Home About us Contact
|
Home About us Contact | ||
|
|
||
Hyperbranched Polymers (hyperbranched + polymer)
Selected AbstractsHyperbranched Polymers for Photolithographic Applications , Towards Understanding the Relationship between Chemical Structure of Polymer Resin and Lithographic PerformancesADVANCED MATERIALS, Issue 10-11 2009Christos L. Chochos A chemically amplified resist based on a hyperbranched polymer resin is demonstrated for the first time. The hyperbranched polymer is synthesized using the atom-transfer radical polymerization (ATRP) technique, and resists prepared from this hyperbranched polymer present good pattern profiles and line-edge roughness (3,) values comparable to those of the reference (commercial) resist. [source] Synthesis and characterization of hyperbranched polymers with increased chemical versatility for imprint lithographic resistsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2008Anzar Khan Abstract Hyperbranched polymers were prepared from a variety of mono- and difunctional monomers and used in the development of novel UV-imprint lithography (UV-IL) resists. The unique physical and chemical properties of these hyperbranched materials significantly increase the range of molecular systems that could be imprinted. Traditional challenges, such as the use of monomers that have low boiling points or the use of insoluble/highly crystalline momomers, are overcome by the preparation of hyperbranched polymers that incorporate these repeat units. In addition, the low viscosity of the hyperbranched macromolecules and the large number of reactive chain ends overcome many difficulties that are traditionally associated with the use of polymeric materials as imprint resists. Hyperbranched polymers containing up to 12 mol % pendant vinyl groups, needed for secondary crosslinking during imprinting, were prepared with a wide range of repeat unit structures and successfully imprinted with features from tens of microns to , 100 nm. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6238,6254, 2008 [source] Hyperbranched polymers from propargyloxysilanes: New types of acetylenic resinsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2001Yingxin Xiao Abstract New hyperbranched polymers (1P,3P) from propargyloxysilanes (1,3) are described. The propargyloxysilanes were prepared from readily available reagents in 53,61% yields. The polymerizations were clean, one-pot hydrosilylation processes catalyzed by Pt/C that were typically complete within 3 h. The polymers contained pendant acetylenic groups that underwent thermally induced crosslinking reactions. Heating the polymers to 1300 °C in flowing nitrogen resulted in weight losses ranging from 33 to 66%. Methyl substitution resulted in lower thermal stability. Further modification of the polymers was demonstrated by the reaction of 1P and 2P with phenylethynyldimethylsilane in the presence of a Pt catalyst. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3383,3391, 2001 [source] Hyperbranched polymers in cationic photopolymerization of epoxy systemsPOLYMER ENGINEERING & SCIENCE, Issue 8 2003M. Sangermano Mixtures of epoxy resins in the presence of epoxy hyperbranched polymers (HBP), in the range of 5,15 wt%, were investigated in the cationic photocuring process. No significant differences in rate of polymerization or final epoxy groups conversion were observed. At low concentration, HBP acts as plasticizer and causes a decrease of the glass transition temperature of the epoxy matrix and of the E, value. At higher concentration (about 15 wt%), two Tg values are evident, indicating a biphasic structure of the system. The SEM analysis of the fracture surface of the samples confirms a particulate structure with separate HBP domains interconnected to the epoxy matrix. In all the samples investigated, a clear increase of the impact resistance was observed, resulting either from the plasticization effect or from the particulate structure induced by the presence of the HBP resin. [source] Synthesis of Highly Fluorescent and Soluble 1,2,4-Linking Hyperbranched Poly(arylenevinylene) Featuring Intramolecular Energy FunnelingADVANCED FUNCTIONAL MATERIALS, Issue 10 2010Zengqi Xie Abstract The synthesis and optical properties of a highly soluble (>200,mg,mL,1) and highly fluorescent (,F in film,=,0.64) 1,2,4-linking hyperbranched poly(arylenevinylene) (1,2,4- hb -PAV) prepared via Wittig reaction of A3 (biphenyl-tricarbaldehyde) and B2 (phosphonium salt) monomers is reported. The molecular weight of 1,2,4- hb -PAV can be precisely controlled by the amount of the base (NaOCH3) used in the polymerization. The absorption and photoluminescence (PL) spectra of 1,2,4- hb -PAV shows distinct red-shifts compared to conventional 1,3,5-linking hyperbranched poly(arylenevinylene) (1,3,5- hb -PAV), attributed to the extended ,-conjugation along ortho - (1,2-) and para - (1,4-) links. The inherent energy gradient from the shorter branches to the longer conjugated stem in 1,2,4- hb -PAV enabled a characteristic energy funneling effect, which is absent in conventional hyperbranched polymer of 1,3,5- hb -PAV. [source] A New Carbazole-Constructed Hyperbranched Polymer: Convenient One-Pot Synthesis, Hole-Transporting Ability, and Field-Effect Transistor PropertiesADVANCED FUNCTIONAL MATERIALS, Issue 16 2009Zhong'an Li Abstract A new hyperbranched polymer (HB-car), constructed fully by carbazole moieties, is successfully synthesized through a one-pot Suzuki coupling reaction. The resultant polymer is well-characterized, and its hole-transporting ability is studied carefully. The device, in which HB-car is utilized as a hole-transporting layer and tris-(8-hydroxyquinoline) aluminum as an electron-emitting layer as well as electron-transporting layer, gives a much higher efficiency (3.05,cd A,1), than that of a poly(N -vinylcarbazole) based device (2.19,cd A,1) under similar experimental conditions. The remarkable performance is attributed to its low energy barrier and enhanced hole-drifting ability in the HB-car based device. In addition, for the first time, a field-effect transistor (FET) based on the hyperbranched polymer is fabricated, and the organic FET device shows that HB-car is a typical p -type FET material with a saturation mobility of 1,×,10,5,cm2 V,1 s,1, a threshold voltage of ,47.1,V, and an on-to-off current ratio of 103. [source] A Hyperbranched, Highly Deliquescent Polymer,ADVANCED MATERIALS, Issue 24 2007L. Tian Atom transfer radical polymerization is used to prepare a highly deliquescent hyperbranched polymer from a monomer containing polymerizable vinyl group and an initiation-ready site for branching and chain growth, as depicted in the figure. The figure also shows the very rapid deliquescence kinetics of this polymer originating from its hyperbranched structure. [source] Hydroxyl-terminated hyperbranched aromatic poly(ether-ester)s: Synthesis, characterization, end-group modification, and optical propertiesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2008Thiyagarajan Shanmugam Abstract Novel AB2 -type monomers such as 3,5-bis(4-methylolphenoxy)benzoic acid (monomer 1), methyl 3,5-bis(4-methylolphenoxy) benzoate (monomer 2), and 3,5-bis(4-methylolphenoxy)benzoyl chloride (monomer 3) were synthesized. Solution polymerization and melt self-polycondensation of these monomers yielded hydroxyl-terminated hyperbranched aromatic poly(ether-ester)s. The structure of these polymers was established using FTIR and 1H NMR spectroscopy. The molecular weights (Mw) of the polymers were found to vary from 2.0 × 103 to 1.49 × 104 depending on the polymerization techniques and the experimental conditions used. Suitable model compounds that mimic exactly the dendritic, linear, and terminal units present in the hyperbranched polymer were synthesized for the calculation of degree of branching (DB) and the values ranged from 52 to 93%. The thermal stability of the polymers was evaluated by thermogravimetric analysis, which showed no virtual weight loss up to 200 °C. The inherent viscosities of the polymers in DMF ranged from 0.010 to 0.120 dL/g. End-group modification of the hyperbranched polymer was carried out with phenyl isocyanate, 4-(decyloxy)benzoic acid and methyl red dye. The end-capping groups were found to change the thermal properties of the polymers such as Tg. The optical properties of hyperbranched polymer and the dye-capped hyperbranched polymer were investigated using ultraviolet-absorption and fluorescence spectroscopy. