Synthesis Of Hyperbranched Polymers Research Articles

Synthesis of Hyperbranched Polymers with Pendent Norbornene Functionalities via RAFT Polymerization of a Novel Asymmetrical Divinyl Monomer

Hyperbranched polymers with numerous pendent norbornene functionalities have been synthesized via the radical polymerization of a novel asymmetrical divinyl monomer bearing a higher reactivity methacrylate group and a lower reactivity norbornene group. Mediated by a rapid reversible addition−fragmentation chain transfer (RAFT) equilibrium, the concentration of polymeric chain radicals is decreased, and thus the gelation did not occur until higher monomer conversions (ca. 90%). An increase in reaction temperature can also significantly promote the formation of the hyperbranched structure owing to the decreased stability of the intermediate radicals derived from the norbornene group, which was confirmed by a model copolymerization system of two single vinyl monomers with similar structures to the vinyl groups in the asymmetrical divinyl monomer. Furthermore, Tri-SEC and conventional Sin-SEC as well as 1H NMR analyses show that hyperbranched structures and higher molecular weights were formed at moderate-to-...

Calculation of the effect of substitution on the yield and topological parameters of hyperbranched polymers synthesized by the cyclotrimerization of mono- and bifunctional monomers

A kinetic model allowing for the effect of substitution has been developed for the synthesis of hyperbranched polymers through the cocyclotrimerization of mono- and bifunctional monomers. The calculation has been performed by means of a mathematical apparatus for generating functions. New theoretical relationships have been obtained that enable one to predict critical conversion and variations in the structural and molecular-mass parameters of hyperbranched polymers during reaction in relation to the initial monomer ratio, relative reactivities of functional groups, and variations in the reactivities during the process.

Synthesis of hyperbranched poly(aryl amine)s via a carbene insertion approach

A novel diazirine functionalised aniline derivative, 3-(3-aminophenyl)-3-methyldiazirine 1, was prepared and employed as an AB(2)-type monomer in the synthesis of hyperbranched polymers; thus providing the first instance in which polyamines have been prepared via carbene insertion polymerisation. Photolysis of the monomer 1 in bulk and in solution resulted in the formation of hyperbranched poly(aryl amine)s with degrees of polymerisation (DP) varying from 9 to 26 as determined by gel permeation chromatography (GPC). In solution, an increase in the initial monomer concentration was generally found to result in a decrease in the molecular weight characteristics of the resulting poly(aryl amine)s. Subsequent thermal treatment of the poly(aryl amine)s caused a further increase in the DP values up to a maximum of 31. Nuclear magnetic resonance (NMR) spectroscopic analysis revealed that the increase in molecular weight upon thermal treatment resulted from hydroamination of styrenic species formed in the initial photopolymerisation or activation of diazirine moieties.

Synthesis of hyperbranched polymer having binaphthol units via oxidative cross‐coupling polymerization

AbstractThe 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

Synthesis, properties, and practical application of hyperbranched polymers

The methods of synthesis of hyperbranched polymers are considered and systematized with main attention focused on such modern and promising procedures of crosslinking free-radical polymerization as living chain and intense chain transfer regimes. The synthetic approach to hyperbranched polymers via free-radical oxidative polymerization is the first to be put forth. The main problems concerning these polymers are formulated, and the recent advances in this field are generalized and elucidated.

Surface‐graft hyperbranched polymer via self‐condensing atom transfer radical polymerization from zinc oxide nanoparticles

AbstractWe 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

Synthesis and polymerization reactions of cyclic imino ethers. II. Preparation of novel hyperbranched polymers from AB2 monomers of 2‐oxazoline type with nonequivalent B units

AbstractTo study the effect of nonequal reactivity of B units in ABx monomers, two novel monomers for synthesis of hyperbranched polymers of the polyaddition type, namely 2‐(2,5‐dihydroxyphenyl)‐2‐oxazoline (2a) and 2‐(2,4‐dihydroxyphenyl)‐2‐oxazoline (2b) were prepared and characterized. Both monomers have one free phenolic group and one hydrogen‐bonded phenolic group with the difference in chemical shift more than 2 ppm. Both monomers undergo thermally initiated polymerization in bulk and in solution at the temperature 220°C during 1 h in bulk and 24 h in solution of 1‐chloronaphthalene. Products are white powders with degree of polymerization 17 and 13 for the respective polymer 3a and 3b. The degree of branching is 0.37 and 0.3 for the respective polymer. The structure of polymers is in agreement with the structure, which was expected from the structure of monomers and consists of linear, dendritic, and terminal units. POLYM. ENG. SCI., 47:1272–1280, 2007. © 2007 Society of Plastics Engineers

Synthesis of hyperbranched polymers with precise conjugation length

AbstractA 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

Calculation of topological parameters of hyperbranched macromolecules synthesized via living radical polymerization

Numerical calculations of the kinetic model of synthesis of hyperbranched polymers in the living radical polymerization mode were performed. Analytical expressions were obtained that make it possible to predict the maximum yield of hyperbranched polymers and their topological parameters, such as the branching frequency; the numbers of living ends, monomer units and multiple bonds per macromolecule; and the degree of conversion at the gel point. The model is based on the use of a branching monomer Mm that contains m ≥ 2 polymerizable bonds in its molecule in combination with a monomer M1 capable of forming linear chains only.

