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Polymer Backbone (polymer + backbone)
Selected AbstractsHigh-Efficiency White-Light Emission from a Single Copolymer: Fluorescent Blue, Green, and Red Chromophores on a Conjugated Polymer Backbone,ADVANCED MATERIALS, Issue 8 2007J. Luo The synthesis and properties of a single copolymer incorporating well-separated blue, green, and red chromophores on a single conjugated polymer backbone are reported. This copolymer is shown to have CIE coordinates of (0.35,0.34) and a luminance efficiency of 6.2,cd,A,1. The color coordinates of the resulting white-light emission remained extremely stable over a wide range of driving voltages. [source] Dispersive Effects in Chemomechanical Reactions with Polyallylamine-Derived HydrogelsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 8 2008Kazuaki Kato Abstract Volume changes of polyallylamine-derived hydrogels crosslinked with glutaraldehyde are determined with a large variety of effector compounds. Monocarboxylic effectors lead to smaller contractions, in contrast to dicarboxylate structures, which allow more effective non-covalent crosslinking between the positively charged nitrogen centers of the polymer backbone. Electroneutral compounds lead to negligible changes, whereas effectors with either a large p -moiety like in naphthoic acid or phenyl derivatives with polarizable substituents induce large contractions. This finding is in line with significant contributions of van der Waals interactions between the effectors within the hydrogel. Chemomechanical differences between regioisomeric effectors such as p - and o -nitrobenzoic acid are in agreement with independent results of dispersive interactions in related complexes. The volume decrease corresponds almost entirely to the gravimetrically determined water content of the gels. The acidity profile shows a strong contraction above pH 10, which is consistent with the known pK value of such polyamines. NMR spectra of the gels indicate strong binding of the effectors by line broadening, which is significant only for the chemomechanically active compounds. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Photochromic Polymers Based on the Photoinduced Opening and Thermal Closing of [1,3]Oxazine RingsADVANCED FUNCTIONAL MATERIALS, Issue 24 2009Massimiliano Tomasulo Abstract Two macromolecular constructs incorporating a single polymer backbone with multiple photochromic side chains are developed. Both systems are prepared from preformed photochromic [1,3]oxazines after the ring-opening polymerization of their norbornene appendages. In solution, UV illumination of these polymers opens the [1,3]oxazine rings in their side chains in less than 6,ns and with a quantum yield of 0.09 in both instances. The photogenerated species incorporate a 4-nitrophenolate chromophore, and hence, their formation is accompanied by the appearance of an intense band in the visible region of the absorption spectrum. The photoproducts revert spontaneously to the original state with first-order kinetics in microseconds. Furthermore, both photochromic polymers tolerate hundreds of switching cycles with no sign of degradation, even in the presence of molecular oxygen. Thus, this design logic and choice of functional building blocks can translate into the realization of innovative photoresponsive materials with excellent photochromic performance. [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] Intercalating Dye Harnessed Cationic Conjugated Polymer for Real-Time Naked-Eye Recognition of Double-Stranded DNA in SerumADVANCED FUNCTIONAL MATERIALS, Issue 9 2009Kan-Yi Pu Abstract Thiazole orange (TO), an intercalating dye, is integrated into cationic poly(fluorene- alt -phenylene) (PFP) to develop a macromolecular multicolor probe (PFPTO) for double-stranded DNA (dsDNA) detection. This polymer design not only takes advantage of the high affinity between TO and dsDNA to realize dsDNA recognition in biological media, but also brings into play the light-harvesting feature of conjugated polymers to amplify the signal output of TO in situ. PFPTO differentiates dsDNA from single-stranded DNA (ssDNA) more effectively upon excitation of the conjugated backbone relative to that upon direct excitation of TO as a result of efficient fluorescence resonance energy transfer from the polymer backbone to the intercalated TO. In the presence of dsDNA, energy transfer within PFPTO is more efficient as compared to that for free TO/PFP system, which leads to better dsDNA discriminability for PFPTO in contrast to that for TO/PFP. The distinguishable fluorescent