A hyperbranched,rotaxane‐type mechanically interlocked polymer

Based on the dibenzo‐24‐crown‐8/1,2‐bis(pyridinium)ethane recognition motif, a hyperbranched mechanically interlocked polymer was prepared by polyesterification of an easily available dynamic trifunctional AB₂ pseudorotaxane monomer. It was characterized by various techniques including ¹H NMR, COSY, NOESY, GPC, viscosity, TGA, dynamic laser light scattering, AFM, and SEM. Its GPC M_n was determined to be 191 kDa with polydispersity 1.7 and its hydrodynamic diameter in a dilute solution in acetone was about 70 nm. This measured M_n value corresponds to about 93 repeating units. The study reported here presents not only a new polymer topology but also a novel and convenient way to prepare mechanically interlocked polymers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4067–4073, 2010     

A convenient room temperature polycondensation toward hyperbranched AB2‐type all‐aromatic polyesters with phenol terminal groups

As a convenient alternative to the classical melt polycondensation the one‐pot solution polycondensation of suitable AB₂ monomers under mild conditions has been successfully adapted to hyperbranched all‐aromatic polyester with phenol terminal groups. The polymerization was performed in solution at room temperature directly using commercially available 3,5‐dihydroxybenzoic acid as monomer and 4‐(dimethylamino) pyridinium 4‐tosylate as catalyst to suppress the formation of N‐acylurea. Different carbodiimides as coupling agents were investigated to find the optimal esterification conditions. The polymers have been characterized extensively and were compared with their well‐known analogs synthesized in melt. The characterization was carried out by NMR spectroscopy, size exclusion chromatography, and asymmetric flow‐field flow fractionation as an alternative separation technique for multifunctional polymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5158–5168, 2009     

Synthesis of unimolecular reversed micelle consisting of a poly(L‐lactide) shell and hyperbranched D‐mannan core

A novel biodegradable unimolecular reversed micelle consisting of a poly(L ‐lactide) (PLA) shell and a hyperbranched D ‐mannan (HBM) core, that is, a chestnut‐shaped polymer (PLA–HBM), was synthesized by the polymerization of L ‐lactide on HBM with 4‐(dimethylamino)pyridine (DMAP) as the catalyst. The obtained polymers were soluble in dimethyl sulfoxide, tetrahydrofuran, and chloroform but insoluble in H₂O. The molecular weights of the PLA chain on PLA–HBM tended to increase with increasing polymerization time. The number of PLA chains on PLA–HBM could be controlled by the ratio of DMAP to the sugar unit in HBM. The obtained copolymer, PLA–HBM, acted as a unimolecular reversed micelle with an encapsulation ability toward the hydrophilic molecule. In addition, the entrapped hydrophilic molecules were slowly released from the core of PLA–HBM, and the release rate was accelerated by the breaking of the PLA chains of the shell when proteinase K as a hydrolase of PLA was used. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 406–413, 2006     

Construction of a hyperbranched supramolecular polymer as a bifunctional antioxidative enzyme model

A HBSP has been designed as a novel bifunctional enzyme model with SOD and GPx activity by host/guest‐directed self‐assembly of MnTPyP‐M‐Ad and 6‐Te‐diCD. The structure of the host/guest complex was elucidated by ¹H NMR spectra, and the HBSP was characterized by SEM, DLS and measurement of catalytic properties. In the bifunctional enzyme model, the Mn(III) porphyrins act as efficient SOD active sites and the tellurol moieties endow GPx activity. The SOD‐like activity (IC₅₀) of this new supramolecular catalyst was found to be 1.05 × 10^?7 M, which corresponds to 2.82% of the activity of the native SOD enzyme. Besides this, the hyperbranched supramolecular polymer also shows a higher GPx activity (ν₀ = 21.7 × 10^?6 M · min^?1) than other supramolecular enzyme models.