Multi-functional monomer derived hyperbranched poly(methyl methacrylate): Kinetic modelling and experimental validation

Multi-functional monomer induced hyperbranched PMMA production has been shown to be a relatively facile, one-step batch solution polymerisation reaction. Essentially, the reaction is a linear polymerisation doped with appropriate amounts of multi-functional monomer (MFM) and chain transfer agent (CTA). A theoretical model for the MFM reaction has been experimentally validated using conversion, number-average molecular weight, and branching data, by employing key reaction parameters from established linear PMMA kinetics. However, the kinetic model has been modified to account for the MFM and CTA contributions, which generate the branched architecture and inhibit the onset of gelation, respectively. An important outcome of this work is the development of a generic model for hyperbranched polymer synthesis, in which the manufacture of other free-radical hyperbranched polymers, of desired architecture or physical properties, can be guided using modelling and optimisation methods.

Hyperbranched Poly(arylene ether amide) via Nucleophilic Aromatic Substitution Reaction

AbstractSummary: New hyperbranched poly(arylene ether amides) with fluorine or hydroxy end groups were synthesized from AB2 or A2B type monomers via a nucleophilic aromatic substitution (SNAr) reaction. Monomer syntheses were facilitated by chemo‐selective amidation reactions, and even a direct synthesis of hyperbranched polymer was possible without isolation of the monomer. The resulting hyperbranched poly(arylene ether amides) showed highly branched characteristics (DB = 0.43–0.53), high glass transition temperatures (Tg > 220 °C), and high thermal stability (Td10 > 420 °C). All hyperbranched polymers were readily soluble in aprotic polar solvents such as DMF, DMSO, and NMP regardless of the end groups. Such a similar solubility pattern may result from the high amide contents and longer branching distances between adjacent branching points in these hyperbranched polymer backbones.Polymerization of AB2 and A2B‐type monomers.imagePolymerization of AB2 and A2B‐type monomers.

Accelerated Methods of Synthesis of Phosphorus‐Containing Dendrimers

AbstractFor Abstract see ChemInform Abstract in Full Text.

Influence of reaction parameters on the synthesis of hyperbranched polymers via reversible addition fragmentation chain transfer (RAFT) polymerization

The synthesis of hyperbranched poly(methyl methacrylate) (PMMA) via reversible addition fragmentation chain transfer (RAFT) polymerization was investigated by varying the ratio chain transfer agent (CTA): monomer (methyl methacrylate, MMA): brancher (ethylene glycol dimethyl methacrylate, EGDMA): free radical initiator (AIBN) at various temperatures (50, 55, 60, 65, 70 °C). The rate of polymerization was observed to increase with temperature and concentration in brancher, whilst it was lowered by an increase in chain transfer agent concentration. The molecular weight of the samples increased with the ratios brancher: CTA and monomer: CTA. The polydispersity of the samples increase with conversion, as the level of branching increases. At fixed concentration in brancher, an increase of CTA concentration led to polymers with lower PDI. The variation of enthalpy ( Δ H ¯ m ) and entropy ( Δ S ¯ m ) relative to the monomer reaction were calculated, and it was observed that an increase in the brancher concentration induced an increase in both Δ H ¯ m and Δ S ¯ m , whilst lower CTA concentrations led to an increase in Δ S ¯ m . The variation in Gibbs energy for the monomer reaction ( Δ G ¯ m ) was calculated at 60 °C, and results confirmed the presence of a retardation effect when increasing CTA concentration generally observed in RAFT polymerization.

One-Pot Hyperbranched Polymer Synthesis Mediated by Reversible Addition Fragmentation Chain Transfer (RAFT) Polymerization

Reversible addition fragmentation chain transfer (RAFT) polymerization was used for the first time to produce poly(methyl methacrylate) hyperbranched polymers via the one-pot copolymerization of methyl methacrylate (MMA) and ethylene glycol dimethacrylate, mediated by 2-(2-cyanopropyl) dithiobenzoate. Hyperbranched structures were characterized by 1H NMR spectroscopy, size exclusion chromatography (SEC), and thermal analyses. Monomer conversions and molecular weight distributions of hyperbranched poly(methyl methacrylate) (PMMA) prepared via RAFT polymerization are much higher and much lower, respectively, than those of the analogous polymers prepared via other living polymerization systems. Furthermore, the living character of the RAFT process was used to polymerize styrene from hyperbranched PMMA precursors (macro chain-transfer agent, macroCTA) and to produce starlike structures with hyperbranched PMMA as the core and polystyrene as the arms. DSC and SEC analyses support the observations made regarding...

