varying the sulfonic acid repartition along the polymer backbones. Their chemical structures are thoroughly characterized by NMR. From these polymers tough membranes are obtained from solution casting method and their water uptake, ionic conductivity, and water/gas permeation properties are determined and compared with those of Nafion membrane. Preliminary fuel cell tests show that SPAEK membranes are promising candidates for fuel cell application. This work brings new insights concerning the beneficial effects of introducing densely sulfonated monomers in a polyarylether macromolecular structure along with fluorinated groups improving conductivity while reducing unwanted excessive swelling. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 771–777     

Helical chirality of π‐conjugated main‐chain induced by polymerization of phenylacetylene with chiral bulky pinanyl groups: Effects of the flexible spacer and polymerization catalyst

Three optically active phenylacetylene polymers with chiral bulky pinanyl groups, (?)‐poly[4‐(dimethylpinanylsilyl)phenylacetylene] [(?)‐poly(PSPA)], (+)‐poly{4‐[3‐(10‐pinanyl)tetramethyldisiloxy]phenylacethylene} [(+)‐poly(PDSPA)], and their copolymer [(?)‐copoly(PSPA/PDSPA)], were synthesized. We observed high chirality in the main‐chain chromophore of (?)‐poly(PSPA), due to the presence of a chiral helix, with circular dichroism spectroscopy. In contrast, (+)‐poly(PDSPA),with flexible SiOSi spacers between the chiral pinanyl group and the main chain, had lower chirality. (?)‐Poly(PSPA), with large circular dichroism signals, was prepared by polymerization with a rhodium catalyst and had a highly stereoregular main chain (high cis‐configuration percentage). However, (?)‐poly(PSPA) prepared with a tungsten catalyst had lower chirality and lower stereoregularity in the main chain. A membrane from (?)‐poly(PSPA) showed enantioselective permeability for tryptophan in an aqueous solution. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1689–1697, 2002     

Synthesis and characterization of hyperbranched poly(urea‐urethane)s based on AA* and B2B* monomers

Hyperbranched aromatic and aliphatic poly(urea‐urethane)s were prepared by the one‐pot method using 2,4‐toluylene diisocyanate (TDI), isophorone diisocyanate, and 2(3‐isocyanatopropyl)cyclohexyl isocyanate as AA* monomers and diethanol amine and diisopropanol amine as B₂B* monomers. The characteristics of the resulting polymers were very sensitive to slight changes in the reaction conditions, such as temperature, concentration, and type of catalyst used, as can be seen from the results of gel permeation chromatography and differential scanning calorimetry. The structures were analyzed in detail using ¹H and ¹³C NMR spectroscopy. By using model compounds, the different isomeric structures of the TDI polymers were deduced, their percentages of their linear, terminal, and dendritic subunits were calculated, and their degree of branching (DB) was determined. DB values up to 70% were reached depending on the reaction conditions and stoichiometry of the monomers. The number of terminal groups decreased significantly when dibutylamine was used to stop the reaction instead of B₂B*, indicating the presence of a significant number of unreacted isocyanate groups in the hyperbranched product when the polyaddition reaction was stopped. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3062–3081, 2004     

Polymerization and characterization of self‐assembled β‐cyclodextrin‐threaded chiral monomers

A helical inclusion complex polymer was fabricated through the polymerization of β‐cyclodextrin‐threaded chiral monomers. The photo induced polymerization of inclusion complex clusters caused shrinkage of the polymer and decreased the pitches, leading to the disappearance of spring‐like construction under TEM. From the results of circular dichroism of the inclusion complex polymer, the helical construction was confirmed, and an entanglement of the polymer chains is proposed. After removal of the β‐cyclodextrins from the pendant groups of the inclusion complex polymer, the helical structure was found to be maintained. The highly ordered molecular arrangement of β‐cyclodextrins removed from the inclusion complex polymer was confirmed using POM. Here we demonstrate the fabrication of helical polymer fibers composed of entangled polymers through self‐assembled β‐cyclodextrin‐threaded chiral monomers. The helical polymer construction was maintained by the entwisted polymer chains even after the removal of β‐cyclodextrins from the pendant groups of the inclusion complex polymer. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2975–2981, 2010     

Synthesis and characterization of optically active helical vinyl polymers via free radical polymerization

A facile synthetic route to prepare the dual‐functional molecule, 2,5‐bis(4′‐carboxyphenyl)styrene, was developed. The esterification of this compound with chiral alcohols, that is, (S)‐(+)‐sec‐butanol/(R)‐(?)‐sec‐butanol, (S)‐(+)‐sec‐octanol/(R)‐(?)‐sec‐octanol, and D ‐(+)‐menthol/L ‐(?)‐menthol, respectively, yielded three enantiomeric pairs of novel vinyl monomers, which underwent radical polymerization to obtain helical polymers with an excess screw sense. These polymers exhibited optical rotations as large as fourfold those of the corresponding monomers. Their helical conformations were quite stable as revealed by the almost unchanged chiroptical properties measured at different temperatures. The polymers with linear alkyl tails in the side‐groups formed irreversibly columnar nematic phases in melt although the corresponding monomers were not liquid crystalline. Whereas, the polymers with cyclic tails generated no mesophase. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2408–2421, 2009     