     

Lead‐sensitive PNIPAM microgels modified with crown ether groups

A series of lead‐sensitive poly(N‐isopropylacrylamide) microgels with pendant crown ether groups were prepared. Their cation‐sensitive behaviors were studied by dynamic light scattering. When ionic strength is not controlled, adding salts causes the microgel particles to deswell. However, when the salt effect is ruled out by keeping a constant ionic strength, adding Pb²⁺ results in much larger swelling. The Pb²⁺‐induced swelling was explained by the formation of host–guest complex between Pb²⁺ and the pendant crown ether groups, which increases the hydrophilicity of the polymer and accordingly the degree of swelling. The lead sensitivity of the microgels increases with increasing crown ether content. For the modified microgel with the highest crown ether content, it swells to ～430% of its original volume at [Pb²⁺] = 10 mM. Other cations also increase the swelling degree of the modified microgels. The extent of the cation‐induced swelling mainly depends on their affinity to the pendant crown ether groups. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4120–4127, 2010     

Synthesis and characterization of hyperbranched polyesters from glycerol‐based AB2 monomer

This article describes the synthesis of a new glycerol‐based AB₂ type monomer—ethyl{3‐[2‐hydroxy‐1‐(hydroxymethyl)ethoxy]propyl}thioacetate ( 4 ) and its application for the preparation of hyperbranched polyesters. The polycondensation of 4 has been performed over a wide range of catalysts and reaction conditions leading to polymers containing solely primary hydroxyl groups. The polycondensation progress has been monitored by means of ¹H NMR. The degree of branching of the polymers showed to be in the range of 0.5 ± 0.03. The obtained polyesters easily undergo hydrolysis or alcoholysis and may be of interest as recycled materials. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3860–3868, 2009     

Synthesis of sulfur‐containing hyperbranched polymers by the bisthiolation polymerization of diethynyl disulfide derivatives

The reaction of phenyl propynyl ether and diphenyl disulfide in the presence of 1 mol % tetrakis(triphenylphosphine)palladium as a model reaction of the polymerization of bis(4‐prop‐2‐ynyloxyphenyl) disulfide ( 1a ) gave a Z‐substituted dithioalkene. No E‐substituted dithioalkene was formed in this reaction. The palladium‐catalyzed bisthiolation polymerization of a diethynyl disulfide derivative, 1a , in benzene, was carried out to give a hyperbranched polymer ( 5a ) containing a Z‐substituted dithioalkene unit after reaction for 4 h at 70 °C. From the gel permeation chromatography analysis (chloroform, PSt standards), the number‐average and weight‐average molecular weights of 5a were found to be 8,100 and 57,000, respectively. The structure of 5a was confirmed by ¹H and ¹³C NMR spectra. The obtained polymer was soluble in common organic solvents such as benzene, acetone, and CHCl₃. Polymerization for more than 5 h gave insoluble products. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3580–3587, 2007     

Synthesis of fluorene‐based hyperbranched polymers for solution‐processable blue,green, red,and white light‐emitting devices

For the purpose of making hyperbranched polymer (Hb‐Ps)‐based red, green, blue, and white polymer light‐emitting diodes (PLEDs), three Hb‐Ps Hb‐ terfluorene ( Hb‐TF ), Hb ‐4,7‐bis(9,9′‐dioctylfluoren‐2‐yl)‐2,1,3‐benzothiodiazole ( Hb‐BFBT ), and Hb‐ 4,7‐bis[(9,9′‐dioctylfluoren‐2‐yl)‐thien‐2‐yl]‐2,1,3‐benzothiodiazole ( Hb‐BFTBT ) were synthesized via [2+2+2] polycyclotrimerization of the corresponding diacetylene‐functionalized monomers. All the synthesized polymers showed excellent thermal stability with degradation temperature higher than 355 °C and glass transition temperatures higher than 50 °C. Photoluminance (PL) and electroluminance (EL) spectra of the polymers indicate that Hb‐TF , Hb‐BFBT , and Hb‐BFTBT are blue‐green, green, and red emitting materials. Maximum brightness of the double‐layer devices of Hb‐TF , Hb‐BFBT , and Hb‐BFTBT with the device configuration of indium tin oxide/poly(3,4‐ethylene dioxythiophene):poly(styrene sulfonate)/light‐emitting polymer/CsF/Al are 48, 42, and 29 cd/m²; the maximum luminance efficiency of the devices are 0.01, 0.02, and 0.01 cd/A. By using host–guest doped system, saturated red electrophosphorescent devices with a maximum luminance efficiency of 1.61 cd/A were obtained when Hb‐TF was used as a host material doped with Os(fptz)₂(PPh₂Me₂)₂ as a guest material. A maximum luminance efficiency of 3.39 cd/A of a red polymer light‐emitting device was also reached when Hb‐BFTBT was used as the guest in the PFO (Poly(9,9‐dioctylfluorene)) host layer. In addition, a series of efficient white devices were, which show low turn‐on voltage (3.5 V) with highest luminance efficiency of 4.98 cd/A, maximum brightness of 1185 cd/m², and the Commission Internationale de l'Eclairage (CIE) coordinates close to ideal white emission (0.33, 0.33), were prepared by using BFBT as auxiliary dopant. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Biodegradable hyperbranched polyesters derived from 1,1,1‐tris(hydroxymethyl)ethane