Facile synthesis of hyperbranched polymers

A modification of the A2 + B3 synthetic approach to the preparation of hyperbranched polymers is suggested providing a convenient route to obtaining high-molecular-weight hydrocarbon polymers starting from 1,3,5-triphenylbenzene and 1,4-bis(chloro-methyl) benzene.

Synthesis of Hyperbranched Polymers by the Anionic Ring-Opening Polymerization of 3,3-Bis(hydroxymethyl)oxetane

The anionic ring-opening polymerization of 3,3-bis(hydroxymethyl)oxetane (BHO) was carried out using t-BuOK as an initiator in the presence of 18-crown-6-ether (18-C-6) in NMP at 180 °C, affording the corresponding hyperbranched polyethers, poly(BHO)s containing an oxetanyl group and many hydroxyl groups at the ends in 83–98% yields. Since the resulting poly(BHO)s were insoluble in common organic solvents, the poly(BHO)s were treated with acetic anhydride to obtain poly(BHO-Ac)s containing acetyl groups at the ends. The Mns and degree of branching (DB) of poly(BHO-Ac)s were in the range of 2600–4400 estimated by SEC and 0.09–0.55 calculated by 13C NMR spectroscopy, respectively. The cationic copolymerization of poly(BHO-Ac) and 3-ethyl-3-phenoxymethyloxetane (EPO) was examined using BF3OEt2 as an initiator in CHCl3 at 0 °C for 24 h, affording pseudo dendritic polymers, poly[poly(BHO-Ac)/EPO]s with Mn=11000–15000 in 58–65% yields. Furthermore, the obtained poly[poly(BHO-Ac)/EPO] was hydrolyzed with KOH to afford the poly[poly(BHO)/EPO] containing many hydroxyl groups.

Synthesis of aryl/alkyl building blocks for dendrimer and hyperbranched polymer synthesis.

Several useful aryl/alkyl building blocks for dendrimer and hyperbranched polymer synthesis were prepared by Suzuki-Miyaura cross-coupling reactions and iododesilylation reactions. The iododesilylations were carried out with iodine monochloride (ICl) in methylene chloride and diethyl ether (10:1). This solvent combination lowered the reagents electrophilicity to the point that the iododesilylation still proceeded absolutely cleanly, but no direct iodination of alkyl-substituted aromatics occurred, which otherwise could not be avoided. [reaction: see text]

Novel Topological Polyphenylazomethines Having Controlled Metal‐Assembling Properties

AbstractFor Abstract see ChemInform Abstract in Full Text.

Control of polymer topology through transition-metal catalysis: synthesis of hyperbranched polymers by cobalt-mediated free radical polymerization.

A novel approach was demonstrated for the synthesis of hyperbranched polymers by direct free radical polymerization of divinyl monomers controlled by a cobalt chain transfer catalyst (1). By controlling the competition between propagation and chain transfer with 1, the free radical polymerization of ethylene glycol dimethacrylate (3) afforded soluble hyperbranched polymers in one pot. The structure of the hyperbranched polymers was confirmed by (1)H and (13)C NMR. The molecular weight and intrinsic viscosity of the hyperbranched polymers were measured by matrix-assisted laser desorption ionization (MALDI) mass spectrometry and size exclusion chromatography (SEC) equipped with triple detectors. The intrinsic viscosities of the hyperbranched polymers are much lower than those of their linear analogues and do not show molecular weight dependence. The unique structure and properties of these hyperbranched polymers combined with the commercial availability of many divinyl monomers and the robustness of free radical polymerization make this new approach attractive for the preparation of new functional materials.

Hybrid Nanoparticles with Hyperbranched Polymer Shells via Self-Condensing Atom Transfer Radical Polymerization from Silica Surfaces

We present the synthesis of hyperbranched polymer−silica hybrid nanoparticles by self-condensing vinyl polymerization (SCVP) via atom transfer radical polymerization (ATRP) from silica surfaces. ATRP initiators were covalently linked to the surface of silica particles, followed by SCVP of an initiator−monomer (“inimer”) which has both a polymerizable acrylic group and an initiating group in the same molecule. Well-defined polymer chains were grown from the surface to yield hybrid nanoparticles comprised of silica cores and hyperbranched polymer shells having multifunctional bromoester end groups, as confirmed by elemental analyses and Fourier transform infrared measurements. Characterization of soluble polymers obtained in solution by gel permeation chromatography (GPC), GPC/viscosity, and NMR suggests the formation of highly branched polymers. Correlation of molecular parameters of the soluble polymers with the polymers grafted on the surface is discussed in view of theoretical considerations. Hydrolysis...