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Pendant Groups (pendant + groups)
Selected AbstractsCarboxy Ester Hydrolysis Promoted by a Dicopper(II) Macrocyclic Polyamine Complex with Hydroxypropyl Pendant GroupsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 9 2004Jin Huang Abstract A dinuclear CuII complex containing a hexaaza macrocyclic ligand bearing two 2-hydroxypropyl pendants, 3,6,9,16,19,22-hexaaza-6,19-bis(2-hydroxypropyl)tricyclo[22.2.2.211,14]triaconta-1,11,13,24,27,29-hexaene (L), was synthesized. The title complex [Cu2(H,2L)Cl2]·6.5H2O was isolated as a blue crystal, orthorhombic, space group Fddd, with a = 16.4581(12), b = 32.248(2), c = 35.830(2) Å, V = 19017(2) Å3, Z = 16, R1 = 0.0690, and wR2 = 0.1546 [I > 2,(I)]. The protonation constants of Cu2L were determined by potentiometric titration, and it was found that the alcoholic hydroxypropyl group of the complex Cu2L exhibits low pKa values of pKa1 = 7.31, pKa2 = 7.83 at 25 °C. The hydrolysis kinetics of 4-nitrophenyl acetate (NA) promoted by the title complex have also been studied. The pH-rate profile for Cu2L gave a sigmoidal curve and showed a second-order rate constant of 0.39 ± 0.02 M,1 s,1 in 10% CH3CN/H2O(v/v), which is greater than that of the dinuclear CuII complex formed by a hexaaza macrocycle without pendants. The reason for the higher catalytic activity of the title complex is discussed. We found that the volume of nucleophile RO, can effect the hydrolysis of the carboxy ester, the nucleophilicity of RO, and the Lewis acidity of the metal macrocycle also affect the carboxy ester hydrolysis. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] ChemInform Abstract: Diastereoselective Synthesis of ,-Dispiroiminolactone Bearing Naphthalene or Bipyridine Pendant GroupsCHEMINFORM, Issue 6 2010Malek T. Maghsoodlou Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Sandwich Dimer Complexes of Zinc Porphyrins Bearing Three-Dimensionally Oriented Redox-Active ,-Conjugated Pendant Groups.CHEMINFORM, Issue 26 2002Toshikazu Hirao Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] On the Rigidity of Polynorbornenes with Dipolar Pendant GroupsCHEMISTRY - A EUROPEAN JOURNAL, Issue 1 2006Wei-Yu Lin Abstract A range of polynorbornenes (PNBs) with fused dipolar pendant groups at C-5,6 positions was synthesized by ring-opening metathesis polymerization catalyzed by a ruthenium carbene complex (Grubbs I). Photophysical studies, EFISH measurements, and atomic force microscopy images have been used to investigate the structures and morphology of these polymers. These results suggest that the polymers may adopt rigid rod-like structures. The presence of the double bonds in PNBs appeared to be indispensable for the rigidity of the polymers. Interaction between unsaturated pendant groups may result in coherent alignment leading to a rod-like structure. [source] On the Tacticity of Polynorbornenes with 5,6- endo Pendant Groups That Contain Substituted Aryl ChromophoresCHEMISTRY - AN ASIAN JOURNAL, Issue 6 2007Wei-Yu Lin Abstract Two dimers and a series of polymers with 5,6- endo pendant aryl groups that contain different substituents at the para positions were synthesized. The conformation and stereochemistry of the dimers and polymers were determined by nonlinear optical analysis (EFISH) as well as UV/Vis and 13C,NMR spectroscopy. The chemical shifts of C7 for the polymers appeared as two peaks in the 13C,NMR spectra when the substituents are electron-withdrawing groups. The percentage decrease in the relative extinction coefficient of the polymers, ,d, was linearly related to the Hammett constant ,. Polynorbornenes with electron-withdrawing substituents may adopt isotactic stereochemistry with all pendant groups aligned in one direction. The nature of the interactions between neighboring chromophores may be one of the most important factors in directing the stereoregularity and conformation of these polymers. The corresponding polymers derived from the exo isomers appeared to be less stereoregular. [source] Calix[4] crowns with Methoxynaphthoylmethyl Pendant GroupsCHINESE JOURNAL OF CHEMISTRY, Issue 11 2003Chuan-Min Jin Abstract The novel calix [4] crowns with two pendant groups were prepared by the alkylation of calix [4] crowns with 6-methoxy-2-bromoacetylnaphthalene. 