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Polyethers
Kinds of Polyethers Selected AbstractsSynthesis of Well-Defined Rod-Coil Diblock Copolymer of Aromatic Polyether and Polyacrylonitrile by Chain-Growth Condensation Polymerization and Atom Transfer Radical PolymerizationMACROMOLECULAR RAPID COMMUNICATIONS, Issue 8 2008Naomi Ajioka Abstract The synthesis of diblock copolymers of aromatic polyether and polyacrylonitrile (PAN) was conducted by chain-growth condensation polymerization (CGCP) and atom transfer radical polymerization (ATRP) from an orthogonal initiator. When CGCP for aromatic polyether was carried out from a PAN macroinitiator obtained by ATRP with an orthogonal initiator, decomposition of the PAN backbone occurred. However, when ATRP of acrylonitrile was conducted from an aromatic polyether macroinitiator obtained by CGCP followed by introduction of an ATRP initiator unit, the polymerization proceeded in a well-controlled manner to yield aromatic polyether- block -polyacrylonitrile (polyether- b -PAN) with low polydispersity. This block copolymer self-assembled in N,N -dimethylformamide to form bundle-like or spherical aggregates, depending on the length of the PAN units in the block copolymer. [source] ChemInform Abstract: Crown Type Macrocycles (V)/(VI) from a Polyether with 4-Pyrone Subunit (I).CHEMINFORM, Issue 26 2001Werner Loewe 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] Characteristics of okadaic acid,induced cytotoxic effects in CHO K1 cellsENVIRONMENTAL TOXICOLOGY, Issue 6 2003C. Huynh-Delerme Abstract This article reports the results of investigations into the process of cell death induced in the Chinese hamster ovary cell K1 subclone (CHO K1) by okadaic acid (OA), a hydrophobic polyether produced by marine dinoflagellates. The IC50 was about 13 nM OA after 24 h of treatment, as determined using neutral red. With the MTT assay, the IC50 was 25 nM, although in this case 25% of the initial staining was still observed at 100 nM. Hoechst staining showed that mitotic figures accumulated at 12 nM OA after a 24- or 48-h treatment. In experiments limited to a 3-day treatment without changing the medium, CHO K1 cells were engaged in the death process at 50 nM OA after about 20 h and at 10 nM OA after 48 h. In many cells nuclear fragmentation that resulted in the apparent appearance of vesicles correlated with increasing cellular volume. But additional cell fragmentation was not observed with any treatment, and the chromatin material seemed to progressively disappear inside the cells. DNA fragmentation was analyzed by electrophoresis and with the TUNEL technique. With both techniques, the DNA was fragmented by 48 h in both 25 and 50 nM OA. Electrophoresis showed that both adherent and nonadherent cells were affected. Annexin-positive/ propidium iodide (PI),negative cells were rarely observed after OA treatment. Some were seen under the scanning cytometer after 20 h at 50 nM OA or after 48 h at 10 nM OA, but they were never detected by flow cytometry. Most of the time scanning cytometry showed either unstained cells or PI-positive (annexin-positive or -negative) cells (48 h, 50 nM, or 72 h, 10 nM). Flow cytometry cytograms showed two cell subpopulations: one composed of a majority of smaller cells, the other of larger cells. The larger cells markedly decreased with time and OA treatment (50 and 100 nM). Stained-cell counting showed that all cells that stained were both annexin- and PI positive and that most PI-positive cells were smaller. Ki67 antigen labeling showed the proliferative activity of CHO K1 cultures but also demonstrated the loss of this activity in smaller cells treated with 50 nM OA for 48 h. We concluded that in our culture conditions the main OA target within CHO K1 cultures was dividing cells. Our results suggest that cells with disturbed metaphase,anaphase enter apoptosis, leading to necrotic daughter cells. © 2003 Wiley Periodicals, Inc. Environ Toxicol 18: 383,394, 2003 [source] Biocompatibility of various root canal filling materials ex vivoINTERNATIONAL ENDODONTIC JOURNAL, Issue 8 2008R. Scotti Abstract Aim, To evaluate the biocompatibility of a resin-based endodontic filler (RealSeal) using the indirect cytotoxicity test. Methodology, Human gingival fibroblasts were cultured ex vivo. Pellets of the materials to be tested were incubated for 24, 48, and 72 h at 37 °C under sterile conditions to obtain their eluates. The fibroblasts were exposed to either diluted (50%) or undiluted eluates for 24 h. A culture medium with foetal calf serum was added to the control wells. Cell viability was estimated by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide method. The data concerning cell viability were statistically analyzed using one-way anova test and Bonferroni multiple comparisons test. Results, Eluates obtained after 24 h of incubation with the resin filler did not reduce cellular viability. An increase in cellular viability, as compared with control cells, was observed in the gutta-percha group. The undiluted eluate from the polyether material was cytotoxic, causing