Synthesis Of Hyperbranched Polymers Research Articles

Efficient coupling by oxygen accelerated photocatalyzed thiol-alkyne chemistry

Thiol reactions have gained attention in many areas of chemical research, such as organic small molecule synthesis, polymer synthesis, and bimolecular coupling due to the “click” chemistry characteristics of this process. This work is a study of a novel method of photochemical thiol-alkyne reactions using alkyl halides and an Ir(ppy)3 photocatalyst. This process is shown to lead to rapid reactions and has the benefit of low catalyst and initiator concentrations relative to reagents. Remarkably, this reaction also has an unusual feature of an increased rate in the presence of oxygen, in contrast to many other types of radical processes. Catalyst and initiator concentrations and reaction conditions are varied in order to gain an understanding of the mechanism of this process. This chemistry is then applied to the synthesis of hyperbranched polymers and polymer networks to demonstrate potential applications.

Construction of Functional Hyperbranched Poly(phenyltriazolylcarboxylate)s by Metal-Free Phenylpropiolate-Azide Polycycloaddition.

The 1,3-dipolar cycloaddition of activated internal alkynes with azides has been developed into an efficient polymerization reaction for constructing functional linear 1,4,5-trisubstitued polytriazoles. However, it is rarely employed for the synthesis of hyperbranched polymers. In this work, metal-free polycycloadditions of tris(3-phenylpropiolate)s (1) and tetraphenylethene-containing diazides (2) are performed in dimethylformamide at 100°C for 7 and 12 h, producing hyperbranched poly(phenyltriazolylcarboxylate)s (hb-PPTCs) with high molecular weights and satisfactory regioregularities in good yields. The hb-PPTCs have good solubility in common organic solvents and high thermal stability. They are non-emissive in solutions, but emit intensively upon aggregation, showing an aggregation-induced emission effect. Their aggregates can work as fluorescent sensors for explosive detection with high sensitivity. Furthermore, the polymers can be utilized for the fabrication of 2D fluorescent patternswith high resolution byUVirradiation throughcoppergrid masks.

Ligand effect in the synthesis of hyperbranched polymers via copper‐catalyzed azide‐alkyne cycloaddition polymerization (CuAACP)

ABSTRACTCopper‐catalyzed azide‐alkyne cycloaddition polymerization (CuAACP) of AB2 monomers demonstrated a chain‐growth mechanism without any external ligand because of the complexation of in situ formed triazole groups with Cu catalysts. In this study, we explored the use of various ligands that affected the polymerization kinetics to tune the polymers’ molecular weights and the degree of branching (DB). Eight ligands were studied, including polyethylene glycol monomethyl ether (PEG350, Mn = 350), tris(benzyltriazolylmethyl)amine (TBTA), 2,6‐bis(1‐undecyl‐1H‐benzo[d]imidazol‐2‐yl)pyridine (Py(DBim)2), 2,2′‐bipyridyl (bpy), 4,4′‐di‐n‐nonyl‐2,2′‐bipyridine (dNbpy), N,N,N′,N″,N″‐pentamethyldiethylenetriamine (PMDETA), N,N,N′,N″,N″‐penta(n‐butyl)diethylenetriamine (PBuDETA), and N,N,N′,N″,N″‐pentabenzyldiethylenetriamine (PBnDETA). All ligands except PEG350 exhibited stronger coordination with Cu(I) than the polytriazole polymer, which freed the Cu catalyst from polymers and resulted in dominant step‐growth polymerization with simultaneous chain‐growth feature. Meanwhile, the use of PEG350 ligand retained the confined Cu in the polymer, demonstrating a chain‐growth mechanism, but lower polymer molecular weights as compared with the no‐external‐ligand polymerization. Results indicated that aliphatic substituent groups on ligands had little effect on the molecular weights and DB of the polymers, but rigid aromatic substituent groups decreased both values. By varying the ligand species and amounts, hyperbranched polymers with DB value ranging from 0.53 ([TBTA]0/[Cu]0 = 5) to 0.98 ([PMDETA]0/[Cu]0 = 2) have been achieved. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 2238–2244