Double-stranded ladderphanes with C2-symmetric planar chiral ferrocene linkers

Eight ladderphanes with C₂-symmetric planar chiral ferrocene linkers are synthesized by ring opening metathesis polymerization of bisnorbornene monomers using Grubbs-I catalyst. The aminobenzoate in both monomers and polymers shows absorption maximum around 320 nm. Both monomers and polymers are Circular dichroism (CD) active. Little enhancements of CD profiles around 320 nm are observed for ladderphanes having chiral chloro- or phenyl-substituted ferrocene linkers. However, ladderphanes with a phenyl substituent on the cyclopendienyl ring exhibits enhancement of CD curves aound 240–300 nm. The congested phenyl moieties in adjacent linkers in this polymer might be well oriented such that interactions between these aromatic substituents on different monomeric units might provoke the enhancement of the CD curves in this region. When the methyl-substituted cyclopendienyl ligand is used for chiral ferrocene linkers, the ladderphanes exhibit two-fold enhancement of CD spectrum around 320 nm. This enhancement is further increased when the cyclopentadienyl ligand contains an additional phenyl substituent, owing to exciton coupling between aminobenzoate moieties in adjacent monomeric units. Moreover, the intensity of the CD curves in the region of 240–300 nm is significantly increased. These results suggest that the later polymer may adopt a posible helical structure. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2999–3010     

Synthesis of a pyrrole‐based methine bridge type liquid‐crystalline conjugated polymer

Conjugated polymers consisting of pyrrole or an N‐substituted pyrrole bridged by methine with a mesogenic group were synthesized. Chemical structures of the products were confirmed with IR, NMR, UV–visible (UV–vis) spectroscopy, and gel permeation chromatography analysis. Liquid crystallinity was examined with differential scanning calorimetry measurements and polarizing optical microscopy observations. Liquid crystal domains of the polymer were macroscopically oriented in one direction by an external magnetic force (10 Tesla). The polymer orientation was confirmed by optical microscopy and X‐ray analysis. One of the polymers exhibited a striated fan‐shaped texture when observed with a polarizing optical microscope. This is attributed to the formation of a chiral smectic C (SmC^*) phase, which is a property of ferroelectricity. Spontaneous polarization of the polymer occurred at 110 nC/cm². © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 616–629, 2005     

Synthesis and hierarchical superstructures of side‐chain liquid crystal polyacetylenes containing galactopyranoside end‐groups

Three kinds of chiral saccharide‐containing liquid crystalline (LC) acetylenic monomers were prepared by click reaction between 2‐azidoethyl‐2,3,4,6‐tetraacetyl‐β‐D ‐galactopyranoside and 1‐biphenylacetylene 4‐alkynyloxybenzoate. The obtained monomers were polymerized by WCl₆‐Ph₄Sn to form three side‐chain LC polyacetylenes containing 1‐[2‐(2,3,4,6‐tetraacetyl‐β‐D ‐galactopyranos‐1‐yl)‐ethyl]‐1H‐[1,2,3]‐triazol‐4′‐biphenyl 4‐alkynyloxybenzoate side groups. All monomers and polymers show a chiral smectic A phase. Self‐assembled hiearchical superstructures of the chiral saccharide‐containing LCs and LCPs in solution state were studied by field‐emission scanning electron microscopy. Because of the LC behavior, the LC molecules exhibit a high segregation strength for phase separation in dilute solution (THF/H₂O = 1:9 v/v). The self‐assembled morphology of LC monomers was dependent upon the alkynyloxy chain length. Increasing the alkynyloxy chain length caused the self‐assembled morphology to change from a platelet‐like texture ( LC‐6 ) to helical twists morphology ( LC‐11 and LC‐12 ). Furthermore, the helical twist morphological structure can be aligned on the polyimide rubbed glass substrate to form two‐dimensional ordered helical patterns. In contrast to LC monomers, the LCP‐11 self‐assembled into much more complicate morphologies, including nanospheres and helical nanofibers. These nanofibers are evolved from the helical cables ornamented with entwining nanofibers upon natural evaporation of the solution in a mixture with a THF/methanol ratio of 3:7. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6596–6611, 2009     

Radical copolymerization of 2‐trifluoromethylacrylic monomers. I. Kinetics of their copolymerization with norbornenes and vinyl ethers as studied by in situ 1H NMR analysis