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5414,5430, 2008 [source] Synthesis of hyperbranched polymer having binaphthol units via oxidative cross-coupling polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 3 2008Tomohisa Temma Abstract The oxidative coupling polymerization of triphenylamine derivatives having 2-naphthol moieties with a CuCl-2,2,-isopropylidenebis(4-phenyl-2-oxazoline) catalyst under an O2 atmosphere was carried out. The polymerization of the monomer bearing both the hydroxynaphthoate and naphthol units afforded a hyperbranched polymer with a high cross-coupling selectivity of > 99%, which showed a number-average molecular weight of 20.3 × 103. In addition, the obtained polymer was quite soluble in THF. The photoluminescence and electrochemical properties of the obtained polymers were also examined. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1034,1041, 2008 [source] Catalytic reactions of oxetanes with protonic reagents and aprotic reagents leading to novel polymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2007Hiroto Kudo Abstract This paper reports new addition reactions of oxetanes with certain protonic reagents such as carboxylic acid, phenol, and thiol, and with certain aprotic reagents such as acyl chloride, thioester, phosphonyl dichloride, silyl chloride, and chloroformate using quaternary onium salts as catalysts. The kinetic study of the addition reactions of oxetanes was also investigated. These new addition reactions were applicable to the synthesis of new polymers. These polyaddition systems could also construct both polymer main chains and reactive side chains. The alternating copolymerization of oxetanes with carboxylic anhydride was performed. Furthermore, it was found that anionic ring-opening polymerization of oxetanes containing hydroxy groups proceeded to afford the hyperbranched polymer (HBP) with an oxetanyl group and many hydroxy groups at the ends of the polymer chains. Alkali developable photofunctional HBPs were synthesized by the polyaddition of bis(oxetane)s or tris(oxetane)s, and their patterning properties were examined, too. The photo-induced cationic polymerization of the polymers with pendant oxetanyl groups and the thermal curing reactions of polyfunctional oxetanes (oxetane resins) were also examined to give the crosslinking materials quantitatively. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 709,726, 2007 [source] Synthesis and characterization of hyperbranched-poly(siloxysilane)-based polymeric photoinitiatorsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2006Qing-Fa Si Abstract Three UV-sensitive, hyperbranched-poly(siloxysilane)-based polymeric photoinitiators, bearing an alkyl phenone moiety linked to the surface of the hyperbranched polymer, were synthesized via the hydrosilylation of hyperbranched poly(siloxysilane) and modified UV-sensitive compounds. Hyperbranched poly(siloxysilane) was prepared via the polyhydrosilylation of the AB2 -type monomer methylvinyldichlorosilane. The chemical structures of the polymeric photoinitiators were characterized with 1H, 13C, and 29Si NMR, elemental analysis, Fourier transform infrared, differential scanning calorimetry, UV spectrophotometry, and thermogravimetric analysis. The UV-curing behaviors of the blends of the hyperbranched polymeric photoinitiators with UV-curable epoxy acrylate (EA) resin were determined by Fourier transform infrared, and the results showed that the initiation efficiency of the polymeric photoinitiators was excellent and that the thermostability of the EA/polymeric photoinitiator curing systems was higher than that of the EA/photoinitiators. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3261,3270, 2006 [source] Effect of dendritic architecture on localized free volume of poly(ether ketone)s as probed by positron annihilation spectroscopyJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 15 2004Seung-Yeop Kwak Model poly(ether ketone)s (PEKs) with architectural variations were studied by positron annihilation lifetime spectroscopy (PALS) to estimate the average void sizes on a sub-nanometer scale, in conjunction with the hyperbranched (H-), the linear (L-), and their 50:50 block combination (HLH-) structures. The PALS distribution confirmed the unique molecular architecture of the hyperbranched polymer, consisting of an interior cavity space formed by loosely linked core and chain ends of relatively tighter free volume space. [source] Synthesis of Fluorinated Hyperbranched Polymers and Their Use as Additives in Cationic PhotopolymerizationMACROMOLECULAR MATERIALS & ENGINEERING, Issue 7 2005Marco Sangermano Abstract Summary: A fluorine containing hyperbranched polymer was synthesized by modifying an aromatic-aliphatic hyperbranched polyester with a semifluorinated alcohol via a Mitsunobu reaction and was subsequently used as an additive in cationic photopolymerization of an epoxy resin. The remaining OH groups of the fluorinated hyperbranched polymer interact with the polymeric carbocation through a chain-transfer mechanism inducing an increase in the final epoxy conversion. The fluorinated HBP induces modification of bulk and surface properties, with an increase in Tg and surface hydrophobicity already reached at very low concentration. The HBFP additive can, therefore, protect the coatings from aggressive solvents, increases hardness, and allows the preparation of a low energy surface coating. Synthesis of fluorinated hyperbranched polyester. [source] Surface-graft hyperbranched polymer via self-condensing atom transfer radical polymerization from zinc oxide nanoparticlesPOLYMER ENGINEERING & SCIENCE, Issue 9 2007Peng Liu We present the synthesis of hyperbranched polymer grafted zinc oxide (ZnO) hybrid nanoparticles by self-condensing vinyl polymerization (SCVP) via surface-initiated atom transfer radical polymerizations (SI-ATRP) from ZnO surfaces. ATRP initiators were covalently linked to the surfaces of ZnO particles, followed by SCVP of an initiator-monomer ("inimer") which has both a polymerizable group and an initiating group in the same molecule. Well-defined polymer chains were grown from the surfaces to yield hybrid nanoparticles comprised of ZnO cores and hyperbranched polymer shells having multifunctional chlorobenzyl functional end groups. The percentage of grafting (PG%) achieved 429% in 6 h, calculated from the elemental analysis results. The hybrid nanoparticles were also characterized using Fourier transform infrared spectroscopy, UV,vis absorption spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, and transmission electron microscopy. POLYM. ENG. SCI., 47:1296,1301, 2007. © 2007 Society of Plastics Engineers [source] Thermal and mechanical properties of a hydroxyl-functional dendritic hyperbranched polymer and trifunctional epoxy resin blendsPOLYMER ENGINEERING & SCIENCE, Issue 10 2001D. Ratna Curing characteristics of blends of a hydroxyl-functionalized dendritic hyperbranched polymer (HBP) and a triglycidyl p-amino phenol (TGAP) epoxy resin have been studied. THe HBP strongly enhances the curing rate owing to the catalytic effect of the hydroxyl groups. THe thermal and dynamic viscoelastic behavior of the blends of various compositions (HBP content 0,20%) have been examined and compared to the neat TGAP matrix. THe glass transition temperature (Tg) gradually decreases with increase in HBP concentration. The blends show a higher impact strength compared to neat TGAP. Scanning electron microscopy analysis indicates a single-phase morphology. [source] A novel calixarene-containing hyperbranched aliphatic polyester incorporated with pendant europium complexesPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 6 2009Jichang Feng Abstract A novel calixarene-containing hyperbranched aliphatic polyester incorporated with pendant europium complexes (H20-Cal-Eu) was synthesized and characterized by FTIR, UV, and element analysis. The polymer H20-Cal-Eu shows a glass-transition temperature (Tg) of 127°C, and a deposition temperature in the range of 280,600°C, as revealed by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively. The investigation on its photoluminescence (PL) properties revealed that the polymer emitted a remarkably strong red luminescence. Furthermore, its half spectral bandwidth of the polymer film is only about 10,nm as determined from luminescence spectra, suggesting that the light is nearly monochromatic. It is proposed that the hyperbranched polymer (HBP) containing rare earth element exhibits great potential as a red light emitting material. Copyright © 2009 John Wiley & Sons, Ltd. [source] Self-assembled hyperbranched poly(para -Phenylene vinylene) monolayers: fabrication and characterization,POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 3-5 2003Wenlong Wang Abstract Covalently-bound self-assembled monolayer of a kind of functional hyperbranched polymer, pyridine-capped hyperbranched poly(para -phenylene vinylene) (Py-HPV), was