Hyperbranched–linear–hyperbranched ABA‐type block copolymers based on poly(ethylene oxide) and polyglycerol

BACKGROUND: Until recently, hyperbranched polymers were thought to be ill‐defined materials that were not useful as building blocks for well‐defined complex polymer architectures. It is a current challenge to develop strategies that offer rapid access to well‐defined hyperbranched block copolymers. RESULTS: A convenient three‐step protocol for the synthesis of double‐hydrophilic hyperbranched–linear–hyperbranched ABA‐type triblock copolymers based on poly(ethylene oxide) (PEO) and hyperbranched polyglycerol (hbPG) is presented. The Bola‐type polymers exhibiting an aliphatic polyether structure were prepared from a linear (lin) linPG‐b‐PEO‐b‐linPG precursor triblock. The materials exhibit low polydispersities (M_w/M_n) in the range 1.19–1.45. The molecular weights of the block copolymers range from 6300 to 26 200 g mol^?1, varying in the length of both the linear PEO chain as well as the hbPG segments. Detailed characterization of the thermal properties using differential scanning calorimetry demonstrates nanophase segregation of the blocks. CONCLUSION: The first example of well‐defined ABA hyperbranched–linear–hyperbranched triblock copolymers with PEO middle block and hbPG A‐blocks is presented. The biocompatible nature of the aliphatic polyether blocks renders these materials interesting for biomedical purposes. These new materials are also intriguing with respect to their supramolecular order and biomineralization properties. Copyright © 2009 Society of Chemical Industry     

Synthesis of novel thermo‐ and redox‐sensitive polypeptide hydrogels

Multi‐responsive hydrogels have recently received considerable attention for bioapplications. Here, novel temperature‐ and redox‐responsive polypetide hydrogels have been developed. Thermo‐sensitive hydrogels based on poly(ethyleneglycol)‐block ‐poly(γ‐propargyl‐l ‐glutamate) (PEG‐PPLG ) were first synthesized by the ring opening polymerization of γ‐propargyl‐l ‐glutamate N ‐carboxyanhydride (PLG‐NCA ) with amino group terminated PEG monomethyl ether (mPEG‐NH₂ ) as macroinitiator and were then functionalized via the ‘thiol‐yne’ click reaction between the propargyl pendents and the thiol‐containing 1‐propanethiol. The sol ? gel phase transition of the obtained copolymer aqueous solution in response to temperature change was studied. The mass loss of the hydrogel in vitro was accelerated in the presence of H₂O₂ , exhibiting a redox‐responsive property. Further, the methyl thiazolyl tetrazolium viability results revealed that this polypetide hydrogel has excellent biocompatibility, presenting potential applications in the biomedical field. © 2016 Society of Chemical Industry     

Soybean oil based thermoset networks via photoinduced CuAAC click chemistry

A simple method based on photochemically induced copper(I)‐catalyzed azide ? alkyne cycloaddition click reaction (CuAAC ) is developed for the preparation of thermoset networks from soybean oils as renewable resources. The incorporation of clickable azide and alkyne functionalities into epoxidized soybean oils is done by simultaneous ring‐opening reactions between the epoxide group of soybean oils and sodium azide and propargyl alcohol, respectively. The obtained azide‐ and alkyne‐functionalized soybean oils are easily transformed crosslinked networks via the photoinduced CuAAC reaction in ambient conditions. The introduction of additional multifunctional monomers in the formulation not only increases the crosslinking density but also improves the mechanical properties of the thermoset material obtained. In a comparison of the two formulations, the sample containing additional multifunctional monomers has a higher glass transition temperature, storage modulus and damping properties. © 2017 Society of Chemical Industry     