an 82 ± 4% decrease in cellular viability. Eluates obtained after 48 h of incubation with the resin filler increased cellular viability, whereas the polyether significantly reduced viability. Gutta-percha did not cause any detectable change. After 72 h of incubation the eluate of the resin filler caused an increase in cellular viability, as did gutta-percha, whereas polyether caused a significant decrease. Conclusions, RealSeal resin filler was nontoxic in this laboratory model. Further investigations are necessary to verify its usefulness in clinical applications. [source] Copolymerization of carbon dioxide and propylene oxide with zinc glutarate as catalyst in the presence of compounds containing active hydrogenJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007L. J. Gao Abstract To enhance the catalytic copolymerization of CO2 and propylene oxide catalyzed by zinc glutarate, the influence of trace of water, ethanol, and propanal on the catalytic activity, the resulted copolymer structure, and the molecular weight and molecular weight distribution of the copolymer were investigated extensively. The experimental results showed that the catalytic activity decreased remarkably in the presence of either trace of ethanol or water, but increased in the presence of trace of propanal. Both 1H-NMR and 13C-NMR spectra suggested that the content of carbonate linkages of resulted copolymer was not effected obviously in the presence of above-mentioned impurities, giving completely alternating poly(propylene carbonate) (PPC). GPC results indicated that these impurities reduced the molecular weights but broadened the molecular weight distributions of resulted copolymers. Finally, the byproduct contents including both propylene carbonate determined by GC and polyether increased with the increase of three impurity concentrations. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] Blends of triazine-based hyperbranched polyether with LDPE and plasticized PVCJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007Jyotishmoy Borah Abstract Triazine-based hyperbranched polyether was obtained by earlier reported method and blended with low density polyethylene (LDPE) and plasticized poly(vinyl chloride) (PVC) separately to improve some desirable properties of those linear polymers. The properties like processability, mechanical properties, flammability, etc. of those linear polymers were studied by blending with 1,7.5 phr of hyperbranched polyether. The mechanical properties were also measured after thermal aging and leaching in different chemical media. SEM study indicates that both polymers exhibit homogenous morphology at all dose levels. The mechanical properties like tensile strength, elongation at break, hardness, etc. of LDPE and PVC increase with the increase of dose level of hyperbranched polyether. The flame retardant behavior as measured by limiting oxygen index (LOI) for all blends indicates an enhanced LOI value compared to the polymer without hyperbranched polyether. The processing behavior of both types of blends as measured by solution viscosity and melt flow rate value indicates that hyperbranched polyether acts as a process aid for those base polymers. The effect of leaching and heat aging of these linear polymers on the mechanical properties showed that hyperbranched polyether is a superior antidegradant compared to the commercially used N -isopropyl- N -phenyl p -phenylene diamine. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 648,654, 2007 [source] Modification of carbon black through grafting multihydroxyl hyperbranched polyether onto its surfaceJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2007Qiang Yang Abstract The hydroxy methyl groups were introduced onto the pristine carbon black surface through the reaction between unsaturated hydrogen atoms of the polycondensed aromatic rings of carbon black and formaldehyde in alkali condition. Using the resultant hydroxy methyl groups on the carbon black surface as the growth point, multihydroxyl hyperbranched polyether was grafted onto the carbon black surface by cationic ring-opening polymerization of 3-ethyl-3-(hydroxymethyl)-oxetane in the presence of BF3·OEt2 to improve its dispersion ability in solvents. It was found that the modified carbon black could be dispersed in polar solvents, such as ethanol, chloroform, and DMF. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2086,2092, 2007 [source] Polyrotaxanes based on polyethers and ,-cyclodextrinJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2009Saloua Chelli Abstract A polyrotaxane in which ,-cyclodextrins (,-CDs) are threaded onto a polyether chain was prepared by polycondensation of a ,-CD/bisphenol A (BPA) inclusion complex with aromatic dihalides. Two dihalides, with and without a side chain, were used. This polycondensation results in a polyrotaxane (or pseudopolyrotaxane for polymers without stoppers) with a 1:1 threading ratio when the side chain is present and 2:3 when there is none. The long side chain prevents dethreading of the macrocycles. The best yield and a good threading ratio were obtained when the polycondensation was performed by liquid,solid phase transfer catalysis without solvent (L/S PTC) using 2,5-bi(iodomethyl)-4-methoxy-(1-octyloxy)benzene as dihalide. The 1H NMR and FTIR spectra show that the products consist of ,-CD and polyether. The 2D NOESY NMR spectrum shows that the polyether chains are included in the ,-CD cavity. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4391,4399, 2009 [source] Pd(0)-catalyzed polycondensation of methyl propargyl carbonate and bisphenols under stoichiometrically imbalanced conditionsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 6 2008Tomonori Takemura Abstract We found that a novel Pd(0)-catalyzed polycondensation of methyl propargyl carbonate (1) and bisphenol analogs 4 such as 4,4,-dihydroxydiphenyl ether (4b) proceeded successfully and gave polyethers 5 having exomethylene groups. The polycondensation was affected by the kind of bisphenol analogs used. The molar ratio of 1 and 4 also affected the polymerization behavior. Polyethers 5 with higher molecular weights were obtained by polymerization with 0.5 equiv of 4 toward 1. The use of 1 equiv of 4 gave poor results. When 4,4,-dihydroxybenzophenone (4d) was employed as a nucleophile, benzenesulfonamide (13) was needed as an additive for obtaining the corresponding polyether with higher molecular weight. The Pd(0)-catalyzed condensation of 1 and p -hydroxyacetophenone was conducted as a model reaction. The desired compound and three by-products were produced. Two of the by-products were formed by reaction of 1 and methanol liberated from 1. The other one appeared to be formed via hydrogenolysis. The formation of the by-products suggested that some terminal reactions took place in the polycondensation of 1 and 4. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2250,2261, 2008 [source] Unusual cationic ring-opening behavior of a novel six-membered ring spiro-orthocarbonate bearing adamantane backbonesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2004Tetsuo Hino Ring-opening reactions of novel six-membered ring spiro-orthocarbonate bearing adamantane backbones 1 were investigated with several cationic initiators. As a result, the decarboxylative product, polyether 4 along with or without cyclic carbonate 3 were unusually formed instead of the anticipated poly(ether-carbonate) 2. The present unexpected reaction behavior can be explained to proceed via predominantly decomposition of starting monomer 1 to cyclic carbonate 3 and oxetane derivative 11 at the initial stage. [source] Investigation of a New Approach to Measuring Contact Angles for Hydrophilic Impression MaterialsJOURNAL OF PROSTHODONTICS, Issue 2 2007Gerard Kugel DMD Purpose: The purpose of this investigation was to examine the initial water contact angles of seven unset impression materials using commercially available equipment, in an effort to determine whether polyether impression materials (Impregum) have lower contact angles and are, therefore, more hydrophilic than VPS impression materials. Materials and Methods: The hydrophilic properties of unset polyether and VPS impression materials were analyzed with respect to their water contact angle measurements using the commercially available Drop Shape Analysis System DSA 10. Twenty-five data points per second were collected via video analysis. There was no delay from start of measurement and data collection. Data was collected for approximately 12 s. Droplet size was determined on the thickness of canula. If the droplets became too small in volume, the water that evaporated during the measurement was large in comparison to the volume of the droplet. Therefore, 5 ,l was chosen as the lowest volume. Five trials were conducted per series for each featured material. Contact angles were calculated using the circle fitting method. Three tests using this technique were designed to control the variables of contact angle measurement with regard to time, the varying amount of fluid in contact with impression material during clinical use, and material thickness. Sample thickness of impression material was controlled by stripping the paste flat on a glass plate using a marking template to ensure a constant film thickness. Tests were conducted in a climatized room at 24°C ± 1°C. Deionized water was used as the fluid. The device was calibrated according to manufacturer's instruction for Young,Laplace fitting prior to the measurements. Results were analyzed using One-Way ANOVA, Tukey test, and t -test, as appropriate. Results: Comparing the fast setting impression materials by One-Way ANOVA and Tukey tests (p < .05) revealed the initial contact angles to range from 66.2 ± 1.5° to 127.5 ± 4.4°, of which the polyether material was the lowest after 45 s (66.2 ± 1.5°), 120 s (70.3 ± 2.8°), and 24 h (80.3 ± 1.0°) after start of the mix. The selected times represent the different stages of unset material, ranging from 45 s as the earliest practical data collection time to 24 h, at which a stone model would be poured. The polyether materials tested exhibited lower contact angles and, thus, significantly