Castor oil-TiO2 hyperbranched poly (ester amide) nanocomposite: a sustainable, green precursor-based anticorrosive nanocomposite coatings

In last decade study on anticorrosive performance of hyperbranched polymer nanocomposites attracted the overwhelming attention of researchers. However, scanty work on oleo hyperbranched polymer coatings are reported in the literature, while no work has been reported on castor oil-TiO2 nanoparticle dispersed hyperbranched poly (ester amide) nanocomposite coatings. Thus, herein we report the synthesis and performance of TiO2 nanoparticle dispersed hyperbranched poly (ester amide) nanocomposite coatings on Physico-mechanical and anticorrosive coatings on carbon steel in 3.5 wt. % HCl, NaCl and NaOH solutions. The synthesis of hyperbranched polymer is based on the simple A2+B3 polycondensation reaction. The structural elucidations of these were done using FTIR and NMR (1H and 13C) spectroscopy while the physico-mechanical tests were conducted by standard ASTM methods. The electrochemical corrosion techniques such as open circuit potential, potentiodynamic polarization, electrochemical impedance spectroscopy and salt spray tests were used to analyse the anticorrosive activity of these coatings. These studies revealed that the TiO2 dispersed hyperbranched poly (ester amide) coatings exhibit far superior physico-mechanical, hydrophobic (contact angle values from 98° to 107°) and anticorrosive properties (icorr 9.89 × 10−7 Acm-2, Ecorr -0.192 V, impedance ∼ 105 Ω cm2, phase angle 77° and Rpore 3.7 × 106) than those of hyperbranched poly (ester amide) and other such earlier reported coating systems.

Facile Synthesis of Hyperbranched Polymers by Sequential Polycondensation.

Hyperbranched polymers are an important class of soft nanomaterial, but the synthesis of hyperbranched polymers with well-defined dendritic structure from readily available monomers remains a challenge in polymer chemistry. We herein report a sequential polycondensation method for the one-pot synthesis of hyperbranched polymers with tunable structure and high degree of branching from commercial available monomers. Specifically, in the polycondensation process of equimolar difunctional haloalkane (A2-type monomers) and trifunctional dihydroxybenzoic acid (CB2-type monomers) using K2CO3 as the base, the aliphatic nucleophilic substitution reactivity sequence of the functional groups derived from CB2 monomers is C > second B > first B ≫ original B, thereby producing hyperbranched poly(ester ether)s with high degree of branching (DB > 0.6). Moreover, the surface functionality of the hyperbranched poly(ester ether)s could be facilely tailored by just introducing A-type monofunctional reagents into the one-pot A2 + CB2 polymerization system.

Hyperbranched Polymers by Light-Induced Self-Condensing Vinyl Polymerization.

Hyperbranched polymers (HBPs), a unique class of dendritic macromolecules, have received continuous interest from macromolecular scientists due to their inherent properties such as high level of functional terminal units, high solubility, and low viscosity. Despite enormous efforts devoted to the synthesis of HBPs by traditional methods such as single and double monomer strategies involving step-growth polymerization and self-condensing vinyl polymerization (SCVP) processes, there have been limited attempts to employ light-induced processes. Photochemical methods, however, exhibit distinct advantages not characteristically disclosed by traditional ones, such as spatial and temporal control, low energy, and site-specific activation. This review, after a brief summary of the conventional methods, presents the unique features and the key functionalities of the inimers for photoinduced SCVP and strategies for preparing HBPs.

Synthesis of Hyperbranched Polymers by Photoinduced Metal-Free ATRP

A novel synthetic strategy for the syntheses of hyperbranched homo and block copolymers was developed. By applying the photoinduced metal-free atom transfer radical polymerization (ATRP) using perylene as photocatalyst, monomer/inimer pairs were transformed into hyperbranched polymer structures under visible light irradiation. Using the halide functional groups in thus-formed structures as initiating sites, further polymerizations were also performed to construct the secondary segments successfully. The strategy described here enables the synthesis of such complex polymeric structures by a simple procedure, under mild and metal-free conditions. All polymers were characterized by spectroscopic and chromatographic techniques.

