V‐shaped graft copolymers via triple click reactions: Diels–alder,copper‐catalyzed azide–alkyne cycloaddition,and nitroxide radical coupling

We report here a simple and universal synthetic pathway covering triple click reactions, Diels–Alder, copper‐catalyzed azide–alkyne cycloaddition (CuAAC), and nitroxide radical coupling (NRC), to prepare well‐defined graft copolymers with V‐shaped side chains. The Diels–Alder click reaction between the furan protected‐maleimide‐terminated poly(ethylene glycol) (PEG) and a trifunctional core ( 1 ) carrying an anthracene, alkyne, and bromide was carried out to yield the corresponding α‐alkyne‐ and α‐bromide‐terminated PEG (PEG‐alkyne/Br) in toluene at 110 °C. Subsequently, the polystyrene or polyoxanorbornene with pendant azide functionality as a main backbone is reacted with the PEG‐alkyne/Br and 2,2,6,6‐tetramethyl‐1‐piperidinyloxy (TEMPO)‐terminated poly(ε‐caprolactone) using the CuAAC and NRC reactions in a one‐pot fashion in N,N′‐dimethylformamide at room temperature to result in the target V‐shaped graft copolymers. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4667–4674     

3‐miktoarm star terpolymers using triple click reactions: Diels–Alder,copper‐catalyzed azide‐alkyne cycloaddition,and nitroxide radical coupling reactions

Well‐defined linear furan‐protected maleimide‐terminated poly(ethylene glycol) (PEG‐MI), tetramethylpiperidine‐1‐oxyl‐terminated poly(ε‐caprolactone) (PCL‐TEMPO), and azide‐terminated polystyrene (PS‐N₃) or ‐poly(N‐butyl oxanorbornene imide) (PONB‐N₃) were ligated to an orthogonally functionalized core ( 1 ) in a two‐step reaction mode through triple click reactions. In a first step, Diels–Alder click reaction of PEG‐MI with 1 was performed in toluene at 110 °C for 24 h to afford α‐alkyne‐α‐bromide‐terminated PEG (PEG‐alkyne/Br). As a second step, this precursor was subsequently ligated with the PCL‐TEMPO and PS‐N₃ or PONB‐N₃ in N,N‐dimethylformamide at room temperature for 12 h catalyzed by Cu(0)/Cu(I) through copper‐catalyzed azide‐alkyne cycloaddition and nitroxide radical coupling click reactions, yield resulting ABC miktoarm star polymers in a one‐pot mode. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Copper(0)‐catalyzed one‐pot synthesis of ABC triblock copolymers via the combination of single electron transfer nitroxide radical coupling reaction and “click” chemistry

The synthesis of ABC triblock copolymers were accomplished by Cu(0)‐catalyzed one‐pot strategy combining single electron transfer‐nitroxide radical coupling (SET‐NRC) reaction with “click” chemistry. First, the precursors α,ω‐heterofunctionalized poly(ethylene oxide) (PEO) with a 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO) group and an alkyne group, polystyrene (PS), and poly(tert‐butyl acrylate) (PtBA) with bromine or azide end group were designed and synthesized, respectively. Then, the one‐pot coupling reactions between these precursors were carried out in the system of Cu(0)/Me₆TREN: The SET‐NRC reaction between bromine group and nitroxide radical group, subsequently click coupling between azide and alkyne group. It was noticeable that Cu(I) generated from Cu(0) by SET mechanism was utilized to catalyze click chemistry. To estimate the effect of Cu(0) on the one‐pot reaction, a comparative analysis was performed in presence of different Cu(0) species. The result showed that Cu(0) with more active surface area could accelerate the one‐pot reaction significantly. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Influence of the type of epoxy hardener on the structure and properties of interpenetrated vinyl ester/epoxy resins

The morphology–toughness relationship of vinyl ester/cycloaliphatic epoxy hybrid resins of interpenetrating network (IPN) structures was studied as a function of the epoxy hardening. The epoxy was crosslinked via polyaddition reactions (with aliphatic and cycloaliphatic diamines), cationic homopolymerization (via a boron trifluoride complex), and maleic anhydride. Maleic anhydride worked as a dual‐phase crosslinking agent by favoring the formation of a grafted IPN structure between the vinyl ester and epoxy. The type of epoxy hardener strongly affected the IPN morphology and toughness. The toughness was assessed by linear elastic fracture mechanics, which determined the fracture toughness and energy. The more compact the IPN structure was, the lower the fracture energy was of the interpenetrated vinyl ester/epoxy formulations. This resulted in the following toughness ranking: aliphatic diamine > cycloaliphatic diamine ≥ boron trifluoride complex > maleic anhydride. For IPN characterization, the width of the entangling bands and the surface roughness parameters were considered. Their values were deduced from atomic force microscopy scans taken on ion‐etched surfaces. More compact, less rough IPN‐structured resins possessed lower toughness parameters than less compact, rougher structured ones. The latter were less compatible according to dynamic mechanical thermal and thermogravimetric analyses. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5471–5481, 2004     

One‐pot double click reactions for the preparation of H‐shaped ABCDE‐type quintopolymer