higher initial hydrophilicity than all measured VPS materials. Additionally, Impregum impression materials are more hydrophilic in the unset stage than in the set stage. VPS may show a stepwise development of hydrophilicity in the set stage that was not observed in the unset stage. Conclusions: The polyether impression materials tested were significantly more hydrophilic before, during, and after setting than that of VPS impression materials. Regardless of the amount of water in contact with the impression material, the polyether impression materials showed a significantly higher hydrophilicity in the unset stage than the VPS materials. The initial contact angle was not dependent on the thickness of the material. All parameters, including variation of time, volume of water droplet, and thickness of material, resulted in different absolute contact angles, but did not lead to a dramatic change in the ranking of the materials with regard to their hydrophilic behavior. [source] Synthesis of Well-Defined Rod-Coil Diblock Copolymer of Aromatic Polyether and Polyacrylonitrile by Chain-Growth Condensation Polymerization and Atom Transfer Radical PolymerizationMACROMOLECULAR RAPID COMMUNICATIONS, Issue 8 2008Naomi Ajioka Abstract The synthesis of diblock copolymers of aromatic polyether and polyacrylonitrile (PAN) was conducted by chain-growth condensation polymerization (CGCP) and atom transfer radical polymerization (ATRP) from an orthogonal initiator. When CGCP for aromatic polyether was carried out from a PAN macroinitiator obtained by ATRP with an orthogonal initiator, decomposition of the PAN backbone occurred. However, when ATRP of acrylonitrile was conducted from an aromatic polyether macroinitiator obtained by CGCP followed by introduction of an ATRP initiator unit, the polymerization proceeded in a well-controlled manner to yield aromatic polyether- block -polyacrylonitrile (polyether- b -PAN) with low polydispersity. This block copolymer self-assembled in N,N -dimethylformamide to form bundle-like or spherical aggregates, depending on the length of the PAN units in the block copolymer. [source] Synthesis and studies of the physical properties of polyaniline and polyurethane-modified epoxy compositesPOLYMER ENGINEERING & SCIENCE, Issue 2 2008Wen-Chin Chiou Two series of toughened, semiconductive polyaniline (PANI)/polyurethane (PU)-epoxy (PANI/PU-EPOXY) nano-composites were prepared using a conductive polymer, PANI, and PU prepolymer-modified-diglycidyl ether of bisphenol A (DGEBA) epoxy. First, the PU prepolymer-modified epoxy oligomer was synthesized by a stoichiometric reaction between the terminal isocyanate groups of the PU prepolymer and the pendent hydroxyl groups of the epoxide. PU prepolymers were made either of polyester (polybutylene adipate, PBA) or polyether (polypropylene glycol, PPG) segments. The composites were characterized by thermal, morphological, mechanical, and electrical studies. Impact strength was enhanced 100% in PU (PPG 2000)-modified composites; whereas, only ca. 30,50% increases in impact strength were observed for the other modified composites. In addition, the thermal stability of this composite proved superior to that of neat epoxy resin, regardless of a PU content at 27.5 wt%. Scanning electron microscopy (SEM) morphology study showed that the spherical PU (PPG 2000) particles (ca. 0.2,0.5 ,m) dispersed within the matrix accounts for these extraordinary properties. The conductivity of the composite increased to ca. 10,9,10,3 S cm,1 upon addition of PANI when tested in the frequency range 1 kHz,13 MHz. This study demonstrated a useful way to simultaneously improve the toughness and conductivity of the epoxy composite, thus rendering it suitable for electromagnetic interference and various charge dissipation applications. POLYM. ENG. SCI., 2008. © 2007 Society of Plastics Engineers [source] Preparation and characterization of novel hybrid thermoplastic poly(ether urethane)/poly(vinylidene fluoride) elastomers, and their application as solid polymer electrolytesPOLYMER INTERNATIONAL, Issue 5 2007Ye Lin Abstract A comb-like polyether, poly(3-2-[2-(2-methoxyethoxy)ethoxy]ethoxymethyl-3,-methyloxetane) (PMEOX), was reacted with hexamethylene diisocyanate and extended with butanediol in a one-pot procedure to give novel thermoplastic elastomeric poly(ether urethane)s (TPEUs). The corresponding hybrid solid polymer electrolytes were fabricated through doping a mixture of TPEU and poly(vinylidene fluoride) with three kinds of lithium salts, LiClO4, LiBF4 and lithium trifluoromethanesulfonimide (LiTFSI), and were characterized using differential scanning calorimetry, thermogravimetric analysis and Fourier transform infrared spectroscopy. The ionic conductivity of the resulting polymer electrolytes was then assessed by means of AC impedance measurements, which reached 2.1 × 10,4 S cm,1 at 30 °C and 1.7 × 10,3 S cm,1 at 80 °C when LiTFSI was added at a ratio of O:Li = 20. These values can be further increased to 3.5 × 10,4 S cm,1 at 30 °C and 2.2 × 10,3 S cm,1 at 80 °C by introducing nanosized SiO2 