Ferrocene-Based Hyperbranched Polytriazoles: Synthesis by Click Polymerization and Application as Precursors to Nanostructured Magnetoceramics.

Ferrocene-based polymers have drawn much attention in the past decades due to their unique properties and promising applications. However, the synthesis of hyperbranched polymers is still a great challenge. Here, two ferrocene-based hyperbranched polytriazoles with high molecular weights are facilely prepared by the click polymerization reactions of ferrocene-containing diazides (1) and tris(4-ethynylphenyl)amine (2) using Cu(PPh3 )3 Br as catalyst in dimethylformamide at 60 °C for 5 and 9 h in satisfactory yields of 54.0% and 52.3%. The resulting polytriazoles are soluble in common organic solvents and thermally stable, with 5% weight loss temperatures up to 307 °C. They can be used as precursors to produce nanostructured ceramics with good magnetizability by pyrolysis at elevated temperature.

Synthesis and post-polymerisation ligations of PEG-based hyperbranched polymers for RNA conjugation via reversible disulfide linkage

The synthesis of architectural polymers with multiple reactive functionalities offers significant promise as platform technologies for development of nano-medicines that require hybrid biomolecule-nanomaterial components. However, there can often be a mismatch in compatibility between the conditions required for the coupling chemistry, while maintaining stability of the biomolecule. This leads to decreased yields and poor functional fidelity. In this report, we describe the synthesis of hyperbranched polymers, where reversible addition fragmentation chaintransfer (RAFT) polymerization is used to control chain molecular weight, end group functionality and the final size of the hyperbranched polymer. Through optimization of the reaction conditions, we demonstrate that branched polymers with controlled size can be synthesized. The subsequent modification of the end-groups within the branched polymer through coupling to small oligonucleotides is then systematically investigated as a function of coupling chemistry. We demonstrate that to achieve the highest degree of coupling, chain extension of the end-group away from the sterically-hindered core of the polymer is required, and that the use of strained alkyne-azide coupling reactions appear to show the highest level of efficiency under the conditions studied. Indeed, when mixed attachment of both fluorescent dye molecules and oligos is attempted under these conditions, almost quantitative end-group modification is achieved. Overall, we highlight the importance of choosing compatible chemistries that allow efficient coupling of biomolecules to synthetic substrates under mild conditions to achieve optimal reaction performance.

Recent Progress on Hyperbranched Polymers Synthesized via Radical-Based Self-Condensing Vinyl Polymerization.

This short review article summarizes recent reports on using controlled radical polymerization (CRP) of inimers (compounds containing initiating group and vinyl group in one molecule) or transmers (compounds containing chain transfer group and vinyl group in one molecule) for the synthesis of hyperbranched polymers. These inimers and transmers that carry numerous functional groups could be homopolymerized, i.e., self-condensing vinyl polymerization, or copolymerized with monovinyl monomers, i.e., self-condensing vinyl copolymerization, using atom transfer radical polymerization (ATRP), nitroxide-mediated polymerization (NMP) or reversible addition fragmentation chain transfer (RAFT) polymerization techniques, producing hyperbranched polymers and hyperstar polymers with tunable molecular weights, compositions and degree of branching. Recent reports that attempted different strategies to regulate polymer–polymer reactions were introduced, demonstrating possible syntheses of hyperbranched polymers with better defined structures and relatively low molecular weight dispersity. Finally, several CRP-produced hyperbranched polymers were discussed on their applications for encapsulation of guest molecules, nanomedicine, diagnostic imaging and catalysis.