Synthesis of biodegradable and biocompatible ABC triblock copolymers

A facile approach is offered to synthesize well‐defined amphiphilic ABC triblock copolymers composed of poly(ethylene glycol) monomethyl ether (MPEO) as A block, poly(L ‐lysine) (PLLys) as B block, and poly(ε‐caprolactone) (PCL) as C block by a combination of ring‐opening polymerization (ROP) and click reactions. The propargyl‐terminated poly(Z‐L ‐lysine)‐block‐poly(ε‐caprolactone) (MPEO‐PzLLys‐PCL) diblock copolymers were synthesized via the ring‐opening polymerization of N^ε‐carbobenzoxy‐L ‐lysine N‐carboxyanhydride (Z‐L ‐Lys NCA) in DMF at room temperature using propargyl amine as an initiator and the resulting amino‐terminated poly(Z‐L ‐lysine) then used in situ as a macroinitiator for the polymerization of ε‐caprolactone in the presence of stannous octoate as a catalyst. The triblock copolymers poly(ethylene glycol) monomethyl ether –block‐poly(Z‐L ‐lysine)‐block‐poly(ε‐caprolactone) (MPEO‐PzLLys‐PCL) were synthesized via the click reaction of the propargyl‐terminated PzLLys‐PCL and azido‐terminated poly(ethylene glycol) monomethyl ether (PEO‐N₃) in the presence of CuBr and 1,1,4,7,7‐pentamethyldiethylenetriamine (PMDETA) catalyst system. After the removal of Z groups of L ‐lysine units, amphiphilic and biocompatible ABC triblock copolymers MPEO‐PLLys‐PCL were obtained. The structural characteristics of these ABC triblock copolymers and corresponding precursors were characterized by NMR, IR, and GPC. These results showed the click reaction was highly effective. Therefore, a facile approach is offered to synthesize amphiphilic and biocompatible ABC triblock copolymers consisting of polyether, polypeptide and polyester. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis of poly(cyclohexene oxide)‐block‐polystyrene by combination of radical‐promoted cationic polymerization,atom transfer radical polymerization and click chemistry

The combination of radical‐promoted cationic polymerization, atom transfer radical polymerization (ATRP) and click chemistry was employed for the efficient preparation of poly(cyclohexene oxide)‐block‐polystyrene (PCHO‐b‐PSt). Alkyne end‐functionalized poly(cyclohexene oxide) (PCHO‐alkyne) was prepared by radical‐promoted cationic polymerization of cyclohexene oxide monomer in the presence of 1,2‐diphenyl‐2‐(2‐propynyloxy)‐1‐ethanone (B‐alkyne) and an onium salt, namely 1‐ethoxy‐2‐methylpyridinium hexafluorophosphate, as the initiating system. The B‐alkyne compound was synthesized using benzoin photoinitiator and propargyl bromide. Well‐defined bromine‐terminated polystyrene (PSt‐Br) was prepared by ATRP using 2‐oxo‐1,2‐diphenylethyl‐2‐bromopropanoate as initiator. Subsequently, the bromine chain end of PSt‐Br was converted to an azide group to obtain PSt‐N₃ by a simple nucleophilic substitution reaction. Then the coupling reaction between the azide end group in PSt‐N₃ and PCHO‐alkyne was performed with Cu(I) catalysis in order to obtain the PCHO‐b‐PSt block copolymer. The structures of all polymers were determined. Copyright © 2010 Society of Chemical Industry     

Synthesis of click‐coupled graphene sheets with hyperbranched polyurethane: Effective exfoliation and enhancement of nanocomposite properties

Graphene oxide (GO) was functionalized with hyperbranched polyurethane (HBPU) via click coupling between azide‐functionalized HBPU and alkynyl‐decorated GO. HBPU‐functionalized GO composites of various compositions were prepared. The azide‐containing HBPU was characterized using Fourier‐transform infrared (FT‐IR) spectroscopy and ¹H‐nuclear magnetic resonance spectroscopy. The HBPU‐functionalized GO composites were characterized using transmission electron microscopy and FT‐IR spectroscopy. The functionalized GO showed excellent dispersion in the HBPU matrix, giving composites with enhanced mechanical and thermal properties. The material properties were effectively regulated by click‐coupled exfoliation of GO with HBPU, enabling the production of high‐performance materials. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44631.     