particles into the polymer electrolytes. Copyright © 2006 Society of Chemical Industry [source] Enantioselective synthesis and antioxidant activity of 3-(3,4-dihydroxyphenyl)-glyceric acid,Basic monomeric moiety of a biologically active polyether from Symphytum asperum and S. caucasicumCHIRALITY, Issue 8 2010Maia Merlani Abstract The racemic and enantioselective synthesis of a novel glyceric acid derivative, namely, 2,3-dihydroxy-3-(3,4-dihydroxyphenyl)-propionic acid as well as the antioxidant activities is described. The virtually pure enantiomers, (+)-(2R,3S)-2,3-dihydroxy-3-(3,4-dihydroxyphenyl)-propionic acid and (,)-(2S,3R)-2,3-dihydroxy-3-(3,4-dihydroxyphenyl)-propionic acid were synthesized for the first time via Sharpless asymmetric dihydroxylation of trans-caffeic acid derivatives using the enantiocomplementary catalysts, (DHQD)2 -PHAL and (DHQ)2 -PHAL. The determination of enantiomeric purity of the novel chiral glyceric acid derivatives was performed by high-performance liquid chromatographic techniques on the stage of their alkylated precursors. The novel glyceric acid derivatives show strong antioxidant activity against hypochlorite and N,N -diphenyl- N -picryl-hydrazyl free radical. Their antioxidant activity is about 40-fold higher than that of the corresponding natural polyether and three-fold higher of trans-caffeic acid itself. Chirality, 2010. © 2010 Wiley-Liss, Inc. [source] Dediazoniation of 1-naphthalenediazonium tetrafluoroborate in aqueous acid and in micellar solutionsINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 6 2008Carlos Bravo-Diaz We have measured the rates and product yields of dediazoniation of 1-naphthalenediazonium (1ND) tetrafluoroborate in the presence and absence of sodium dodecyl sulfate (SDS) micellar aggregates by employing a combination of UV,vis spectroscopy and high-performance liquid chromatography (HPLC) measurements. Kinetic data were obtained by a derivatization procedure with product yields were determined by HPLC. HPLC chromatograms show that in aqueous acid and in micellar solutions only one dediazoniation product is formed in significant quantities, 1-naphthol (NOH), and the observed rate constants (kobs) are the same when 1ND loss is monitored spectrometrically and when NOH formation is monitored by HPLC. Activation parameters were obtained both in the presence and absence of SDS micellar aggregates. In both the systems, the enthalpies of activation are high and the entropies of activation are positive. The enthalpy of activation in the absence of SDS is very similar to that in the presence of SDS micelles, but the entropy of activation is lower by a factor of 4. As a consequence, SDS micelles speed up the thermal decomposition of 1ND and increase kobs by a factor of 1.5 when [SDS] = 0.02 M. In contrast, results obtained in the presence of complexing systems such as crown ethers and polyethers show significant stabilization of the parent arenediazonium ions. Kinetic and HPLC data are consistent with the heterolytic DN + AN mechanism that involves the rate-determining fragmentation of the arenediazonium ion into a very reactive phenyl cation that reacts competitively with available nucleophiles. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 301,309, 2008 [source] The synthesis of block copolyetherketones based on 4,4,-dichlorodiphenylketone, phenolphthaleine, and bisphenol A and investigation of their propertiesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2008S. Ozden Abstract Block structured polyethers based on phenolphthaleine, 4,4,-dichlorodiphenylketone, and bisphenol A with different degrees condensation (n = 1, 5, 10, and 20) were synthesized by means of acceptor-catalytic polycondensation. Equaimolar quantities of chloranhydrides of iso- and terephthalic acids were used. Higher molecular masses were obtained from longer oligoketones with higher condensation degrees. Better molecular packing, increased thermal and mechanical properties were obtained with higher condensation degrees of oligoketones. © 2007 Wiley Periodicals, Inc. JAppl Polym Sci, 2008 [source] Synthesis of amidocrownophanes with 27- and 28-membered rings and their molecular recognition toward urea and its derivativesJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 4 2005Kazuhisha Hiratani Novel crownophanes with 27- and 28-membered rings having two hydroxyl groups, two amide groups, and aromatic moieties such as naphthalene, pyridine, and phenyl rings were successfully synthesized by a one-step reaction from the corresponding macrocyclic polyethers via "tandem Claisen rearrengement" in moderate yields. They can solubilize urea and its derivatives into chloroform solution, while the corresponding macrocyclic polyethers do not solubilize them. According to NMR studies, crownophanes 1 and 2 interact with urea and its derivatives forming 1:1 complexes. [source] Polyrotaxanes based on polyethers and ,-cyclodextrinJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2009Saloua Chelli Abstract A polyrotaxane in which ,-cyclodextrins (,-CDs) are threaded onto a polyether chain was