Synthesis of hyperbranched polymers from vegetable oil based monomers via ozonolysis pathway

ABSTRACTIn this work, a variety of hyperbranched polymers (HBPs), such as hyperbranched polycarbonates, polyesters, polyurethanes and polyacetals, was successfully synthesized from castor oil and soybean oil based monomers via a A2 + B3 polycondensation. First, B3 monomer triols (TriOL), trialdehydes (TriAD), and tricarboxylic acids (TriAC) were obtained by ozonolysis of castor oil and soybean oil with following reductive or oxidative treatment. Their structures were characterized by 1H NMR and ATR‐FTIR spectroscopy as well as electrospray ionization‐Time of Flight‐mass spectrometry. These trifunctional B3 monomers were applied in the preparation of HBPs. The resulting HBPs had number averaged molar mass (Mn) up to 9400 g/mol and weight averaged molar mass (Mw) up to 40,000 g/mol. Through adjusting the initial molar ratio of A2 to B3 monomers, hydroxyl terminated (from TriOL monomers) or carboxylic acid (from TriAC monomers) terminated HBPs could be obtained. All the HBPs were characterized by 1H NMR, size exclusion chromatography, and DSC. These HBPs are potential candidates for the synthesis of cross‐linked polymeric materials or in biomedical applications. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 2104–2114

Synthesis and characterization of poly(ethylene glycol) (PEG) based hyperbranched polyurethanes as thermal energy storage materials

In the present work, hyperbranched polyurethanes were prepared by using oligomeric A2+B3 approach. The synthesis of hyperbranched polymers was carried out by reaction of trimethylolpropane (TMP) with poly(ethylene glycol) (PEG) terminated isophorone diisocyanate (IPDI). The prepared hyperbranched polymers were confirmed by Fourier transform infrared spectroscopy (FTIR) and 1H nuclear magnetic resonance (1H NMR). The crystallization properties studied with X-ray diffraction (XRD) and polarized optical microscopy (POM) indicated that hyperbranched polymers had crystalline structure and degree of crystallization reduces with introduction of hard segment. The maximum latent heat of fusion was found to be 145Jg−1 at 55°C. Field emission scanning electron microscopy (FESEM) showed presence of homogeneous structure and thermogravimetric analysis (TGA) results indicated that the materials have good thermal stability. Thermal reliability tests from 20 thermal cycles demonstrate that enthalpy of hyperbranched polyurethanes improves with thermal cycling without any chemical degradation. These materials can be successfully used as polymeric phase change materials for thermal energy storage applications.

Rational Synthesis of Hyperbranched Poly(ester)s

Hyperbranched poly(ester)s have a variety of unique properties as a result of their abundance of end groups which make them useful in a range of applications. The synthesis of hyperbranched polymers has generally been carried out using empirically derived procedures to avoid gelation. However, such synthetic strategies lead to materials with unpredictable molecular weight and properties. It has now been demonstrated that modeling may be utilized to direct the synthesis of hyperbranched poly(ester)s from a variety of monomers to form well-defined structures and terminal-group functionality while avoiding gelation. In particular, Macosko–Miller modeling permits the synthesis of hyperbranched poly(ester)s of specific molecular weights and end-group functionality even for multifunctional monomers for which functional groups are not equally reactive.

Synthesis, characterization and dielectric relaxation study of hyperbranched polymers with different molecular architecture

Abstract Hyperbranched polymers are macromolecular systems of high branching density. They play a key role in the forefront of macromolecular synthesis for having features different from those of non-hyperbranched polymers and unique properties that make them amenable for use in a variety of applications. This paper presents the results from the synthesis of hyperbranched polymers of different molecular architecture, i.e., spherical and cylindrical. Also characterization of their thermal and dynamic properties is provided. Atom transfer radical polymerization from star and linear pre-former macroinitiators produced hyperbranched systems based on methyl methacrylate and lauryl methacrylate. Thermal characterizations by TGA and DSC allowed different types of interactions and degradation mechanisms as a function of the determined polymer architecture. NMR studies revealed the effect of molecular architecture on monomers tacticity along the molecular brushes. Spherical architecture yielded a higher isotactic percentage than cylindrical architecture did, thus indicating a specific stereochemistry as a function of the macro-initiator morphology. Broadband dielectric spectroscopy, one of the most powerful techniques to study the dynamics of molecular systems revealed not only different patterns of behavior of hyperbranched polymers of different architectures but also results in agreement with NMR on stereochemistry as a function of molecular architecture.