A new synthetic approach to asymmetric amphiphilic ABA′ block copolymers by ATRP and click reactions

Well‐defined asymmetric amphiphilic ABA′ block copolymers composed of poly(ethylene oxide) monomethylene ether (MPEO) with different molecular weights as A or A′ block and poly(styrene) (PS) as B block were synthesized by the combination of atom transfer radical polymerization (ATRP) and click reactions. First, bromine‐terminated diblock copolymer poly(ethylene oxide) monomethylene ether‐block‐poly(styrene) (MPEO‐PS‐Br) was prepared by ATRP of styrene initiated with macroinitiator MPEO‐Br, which was prepared from the esterification of MPEO and 2‐bromoisobutyryl bromide. Then, the azido‐terminated diblock copolymers MPEO‐PS‐N₃ were prepared through the bromine substitution reaction with sodium azide. Propargyl‐terminated MPEO with a different molecular weight was prepared under the basic condition from propargyl alcohol and p‐toluenesulfonyl‐terminated MPEO, which was prepared through the esterification of MPEO and p‐toluenesulfochloride using pyridine as solvent. Asymmetric amphiphilic ABA′ block copolymers, with a wide range of number–average molecular weights from 1.92 × 10⁴ to 2.47 × 10⁴ and a narrow polydispersity from 1.03 to 1.05, were synthesized via a click reaction of the azido‐terminated diblock copolymers and the propargyl‐terminated MPEO in the presence of CuBr and 1,1,4,7,7‐pentamethyldiethylenetriamine (PMDETA) catalyst system. The structures of these ABA′ block copolymers and corresponding precursors were characterized by NMR, IR, and GPC. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Functionalization of multi‐walled carbon nanotubes with poly(ε‐caprolactone) using click chemistry

Multi‐walled carbon nanotubes (MWNTs) were covalently functionalized with poly(ε‐caprolactone) (PCL) using click chemistry. First, chlorine moiety‐containing PCL was synthesized by the copolymerization of α‐chloro‐ε‐caprolactone with ε‐caprolactone monomer using ring opening polymerization, and further converted to azide moiety‐containing PCL. The alkyne‐functionalized MWNTs were prepared with the treatment of p‐amino propargyl ether using a solvent free diazotization procedure. The covalent functionalization of alkyne‐derived MWNTs with azide moiety‐containing PCL was accomplished using Cu(I)‐catalyzed [3+2] Huisgen dipolar cycloaddition click chemistry. The PCL‐functionalization of MWNTs was confirmed by the measurements of Fourier transform infra‐red, NMR, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis,characterization, and photo‐responsive properties of Y‐shaped amphiphilic azo triblock copolymer

In this study, we report the synthesis, characterization, and photo‐responsive properties of a new Y‐shaped amphiphilic azo triblock copolymer composed of two isotropic polyethylene glycol (PEG) blocks and an azobenzene liquid crystalline block. The azo block, with two ending groups suitable for the azo coupling reaction, is polymerized by atom transfer radical polymerization with a synthesized initiator containing two functional terminal groups. The macromolecular diazonium salts are prepared by the diazotization of PEG terminated with an amino group. The triblock copolymer is obtained by the azo coupling reaction between the azo block and macromolecular diazonium salts in DMF under mild condition. The intermediates and the obtained triblock copolymer are characterized by ¹H NMR, FT‐IR, GPC, POM, DSC, TEM, and UV‐vis. The photoinduced isomerization behavior of the azo copolymer is investigated by UV‐vis. With the addition of water into the solution of the triblock copolymer, spherical aggregates with an average diameter of about 400 nm can be easily obtained. The aggregates are elongated when irradiated with polarized 365 nm UV light. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43695.     