prepared by polycondensation of a ,-CD/bisphenol A (BPA) inclusion complex with aromatic dihalides. Two dihalides, with and without a side chain, were used. This polycondensation results in a polyrotaxane (or pseudopolyrotaxane for polymers without stoppers) with a 1:1 threading ratio when the side chain is present and 2:3 when there is none. The long side chain prevents dethreading of the macrocycles. The best yield and a good threading ratio were obtained when the polycondensation was performed by liquid,solid phase transfer catalysis without solvent (L/S PTC) using 2,5-bi(iodomethyl)-4-methoxy-(1-octyloxy)benzene as dihalide. The 1H NMR and FTIR spectra show that the products consist of ,-CD and polyether. The 2D NOESY NMR spectrum shows that the polyether chains are included in the ,-CD cavity. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4391,4399, 2009 [source] Synthesis and degradation of biomedical materials based on linear and star shaped polyglycidolsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2009Helmut Keul Abstract Linear and star shaped polyglycidols (synonym with polyglycerols) are prepared in a controlled ring opening polymerization of protected glycidols. Beside the molar mass and the polydispersity, the architecture of the polyglycidols is controlled by using mono- and multifunctional mono- and polydispers initiators. Copolymers of dissimilarly protected glycidols as well as copolymers with nonfunctional oxiranes were prepared by means of anionic polymerization while copolymers of protected glycidol with tetrahydrofuran were prepared by means of cationic polymerization. Polyethers with functional groups in the side chains (functional polyethers) with special emphasis on polyglycidols (containing hydroxymethyl groups in the side chains) were used to prepare multifunctional polymers and (hetero)grafted polymer brushes via chemical and enzyme catalyzed reaction. The potential of poly(glycidol- graft -,-caprolactone)- co -glycidol) prepared via enzyme catalyzed grafting of polyglycidols using ,-caprolactone as a monomer and Lipase B from Candida antarctica as a catalyst is presented. Finally, comparative degradation studies of densely and loosely grafted polyglycidols are presented and discussed. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3209,3231, 2009 [source] Phase behavior and photo-responsive studies of photoactive liquid crystalline hyperbranched polyethers containing benzylidene moietyJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2009V. Srinivasa Rao Abstract Two sets of hyperbranched polyether epoxies were synthesized to study the effect of substituent, rigidity, and nature of photoactive unit on the thermal and photoresponsive properties. Each set was comprised of one molecule with an acyclic moiety in the repeating unit, and two molecules with a cyclic moiety of varying rigidity (cycle size) in the repeating unit. Two substituents on aromatic rings in the repeating unit were present in one set, and other set was without a substituent. The mesogenic and photoresponsive properties were studied and correlated to the varied structural parameters. The effects of varied molecular structural parameters on phase behavior and photoresponsive properties were very prominent. Out of six monomeric diols, only four have exhibited liquid crystalline phase while the polymers corresponding to all monomeric diols revealed mesophase. The findings in photoresponsive properties were further supported by molecular modeling studies. The changes in refractive index, photoviscosity, and fluorescence intensity with irradiation time substantiated the spectral pattern observed in UV-Vis spectroscopy. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2774,2786, 2009 [source] Hyperbranched cyclic and multicyclic polymers by "a2+b4" polycondensationsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 8 2009Hans R. Kricheldorf Abstract At first, theoretical aspects of "a2+b4" polycondensations (meaning polycondensations of difunctional and tetrafunctional monomers) are discussed and compared with what is known about "a2+b3" polycondensations. The following review of experimental results is subdivided into three sections. First, syntheses of hyperbranched polyethers and polyesters by polycondensations based on equimolar feed ratios will be reported. Second, kinetically controlled (i.e., irreversible) syntheses of multicyclic polymers using equifunctional feed ratios (i.e., a2/b4 ratios of 2:1) will be described. In the third section, syntheses of multicyclic polymers via thermodynamically controlled (reversible) "a2+b4" polycondensations will be discussed. Characteristic for these polycondensations are again equifunctional feed ratios and metal alkoxides as "a2" or "b4" monomers, which catalyze rapid equilibration reactions. Finally, potential applications of the new polymers will shortly be mentioned. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1971,1987, 2009 [source] Pd(0)-catalyzed polycondensation of methyl propargyl carbonate and bisphenols under stoichiometrically imbalanced conditionsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 6 2008Tomonori Takemura Abstract We found that a novel Pd(0)-catalyzed polycondensation of methyl propargyl carbonate (1) and bisphenol analogs 4 such as 4,4,-dihydroxydiphenyl ether (4b) proceeded successfully and gave polyethers 5 having exomethylene groups. The polycondensation was affected by the kind of bisphenol analogs used. The molar ratio of 1 and 4 also affected the polymerization behavior. Polyethers 5 with higher molecular weights were obtained by polymerization with 0.5 equiv of 4 toward 1. The use of 1 equiv of 4 gave poor results. When 4,4,-dihydroxybenzophenone (4d) was employed as a nucleophile, benzenesulfonamide (13) was needed as an additive for obtaining the corresponding polyether with higher molecular weight. The Pd(0)-catalyzed condensation of 1 and p -hydroxyacetophenone was conducted as a model reaction. The desired compound and three by-products were produced. Two of the by-products were formed by reaction of 1 and methanol liberated from 1. The other one appeared to be formed via hydrogenolysis. The formation of the by-products suggested that some terminal reactions took place in the polycondensation of 1 and 4. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2250,2261, 2008 [source] Thermally dissociable pseudo -polyrotaxane as a supramolecular shrinkage suppressor for epoxy,amine curing systemJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 6 2008Yukio Isobe Addition of pseudo -polyrotaxanes (PPRtxs) consisting of cyclodextrins (CDs) and amine-terminated polyethers to epoxy,amine curing system remarkably suppressed the volume shrinkage on the curing reaction. The PPRtx underwent thermal dissociation with creation of free volume, which efficiently contributed to the suppression of volume shrinkage. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.] [source] Multicyclic polyethers by the polycondensation of 1,2- or 1,3-dicyanotetrafluorobenzene with flexible diphenolsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2006Hans R. Kricheldorf Abstract 1,2-Dicyanotetrafluorobenzene (1,2-DCTB) was polycondensed with various flexible diphenols in a molar ratio of 1:2, and experimental parameters such as the concentration and temperature were varied. Certain diphenols allowed a complete substitution of all CF bonds, so perfect multicyclic polyethers (BnCN, where B stands for bridge units, C represents cycles, and N is the degree of polymerization) were the main reaction products. Despite complete conversion, gelation was avoidable under optimized reaction conditions. However, in the case of 1,3-dicyanotetrafluorobenzene (1,3-DCTB), complete tetrasubstitution was not feasible with a feed ratio of 1:2. Yet, because of the inductive and mesomeric electronic interactions of all substituents in 1,3-DCTB, the three CF groups in the ortho position with respect to the cyano groups were significantly more reactive than the fourth CF bond. Therefore, polycondensations with diphenols in a 3:2 feed ratio showed a relatively clean course, yielding soluble multicycles of structure Bn /2CN. All the multicyclic polyethers were amorphous and possessed molar mass distributions with polydispersities greater than 2. Heating with Cu2+ salts caused crosslinking of the multicycles derived from 1,2-DCTB because of the formation of phthalocyanine complexes. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5546,5556, 2006 [source] Synthesis and characterization of ether derivatives of brominated poly(isobutylene- co -isoprene)JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2006Sergio A. Guillén-Castellanos Abstract Variations of the Williamson ether synthesis were employed to prepare a range of new derivatives of brominated poly(isobutylene- co -isoprene) (BIIR). Unambiguous characterization of the polymeric products was accomplished by spectroscopic comparisons to low-molecular-weight analogues derived from brominated 2,2,4,8,8-pentamethyl-4-nonene, which served as a model for the reactive functionality found within BIIR. The substitution of bromide from BIIR occurred at moderate temperatures with stoichiometric amounts of quaternary ammonium phenoxide to yield O-alkylation products in high yields. Simple mixtures of BIIR, KOH, and aliphatic alcohols generated the desired allylic ethers when heated above 110 °C in the absence of quaternary ammonium salts. Knowledge gained from these small-molecule alkylations was used to prepare graft copolymers from BIIR and poly(ethylene oxide) through the exploitation of the apparent ability of polyethers to activate potassium alkoxides in nucleophilic substitutions. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 983,992, 2006 [source] Cyclic poly(pyridine ether)s by the polycondensation of 2,6-difluoropyridine with various diphenolsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2005Hans R. Kricheldorf Abstract The bistrimethylsilyl derivatives of six different diphenols were polycondensed with 2,6-difluoropyridine in N -methylpyrrolidone in the presence of K2CO3. On the basis of previous studies, the reaction conditions were optimized for almost quantitative conversions. The feed ratio was systematically varied to optimize the molecular weight. A 2 mol % excess of 2,6-difluoropyridine was needed to obtain maximum molecular weights. In the matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectra of the optimized polyethers, only cycles were found (detectable up to 5000 Da). Obviously, the relatively low molecular weights obtained under optimized conditions resulted from a limitation of the chain growth by cyclization, indicating a high cyclization tendency for poly(pyridine ether)s. The size exclusion chromatography measurements not only proved low molecular weights but also demonstrated the existence of bimodal mass distributions and high polydispersities. Protonation of the poly(pyridine ether)s required strong acids such as methane or trifluoromethane sulfonic acid. The solubilities of the neutral and protonated polyethers derived from bisphenol A were studied in various solvents. The MALDI-TOF mass spectra proved that protonation at 20,25 °C did not cause cleavage of ether bonds. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4781,4789, 2005 [source] Hyperbranched polyethers by ring-opening polymerization: Contribution of activated monomer mechanismJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2003Przemys, aw Kubisa Abstract Propagation in the cationic ring-opening polymerization of cyclic ethers involves nucleophilic attack of oxygen atoms from the monomer molecules on the cationic growing species (oxonium ions). Such a mechanism is known as the active chain-end mechanism. If hydroxyl groups containing compounds are present in the system, oxygen atoms of HO groups may compete with cyclic ether oxygen atoms of monomer molecules in reaction with oxonium ions. At the proper conditions, this reaction may dominate, and propagation may proceed by the activated monomer mechanism, that is, by subsequent addition of protonated monomer molecules to HO terminated macromolecules. Both mechanisms may contribute to the propagation in the cationic polymerization of monomers containing both functions (i.e., cyclic ether group and hydroxyl groups) within the same molecule. In this article, the mechanism of polymerization of three- and four-membered cyclic ethers containing hydroxymethyl substituents is discussed in terms of competition between two possible mechanisms of propagation that governs the structure of the products,branched polyethers containing multiple terminal hydroxymethyl groups. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 457,468, 2003 [source] Synthesis and optical properties of soluble polyethers containing oligophenyl in the main chain and p -styrylbenzene side groupsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2002Ioakim K. Spiliopoulos Abstract New polyethers containing alternating conjugated segments of p -terphenyl or p -quinquephenyl with p -styrylbenzene side groups and aliphatic spacers were synthesized with pyrylium salts. They had moderate molecular weights, were amorphous, and dissolved in tetrahydrofuran, chloroform, and other common organic solvents. The glass-transition temperatures were 68,82 and 110,153 °C for the polymers that carried p -terphenyl and p -quinquephenyl moieties, respectively. The absorption spectra showed a peak around 325 nm, and the band gaps were 3.27,3.34 eV, which were calculated from the onset absorption in solution. The photoluminescence maxima were at 393,398 nm in solution and 422,449 nm in thin films, indicating that the polymers were violet-blue-emitting materials. The photoluminescence quantum yields in solution were up to 0.25. The polymers displayed both in concentrated solutions and in the solid state intramolecular or intermolecular interactions. The polarity of the solvent influenced the shape of the photoluminescence curve. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 682,693, 2002; DOI 10.1002/pola.10151 [source] Synthesis and properties of amorphous blue-light-emitting polymers with high glass-transition temperaturesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2001V. Deimede Abstract A series of soluble poly(arylene ether)s containing the phenylphosphine oxide moiety were synthesized by the polymerization of substituted oligophenylene diols with bis(fluorophenyl)phenylphosphine oxide. These amorphous polyethers had well-defined structures and showed blue photoluminescence combined with good thermal stability, especially when phenyl or ethoxy side groups were used. The glass-transition temperatures increased when the size of the oligophenylene segment increased from three to five rings or when the length of the alkoxy substituents decreased. Polymers with glass-transition temperatures up to 270 °C were obtained. The absorption and photoluminescent spectra shifted to longer wavelengths with an increase in the oligophenylene block. A redshift was also observed on photoluminescent spectra in the transition from solution to the solid state. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3168,3179, 2001 [source] | ||||||||||||||||