Effect of Monomer Structure on the CuAAC Polymerization To Produce Hyperbranched Polymers

A series of AB2-R monomers that were composed of one alkynyl group (A), two azido groups (B2), and a dangling group (R) were applied in the copper-catalyzed azide–alkyne cycloaddition (CuAAC) polymerization for synthesis of hyperbranched polymers. Several structural variables, including the linker between the alkynyl group and the diazido unit (S1), the linker between the two azido groups (S2), and the composition of R group, were systematically changed to study their effects on the polymerization kinetics, the molecular weights, and the degree of branching (DB) of the hyperbranched polymers. Within the investigation, all polymerizations eventually showed chain-growth features although their starting moments when exhibiting linear increase of molecular weights based on conversions were delayed by the increased length of S1 linker, but little influenced by S2 and R groups. The AB2-R monomer with longer S1 linker, due to slower hopping of Cu catalysts between neighboring structural units, resulted in more l...

Second-Order Nonlinear Optical Dendrimers and Dendronized Hyperbranched Polymers.

Second-order nonlinear optical (NLO) dendrimers with a special topological structure were regarded as the most promising candidates for practical applications in the field of optoelectronic materials. Dendronized hyperbranched polymers (DHPs), a new type of polymers with dendritic structures, proposed and named by us recently, demonstrated interesting properties and some advantages over other polymers. Some of our work concerning these two types of polymers are presented herein, especially focusing on the design idea and structure-property relationship. To enhance their comprehensive NLO performance, dendrimers were designed and synthesized by adjusting their isolation mode, increasing the number of the dendritic generation, modifying their topological structure, introducing isolation chromophores, and utilizing the Ar-ArF self-assembly effect. To make full use of the advantages of both the structural integrity of dendrimers and the convenient one-pot synthesis of hyperbranched polymers, DHPs were explored by utilizing low-generation dendrons as big monomers to construct hyperbranched polymers. These selected works could provide valuable information to deeply understand the relationship between the structure and properties of functional polymers with dendritic structures, but not only limited to the NLO ones, and might contribute much to the further development of functional polymers with rational design.

Synthesis of hyperbranched polymers towards efficient boron reclamation via a hybrid ultrafiltration process

Two hyperbranched polymers, hyperbranched polyglycidol (HPG) and 2, 3-Dihydroxypropyl-hyperbranched polyethylenimine (Diol-HPEI), were synthesized and studied as polychelatogens for boron reclamation via a hybrid ultrafiltration process, with the objectives of evaluating the key factors for polymer–boron chelation and improving boron rejection efficiency. Their chemical structures were unveiled by FTIR and XPS analyses whilst molecular weights were carefully tailored in order to be fully retained by a commercial ultrafiltration (UF) membrane. The chelation capacity of the two polymers was compared under different operating conditions i.e., chelating temperature, polymer loading and pH. It appears that Diol-HPEI prominently outperforms HPG because the tertiary amine group may be more competent than the ether group in terms of their protonation capability. Eventually, a rejection of 66–91% was achieved with a Diol-HPEI polymer loading of 100g per g boron in the pH range of 6.9–9.0. Besides, the effects of interfering ions, i.e., Na+, Mg2+, Cl− and SO42- on polymer–boron interactions were examined in the Diol-HPEI/boron solution at the neutral condition. Results reveal that divalent cations may exert more negative influence on boron rejection owing to the competition between them and boron to form complexes with chelating polymers. These findings may provide useful insights in design of efficient boron-chelating polymers.