1H NMR titration and picrate extraction experiments indicated that they exhibit higher complexing efficiency than their parent compounds and possess obvious selectivity for Na+ or K+, respectively, and that the cation is encapsulated inside the preorganized ionophoric cavity defined by carbonyl oxygens, the crown ether and the phenoxy oxygens. From UV and fluorescent spectra it is revealed that calix [4]-crown-4 3a with 6-methoxy-2-naphthoylmethyl pedant groups exhibits remarkable cation-induced photophysical effects and it could be utilized as a selective fluorescent sensor for Ca2+. [source] Poly(methacrylic acid-ethylene glycol dimethacrylate) monolith in-tube solid-phase microextraction applied to simultaneous analysis of some amphetamine derivatives in urine by capillary zone electrophoresisELECTROPHORESIS, Issue 16 2005Fang Wei Abstract A method based on in-tube solid-phase microextraction and capillary zone electrophoresis (CZE) was proposed for simultaneously determining four amphetamines (amphetamine, methamphetamine, 3,4-methylenedioxyamphetamine, and 3,4-methylenedioxymethamphetamine) in urine. A poly(methacrylic acid-ethylene glycol dimethacrylate) monolithic capillary column, which can provide sufficient extraction efficiency, was introduced for the extraction of amphetamines from urine samples. The hydrophobic main chains and acidic pendant groups of the monolithic column make it a superior material for extraction of basic analytes from aqueous matrix. After extraction, the samples were analyzed by CZE. The best separation was achieved using a buffer composed of 0.1,M disodium hydrogen phosphate (adjusted to pH,4.5 with 1,M hydrochloric acid) and 20% methanol v/v, with a temperature and voltage of 25°C and 20,kV, respectively. By applying electrokinetic injection with field-amplified sample stacking, detection limits of 25,34,µg/L were achieved. Excellent method of reproducibility was found over a linear range of 0.1,5,mg/L. Determination of these analytes from abusers' urine sample was also demonstrated. [source] Synthesis of New Tripodal Tri-Functionalized Hydrotris(indazol-1-yl)borate Ligands and X-ray Structures of Their Cyclopentadieneruthenium ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 5 2006Alexandre Carella Abstract Two new tripodal ligands designed to anchor complexes onto surfaces have been synthesized. They integrate ester or thioether functions at the 6-position of the indazoles. Potassium hydrotris[6-(ethoxycarbonyl)indazolyl]borate and potassium hydrotris{6-[(ethylsulfanyl)methyl]indazolyl}borate exhibit three pendant groups oriented to anchor complexes onto an oxide and a metallic surface, respectively. Their complexation with [RuCp(CH3CN)3]PF6 yielded two piano-stool-shaped complexes that were characterized by X-ray diffraction. Comparison with the synthesized unfunctionalized analog showed that the three 6-substituted functions do not interfere with the coordination site and are particularly well oriented for surface deposition.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Synthesis of Zwitterionic Water-Soluble Oligofluorenes with Good Light-Harvesting AbilityADVANCED FUNCTIONAL MATERIALS, Issue 13 2010Chengfen Xing Abstract A new water-soluble zwitterionic oligofluorene bearing carboxylic acid and quaternary ammonium as pendant groups (OF-1) is synthesized and characterized. It forms aggregates by intermolecular electrostatic interactions and exhibits similar light-harvesting ability as that of conjugated polymers. Efficient fluorescence resonance energy transfer (FRET) occurs from OF-1 to double-stranded DNA tagged with fluorescein (dsDNA-F1). A photoresponsive oligofluorene (OF-3) is also synthesized by protecting OF-1 with 1-(2-nitrophenyl)ethanol. Photolysis of OF-3 can produce OF-1 to result in a fluorescence "turn-on" response, thus the FRET from OF-3 to dsDNA-Fl can be turned on by light irradiation. OF-3 offers the potential for remote DNA sensing. [source] Dye-Doped Polyhedral Oligomeric Silsesquioxane (POSS)-Modified Polymeric Matrices for Highly Efficient and Photostable Solid-State LasersADVANCED FUNCTIONAL MATERIALS, Issue 20 2009Roberto Sastre Abstract