color for PFPTO solutions in the presence of dsDNA allows naked-eye detection of dsDNA with the assistance of a hand-held UV lamp. The significant advantage of this macromolecular fluorescent probe is that naked-eye detection of label-free dsDNA can be performed in biological media in real-time. [source] Enzyme-Mediated Deposition of a TiO2 Coating onto Biofunctionalized WS2 Chalcogenide Nanotubes,ADVANCED FUNCTIONAL MATERIALS, Issue 2 2009Muhammad Nawaz Tahir Abstract A chemically specific and facile method for the biofunctionalization of WS2 nanotubes (NT-WS2) is reported. The covalent modification strategy is based on the affinity of the nitrilotriacetic acid (NTA) side chain, which serves as a ligand for the surface binding to NT-WS2 and simultaneously as an anchor group for the binding of His-tagged proteins to the polymer backbone. The polymer functionalized WS2 nanotubes can be solubilized either in water or organic solvents; they are stable for at least one week. The probes were characterized by FT-IR and UV-vis spectroscopy. The immobilization of silicatein, a hydrolytic protein encountered in marine sponges, was visualized by scanning force microscopy (SFM) and confocal laser scanning microscopy (CLSM). The formation of the biotitania coating mediated by the immobilized silicatein onto the surface was characterized by scanning electron microscopy (SEM), and transmission electron microscopy (TEM). [source] The Influence of UV Irradiation on Ketonic Defect Emission in Fluorene-Based Copolymers,ADVANCED FUNCTIONAL MATERIALS, Issue 17 2008Horst Scheiber Abstract The influence of UV irradiation in inert atmosphere on the emission spectrum of fluorenone containing poly[9,9-bis(2-ethyl)hexylfluorene] (PF2/6) has been investigated by means of optical absorption, photoluminescence (PL) and Fourier transform infrared (FTIR) spectroscopy. It is shown that a substantial reduction of green emission arising from ketonic defect sites can be achieved by irradiation of thin films with UV light. This is found to be accompanied by partial cross-linking of the films. FTIR measurements show no reduction of the C=O stretching mode upon irradiation, and, moreover, the degree of cross-linking does not scale with the relative fluorenone content (0.1, 0.5, and 5%). Therefore, the reduced emission intensity in the green spectral region is rather associated with the occurrence of interruptions in the polymer backbone, which reduce the effective conjugation length and subsequently inhibit the energy transfer onto the ketonic defect sites. The found results enabled us to build organic light emitting devices (OLEDs) that can be structured by selective illumination of the emitting layer with an intense UV light source. This method allows for the fabrication of rather efficient (2000,cd,m,2 at 7,V) two-color OLEDs. [source] High-Efficiency White-Light Emission from a Single Copolymer: Fluorescent Blue, Green, and Red Chromophores on a Conjugated Polymer Backbone,ADVANCED MATERIALS, Issue 8 2007J. Luo The synthesis and properties of a single copolymer incorporating well-separated blue, green, and red chromophores on a single conjugated polymer backbone are reported. This copolymer is shown to have CIE coordinates of (0.35,0.34) and a luminance efficiency of 6.2,cd,A,1. The color coordinates of the resulting white-light emission remained extremely stable over a wide range of driving voltages. [source] Redox-Tunable Defects in Colloidal Photonic Crystals,ADVANCED MATERIALS, Issue 20 2005F. Fleischhaker Reversible tuning of an intragap transmitting state induced by redox cycling is accomplished using a redox-active polyelectrolyte multilayer planar defect embedded in a colloidal photonic crystal (CPC). The wavelength position of the defect state can be changed by changing the oxidation state of the ferrocene moieties in the polymer backbone (see Figure). This could find applications in electrochemically tunable microcavities and CPC-based laser sources. [source] Biocatalytic Route to Ascorbic Acid-Modified Polymers for Free-Radical ScavengingADVANCED MATERIALS, Issue 15 2003A. Singh Ascorbic acid functionalized polymers (see Figure) for free radical scavenging have been synthesized via a two step biocatalytic route. The ascorbic acid retained antioxidant activity, and this functional antioxidant on a polymer backbone has implications for consumer-related applications like foods, pharmaceuticals, and personal care products. [source] A Highly Selective, Polymer-Supported Organocatalyst for Michael Additions with Enzyme-Like BehaviorADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 