Synthesis of three‐arm poly(ethylene glycol) by combination of controlled anionic polymerization and ‘click’ chemistry

Poly(ethylene glycol) (PEG) is an important water‐soluble polymer, which is widely used in the biomedical field because of its good biodegradability, biocompatibility and permeability. It is usually synthesized by anionic polymerization of ethylene oxide but side reactions lead to the formation of some oligomers. High molecular weight PEG can be obtained, however, through coordinated anionic polymerization. Recently a novel controlled anionic polymerization based on the initiating system ammonium bromide/trialkylaluminium was reported. Related studies have shown that the controlled anionic polymerization allows the synthesis of linear polyethers with low dispersity in a wide range of molecular weights at ambient temperature. Unfortunately, so far this controlled anionic polymerization has not been used to synthesize polymers with complex architectures. In the work reported here, controlled anionic polymerization was combined with ‘click’ chemistry for the first time to synthesize polyethers with multiple arms. Firstly, controlled anionic polymerization was employed to synthesize a linear bromine‐terminated PEG (PEG‐Br) using ethylene oxide as the monomer and tetraoctylammonium bromide/triisobutylaluminium as the initiating system at room temperature. The terminal bromine in the PEG thus synthesized was then converted into an azide group by the reaction of PEG‐Br and sodium azide. A trifunctional linking agent was also prepared by the reaction of trimethylolpropane and propiolic acid. By using ‘click’ chemistry, a three‐arm PEG was finally obtained through the reaction of the azide‐terminated PEG and the trifunctional linking agent. The chemical structure of the polymer thus synthesized was characterized using infrared spectroscopy, NMR spectroscopy, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry and size‐exclusion chromatography with multi‐angle laser light scattering. It was found that the synthesized polyether possesses the designed structure. Considering the wide applicability of controlled anionic polymerization and ‘click’ chemistry, their combination is a valuable way to synthesize various polyethers with multiple arms. Copyright © 2009 Society of Chemical Industry     

Functionalization of amphiphilic coil-rod-coil triblock copolymer poly(2-vinylpyridine)-b-poly(n-hexyl isocyanate)-b-poly(2-vinylpyridine) with florescence moiety and C60

We recently achieved quantitative synthesis of an amphiphilic coil-rod-coil triblock copolymer, poly(2-vinylpyridine)-b-poly(n-hexyl isocyanate)-b-poly(2-vinylpyridine), by coupling in situ living diblock copolymer poly(2-vinylpyridine)-b-poly(n-hexyl isocyanate) (P2VP-b-PHIC) using malonyl chloride in the presence of pyridine. This led to the introduction of an active methylene group that is a site for further functionalization in the rod block. The Michael addition reaction of the triblock copolymer with 7-(4-trifluoromethyl) coumarin acrylamide led to copolymer bearing a fluorescent pendent in the rod block. The fluorescent labeled copolymers were isolated in ∼94% yields. Similarly C₆₀ pendent was introduced to the rod block by the Bingel reaction. The yields of C₆₀ functionalized copolymers were ∼54%. The precursor and functionalized amphiphilic coil-rod-coil copolymer show diverse morphologies, such as micelles and vesicles by simply changing the solvent. For the C₆₀ functionalized block copolymer, structural constraints in micelles and vesicles prevented C₆₀ pendents to aggregate.     

Synthesis and Self-Assembly of β-Cyclodextrin Terminated DMA/NIPAM Diblock Copolymers

A series of β-cyclodextrin (β-CD) terminated diblock copolymers has been prepared via click reaction. The Huisgen cycloaddition between alkyne decorated copolymer and azide functionalized β-CD was performed in organic solvent in the presence of a Cu(I) catalyst, resulting in the formation of β-CD terminated diblock copolymers, which contain thermally responsive poly(N-isopropylacrylamide) (PNIPAM) block and hydrophilic poly(N,N-dimethylacrylamide) (PDMA) block. Using dynamic light scattering and fluorescence spectroscopy measurements, it is demonstrated that these β-CD functionalized block copolymers are capable of reversibly forming micelles in response to changes in solution temperature and that the critical micelle concentration, micellar size, and transition temperature are dependent on both the NIPAM block length and the polymer functionalization.     