Low molar mass hyperbranched polyesters were prepared by polycondensation of 1,1,1‐tris(hydroxymethyl)ethane and various dimethyl esters of aliphatic dicarboxylic acids in bulk. The usefulness of nontoxic bismuth salts as transesterification catalysts for these polycondensations was studied. The maximum conversion increased, and the reaction time decreased in the following sequence of increasing reactivity: dimethyl sebacate < adipate < glutarate < succinate. Regardless of the monomer combination, gelation occurred at conversions > 91.5%. The hyperbranched structure was proven by ¹H NMR spectroscopy and the absence of cyclic elements by MALDI‐TOF mass spectrometry. Quantitative acylation of all CH₂OH groups was achieved with an excess of acetic anhydride or methycrylic anhydride. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 231–238, 2009     

Synthesis of novel hyperbranched polymers featuring oxazoline linear units and their application in fast‐drying solvent‐borne coating formulations

Novel acid‐terminated hyperbranched polymers (HBPs) containing adipic acid and oxazoline monomers derived from oleic and linoleic acid have been synthesized via a bulk polymerization procedure. Branching was achieved as a consequence of an acid‐catalyzed opening of the oxazoline ring to produce a trifunctional monomer in situ which delivered branching levels of >45% as determined by ¹H and ¹³C NMR spectroscopy. The HBPs were soluble in common solvents, such as CHCl₃, acetone, tetrahydrofuran, dimethylformamide, and dimethyl sulfoxide and were further functionalized by addition of citronellol to afford white‐spirit soluble materials that could be used in coating formulations. During end group modification, a reduction in branching levels of the HBPs (down to 12–24%) was observed, predominantly on account of oxazoline ring reformation and trans‐esterification processes under the reaction conditions used. In comparison to commercial alkyd resin paint coatings, formulations of the citronellol‐functionalized hyperbranched materials blended with a commercial alkyd resin exhibited dramatic decreases of the blend viscosity when the HBP content was increased. The curing characteristics of the HBP/alkyd blend formulations were studied by dynamic mechanical analysis which revealed that the new coatings cured more quickly and produced tougher materials than otherwise identical coatings prepared from only the commercial alkyd resins. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 3964–3974     

Synthesis and self‐assembly of hyperbranched polymers with benzoyl terminal arms

Hyperbranched polyesters (HPs) with a variable content of benzoyl terminal groups were synthesized through the chemical modification of the HPs' cores by substituting a controlled fraction of the terminal hydroxyl groups with benzoyl chloride. The resulting hyperbranched polymers that were modified by benzoyl groups (HPs‐B) were characterized by ¹H NMR, FTIR, differential scanning calorimetry (DSC), and gel permeation chromatography (GPC). Research results revealed that self‐assembled structures could be formed in selected solvents (acetone/n‐hexane). It was found that the morphologies of self‐assembled structures could be adjusted by controlling the content of outside benzoyl terminal groups in the hyperbranched polymers, the volume ratio of acetone with n‐hexane, and the concentration of the hyperbranched polymers with benzoyl terminal arms. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5554–5561, 2005     

One‐pot synthesis and characterization of hyperbranched poly(ester‐amide)s from commercially available dicarboxylic acids and multihydroxyl secondary amines

A convenient and cost‐effective strategy for synthesis of hyperbranched poly(ester‐amide)s from commercially available dicarboxylic acids (A₂) and multihydroxyl secondary amine (CB₂) has been developed. By optimizing the conditions of model reactions, the AB₂‐type intermediates were formed dominantly during the initial reaction stage. Without any purification, the AB₂ intermediate was subjected to thermal polycondensation in the absence of any catalyst to prepare the aliphatic and semiaromatic hyperbranched poly(ester‐amide)s bearing multi‐hydroxyl end‐groups. The FTIR and ¹H NMR spectra indicated that the polymerization proceeded in the proposed way. The DBs of the resulting polymers were confirmed by a combination of inverse‐gated decoupling ¹³C NMR, and DEPT‐135 NMR techniques. The DBs of the hyperbranched poly(ester‐amide)s were in the range of 0.44–0.73, depending on the structure of the monomers used. The hyperbranched polymers exhibited moderate molecular weights with relatively broad distributions determined by SEC. All the polymers displayed low inherent viscosity (0.11–0.25 dL/g) due to the branched nature. Structural and end‐group effects on the thermal properties of the hyperbranched polymers were investigated using DSC. The thermogravimetric analysis revealed that the resulting polymers exhibit reasonable thermal stability. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5077–5092, 2008     

