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AB2 Monomer (ab2 + monomer)
Selected AbstractsSynthesis of Well-Defined Hyperbranched Polyamides by Condensation Polymerization of AB2 Monomer through Changed Substituent Effects,ANGEWANDTE CHEMIE, Issue 32 2009Yoshihiro Ohta Der Wechsel des Substituenteneffekts beim Übergang vom Monomer zum Polymer kann genutzt werden, um die selektive Kondensationspolymerisation eines AB2 -Monomers an einem Kernmolekül zu steuern (siehe Schema). Man erhält hochverzweigte Polyamide mit sehr niedriger Polydispersität und einem über das Monomer/Kern-Verhältnis kontrollierbaren Molekulargewicht. [source] Development of an efficient route to hyperbranched poly(arylene ether sulfone)sJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 14 2005Patrick Himmelberg Abstract A two-step route to an AB2 monomer that underwent polymerization via nucleophilic aromatic substitution to afford hyperbranched poly(arylene ether sulfone)s (HB PAES) was developed. The synthesis of 3,5-difluoro-4,-hydroxydiphenyl sulfone (4) was accomplished by the reaction of 3,5-difluorophenylmagnesium bromide with 4-methoxyphenylsulfonyl chloride, followed by deprotection of the phenol group with HBr in acetic acid. The polymerization of 4 in the presence of 3,4,5-trifluorophenylsulfonyl benzene or tris(3,4,5-trifluorophenyl)phosphine oxide as a core molecule afforded HB PAES with number-average molecular weights ranging from 3400 to 8400 Da and polydispersity index values ranging from 1.5 to 4.8. The presence of cyclic oligomeric species, formed by an intramolecular cyclization process, was a contributing factor to the relatively low molecular weights. The degree of branching (DB) of the HB PAES samples was estimated by a comparison of the 19F NMR spectra of the polymer samples with those of a series of model compounds, and DB values ranging from 0.51 to 0.70 were determined. The glass-transition temperatures for the HB PAES samples were in the range of 205,222 °C, as determined by differential scanning calorimetry. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43:3178,3187, 2005 [source] Synthesis and characterization of new hyperbranched poly(aryl ether oxadiazole)sJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2001Fang-Iy Wu Abstract A new AB2 monomer was synthesized for use in the preparation of a hyperbranched poly(aryl ether oxadiazole) with terminal phenol functionality. The AB2 monomer contains two phenolic groups and a single aryl fluoride group that is activated toward nucleophilic displacement by the attached oxadiazole ring. The nucleophilic substitution of the fluoride with the phenolate groups led to the formation of an ether linkage. Subsequently, a hyperbranched poly(aryl ether oxadiazole) having approximately a 44% degree of branching, as determined by a combination of model compound studies and 1H NMR, was obtained. The terminal phenolic groups underwent facile functionalization, furnishing hyperbranched polymers with a variety of functional chain ends. The nature of the chain-end groups had a significant influence on the physical properties of the polymers, such as the glass-transition temperature and their solubility. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3851,3860, 2001 [source] Preparation and Characterisation of Pd Nanoclusters in Hyperbranched Aramid Templates to be used in Homogeneous CatalysisMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 12 2003Daniela Tabuani Abstract In the present paper the potential use of hyperbranched (HB) aramids as metallic solution stabilisers and carriers for homogeneous catalysis is outlined. Aramids, synthesised either from A2,+,B3 reagents [namely, p -phenylenediamine (PPD) and trimesic acid (TMA)] or from an AB2 monomer [i.e., 5-(4-aminobenzamido)isophtalic acid, named ABZAIA], have been used to stabilise palladium nanoclusters dispersed in two solvent media, namely N,N, -dimethylformamide (DMF) and dimethyl sulfoxide (DMSO). The influence of the nature of the polymeric support as well as of the solvent medium on both cluster dimensions and stability of the solutions has been investigated. Indeed, the interactions between the polymeric support and the metallic precursor (PdCl2), as revealed by 1H NMR spectroscopy, involve only the amino groups of the HB aramids. Metal nanocluster dimensions and stability are strongly dependent on the polymer used as a stabilizer. Transmission electron microscopy (TEM) analysis has shown that the presence of HB polymer in the solution reduces cluster dimensions and allows the obtaining of stable systems. The low concentration of NH2 end groups in the poly(AB2) system leads to the formation of Pd particles of rather low dimensions with a high tendency to aggregate. All prepared solutions are stable under inert atmosphere for at least a month, with an improved stabilisation when using the poly(A2,+,B3) system for more than five months. A TEM micrograph of poly(ABZAIA)/Pd from a DMSO solution. [source] Microwave-Assisted One-Pot Synthesis of Hyperbranched Epoxide-Amine AdductsMACROMOLECULAR RAPID COMMUNICATIONS, Issue 16 2009Julia Theis Abstract Hyperbranched epoxide-amine adducts were synthesized by a one-pot microwave (MW) assisted reaction. 