prepared on hydrophilic quartz or single-crystal silicon substrates using siloxane self-assembly techniques. The assembling procedure was characterized by contact angle measurement, X-ray photoelectron spectroscopy (XPS), UV-vis spectra and fluorescence spectroscopy. Atomic force microscopy (AFM) was also used to investigate the surface morphology and microstructure of the resulting Py-HPV self-assembled monolayer. Copyright © 2003 John Wiley & Sons, Ltd. [source] Layer-by-Layer Deposition of Rhenium-Containing Hyperbranched Polymers and Fabrication of Photovoltaic CellsCHEMISTRY - A EUROPEAN JOURNAL, Issue 1 2007Chui Wan Tse Abstract Multilayer thin films were prepared by the layer-by-layer (LBL) deposition method using a rhenium-containing hyperbranched polymer and poly[2-(3-thienyl)ethoxy-4-butylsulfonate] (PTEBS). The radii of gyration of the hyperbranched polymer in solutions with different salt concentrations were measured by laser light scattering. A significant decrease in molecular size was observed when sodium trifluoromethanesulfonate was used as the electrolyte. The conditions of preparing the multilayer thin films by LBL deposition were studied. The growth of the multilayer films was monitored by absorption spectroscopy and spectroscopic ellipsometry, and the surface morphologies of the resulting films were studied by atomic force microscopy. When the pH of a PTEBS solution was kept at 6 and in the presence of salt, polymer films with maximum thickness were obtained. The multilayer films were also fabricated into photovoltaic cells and their photocurrent responses were measured upon irradiation with simulated air mass (AM) 1.5 solar light. The open-circuit voltage, short-circuit current, fill factor, and power conversion efficiency of the devices were 1.2 V, 27.1 ,,A,cm,2, 0.19, and 6.1×10,3,%, respectively. The high open-circuit voltage was attributed to the difference in the HOMO level of the PTEBS donor and the LUMO level of the hyperbranched polymer acceptor. A plot of incident photon-to-electron conversion efficiency versus wavelength also suggests that the PTEBS/hyperbranched polymer junction is involved in the photosensitization process, in which a maximum was observed at approximately 420 nm. The relatively high capacitance, determined from the measured photocurrent rise and decay profiles, can be attributed to the presence of large counter anions in the polymer film. [source] Immobilisation of the BINAP Ligand on Dendrimers and Hyperbranched Polymers: Dependence of the Catalytic Properties on the Linker UnitADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 4 2009Jutta Abstract A series of immobilised Carbo-BINAP ligands has been synthesised using poly(propylene imine) (PPI) dendrimers as soluble supports. They contain up to 64 BINAP ligands at their periphery without an additional linking unit. Despite the high steric requirements of the ligand, all dendrimers could be completely functionalised, resulting in the immobilised systems in good yields. Furthermore, the immobilisation strategy that worked out for the fixation of AMINAP ligands with additional linking units as well as of Carbo-BINAP ligands without additional linking units on dendrimers has thus been extended to less regularly hyperbranched poly(ethylene imines) (PEI) as soluble supports. In that way it has been possible to attach on average 9, 26, and 138 Glutaroyl-AMINAP or Carbo-BINAP ligands to PEIs of different molecular weights. The catalytic properties of these systems in the copper-catalysed hydrosilylation of acetophenone were investigated. The dendritic PPI-bound Carbo-BINAP ligands displayed a strong dependence of enantioselectivity and activity on the generation of the dendrimer. For the Carbo-BINAP and Glutaroyl-AMINAP ligands immobilised on the hyperbranched polymers, however, activities and enantioselectivities comparable to those of the mononuclear catalysts were found. The macromolecular, immobilised BINAP ligands could be recycled several times without any observable loss of activity or enantioselectivity. [source] Broadband dielectric spectroscopy on the molecular dynamics in different generations of hyperbranched polyesterJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2009Gamal Turky Abstract Dielectric spectroscopy (10,2 Hz to 106 Hz) was employed to investigate the molecular dynamics of hyperbranched