Radical copolymerizations of electron‐deficient 2‐trifluoromethylacrylic (TFMA) monomers and electron‐rich norbornene derivatives and vinyl ethers with azobisisobutyronitrile were investigated by analyzing the kinetics in situ with ¹H NMR. Although none of the monomers underwent radical homopolymerization under normal conditions, they copolymerized readily, producing a copolymer containing 60–70 mol % TFMA. Terpolymerization involving these monomers was also investigated. The rates of copolymerization and kinetic chain lengths were determined in some cases on the basis of the in situ kinetics analysis. These radial copolymerizations of TFMA provide a basis for the preparation of chemical‐amplification resist polymers for emerging 157‐nm lithography. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1468–1477, 2004     

Synthesis and helicity of optically active poly(N‐propargylphosphonamidates) having chiral phosphorus center

Novel chiral N‐propargylphosphonamidate monomers (HC?CCH₂NHP(?O)R? O? menthyl, 1 : R = CH₃, 2 : R = C₂H₅, 3 : R = n‐C₃H₇, 4 : R = Ph) were synthesized by the reaction of the corresponding phosphonic dichlorides with menthol and propargylamine. Pairs of diastereomeric monomers 1 – 4 with different ratios were obtained due to the chiral P‐center and menthyl group. One diastereomer could be separated from another one in the cases of monomers 1 and 2 . Polymerization of 1 – 4 with (nbd)Rh⁺[η⁶‐C₆H₅B^?(C₆H₅)₃] as a catalyst in CHCl₃ gave the polymers with number‐average molecular weights ranging from 5000 to 12,000 in 65–85%. Poly( 1 )–poly( 4 ) exhibited quantitative cis contents, and much larger specific rotations than 1 – 4 did in CHCl₃. The polymers showed an intense Cotton effect around 325 nm based on the conjugated polyacetylene backbone. It was indicated that the polymers took a helical structure with predominantly one‐handed screw sense, and intramolecular hydrogen bonding between P?O and N? H of the polymers contributed to the stability of the helical structure. Poly( 1a ) and poly( 2a ) decreased the CD intensity upon raising CH₃OH content in CHCl₃/CH₃OH. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1515–1524, 2007     

Development of ionomer membranes for fuel cells

In this contribution an overview is given about the state-of-the-art at the membrane development for proton-conductive polymer (composite) membranes for the application membrane fuel cells, focusing on the membrane developments in this field performed at ICVT.For preparation of the polymers, processes have been developed for sulfonated arylene main-chain polymers as well as for arylene main-chain polymers containing basic N-containing groups, including a lithiation step. Covalently cross-linked polymer membranes have been prepared by alkylation of the sulfinate groups of sulfinate group-containing polymers with α,ω-dihalogenoalkanes. The advantage of the covalently cross-linked ionomer membranes was their dimensional stability even at temperatures of 80–90°C, their main disadvantage their brittleness when drying out, caused by the inflexible covalent network. Sulfonated and basic N-containing polymers (commercial polymers as well as self-developed ones) have been combined to acid–base blends containing ionic cross-links. The main advantage of these membrane type was its flexibility even when dried-out, its good to excellent thermal stability, and the numerous possibilities to combine acidic and basic polymers to blend membranes having fine-tuned properties. The main disadvantage of this membrane type was the insufficient dimension stability at T>70–90°C, caused by breakage of the ionic cross-links, where the ionic cross-links broke as easier as lower the basicity of the polymeric base was. Some of the acid–base blend membranes were applied to H₂ membrane fuel cells and to direct methanol fuel cells up to 100°C, yielding the result that these membranes show very good perspectives in the membrane fuel cell application.     

Facile synthesis and characterization of hyperbranched poly(ether amide)s generated from Michael addition polymerization of in situ created AB2 monomers

A new straightforward strategy for synthesis of novel hyperbranched poly (ether amide)s from readily available monomers has been developed. By optimizing the reaction conditions, the AB₂‐type monomers were formed dominantly during the initial reaction stage. Without any purification, the AB₂ intermediate was subjected to further polymerization in the presence (or absence) of an initiator, to prepare the hyperbranched polymer‐bearing multihydroxyl end‐groups. The influence of monomer, initiator, and solvent on polymerization and the molecular weight (MW) of the resultant polymers was studied thoroughly. The MALDI–TOF MS of the polymers indicated that the polymerization proceeded in the proposed way. Analyses of ¹H NMR and ¹³C NMR spectra revealed the branched structures of the polymers obtained. These polymers exhibit high‐moderate MWs and broad MW distributions determined by gel permeation chromatography (GPC) in combination with triple detectors, including refractive index, light scattering, and viscosity detectors. In addition, the examination of the solution behavior of these polymers showed that the values of intrinsic viscosity [η] and the Mark–Houwink exponent α were remarkably lower compared with their linear analogs, because of their branched nature. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4309–4321, 2007