Influence of alkyl chains of amphiphilic hyperbranched poly(ester amine)s on the phase‐transfer performances for acid dye and the aggregation behaviors at the interface

Hyperbranched poly(ester amine) (HPEA) with terminal secondary amine groups was synthesized by the Michael addition reaction between piperazine and trimethylolpropanetriacrylate with a molar ratio of 13:6. It was further reacted with a series of aliphatic acid chlorides, including stearoyl chloride, dodecanoyl chloride, and octanoyl chloride, to yield three modified amphiphilic hyperbranched polymers, which were termed HPEA‐C18, HPEA‐C12, and HPEA‐C8, respectively. These polymers were characterized with Fourier transform infrared, ¹H NMR, gel permeation chromatography, and differential scanning calorimetry measurements. Because of the existence of interior tertiary amine groups, the modified amphiphilic polymers were used as host molecules to extract the guest acid dye, methyl orange (MO), from the aqueous layer to the organic layer on the basis of the acid–base interaction. The influences of the pH of the aqueous layer and the length of the alkyl chains in the modified polymers on the phase‐transfer performances were investigated. The results indicated that more MO molecules could be extracted at a lower pH because of the formation of more quaternary ammonium ions within the host molecules. As the length of the alkyl chains in the modified polymers increased, both the transfer capability and the intermolecular aggregation at the interface were enhanced. The extracted MO could be reversibly released from the organic layer to the aqueous layer under basic conditions. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2921–2930, 2005     

Facile construction of multivalent targeted drug delivery system from Boltorn® series hyperbranched aliphatic polyester and folic acid

The conjugation of PAMAM dendrimer and folic acid is a well‐studied multivalent targeted drug delivery system, but it is expensive and difficult to be synthesized. To construct an inexpensive and well‐defined multivalent targeted drug delivery system, a cheap carrier — Boltorn® series hyperbranched aliphatic polyester — was proposed as the nanodevice to carry fluorescein, folic acid, and methotrexate. The construction follows a facile route: (1) synthesizing the carrier — a hybrid hyperbranched polymer with acyclic hydroxyls and cyclic carbonate, (2) linking fluorescein to the hyperbranched polymer via the acyclic hydroxyls, (3) opening the ring of the cyclic carbonate with the amino group of folic acid, and (4) attaching the drug methotrexate to the resulting hydroxyls by ring‐opening reaction. In this route, the peripheral hydroxyls of the hyperbranched polymer are divided into two groups and reacted with three reagents in sequence to form the desired multivalent targeted drug delivery system. Copyright © 2009 John Wiley & Sons, Ltd.     

Formation of a supramolecular hyperbranched polymer from self-organization of an AB2 monomer containing a crown ether and two paraquat moieties

An AB2 monomer containing a bis(m-phenylene)-32-crown-10 and two paraquat moieties was designed and prepared. It self-organized to form a supramolecular hyperbranched polymer in solution.     

Photoluminescence of bridged polysilsesquioxanes containing urea groups: Doping with Safranine‐O to generate red‐light emission

Bridged polysilsesquioxanes containing urea groups (ureasils) exhibit a broad photoluminescent emission in the visible spectrum. For a particular bridged polysilsesquioxane synthesized by the hydrolytic condensation of a precursor prepared by reaction of 4,4′‐[1,3 phenylenebis‐(1‐methylethylidene)]bis(aniline) (BSA) with 3‐(isocyanatepropyl)triethoxysilane (IPTES), we show that the broad photoluminescent band could be transformed into a relatively narrow emission band located in the red region of the spectra, by doping with Safranine‐O. The spectral overlap between the host emission and the dye absorption generated an efficient energy transfer process (antenna effect). Absorption, emission, and triplet–triplet absorption spectra revealed an efficient dispersion of the dye in the ureasil as well as the presence of strong host‐guest specific interactions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 289–296, 2008     

Reduction‐cleavable hyperbranched polymers with limited intramolecular cyclization via click chemistry