Here, the design, synthesis, and characterization of laser nanomaterials based on dye-doped methyl methacrylate (MMA) crosslinked with octa(propyl-methacrylate) polyhedral oligomeric silsesquioxane (8MMAPOSS) is reported in relation to their composition and structure. The influence of the silicon content on the laser action of the dye pyrromethene 567 (PM567) is analyzed in a systematic way by increasing the weight proportion of POSS from 1 to 50%. The influence of the inorganic network structure is studied by replacing the 8MMAPOSS comonomer by both the monofunctionalized heptaisobutyl-methacryl-POSS (1MMAPOSS), which defines the nanostructured linear network with the POSS cages appearing as pendant groups of the polymeric chains, and also by a new 8-hydrogenated POSS incorporated as additive to the polymeric matrices. The new materials exhibit enhanced thermal, optical, and mechanical properties with respect to the pure organic polymers. The organization of the molecular units in these nanomaterials is studied through a structural analysis by solid-state NMR. The domain size of the dispersed phase assures a homogeneous distribution of POSS into the polymer, thus, a continuous phase corresponding to the organic matrix incorporates these nanometer-sized POSS crosslinkers at a molecular level, in agreement with the transparency of the samples. The silicon,oxygen core framework has to be covalently bonded into the polymer backbone instead of being a simple additive and both the silica content and crosslinked degree exhibit a critical influence on the laser action. [source] Radical Polymers for Organic Electronic Devices: A Radical Departure from Conjugated Polymers?ADVANCED MATERIALS, Issue 22 2009Kenichi Oyaizu Abstract Radical polymers are aliphatic or nonconjugated polymers bearing organic robust radicals as pendant groups per repeating unit. A large population of the radical redox sites allows the efficient redox gradient-driven electron transport through the polymer layer by outer-sphere self-exchange reactions in electrolyte solutions. The radical polymers are emerging as a new class of electroactive materials useful for various kinds of wet-type energy storage, transport, and conversion devices. Electric-field-driven charge transport by hopping between the densely populated radical sites is also a remarkable aspect of the radical polymers in the solid state, which leads to many dry-type devices such as organic memories, diodes, and switches. [source] Synthesis and radioiodination of 7-(3,-ammoniopropyl)-7,8-dicarba- nido -undecaborate(-1), (ANC)JOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 9 2004Senait Ghirmai Abstract Derivatives of nido -carborate have potential use in tumour targeting as hydrophilic boron-rich compounds for boron neutron capture therapy (BNCT) and as pendant groups for attachment of radiohalogens to tumour-seeking molecules. For this purpose, functionalized derivatives of nido -carborates that can be conjugated to biomolecules should be synthesized and evaluated. In this study, racemic 1, 7-(3,-ammoniopropyl)-7,8-dicarba- nido -undecaborate(-1) (acronym ANC) was obtained by degradation of the corresponding aminopropyl- o -carborane, which was synthesized in three steps from 1- tert -butyldimethylsilyl-2-(3-bromopropyl)- o -carborane, with sodium hydroxide in absolute ethanol. The racemate 1 was radioiodinated (125I) using the Chloramine-T method. Radio-TLC results showed that radiolabelling with 125I was achieved in a yield greater than 95%. Copyright © 2004 John Wiley & Sons, Ltd. [source] New fluorene-based copolymers containing oxadiazole pendant groups: Synthesis, characterization, and polymer stabilityJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2009Dmitrij Bondarev Abstract A series of fluorene-based copolymers containing hole blocking/electron transporting diphenyloxadiazole units were synthesized by means of Suzuki-Miyaura coupling of selected aromatic dibromo- and diboronato- derivatives catalyzed with a Pd(PPh3)4 catalyst. All of the copolymers with various composition of main-chain units were characterized by SEC chromatography, NMR, UV,vis, fluorescence and IR spectroscopy, and DSC. The emission stability of fluorene copolymers was improved by the replacement of alkyl groups on the C-9 carbon of fluorene with aryl groups or by the incorporation of anthracene units into the copolymer main chain. A comparison of luminescence properties of pristine and annealed thin layers of studied copolymers was performed. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4532,4546, 2009 [source] Dual responsive poly(N -isopropylacrylamide) hydrogels having spironaphthoxazines as pendant groupsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2009Erandimala U. Kulawardana Abstract Stimuli responsive hydrogels (PNIPAAm-MSp) with a thermoresponsive backbone and photochromic pendant groups were synthesized via free radical polymerization using N -isopropylacrylamide, modified spironaphthoxazines with a polymerizable double bond (MSp) as photochromic monomer, the crosslinker N,N,-methylenebis(acrylamide) and the initiator 2,2,-azobis(isobutyronitrile) in dimethylsulfoxide. The polymers are dual responsive, in that poly(N -isopropylacrylamide) (PNIPAAm) responds to temperature changes whereas the pendant spironaphthoxazines respond to light. Irradiation enhanced the water absorption of the polymers while increases in temperature decreased it. The irradiated PNIPAAm-MSp showed best water absorption at 0 °C (Q = 3.25) while water desorbed at higher temperatures (35 °C; Q = 0.30); where Q is the amount of water absorbed by a gram of dry polymer. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3318,3325, 2009 [source] Synthesis of liquid crystalline poly(1-pentyne)s and fabrication of polyacetylene,perovskite hybridsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2006Jianli Hua Abstract Poly(1-pentyne)s containing biphenyl and phthalimido pendant groups with different spacer lengths {P1(m); [HCC(CH2)3OBiphOCO(CH2)mN(CO)2C6H4]n, Biph4,4,biphenylyl; m = 7, 10} are synthesized in satisfactory yields by WCl6 -Ph4Sn catalyst in toluene at elevated temperatures. The structures and properties of the polymers are characterized and evaluated by IR, NMR, TGA, DSC, POM, and XRD analyses. Both of the polymers are thermally stable (Td , 300 °C) and exhibit nematicity at high temperatures. Their phthalimido groups are converted into amino groups by hydrolysis, which can, after acidification, complex with lead(II) bromide to furnish polyacetylene,perovskite hybrids in high yields. The organic components contribute good solubility to the hybrids, while the perovskite framework induces the polyacetylene chains to align within the inorganic sheets. The hybrids emit a strong UV light of 374 nm upon photoexcitation, whose quantum yield increases with an increase in the spacer length. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3538,3550, 2006 [source] Fabrication of novel conjugated polymer nanostructure: Porphyrins and fullerenes conjugately linked to the polyacetylene backbone as pendant groupsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2005Ning Wang Abstract A new series of conjugated polyacetylenes with conjugately linked fullerene and porphyrin groups as pendant units were prepared by a copolymerization reaction catalyzed by chloronorbornadiene rhodium(I)dimer-triethylamine ([Rh(nbd)Cl]2 -NEt3) in anhydrous CHCl3. These polymers were characterized with UV,vis spectroscopy, fluorescence spectroscopy, and voltammetry. Scanning electron microscopy indicated that the morphology of the copolymers consisted of uniform nanorods with a diameter of about 100 nm and a length of about 300 nm. Thin films of the copolymers produced steady and prompt photocurrent at an irradiation of 20.0 mW cm,2 of white light, which was higher than that of a mixture of poly[5-(4-Ethynyl-phenyl)-10,15,20-tris(4-carbomethoxyphenyl)porphyrin zinc] and C60. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2851,2861, 2005 [source] Synthesis and characterization of multiblock copolymers based on L -lactic acid, citric acid, and poly(ethylene glycol)JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2003Fanglian Yao Abstract Because poly(L -lactic acid) (PLLA) is a biodegradable polyester with low immunogenicity and good biocompatibility, it is used as a biomaterial. However, hydrophobic PLLA does not have any reactive groups. Thus, its application is limited. To increase the hydrophilicity of PLLA and accelerate its degradation rate, functionalized pendant groups and blocks were introduced through copolymerization with citric acid and poly(ethylene glycol) (PEG), respectively. This article describes the synthesis and characterization of poly(L -lactic- co -citric acid) (PLCA)-PLLA and PLCA-PEG multiblock copolymers. The results indicated that the hydrolysis rate was enhanced, and the hydrophilicity was improved because of the incorporation of carboxyl groups in PLCA-PLLA. The joining of the PEG block led to improved hydrophilicity of PLCA, and the degradation rate of PLCA-PEG accelerated as compared with that of PLCA-PLLA. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2073,2081, 2003 [source] Synthesis of new crosslinkable polymers by chemoselective polymerizations of 2-(1-aziridinyl)ethyl methacrylateJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2003Takashi Ishizone The anionic vinyl polymerization of 2-(1-aziridinyl)ethyl methacrylate (1) quantitatively proceeded with diphenylmethylpotassium in the presence of diethylzinc in tetrahydrofuran at ,78 °C for 12 h to form a polymethacrylate (2) with an aziridine ring in each repeating unit. The resulting polymer 2 possessed the predicted molecular weight and narrow molecular weight distribution (weight-average molecular/number-average molecular weight < 1.1) and became readily insoluble by treatment with adipic acid via the crosslinking of the pendant aziridinyl moiety. A poly(ethylene imine) bearing methacryloyl pendant groups was obtained with triethyloxonium tetrafluoroborate via the cationic ring-opening polymerization of 1 in heptane/dichloromethane at 0 °C for 2 h. [source] Conformational Behaviour of Comb-Like Poly(4-vinylpyridinium) Salts and their Complexes with Surfactants in Solution and on a Flat SurfaceMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 2 2007Marat O. Gallyamov Abstract We synthesised P4VP bromides with octyl and dodecyl pendant groups; the bromide anions in these polymer salts were further substituted with dodecylsulfate or bis(2-ethylhexylsuccinate) anions. Direct SFM visualisation of the original P4VP chains, of the macromolecular salts and of their complexes, showed that the attachment of the pendant groups and especially the complexation with the surfactants promotes stretching of the macromolecules while adsorbing on mica substrate. On the other hand, viscosimetry showed that in solution (chloroform) the comb-like chains and their complexes with dodecylsulfate had more compact conformations than those of the original P4VP. The scaling exponents describing the correlation between the contour length and the end-to-end distance of the adsorbed macromolecules were found to be ca. 3/4, which is indicative of 2D self-avoiding walk statistics. [source] Synthesis and SFM Study of Comb-Like Poly(4-vinylpyridinium) Salts and Their Complexes with SurfactantsMACROMOLECULAR RAPID COMMUNICATIONS, Issue 13 2006Marat O. Gallyamov Abstract Summary: Poly(4-vinylpyridinium) bromides containing octyl and dodecyl pendant groups were synthesized. Bromide anions in these polymer salts were substituted with dodecylsulfate and bis(2-ethylhexylsuccinate) anions using ion-exchange reactions. Initially, P4VP and its derivatives loaded with hydrophobic groups were deposited on a mica surface from diluted solutions in chloroform for visualization. Images of single adsorbed macromolecules were obtained using scanning force microscopy. Original P4VP chains form partially compacted self-intersecting coils. Loading the polymer chains with large hydrophobic groups and especially the increase in the number of alkyl tails (see Figure) per monomer unit of the polymer chain leads to the stretching of the coils, and the comb-like macromolecules adopt more and more extended self-avoiding 2D conformations when deposited on the substrate. Polymer chains with large hydrophobic groups and increasing number of alkyl tails per monomer unit of the polymer chain. [source] Synthesis and Functionalization of Isotactic Poly(propylene) Containing Pendant Styrene GroupsMACROMOLECULAR RAPID COMMUNICATIONS, Issue 20 2004Junfeng Zou Abstract Summary: Copolymerization of