Dendritic macromolecules containing several types of functional groups

Dendritic macromolecules containing several types of functional groups were successfully synthesized through divergent method. Poly(ethylene glycol) was functionalized using cyanuric chloride and it was reacted with p‐toluidine at room temperature and a macromolecule containing chloride and methyl functional groups (PEG‐Cl₂‐Me₂) was obtained. Substitution of chloride functional groups of PEG‐Cl₂‐Me₂ by hydroxyl functional groups led to a macromolecule containing methyl and hydroxyl functional groups (PEG‐Me₂‐OH₄). Hydroxyl functional groups of PEG‐Me₂‐OH₄ were reacted with cyanuric chloride and PEG‐Me₂‐Cl₈ was obtained. Finally, PEG‐Me₂‐Cl₈ was reacted with p‐aminophenol at room temperature and a macromolecule containing methyl, hydroxyl, and chloride functional groups (PEG‐Me₂‐(PhOH)₄‐Cl₄) was obtained. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and properties of click coupled graphene oxide sheets with three‐dimensional macromolecules

A facile click chemistry approach to the functionalization of three‐dimensional hyperbranched polyurethane (HPU) to graphene oxide (GO) nanosheets is presented. HPU‐functionalized GO samples of various compositions were synthesized by reacting alkyne‐functionalized HPU with azide‐functionalized GO sheets. The morphological characterization of the HPU‐functionalized GO was performed using transmission electron microscopy and its chemical characterization was carried out using Fourier transform‐infrared spectroscopy, nuclear magnetic resonance spectroscopy, and X‐ray photoelectron spectroscopy. The graphene sheet surfaces were highly functionalized, leading to improved solubility in organic solvents, and consequently, enhanced mechanical, thermal, and thermoresponsive and photothermal shape memory properties. The strategy reported herein provides a very efficient method for regulating composite properties and producing high performance materials. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43358.     

Synthesis of functionalized polylactide by cationic activated monomer polymerization

Functionalized polylactides (PLAs) containing acryloyl, methacryloyl or propargyl end groups have been obtained by cationic ring-opening polymerization performed in the presence of appropriate alcohols (HEMA, HEA, propargyl alcohol) as initiators and triflic acid as a catalyst. ¹H NMR, MALDI TOF and GPC analysis indicated almost quantitative initiation and confirmed the expected structure and molecular masses of the obtained PLAs. The conditions were found in which transesterification process (usually accompanying the cyclic esters propagation) can be avoided. PLAs functionalized with double bond were successfully homopolymerized and copolymerized with butyl acrylate in the presence of AIBN. PLA with triple bond at one chain end was effectively coupled with a model azide by 1,3-dipolar Huisgen cycloaddition (“click” reaction) in order to prove its ability to be further functionalized.     

Linear‐dendritic copolymers as nanocatalysts

Functionalized poly(ethylene glycol) (PEG) containing four chloride end functional groups (PEG‐Cl₄) was synthesized through reaction between cyanuric chloride and PEG‐(OH)₂. Chloride end functional groups of PEG‐Cl₄ were able to initiate the ring opening polymerization of 2‐ethyl‐2‐oxazoline and star copolymers containing a PEG core, and poly(2‐ethyl‐2‐oxazoline) (POX) arms were obtained. Polymerization was quenched using diethanolamine, and star copolymers containing hydroxyl end functional groups (PEG‐POX‐OH) were obtained. ε‐Caprolactone was then polymerized using the hydroxyl end functional groups of star copolymers and amphiphilic linear‐dendritic copolymers containing PEG and POX, and poly(caprolactone) (PCL) blocks were synthesized. Linear‐dendritic copolymers were able to load the organic and inorganic guest molecules. Application of host‐guest systems such as nanocatalyst for Heck chemical reaction was also investigated. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis of well‐defined dendritic hyperbranched polymers by iterative methodologies using living/controlled polymerizations