polyesters where the number of the generation is systematically varied from 2 to 5. As a first result, the dielectric properties depends strongly on the generation of the hyperbranched polymers. For higher generations (3 to 5) at temperatures below Tg two relaxation processes are observed, a ,-process at lower temperatures and a ,-process at higher ones. The apparent activation energies are around 100 kJ/mol which seems to be too high for truly localized processes. For the Generation 2, only the ,-process is observed. For all investigated polymers the dielectric ,-relaxation could not be observed because of strong conductivity effects. Therefore, the conductivity is systematically analyzed which obeys the peculiarities found to be characteristic for semiconducting disordered materials. Especially, the Barton/Nakajima/Namikawa relationship is found to be valid. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Water-soluble, thermoresponsive, hyperbranched copolymers based on PEG-methacrylates: Synthesis, characterization, and LCST behaviorJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2010Mario Luzon Abstract A series of water-soluble thermoresponsive hyperbranched copoly(oligoethylene glycol)s were synthesized by copolymerization of di(ethylene glycol) methacrylate (DEG-MA) and oligo(ethylene glycol) methacrylate (OEG-MA, Mw = 475 g/mol), with ethylene glycol dimethacrylate (EGD-MA) used as the crosslinker, via reversible addition fragmentation chain transfer polymerization. Polymers were characterized by size exclusion chromatography and nuclear magnetic resonance analyses. According to the monomer composition, that is, the ratio of OEG-MA: DEG-MA: EGD-MA, the lower critical solution temperature (LCST) could be tuned from 25 °C to 90 °C. The thermoresponsive properties of these hyperbranched copolymers were studied carefully and compared with their linear analogs. It was found that molecular architecture influences thermoresponsive behavior, with a decrease of around 5,10 °C in the LCST of the hyperbranched polymers compared with the LCST of linear chains. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2783,2792, 2010 [source] Synthesis of hyperbranched degradable polymers by atom transfer radical (Co)polymerization of inimers with ester or disulfide groupsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 24 2009Nicolay V. Tsarevsky Abstract Degradable hyperbranched polymers with multiple alkyl halide chain ends were synthesized by the atom transfer radical polymerization of inimers containing ester (2-(2,-bromopropionyloxy)ethyl acrylate) or disulfide (2-(2,-bromoisobutyryloxy)ethyl 2,,-methacryloyloxyethyl disulfide) groups. Both the homo- and copolymerizations (with styrene in the former case and methyl methacrylate in the latter) were studied. The hyperbranched polymers derived from the ester-type inimer were hydrolytically degradable under basic conditions, whereas those derived from the disulfide-containing inimer could be efficiently degraded in the presence of reducing agents such as tributylphosphine. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2009 [source] Synthesis and characterization of hyperbranched polymers with increased chemical versatility for imprint lithographic resistsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2008Anzar Khan Abstract Hyperbranched polymers were prepared from a variety of mono- and difunctional monomers and used in the development of novel UV-imprint lithography (UV-IL) resists. The unique physical and chemical properties of these hyperbranched materials significantly increase the range of molecular systems that could be imprinted. Traditional challenges, such as the use of monomers that have low boiling points or the use of insoluble/highly crystalline momomers, are overcome by the preparation of hyperbranched polymers that incorporate these repeat units. In addition, the low viscosity of the hyperbranched macromolecules and the large number of reactive chain ends overcome many difficulties that are traditionally associated with the use of polymeric materials as imprint resists. Hyperbranched polymers containing up to 12 mol % pendant vinyl groups, needed for secondary crosslinking during imprinting, were prepared with a wide range of repeat unit structures and successfully imprinted with features from tens of microns to , 100 nm. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6238,6254, 2008 [source] Effect of molecular architecture and size of mesogen on phase behavior and photoactive properties of photoactive liquid crystalline hyperbranched polyester epoxies containing benzylidene moietyJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2008V. Srinivasa Rao Abstract A series of photoactive liquid crystalline linear and hyperbranched polyester epoxies were synthesized by polyaddition of photoactive bis benzylidene alkanone diol monomers and terephthalic acid and trimesic acid respectively with good yield. The effect of molecular architecture (linear and hyperbranched), size of mesogenic unit (cyclic and acyclic units) on the physicochemical, thermal, mesogenic, and photoactive properties of hyperbranched polymers were studied and compared. Degree of branching of hyperbranched polymers was found to be in the range of 0.46,0.49. Monomers containing cyclic moieties only exhibited nematic mesophase, while all polymers exhibited typical nematic mesophase. Intermolecular photo cycloaddition reaction was studied by ultraviolet,visible spectra (UV,vis) and NMR spectroscopy and photo viscosity measurement of UV irradiated polymer solutions. Faster photo induced behavior of hyperbranched polymers containing acyclic alkanone moiety, as compared to polymers containing cycloalkanone moieties, was observed. The change in the refractive index was found to be in the range of 0.02,0.024. Substantial variation of refractive index indicates that this polymer could be used for optical recording. All the polymers were also found to be fluorescent in nature. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 552,563, 2008 [source] Synthesis of hyperbranched polymers with precise conjugation lengthJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 6 2007Jing Li Abstract A set of AB2 type monodisperse conjugated oligomers carrying two bromo functional groups and one boronic ester functional group were prepared by iterative deprotection and Sonogashira cross-coupling reactions. Suzuki polycondensation of these AB2 type monodisperse oligomers afforded hyperbranched polymers. The hyperbranched conjugated polymers we prepared possess not only precisely controlled conjugation length like monodisperse conjugated oligomers but also the structural feature of hyperbranched polymers. Optical property investigation demonstrated that the maximum absorption and emission wavelength red-shifted along with the increasing of the conjugation length between the two branching points and the hyperbranched structure could effectively reduce the aggregation of the conjugated polymer chains. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1084,1092, 2007 [source] Precise synthesis of well-defined dendrimer-like star-branched polymers by iterative methodology based on living anionic polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 23 2006Akira Hirao Abstract Dendrimer-like star-branched polymers recently developed as a new class of hyperbranched polymers, which resemble well-known dendrimers in branched architecture, but comprise polymer chains between junctions, are reviewed in this highlight article. In particular, we focus on the precise synthesis of various dendrimer-like star-branched polymers and block copolymers by the recently developed methodology based on iterative divergent approach using living anionic polymers and 1,1-bis(3- tert -butyldimethylsilyloxymethylphenyl)ethylene. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6659,6687, 2006 [source] Hyperbranched polymers from propargyloxysilanes: New types of acetylenic resinsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2001Yingxin Xiao Abstract New hyperbranched polymers (1P,3P) from propargyloxysilanes (1,3) are described. The propargyloxysilanes were prepared from readily available reagents in 53,61% yields. The polymerizations were clean, one-pot hydrosilylation processes catalyzed by Pt/C that were typically complete within 3 h. The polymers contained pendant acetylenic groups that underwent thermally induced crosslinking reactions. Heating the polymers to 1300 °C in flowing nitrogen resulted in weight losses ranging from 33 to 66%. Methyl substitution resulted in lower thermal stability. Further modification of the polymers was demonstrated by the reaction of 1P and 2P with phenylethynyldimethylsilane in the presence of a Pt catalyst. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3383,3391, 2001 [source] Cyclic Polymers by Kinetically Controlled Step-Growth PolymerizationMACROMOLECULAR RAPID COMMUNICATIONS, Issue 5-6 2003Hans R. Kricheldorf Abstract The theory of step-growth polymerizations including the cascade theory is discussed in the light of new results focussing on the role of cyclization reactions. The identification of cyclic oligomers and polymers in reaction products of step-growth polymerizations has been eased considerably by means of MALDI-TOF mass spectrometry. Experimental examples concern syntheses of polyesters, polycarbonates, polyamides, polyimides, poly(ether sulfone)s, poly(ether ketone)s and polyurethanes. It was found in all cases that the percentage and molecular weight of the cycles increases when the reaction conditions favor high molecular weights. In the absence of side reactions all reaction products will be cycles when conversion approaches 100%. Cyclization may even take place in the nematic phase but even-numbered cycles are favored over odd-numbered ones due to electronic interactions between mesogens aligned in parallel. In contrast to Flory's cascade theory, cyclization also plays a decisive role in polycondensations of abn -type monomers, and at 100% conversion all hyperbranched polymers have a cyclic core. Furthermore, it is demonstrated that in a2+b3 polycondensations intensive cyclization in the early stages of the process has the consequence that either no gelation occurs or the resulting networks consist of cyclic and bicyclic oligomers as building blocks. Finally, a comparison between cyclization of synthetic polymers and biopolymers is discussed. Schematic representation of a network structure mainly consisting of cyclic oligomers and multicyclic building blocks as derived from "a2" + "b3" polycondensation. [source] Mean-Square Radius of Gyration and Degree of Branching of Highly Branched Copolymers Resulting from the Copolymerization of AB2 With AB MonomersMACROMOLECULAR THEORY AND SIMULATIONS, Issue 8 2004Zhiping Zhou Abstract Summary: The evolution of the various structural units incorporated into hyperbranched polymers formed from the copolymerization of AB2 and AB monomers has been derived by the kinetic scheme. The degree of branching was calculated with a new definition given in this work. The degree of branching monotonously increased with increasing A group conversion (x) and the maximum value could reach 2r/(1,+,r)2, where r is the initial fraction of AB2 monomers in the total. Like the average degree of polymerization, the mean-square radius of gyration of the hyperbranched polymers increased moderately with A group conversion in the range x,<,0.9 and displayed an abrupt rise when the copolymerization neared completion. The characteristic ratio of the mean-square radius of gyration remained constant for the linear polymers. However, the hyperbranched polymers did not possess this character. In comparison with the linear polymerization, the weight average and z -average degree of polymerization increased due to the addition of the branched monomer units AB2 and the mean-square radius of gyration decreased quickly for the products of copolymerization. [source] The effect of hyperbranched polymers on processing and thermal stability of biodegradable polyestersPOLYMER ENGINEERING & SCIENCE, Issue 3 2009Yanir Shaked Nanomodification of poly-hydroxy-butyrate (PHB), with hyperbranched polymers (HBP), was studied. Solid-hyperbranched polyesters of different generations were incorporated into a biobased and biodegradable, thermoplastic, polyester. Thermal, rheological, and molecular weight measurements had indicated that due to the interactions between the hydroxyl groups and the polar esters in PHB, the rate of recrystallization was significantly increased. Furthermore, the degree of crystallinity and nonisothermal crystallization temperature were also increased. Molecular weight measurements did not indicate a reduction or retention when HBPs were incorporated. These results are of great significance for the processing of biodegradable polymers and specifically for PHB, where improved processability and enhanced crystallization are of importance. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers [source] | |||||||||||||||||||||||||