Design a Highly Reactive Trifunctional Core Molecule To Obtain Hyperbranched Polymers with over a Million Molecular Weight in One-Pot Click Polymerization

We present the first one-pot one-batch synthesis of hyperbranched polymers with over a million molecular weight and low polydispersity in the copper-catalyzed alkyne–azide cycloaddition (CuAAC) polymerization of AB2 monomer. In contrast to the traditional triazido core molecule that failed to produce high molecular weight polymer, a novel tris-triazoleamine-based B3 molecule was designed, which complexed with CuI catalyst and activated the azido reactivity in both B3 and B3-containing polymers. The polymerization demonstrated linear increase of polymer molecular weights with the feed ratio of [AB2]0:[B3]0 with no need of slow monomer addition. At the same time, a higher ratio of [CuI]0:[B3]0 showed no influence on molecular weight but significantly increased the polymerization rate and produced hyperbranched polymers with higher degree of branching. The one-pot polymerization using [AB2]0:[B3]0:[Cu]0 = 2700:1:10 produced hyperbranched polymers with molecular weight Mn = 1.01 × 106 and polydispersity Mw/Mn...

Synthesis of hyperbranched polymers and hyperbranched block copolymers through “A2 + B3” click reaction

Long-chain hyperbranched and hyperbranched block polymers were synthesized through Cu catalyzed azide-alkyne cycloaddition (CuAAC) of A2 macromonomers with two alkyne groups and B3 coupling reagent with three azide groups. Polystyrene (PSt) homopolymers and block copolymers of styrene and butyl acrylate (P(St-b-BA-b-St)) with two alkyne groups were obtained via reversible addition-fragmentation chain transfer (RAFT) polymerization using a RAFT agent with two alkyne groups, S, S′-bis(α, α′-dimethyl – α″-propargyl acetate) trithio carbonate (BPTTC). Besides, the hyperbranched block copolymers were also prepared through the successive RAFT polymerization of BA with the hyperbranched PSt as RAFT agents. The evidence of 1H NMR, IR and GPC-Viscosity-MALLS measurements conformed the structure of the polymers. Dpws, the ratio of the weight average molecular weights of the hyperbranched polymers to those of the macromonomers, reached above 60 at most, calculated from MALLS measurement, which showed a high degree of the coupling reaction. The degree of branched of the hyperbranched polymers kept on increasing with the reaction time, according to the branching factor, g′.

Synthesis of hyperbranched polymers by free radical addition‐coupling polymerization with A3/B2 and A2A′/B2 approaches

ABSTRACTTwo tribromide compounds, 1,3‐(propanoic acid, 2‐bromo‐)‐2‐(2‐bromo‐1‐oxopropylamino)propyl ester (A1) and trimethylolpropane tris(2‐bromopropionate) (A2), were synthesized. By Cu/N,N,N′,N′,N″‐pentamethyldiethylenetriamine (PMDETA)‐mediated radical addition‐coupling polymerization (RACP) of 2‐methyl‐2‐nitrosopropane (MNP) with the tribromide compounds, two types of hyperbranched polymers were synthesized under mild conditions, respectively. Polymerization degrees of the polymers increased with time gradually, which is in line with a step‐growth polymerization mechanism. By tracing the polymerization process by gel permeation chromatography and NMR analysis, proper reaction conditions to get hyperbranched polymers was obtained. Based on the results of NMR analysis on the polymer chain structure, mechanism of forming hyperbranched polymer has been proposed, which includes formation of carbon radicals from the tribromo monomer through single electron transfer, their reaction with MNP to form nitroxide radicals, and cross‐coupling reaction of the nitroxide radicals with other carbon radicals. The gelation point of the A2‐MNP system is larger than that of the A1‐MNP system, indicating that probability of intramolecular cyclization in A2‐MNP RACP system is higher than the A1‐MNP system. The reactivity of —NHCOCH(CH3)Br group of A1 is lower than its two —OCOCH(CH3)Br groups, and this resulted in longer distance between two adjacent branch points in the hyperbranched polymer of A1‐MNP than the A2‐MNP system. It is possible to adjust the chain structure of RACP‐based hyperbranched polymer by changing the reactivity of the functional groups in A3 monomer. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41972.