18 2009Esther Alza Abstract A polymer-supported ,,,-diarylprolinol silyl ether displays catalytic activity and enantioselectivity comparable to the best homogeneous catalysts in the Michael addition of aldehydes to nitroolefins. Above all, the combination of polymer backbone, triazole linker, and catalytic unit confers to it an unprecedented substrate selectivity in favor of linear, short-chain aldehydes. [source] Poly(O -anisidine) coatings electrodeposited onto AL-2024: Synthesis, characterization, and corrosion protection evaluationADVANCES IN POLYMER TECHNOLOGY, Issue 4 2004Kunal Shah Abstract Poly(O -anisidine) coating was successfully electrodeposited onto Al-2024. Cyclic voltammetry and reflection absorption infrared spectroscopy (RAIR) analysis were carried out in order to fully understand the formation and structure of the resulting polymer coating. RAIR spectrum showed the characteristics peaks of poly(O -anisidine). As the reaction time was varied, the CV peak shifted from 0.75 to 0.81 V vs. SCE suggesting that a change in structure of the polymer from a reduced state to a partially oxidized form has occurred. UV spectrum showed two peaks at 320 and 620 nm suggesting the presence of conjugation on the polymer backbone. The deposition of the poly(O -anisidine) onto the substrate was controlled by nucleation and growth mechanism. DC polarization technique was used to evaluate the corrosion protection offered by poly(O -anisidine) coatings. Preliminarily data shows that these coatings help to ennoble the surface of the substrate. © 2004 Wiley Periodicals, Inc. Adv Polym Techn 23: 291,297, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20024 [source] Novel bioactive scaffolds with fibronectin recognition nanosites based on molecular imprinting technologyJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Elisabetta Rosellini Abstract Biomimetic materials for application in the field of tissue engineering are usually obtained through covalent bonding between the polymer backbone and the bioactive molecules. A totally new approach, proposed for the first time by our research group, for the creation of advanced synthetic support structures for cell adhesion and proliferation is represented by molecular imprinting (MI) technology. In this article, we describe the synthesis and characterization of molecularly imprinted polymers with recognition properties toward a fibronectin peptide sequence and their application as functionalization structures. Polymers, in the form of densely fused microgel particles, were obtained by precipitation polymerization. The imprinted particles showed good performance in terms of recognition capacity and quantitative rebinding; moreover, the epitope effect was observed, with the particles able to recognize and rebind not only the specific peptide sequence but also a larger fibronectin fragment. The cytotoxicity tests showed normal vitality in C2C12 myoblasts cultured in a medium that was put in contact with the imprinted particles. Therefore, imprinted particles were used to functionalize synthetic polymeric films by deposition on their surface. The deposition of the imprinted particles did not alter their specific recognition and rebinding behavior. The most remarkable result was obtained by the biological characterization: in fact, the functionalized materials appeared able to promote cell adhesion and proliferation. These results are very promising and suggest that MI can be used as an innovative functionalization technique to prepare bioactive scaffolds with an effective capacity for improving tissue regeneration. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Modification induced by alpha particle irradiationin Makrofol polycarbonateJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008S. A. Nouh Abstract Makrofol DE 1-1 CC polycarbonate samples were exposed to alpha particles of initial energies at levels between 5.1 and 34 MeV. The modifications induced in polycarbonate samples due to the alpha particle irradiation have been studied through different characterization techniques such as X-ray diffraction (XRD), infrared spectroscopy, intrinsic viscosity, and color difference studies. The infrared spectroscopy indicated that the intensities of the characteristic absorption bands decrease with increasing the deposited alpha energy in the range 5.1,8.4 MeV, indicating that the degradation is the dominant mechanism at this range. At the same time, an increase in the OH groups was observed at the same energy range 5.1,8.4 MeV due to the degradation of carbonate group and the H abstraction from the polymer backbone to form hydroxyl groups. The degradation reported by IR spectroscopy enhanced the degree of ordering in the degraded samples as revealed by XRD technique. Additionally, this degradation decreases the intrinsic viscosity from 0.56 to 0.43 at 35°C, indicating a decrease in the average molecular mass. The non irradiated Polycarbonate polymer is nearly colorless. It showed significant darkness sensitivity towards alpha particle irradiation, indicated by an increase in the color intercept L* from 33.6 to 36.7. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Preparation of ethylene/1-octene copolymers from ethylene stock with tandem catalytic systemJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008Tao Jiang Abstract Tandem catalysis offers a novel synthetic route to the production of linear low-density polyethylene. This article reports the use of homogeneous tandem catalytic systems for the synthesis of ethylene/1-octene copolymers from ethylene stock as the sole monomer. The reported catalytic systems involving a highly selective, bis(diphenylphosphino)cyclohexylamine/Cr(acac)3/methylaluminoxane (MAO) catalytic systems for the synthesis of 1-hexene and 1-octene, and a copolymerization metallocene catalyst, rac -Et(Ind)2ZrCl2/MAO for the synthesis of ethylene/1-octene copolymer. Analysis by means of DSC, GPC, and 13C-NMR suggests that copolymers of 1-hexene and ethylene and copolymers of 1-octene and ethylene are produced with significant selectivity towards 1-hexene and 1-octene as comonomers incorporated into the polymer backbone respectively. We have demonstrated that, by the simple manipulation of the catalyst molar ratio and polymerization conditions, a series of branched polyethylenes with melting temperatures of 101.1,134.1°C and density of 0.922,0.950 g cm,3 can be efficiently produced. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Poly(glutamic acid) poly(ethylene glycol) hydrogels prepared by photoinduced polymerization: Synthesis, characterization, and preliminary release studies of protein drugsJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2002Zhiqiang Yang Abstract A class of new biodegradable hydrogels based on poly(ethylene glycol) methacrylate-graft-poly(glutamic acid) and poly(ethylene glycol) dimethacrylate was synthesized by photoinduced polymerization. Because all the polymeric constituents were highly hydrophilic, crosslinking could be performed in aqueous solutions. This type of crosslinked hydrogel was prepared by modifying a select number of acidic side-groups on poly(glutamic acid) with poly(ethylene glycol) methacrylate. These modified chains were then crosslinked in the presence of poly(ethylene glycol) dimethacrylate under a photoinduced polymerization at a wavelength of 365 nm. Swelling experiments were conducted to study the crosslinking density, pH-responsive behavior, and degradation of the hydrogel. Results showed that the degree of swelling of this type of hydrogels increased as the crosslinker concentration (or density) was reduced. Because of the presence of acidic side chains on poly(glutamic acid), swelling behavior was found to be pH-responsive, increasing at high pH in response to the increase in the amount of ionized acidic side chains. The degradation rate of these hydrogels also varied with pH. More rapid degradation was observed under stronger alkaline conditions because of the hydrolysis of the ester bonds between the crosslinker and the polymer backbone. Practically useful degradation rates could be achieved for such hydrogels under physiological conditions. Drug release rates from these hydrogels were found to be proportional to the protein molecular weight and the crosslinker density; increasing at lower protein molecular weight or crosslinker density. The preliminary findings presented in this article suggest that this class of biodegradable hydrogels could be an attractive avenue for drug delivery applications. The specific photoinduced crosslinking chemistry used would permit hydrogels to be synthesized in existence of the entrapped macromolecular drugs including peptides, proteins, and cells. In addition, the rapid feature of this polymerization procedure along with the ability to perform hydrogel synthesis and drug loading in an aqueous environment would offer great advantages in retaining drug activity during hydrogel synthesis. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 62: 14,21, 2002 [source] Surface modification of poly(glycolic acid) (PGA) for biomedical applicationsJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 5 2003Kyung-Bok Lee Abstract The immobilization of biological ligands (such as biotin and peptides) onto biodegradable polymer surfaces, including poly(glycolic acid) (PGA) sutures, is complicated by the absence of functional groups on the polymer backbone. We demonstrate a method for overcoming this problem, by attaching (+)-biotinyl-3,6,9-trioxaundecanediamine to the surface of PGA sutures, which immobilizes the ligand through an amide bond between amine (ligands) and carboxylic acid groups (surface-hydrolyzed PGA sutures). Fluorescence microscopy was used to verify the attachment of the biotin ligand to the surface of the PGA suture after a complexation with fluorescein-conjugated streptavidin. The strategy can be generalized to surface modifications of other biodegradable aliphatic polyesters, which would improve the properties of the polymers in biomedical applications such as active targeting of drugs based on ligand-attached, polymeric drug delvery systems. © 2003 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 92:933,937, 2003 [source] Synthesis and properties of mesogen-jacketed liquid crystalline polymers containing bistolane mesogenJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2010Zhen Lin Zhang Abstract On the basis of the concept of mesogen-jacketed liquid crystalline polymers, a series of new methacrylate monomers, (2,5- bis[2-(4,-alkoxyphenyl) ethynyl] benzyl methacrylate (MACn, n = 4, 6, 8, 10, and 12) and 2,5- bis[2-(6,-decanoxynaphthyl) ethynyl] benzyl methacrylate (MANC10), and their polymers, PMACn (n = 4, 6, 8, 10, and 12) and PMANC10 were synthesized. The bistolane mesogen with large ,-electron conjugation were side-attached to the polymer backbone via short linkages. Various characterization techniques such as differential scanning calorimetry, wide-angle X-ray diffraction, and polarized light microscopy were used to study their mesomorphic phase behavior. The polymer PMACn with shorter flexible substituents (n = 4) forms the columnar nematic (,N) phase, but other polymers with longer flexible tails (n = 6, 8, 10, and 12) can develop into a smetic A (SA) phase instead of a ,N phase. The PMANC10 containing naphthyl can also form a well-defined SA phase. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 [source] Deactivation reactions in the modeled 2,2,6,6-tetramethyl-1-piperidinyloxy-mediated free-radical polymerization of styrene: A comparative study with the 2,2,6,6-tetramethyl-1-piperidinyloxy/acrylonitrile systemJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2007Andrzej Kaim Abstract The competitiveness of the combination and disproportionation reactions between a 1-phenylpropyl radical, standing for a growing polystyryl macroradical, and a 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) radical in the nitroxide-mediated free-radical polymerization of styrene was quantitatively evaluated by the study of the transition geometry and the potential energy profiles for the competing reactions with the use of quantum-mechanical calculations at the density functional theory (DFT) UB3-LYP/6-311+G(3df, 2p)//(unrestricted) Austin Model 1 level of theory. The search for transition geometries resulted in six and two transition structures for the radical combination and disproportionation reactions, respectively. The former transition structures, mainly differing in the out-of-plane angle of the NO bond in the transition structure TEMPO molecule, were correlated with the activation energy, which was determined to be in the range of 8.4,19.4 kcal mol,1 from a single-point calculation at the DFT UB3-LYP/6-311+G(3df, 2p)//unrestricted Austin Model 1 level. The calculated activation energy for the disproportionation reaction was less favorable by a value of more than 30 kcal mol,1 in comparison with that for the combination reaction. The approximate barrier difference for the TEMPO addition and disproportionation reaction was slightly smaller for the styrene polymerization system than for the acrylonitrile polymerization system, thus indicating that a ,-proton abstraction through a TEMPO radical from the polymer backbone could diminish control over the radical polymerization of styrene with the nitroxide even more than in the latter system. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 232,241, 2007 [source] Relationship between the liquid crystallinity and field-effect-transistor behavior of fluorene,thiophene-based conjugated copolymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2006Eunhee Lim Abstract A series of fluorene,thiophene-based semiconducting materials, poly(9,9,-dioctylfluorene- alt -,,,,-bisthieno[3,2- b]thiophene) (F8TT2), poly(9,9,-di(3,6-dioxaheptyl)fluorene- alt -thieno[3,2- b]thiophene) (BDOHF8TT), poly(9,9,-di(3,6-dioxaheptyl)fluorene- alt -bithiophene) (BDOHF8T2), and poly(9,9,-dioctylfluorene- co -bithiophene- co -[4-(2-ethylhexyloxyl)phenyl]diphenylamine) (F8T2TPA), was synthesized through a palladium-catalyzed Suzuki coupling reaction. F8TT2, BDOHF8TT, BDOHF8T2, and F8T2TPA films exhibited photoluminescence maxima at 523, 550, 522, and 559 nm, respectively. Solution-processed field-effect transistors (FETs) fabricated with all the copolymers except F8T2TPA showed p -type organic FET characteristics. Studies of the differential scanning calorimetry scans and FETs of the polymers revealed that more crystalline polymers gave better FET device performance. The greater planarity and rigidity of thieno[3,2- b]thiophene in comparison with bithiophene resulted in higher crystallinity of the polymer backbone, which led to improved FET performance. On the other hand, the random incorporation of the triphenylamine moiety into F8T2TPA caused the polymer chains to lose crystallinity, resulting in an absence of FET characteristics. With this study, we could assess the liquid-crystallinity dependence of the field-effect carrier mobility on organic FETs based on liquid-crystalline copolymers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4709,4721, 2006 [source] Improved EL efficiency of fluorene-thieno[3,2- b]thiophene-based conjugated copolymers with hole-transporting or electron-transporting units in the main chainJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 1 2006Eunhee Lim Abstract New electroluminescent polymers (poly(9,9,-dioctylfluorene- co -thieno[3,2- b]thiophene- co -benzo[2,3,5]thiadiazole) (P1) and poly(9,9,-dioctylfluorene- co -thieno[3,2- b]thiophene- co -benzo[2,3,5]thiadiazole- co -[4-(2-ethylhexyloxyl)phenyl]diphenylamine (P2)) possess hole-transporting or electron-transporting units or both in the main chains. Electron-deficient benzothiadiazole and electron-rich triphenylamine moieties were incorporated into the polymer backbone to improve the electron-transporting and hole-transporting characteristics, respectively. P1 and P2 show greater solubility than poly(9,9,-dioctylfluorene- co -thieno[3,2- b]thiophene (PFTT), without sacrificing their good thermal stability. Moreover, owing to the incorporation of the electron-deficient benzothiadiazole unit, P1 and P2 exhibit remarkably lower LUMO levels than PFTT, and thus, it should facilitate the electron injection into the polymer layer from the cathode electrode. Consequently, because of the balance of charge mobility, LED devices based on P1 and P2 exhibit greater brightness and efficiency (up to 3000 cd/m2 and 1.35 cd/A) than devices that use the pristine PFTT. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 243,253, 2006 [source] Polyquinolines containing both spirobifluorene and cardofluorene units: Synthesis and characterizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2004Ching-Hsin Chen Abstract We have synthesized aromatic polyquinolines containing both spirobifluorene and cardofluorene moieties in the main chain by applying acid-catalyzed Friedländer quinoline synthesis. The incorporation of these rigid nonplanar structures into the polymer backbone, which restricts segmental mobility, significantly increases both the glass-transition temperature and thermal stability, while providing enhanced solubility as a result of a decrease in the degree of molecular packing and crystallinity. We have also examined the optical and electrochemical properties of these polyquinolines. The low-lying lowest unoccupied molecular orbital energy level and quasireversible electrochemical reduction of these polyquinolines suggest their potential for use as electron-injecting/transporting materials in polymer light-emitting diodes. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3314,3322, 2004 [source] Homologous series of alkylsilylphenyl-substituted poly (p -phenylenevinylene)s for light-emitting diodesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2004Sung-Ho Jin Abstract Substituent-induced electroluminescence polymers,poly[2-(2-dimethyldodecylsilylphenyl)-1,4-phenylenevinylene] [(o -R3Si)PhPPV], poly[2-(3-dimethyldodecylsilylphenyl)-1,4-phenylenevinylene] [(m -R3Si)PhPPV], and poly[2-(4-dimethyldodecylsilylphenyl)-1,4-phenylenevinylene] [(p -R3Si)PhPPV],were synthesized according to the Gilch polymerization method. The band gap and spectroscopic data were tuned by the dimethyldodecylsilyl substituent being changed from the ortho position to the para position in the phenyl side group along the polymer backbone. The weight-average molecular weights and polydispersities were 8.0,96 × 104 and 3.0,3.4, respectively. The maximum photoluminescence wavelengths for (o -R3Si)PhPPV, (m -R3Si)PhPPV, and (p -R3Si)PhPPV appeared around 500,530 nm in the green emission region. Double-layer light-emitting diodes with an indium tin oxide/poly(3,4-ethylenedioxythiophene)/polymer/Al configuration were fabricated with these polymers. The turn-on voltages and the maximum brightness of (o -R3Si)PhPPV, (m -R3Si)PhPPV, and (p -R3Si)PhPPV were 6.5,8.7 V and 1986,5895 cd/m2, respectively. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2347,2355, 2004 [source] New functionalized polyesters to achieve controlled architecturesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 3 2004Anna Finne Abstract Following our continued interest in the production of bioerodible and biodegradable functional polymers for biomedical applications, we synthesized and characterized new unsaturated polyesters. The presence of functional groups in the polymer backbone provided sites for chemical modification, and through a variation in the structure, the physical properties, such as the hydrophilicity and solubility, could be affected. With 1,1-di- n -butyl-stanna-2,7-dioxacyclo-4-heptene as the initiator in the ring-opening polymerization of polyesters, a new set of functionalized polyesters was created. The polymerization of ,-caprolactone resulted in poly(,-caprolactone) with a double bond incorporated into the structure. The polymers were obtained in a controlled manner with low molecular dispersities. The double bond was previously incorporated into L -lactide polymers, and the two reactions were compared in this study. The conversion of ,-caprolactone, with a degree of polymerization of 50, was completed within 140 min, whereas for L -lactide, only a 45% conversion took place in the same period of time. The dispersities were somewhat higher with ,-caprolactone because of the higher reaction rate and, therefore, lower selectivity. The incorporated CC double bond in the polyesters provided a variety of opportunities for further modifications. In this case, the double bond of the L -lactide macromonomers was oxidized into epoxides. Epoxidation was carried out with m -chloroperoxybenzoic acid as a chemical reagent. The conversion of the double bonds into epoxides was completed, and the obtained yields were good (>95%). As a result of the mild reaction conditions, the epoxidation of the double bond was carried out quantitatively without any side reactions. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 444,452, 2004 [source] Synthesis and characterization of novel crosslinkable polymers with a nonlinear optical chromophore as a pendant groupJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2001Sung-Ho Jin Abstract New crosslinkable polymers with a nonlinear optical (NLO) active chromophore as a pendant group were synthesized by condensation chain polymerization via palladium-catalyzed carbon,carbon coupling reactions. The polymerization yields were almost quantitative between the diiodobenzene (DIB) and diethyldipropargyl malonate (DEDPM) or 4-(dimethylamino)-4,-(6-dipropargylacetoxypropylsulfonyl)stilbene (DASS-6) monomers. To improve the molecular weight and mechanical properties of the NLO active polymer, we carried out the copolymerization with DIB and DASS-6 with various feed ratios of DEDPM. The resulting polymers were soluble in organic solvents and spun-cast onto indium tin oxide-coated glass substrates to make thin films. The molecular structures of the resulting polymers were characterized with various instrumental methods to confirm the carbon,carbon coupling reactions between the DIB and diacetylene monomers. The absorption of the ultraviolet,visible spectrum of the resulting polymers was drastically reduced after thermal curing at 160 °C because of the crosslinking of the reactive acetylene group in the polymer backbone. The electrooptic coefficient (r33) measured at 1.3 ,m ranged from 7 to 15 pm/V. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4025,4034, 2001 [source] A simple HPLC-MS method for the quantitative determination of the composition of bacterial medium chain-length polyhydroxyalkanoatesJOURNAL OF SEPARATION SCIENCE, JSS, Issue 10 2008Andreas Grubelnik Abstract Bacterial poly(hydroxyalkanoates) (PHAs) vary in the composition of their monomeric units. Besides saturated side-chains, unsaturated ones can also be found. The latter leads to unwanted by-products (THF ester, secondary alcohols) during acidic cleavage of the polymer backbone in the conventional analytical assays. To prevent these problems, we developed a new method for the reductive depolymerization of medium chain-length PHAs, leading to monomeric diols that can be separated and quantified by HPLC/MS. Reduction is performed at room temperature with lithium aluminum hydride within 5,15 min. The new method is faster and simpler than the previous ones and is quantitative. The results are consistent with the ones obtained by quantitative 1H NMR. [source] A Polycation Scaffold Presenting Tunable "Click" Sites: Conjugation to Carbohydrate Ligands and Examination of Hepatocyte-Targeted pDNA DeliveryMACROMOLECULAR BIOSCIENCE, Issue 6 2010Chen-Chang Lee Abstract A versatile polycation scaffold that can easily be modified with targeting ligands has been designed, synthesized, and characterized. A series of galactose-containing polymers has been produced to demonstrate the ease of modification of this polynucleotide delivery vehicle motif via the click reaction and to study how various structural modifications affect recognition by ASGPr on hepatocytes. A small library of structures was created where DCS and alkyl spacer length between the targeting group and the polymer backbone was varied. The novel polymer scaffold described proves to be a valuable tool for understanding structure/activity relationships of complexes made with receptor-targeted polymers. [source] Synthesis and Characterisation of Poly[oligo(, -caprolactone)L -malate- graft -poly(L -lactide)]MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 7 2010Christian Hahn Abstract Graft copolyesters with a PCL backbone and PLLA side chains were successfully prepared in three steps avoiding transesterification. First , -caprolactone was polymerised with 1,6-hexane diol as initiator to obtain hydroxytelechelic oligo(, -caprolactone)s. These diols were then subjected,in the second step,to polycondensation with L -malic acid yielding in linear poly[oligo(, -caprolactone)L -malate] having secondary hydroxyl functions in the side chain. For both reactions scandium triflate Sc(OTf)3 was used as a catalyst. In the third step various amounts of L -lactide were grafted from the polymer backbone using Zn(oct)2 as catalyst. The successful reaction was confirmed by NMR and SEC (size exclusion chromatography) analysis. Further the thermal properties of the graft copolymers with different graft lengths were determined via differential scanning calorimetry. [source] Influence of Grafting on the Solution Properties and the Dissociation Behavior of Ionic/Nonionic Grafted CopolymersMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 6 2007Jens Weber Abstract A new synthetic approach towards grafted terpolymers based on a poly[(methyl vinyl ether)- alt -(maleic anhydride)] backbone and poly(ethylene glycol) monomethyl ether (MPEG) side chains is presented. Resulting comb polymers with controllable grafting degree still have highly reactive anhydride moieties along the polymer backbone, as proved by IR spectroscopy. Grafting degree depends on the anhydride hydroxide stoichiometric ratio. It is not influenced by the molecular weight of MPEG. An increase in the grafting degree leads to a contraction of the polymer in the solution. Evaluation of potentiometric titration data gave a deeper insight into the dissociation process. The copolymers showed a two-step dissociation behavior. No significant influence of the grafting degree on the acidic strength was observed, whilst there is a strong effect of the grafting degree on the free energy change upon neutralization ,Gel. Grafting leads to a higher change in free energy ,Gel,1 for the first step but to lower ,Gel,2 required for the second step. [source] A Water-Soluble ,-Conjugated Polymer with up to 100 mg,·,mL,1 SolubilityMACROMOLECULAR RAPID COMMUNICATIONS, Issue 16 2007Huiping Wang Abstract A cationic water-soluble polyfluorene (P2) containing a high density of tetraalkylammonium side chains in polymer backbone was synthesized and characterized. The polymer shows excellent water solubility up to 100 mg,·,mL,1 as well as high photoluminescence (PL) quantum yield of 44% in water. The relatively high cationic density and appropriate side chain length of the polymer are the key factors to achieve such high water solubility. The reduction potential of P2 is decreased as compared with its neutral polymer, reflecting the enhanced electron injection abilities. The standard NPB/Alq3 device using such a polymer as the electron injection layer shows nearly three-fold enhancement in the electroluminescence (EL) efficiency. [source] | |||||||||||||||||||||||||||||||