In this contribution, we present new reduction‐cleavable hyperbranched disulfide bonds‐containing poly(ester triazole)s with limited intramolecular cyclization, which can be synthesized by the Cu(I)‐catalyzed azide–alkyne cycloaddition (CuAAC) of A₂ monomer of dipropargyl 3,3′‐dithiobispropionate and B₃ monomer of tris(hydroxymethyl)ethane tri(4‐azidobutanoate). The hyperbranched poly(ester triazole)s possess numerous terminal groups and weight‐average molecular weight up to 20,400 g mol^?1 with a polydispersity index in the range 1.57–2.17. The CuAAC introduces rigid triazole units into the backbones of hyperbranched poly(ester triazole)s and reduces intramolecular cyclization, which is proved by topological analysis and ¹H NMR spectroscopy. The disulfide bonds on backbones endow the reduction‐cleavable feature to the hyperbranched poly(ester triazole)s at the presence of dithiothreitol. It gives a novel and convenient methodology for the synthesis of reduction‐responsive functional polymer with controlled topologies, and the reduction‐cleavable hyperbranched poly(ester triazole)s with limited intramolecular cyclization are expected to possess potential in the application of stimuli‐responsive anticancer drug nanocarriers. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2374–2380     

Synthesis and characterization of highly stable blue‐light‐emitting hyperbranched conjugated polymers

Polyfluorene homopolymer ( P1 ) and its carbazole derivatives ( P2 – P4 ) have been prepared with good yield by Suzuki coupling polymerization. P2 is an alternating copolymer based on fluorene and carbazole; P3 is a hyperbranched polymer with carbazole derivative as the core and polyfluorene as the long arms; P4 is a hyperbranched polymer with carbazole derivative as the core and the alternating fluorene and carbazole as the long arms. These polymers show highly thermal stability, and their structures and physical properties are studied using gel permeation chromatography, ¹H NMR, ¹³C NMR, elemental analysis, Fourier transform infrared spectroscopy, thermogravimetry, UV–vis absorption, photoluminescence, and cyclic voltammetry (CV). The influence of the incorporation of carbazole and the hyperbranched structures on the thermal, electrochemical, and electroluminescent properties has been investigated. Both carbazole addition and the hyperbranched structure increase the thermal and photoluminescent stability. The CV shows an increase of the HOMO energy levels for the derivatives, compared with polyfluorene homopolymer ( P1 ). The EL devices fabricated by these polymers exhibit pure blue‐light‐emitting with negligible low‐energy emission bands, indicating that the hyperbranched structure has a strong effect on the PLED characteristics. The results imply that incorporating carbazole into polyfluorene to form a hyperbranched structure is an efficient way to obtain highly stable blue‐light‐emitting conjugated polymers, and it is possible to adjust the property of light‐emitting polymers by the amount of carbazole derivative incorporated into the polymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 790–802, 2008     

Cyclodextrins in Polymer Synthesis: Crosslinking Water‐Soluble Unsaturated Polyester Resins Using a Cyclodextrin/Styrene Complex in Aqueous Medium

A new method was developed to crosslink water‐soluble unsaturated polyester resins prepared from maleic anhydride and poly(ethylene glycol) in water as the solvent. Crosslinking was carried out with various molar ratios of the host‐guest complex consisting of styrene as the guest and methylated β‐cyclodextrin as the host. Polymerizations were performed in water with K₂S₂O₈/Na₂S₂O₅ as free radical initiator at 25 °C. Thermal properties of the networks obtained depend on the amount of styrene incorporated into the polymer.

Acceleration effect of me‐β‐CD during crosslinking of an unsaturated polyester with styrene in water: (a) monomer complexed with me‐β‐CD, and (b) with uncomplexed monomer.     

Synthesis and characterization of water‐soluble hyperbranched poly(ester amine)s from diacrylates and diamines

Various water‐soluble hyperbranched poly(ester amine)s were synthesized by the direct polyaddition of diamines to diacrylates in the absence of a catalyst. Each diamine contained a secondary amino group and a primary amino group such as 1‐(2‐aminoethyl)piperazine, N‐methyl‐1,3‐propanediamine, or N‐ethylethylenediamine. When the ratio of diacrylate to diamine was 1/1, no gelation was observed throughout the polymerization. When the ratio of diacrylate to diamine was 3/2, no crosslinking occurred in the diluted solution, whereas an insoluble network formed in the concentrated solution. Fourier transform infrared and mass spectrometry were used to investigate the reaction procedure. The secondary amino group of diamine reacted faster with the vinyl group of diacrylate; this resulted in the formation of the intermediate with an acrylate group and two active hydrogen atoms attached to a nitrogen atom. Further self‐polyaddition of the intermediate, a kind of AB₂‐type monomer, gave the hyperbranched poly(ester amine). © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2340–2349, 2002