This review presents firstly the synthesis of various dendritic hyperbranched polymers with well‐defined structures by generation‐based growth methodologies using living/controlled polymerization. Secondly, the synthesis of dendritic hyperbranched poly(methyl methacrylate)s (PMMAs) and their functionalized block copolymers using a novel iterative methodology is described. The methodology involves a two‐reaction sequence in each iterative process: (a) a linking reaction of α‐functionalized living anionic PMMA with tert‐butyldimethylsilyloxymethylphenyl (SMP) groups with benzyl bromide (BnBr)‐chain‐end‐functionalized polymer and (b) a transformation reaction of the SMP groups into BnBr functions. This reaction sequence is repeated several times to construct high‐generation (maximum seventh generation) dendritic hyperbranched polymers. Similar branched architectural block copolymers have also been synthesized by the same iterative methodology using other α‐functionalized living anionic polymers. Surface structures of the resulting dendritic hyperbranched block copolymers composed of PMMA and poly(2‐(perfluorobutyl)ethyl methacrylate) segments have been characterized using X‐ray photoelectron spectroscopy and contact angle measurements. Solution behaviors of dendritic hyperbranched PMMAs with different generations and branch densities are discussed based on their intrinsic viscosities, g′ values and R_h values. Copyright © 2007 Society of Chemical Industry     

Biomimetic crystallization of calcium carbonate in the presence of water‐soluble zwitterionic block copolymer

Crystallization of calcium carbonate (CC) in aqueous solutions by gas‐liquid diffusion procedure was investigated systematically in the presence of poly(4‐sulfonic acid diphenylamine)‐block‐poly(ethylene glycol) (PSDA‐b‐PEG), wherein the PSDA block is a polymeric zwitterion. PSDA‐b‐PEG was synthesized with the reaction of tosylated PEG and amine‐functionalized PSDA and was characterized by nuclear magnetic resonance. The parameters such as, block copolymer concentration, crystallization time and initial pH were considered as indicators of block copolymer's capability in controlling the morphology of CC particles_. The particles were characterized by Fourier transform infrared, scanning electron microscopy, and X‐ray diffraction. The results suggest that PSDA‐b‐PEG is a suitable template to control the growth mechanism of CC to produce meso‐sized particles with different morphologies. POLYM. ENG. SCI., 59:96–102, 2019. © 2018 Society of Plastics Engineers     

Crystallization behavior of biodegradable amphiphilic poly(ethylene glycol)‐poly(L‐lactide) block copolymers

Poly(ethylene glycol)‐poly(L ‐lactide) diblock and triblock copolymers were prepared by ring‐opening polymerization of L ‐lactide with poly(ethylene glycol) methyl ether or with poly(ethylene glycol) in the presence of stannous octoate. Molecular weight, thermal properties, and crystalline structure of block copolymers were analyzed by ¹H‐NMR, FTIR, GPC, DSC, and wide‐angle X‐ray diffraction (WAXD). The composition of the block copolymer was found to be comparable to those of the reactants. Each block of the PEG–PLLA copolymer was phase separated at room temperature, as determined by DSC and WAXD. For the asymmetric block copolymers, the crystallization of one block influenced much the crystalline structure of the other block that was chemically connected to it. Time‐resolved WAXD analyses also showed the crystallization of the PLLA block became retarded due to the presence of the PEG block. According to the biodegradability test using the activated sludge, PEG–PLLA block copolymer degraded much faster than PLLA homopolymers of the same molecular weight. © 1999 John Wiley amp; Sons, Inc. J Appl Polym Sci 72: 341–348, 1999     

High-efficiency synthesis of dendrimer-like poly(ethylene oxide) via “arm-first” approach

In this study, a dendrimer-like polymer based on poly(ethylene oxide) (PEO) was synthesized through a combination of anionic ring-opening polymerization (AROP) and click reaction via arm-first method. Firstly, the polymeric arm, a linear PEO with one alkynyl group and two bromo groups, was synthesized by AROP of ethylene oxide followed by functionalization with propargyl bromide and esterified with 2-bromopropionic bromide. Second, a star PEO carrying three azide groups was synthesized though AROP of ethylene oxide used 1,1,1-tris(hydrosymethyl) ethane as initiator followed esterificated with 2-bromopropionic acid and azidation. By azide–alkyne click reactions between the azide-terminated PEO star polymer and linear PEO with functionalization alkynyl group, a three generation dendrimer-like PEO, G3-PEO-24Br, was successfully synthesized. The resulting polymers were observed to have precisely controlled molecular weights and compositions with narrow molecular weight distributions.