propylene and 1,4-divinylbenzene was successfully performed by a MgCl2 -supported TiCl4 catalyst, yielding isotactic poly(propylene) (i -PP) polymers containing a few pendant styrene groups. With a metalation reaction with butyllithium and a hydrochlorination reaction with dry hydrogen chloride, the pendant styrene groups were quantitatively transformed into benzyllithium and 1-chloroethylbenzene groups, respectively, which allowed the synthesis of i -PP-based graft copolymers by living anionic and atom transfer radical (ATRP) polymerization mechanisms. The incorporation of styrene pendant groups into isotactic poly(propylene) using a Zeigler,Natta catalyst gave functionalized polymers able to undergo living anionic and atom transfer radical (ATRP) polymerizations. [source] Photoluminescent behavior of poly(3-hexylthiophene) derivatives with a high azobenzene content in the side chainsPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 5 2005Xiongyan Zhao Abstract A series of polythiophene derivatives with substantially higher azobenzene contents in the side chains were prepared via copolymerization of 3-hexylthiophene with four different types of 4-((4-(phenyl)azo)phenoxy)alkyl-3-thienylacetate. The alkyl spacers with different lengths, i.e. butyl, hexyl, octyl and undecyl groups were used between the azobenzene group and the thiophene ring. The compositions, structures and thermal properties of these polythiophene derivatives were characterized. The structural dependence of photoluminescent emission, photochromic behavior of these copolymers were systematically studied and compared with poly(3-hexylthiophene). The results show that the azobenzene substitution renders the polythiophene some interesting optical properties that can be modulated by UV light irradiation. In the azobenzene modified polythiophene, the intensity of photoluminescent emission associated with the conjugated polythiophene main chain was found to decrease significantly upon UV irradiation. The finding suggests that the photo-induced trans - cis isomerization of the azobenzene pendant groups has a significant effect on photoluminescent emission, particularly when short spacers are used between azobenzene groups and the main chain. However, the effect becomes less prominent when longer spacers are used between the azobenzene group and the main chain. Furthermore, UV irradiation of the copolymers also resulted in an increase in intensity and broadening of bandwidth for the absorption peak associated with the polythiophene backbones. Again the magnitude of intensity changes upon UV irradiation were found to be dependent on the spacer length between the azobenzene group and polythiophene main chain. Copyright © 2005 John Wiley & Sons, Ltd. [source] Methylation of acidic moieties in poly(methyl methacrylate-co-methacrylic acid) copolymers for end-group characterization by tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 14 2010Rémi Giordanengo The complete structural characterization of a copolymer composed of methacrylic acid (MAA) and methyl methacrylate (MMA) units was achieved using tandem mass spectrometry. In a first step, collision-induced dissociation (CID) of sodiated MAA-MMA co-oligomers allowed us to determine the co-monomeric composition, the random nature of the copolymer and the sum of the end-group masses. However, dissociation reactions of MAA-based molecules mainly involve the acidic pendant groups, precluding individual characterization of the end groups. Therefore, methylation of all the acrylic acid moieties was performed to transform the MAA-MMA copolymer into a PMMA homopolymer, for which CID mainly proceeds via backbone cleavages. Using trimethylsilyldiazomethane as a derivatization agent, this methylation reaction was shown to be complete without affecting the end groups. Using fragmentation rules established for PMMA polymers together with accurate mass measurements of the product ions and knowledge of reagents used for the studied copolymer synthesis, a structure could be proposed for both end groups and it was found to be consistent with signals obtained in nuclear magnetic resonance spectra. Copyright © 2010 John Wiley & Sons, Ltd. [source] On the Rigidity of Polynorbornenes