4-(2,3-epoxypropyl-1-oxy)benzonitrile was hydrogenated using Pd/C under microwave conditions, forming the AB2 monomer 1-aminomethyl-4-(2,3-epoxypropyl-1-oxy)benzene. Depending on the reaction temperature this monomer immediately reacts to give hyperbranched epoxide-amine adducts. Mass spectrometric investigations proved the formation of a homologous series of oligomers containing up to six repeating units. Due to the complexing properties of the poly(amino alcohol) moieties in the presence of Cu2+ ions, large aggregates were formed. [source] Percolation model of hyperbranched polymerizationMACROMOLECULAR SYMPOSIA, Issue 1 2003Henryk Galina Abstract Computer simulations of the step-growth homopolymerization of an AB2 monomer have been carried out on a square lattice. No rearrangements of units were made between reaction events. Instead, the capture radius, i.e., the maximum distance between the randomly selected unit and its reaction partner was changed. The reaction was considered as controlled either by diffusion and local concentration fluctuations or by the law of mass action (classical limit). The size distribution of polymer species and the extent of cyclization reactions in the polymerization are discussed. [source] Dendritic polyisophthalate endcapped with naphthyl groups for holographic recording,POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 9 2004Huiguang Kou Abstract A novel dendritic polyisophthalate with 12 naphthyl groups at the chain ends was synthesized from 5-hydroxyisophthalic acid as an AB2 monomer, 1,3,5-benzenetricarbonyl trichloride as an ,initiator core' molecule, and , -naphthol as an endcapping reagent, via a stepwise growth process. An average molecular weight of 2860,g,mol,1, and a refractive index of 1.618 at 650,nm were obtained by gel permeation chromatography and ellipsometry, respectively. A photopolymerizable recording dry film incorporating this dendrimer as a polymeric binder was used for holographic recording. Diffraction gratings with diffraction efficiency exceeding 80%, together with a modulation index of 10,2 were obtained. Copyright © 2004 John Wiley & Sons, Ltd. [source] Synthesis and Characterization of the Nitrogen-Rich Hyperbranched Polymers , Poly([1,2,3]-Triazole-[1,3,5]-Triazine)sPROPELLANTS, EXPLOSIVES, PYROTECHNICS, Issue 6 2008Georgiy Abstract Novel hyperbranched poly([1,2,3]-triazole-[1,3,5]-triazine)s (HBP TT) were synthesized by a 1,3-dipolar cycloaddition reaction from AB2 monomer , 2-azido-4,6-bis-prop-2-yn-1-yloxy- [1,3,5]-triazine (ABPOT). The monomer contains one azide group A and two terminal alkyne units B. Thermal polymerization of ABPOT in bulk or in DMF solution leads to hyperbranched polymers containing both 1,4- and 1,5-disubstituted [1,2,3]-triazoles. The monomer was also polymerized catalytically in the presence of Cu(I) salts under mild reaction conditions in DMSO solution and in bulk affording hyperbranched poly-[1,2,3]-triazoles 1,4-disubstituted only. The reactions lead to the products soluble in aprotic polar solvents like DMSO or DMF. Side reactions can proceed in a few cases, particularly: (i) homocoupling of alkyne groups, leading to the formation of insoluble products as a result of cross-linking, (ii) isomerization of propynyloxytriazine fragments to propynyl- or propadienyltriazinone ones, and (iii) hydrolysis of triple bonds without the loss of solubility. Heats of formation of monomer and synthesized polymers were calculated from their combustion heats. All products were characterized by NMR-, IR-spectroscopy, and size exclusion chromatography (SEC) data. The obtained results open the prospect for the use of HBP TT as the high-enthalpy modifiers for energetic and non-energetic binders. [source] UV-activated hydrosilylation: a facile approach for synthesis of hyperbranched polycarbosilanesAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 7 2009Guo-Bin Zhang Abstract A facile approach for synthesis of hyperbranched polycarbosilane from AB2 monomer via UV-activated hydrosilylation is presented in this communication. The polymerization process was monitored using real-time FTIR spectroscopy and the resulting hyperbranched polycarbosilanes were characterized using 1H-NMR, 13C-NMR, 29Si-NMR and SEC/MALLS. It is found that hyperbranched polycarbosilane can be synthesized from methyldiallylsilane via UV-activated hydrosilylation with bis(acetylacetonato)platinum(II) as catalyst. The polymerization activated by UV irradiation was much faster than that under thermal conditions. The similar degree of branching, average number of branch units and the exponent of the Mark,Houwink equation demonstrate that the hyperbranched polycarbosilane synthesized via UV-activated polyhydrosilylation possesses almost the same branching structure as that synthesized via thermal-activated polyhydrosilylation. Copyright © 2009 John Wiley & Sons, Ltd. [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] Electroactive Linear,Hyperbranched Block Copolymers Based on Linear Poly(ferrocenylsilane)s and Hyperbranched Poly(carbosilane)sCHEMISTRY - A EUROPEAN JOURNAL, Issue 36 2009Frederik Wurm Dipl.-Chem. Abstract A convenient two-step protocol is presented for synthesis of linear-hyperbranched diblock copolymers consisting of a linear, organometallic poly(ferrocenylsilane) (PFS) block and hyperbranched poly(carbosilane) (hbPCS) segments. Linear PFS diblock copolymers were synthesized through photolytic ring-opening polymerization of dimethyl[1]silaferrocenophane as the first block and methylvinyl[1]silaferrocenophane as the second. These block copolymers served as polyfunctional cores in a subsequent hydrosilylation polyaddition of different silane-based AB2 monomers. Three AB2 monomers (methyldiallylsilane; methyldiundecenylsilane, and ferrocenyldiallylsilane) were investigated; they introduced structural diversity to the hyperbranched block and showed variable reactivity for the hydrosilylation reaction. In the case with the additional ferrocene moiety in the ferrocenyldiallylsilane monomer, an electroactive hyperbranched block was generated. No slow monomer addition was necessary for molecular-weight control of the hyperbranching polyaddition, as the core had much higher functionality and reactivity than the carbosilane monomers. Different block ratios were targeted and hybrid block copolymers with narrow polydispersity (<1.2) were obtained. All the resulting polymers were investigated and characterized by size exclusion chromatography, NMR spectroscopy, cyclic voltammetry, and TEM, and exhibited strongly anisotropic aggregation. [source] | |||||||||||||