with Dipolar Pendant GroupsCHEMISTRY - A EUROPEAN JOURNAL, Issue 1 2006Wei-Yu Lin Abstract A range of polynorbornenes (PNBs) with fused dipolar pendant groups at C-5,6 positions was synthesized by ring-opening metathesis polymerization catalyzed by a ruthenium carbene complex (Grubbs I). Photophysical studies, EFISH measurements, and atomic force microscopy images have been used to investigate the structures and morphology of these polymers. These results suggest that the polymers may adopt rigid rod-like structures. The presence of the double bonds in PNBs appeared to be indispensable for the rigidity of the polymers. Interaction between unsaturated pendant groups may result in coherent alignment leading to a rod-like structure. [source] On the Tacticity of Polynorbornenes with 5,6- endo Pendant Groups That Contain Substituted Aryl ChromophoresCHEMISTRY - AN ASIAN JOURNAL, Issue 6 2007Wei-Yu Lin Abstract Two dimers and a series of polymers with 5,6- endo pendant aryl groups that contain different substituents at the para positions were synthesized. The conformation and stereochemistry of the dimers and polymers were determined by nonlinear optical analysis (EFISH) as well as UV/Vis and 13C,NMR spectroscopy. The chemical shifts of C7 for the polymers appeared as two peaks in the 13C,NMR spectra when the substituents are electron-withdrawing groups. The percentage decrease in the relative extinction coefficient of the polymers, ,d, was linearly related to the Hammett constant ,. Polynorbornenes with electron-withdrawing substituents may adopt isotactic stereochemistry with all pendant groups aligned in one direction. The nature of the interactions between neighboring chromophores may be one of the most important factors in directing the stereoregularity and conformation of these polymers. The corresponding polymers derived from the exo isomers appeared to be less stereoregular. [source] Calix[4] crowns with Methoxynaphthoylmethyl Pendant GroupsCHINESE JOURNAL OF CHEMISTRY, Issue 11 2003Chuan-Min Jin Abstract The novel calix [4] crowns with two pendant groups were prepared by the alkylation of calix [4] crowns with 6-methoxy-2-bromoacetylnaphthalene. 1H NMR titration and picrate extraction experiments indicated that they exhibit higher complexing efficiency than their parent compounds and possess obvious selectivity for Na+ or K+, respectively, and that the cation is encapsulated inside the preorganized ionophoric cavity defined by carbonyl oxygens, the crown ether and the phenoxy oxygens. From UV and fluorescent spectra it is revealed that calix [4]-crown-4 3a with 6-methoxy-2-naphthoylmethyl pedant groups exhibits remarkable cation-induced photophysical effects and it could be utilized as a selective fluorescent sensor for Ca2+. [source] Dielectric properties of thermosetting material nanocompositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007Newton Luiz Dias Filho Abstract The dieletric relaxation properties of thermosetting material nanocomposites based on spherosilicate nanoplatforms were studied from room temperature to 170°C, varying the frequency from 10 to 1000 KHz. Permittivity (,,), dielectric loss (,,), and activation energy (Ea) were calculated. The results of dielectric relaxation were confirmed by those of the final properties. The dielectric loss amplitude decreases with increasing ODPG content until about 70,73 wt % and slightly increases at higher ODPG content. This means that the increasing of the ODPG content in the composite samples decreases the number of pendants groups and/or increases crosslink density, causing decreased motion of organic tethers, and subsequently decreasing of the dipolar mobility. The results of apparent activation energy, fracture toughness and tensile modulus mechanical properties show the same profile with respect to ODPG content, in the sense that they exhibit maxima around 70 wt % ODPG. For the ODPG/MDA composites, this formulation of 70 wt % ODPG containing excess of amine is not composition where the highest crosslinked density is reached. This implies that the best mechanical properties and Ea are provided by some degree of chain flexibility. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] | |||||||||||||||||||||||||