We employed for the first time double click reactions: Cu(I) catalyzed azide‐alkyne 1,3‐dipolar cycloaddition and Diels–Alder (4 + 2) reactions for the preparation of H‐shaped polymer possessing pentablocks with different chemical nature (H‐shaped quintopolymer) using one‐pot technique. H‐shaped quintopolymer consists of poly(ethylene glycol) (PEG)‐poly(methylmethacrylate) (PMMA) and poly(ε‐caprolactone) (PCL)‐polystyrene (PS) blocks as side chains and poly (tert‐butylacrylate) (PtBA) as a main chain. For the preparation of H‐shaped quintopolymer, PEG‐b‐PMMA and PCL‐b‐PS copolymers with maleimide and alkyne functional groups at their centers, respectively, were synthesized and simply reacted in one‐pot with PtBA with α‐anthracene‐ω‐azide end functionalities in N,N‐dimethylformamide (DMF) using CuBr/N,N,N′,N″,N″‐pentamethyldiethylenetriamine (PMDETA) as catalyst at 120 °C for 48 h. The precursors and the target H‐shaped quintopolymer were characterized comprehensively by ¹H NMR, UV, FTIR, GPC, and triple detection GPC. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3409–3418, 2009     

Linear tetrablock quaterpolymers via triple click reactions,azide‐alkyne,diels–alder,and nitroxide radical coupling in a one‐pot fashion

Azide‐alkyne and Diels–Alder click reactions together with a click‐like nitroxide radical coupling reaction were used in a one‐pot fashion to generate tetrablock quaterpolymer. The various living polymerization generated linear polymers with orthogonal end‐functionalities, maleimide‐terminated poly(ethylene glycol) (PEG‐MI), anthracene‐ and azide‐terminated polystyrene, alkyne‐ and bromide‐terminated poly(tert‐butyl acrylate) or alkyne‐poly(n‐butyl acrylate), and tetramethylpiperidine‐1‐oxyl (TEMPO)‐terminated poly(ε‐caprolactone) (PCL‐TEMPO) were clicked together in a one‐pot fashion to generate PEG‐b‐PS‐b‐PtBA‐b‐PCL or PEG‐b‐PS‐b‐PnBA‐b‐PCL quaterpolymer using Cu(0), CuBr, and N,N,N′,N″,N″‐pentamethyldiethylenetriamine as catalyst in dimethyl formamide at 80 °C for 36 h. Linear precursors and target quaterpolymers were analyzed via ¹H NMR and gel permeation chromatography. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis and optical properties of organic–inorganic hybrid semi‐interpenetrating polymer network gels containing polyfluorenes

Organic–inorganic hybrid semi‐interpenetrating polymer network (semi‐IPN) gels containing polyfluorenes (PFs) are synthesized by hydrosilylation reaction of joint and rod molecules in toluene, where PFs are poly(9,9‐dihexylfluorene‐2,7‐diyl) (PF6) or, poly(9,9‐dioctylfluorene‐2,7‐diyl) (PF8), joint molecules are 1,3,5,7‐tetramethylcyclotetrasiloxane (TMCTS), or 1,3,5,7,9,11,13,15‐octakis(dimethylsilyloxy)pentacyclo‐[9,5,1,1,1,1]octasilsesquioxane (POSS), and rod molecules are 1,5‐hexadiene (HD) or 1,9‐decadiene (DD). The semi‐IPN gels containing low molecular weight PF6 show higher photoluminescence efficiency (?_g) than the toluene solution of PF6L (?_s). The semi‐IPN gels composed of long rod molecule of DD and cubic joint molecule of POSS show the most effective increase in the emission intensity. The emission intensity of PF6L increases as formation of the network in the POSS‐DD semi‐IPN gel. The POSS‐DD semi‐IPN gels containing high molecular weight PF6 and PF8 also show the increase of emission intensity than those of the toluene solutions. The semi‐IPN synthesized in cyclohexane show syneresis and phase separation between network structure and PF chains. The semi‐IPN gels containing PF8 show emission peaks at 450 and 470 nm derived from β‐sheet structure of PF8. A systematic study clears correlation between emission property and network structure and/or composition of semi‐IPN gels. The semi‐IPN gels provide emissive self‐standing soft materials with high efficiency and in a narrow wavelength range emission. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 973–984     

Multiarm star block and multiarm star mixed‐block copolymers via azide‐alkyne click reaction

The synthesis of multiarm star block (and mixed‐block) copolymers are efficiently prepared by using Cu(I) catalyzed azide‐alkyne click reaction and the arm‐first approach. α‐Silyl protected alkyne polystyrene (α‐silyl‐alkyne‐PS) was prepared by ATRP of styrene (St) and used as macroinitiator in a crosslinking reaction with divinyl benzene to successfully give multiarm star homopolymer with alkyne periphery. Linear azide end‐functionalized poly(ethylene glycol) (PEG‐N₃) and poly (tert‐butyl acrylate) (PtBA‐N₃) were simply clicked with the multiarm star polymer described earlier to form star block or mixed‐block copolymers in N,N‐dimethyl formamide at room temperature for 24 h. Obtained multiarm star block and mixed‐block copolymers were identified by using ¹H NMR, GPC, triple detection‐GPC, atomic force microscopy, and dynamic light scattering measurements. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 99–108, 2010     

Antimicrobial loading into and release from poly(ethylene glycol)/poly(acrylic acid) semi‐interpenetrating hydrogels

Electrostatic interactions within a semi‐interpenetrating network (semi‐IPN) gel can control the postsynthesis loading, long‐term retention, and subsequent release of small‐molecule cationic antibiotics. Here, electrostatic charge is introduced into an otherwise neutral gel [poly(ethylene glycol) (PEG)] by physically entrapping high‐molecular‐weight poly(acrylic acid) (PAA). The network structure is characterized by small‐angle neutron scattering. PEG/PAA semi‐IPN gels absorb over 40 times more antibiotic than PAA‐free PEG gels. Subsequent soaking in physiological buffer (pH 7.4; 0.15 M NaCl) releases the loaded antibiotics for periods as long as 30 days. The loaded gels elute antibiotics with diffusivities of 4.46 × 10^?8 cm²/s (amikacin) and 2.08 × 10^?8 cm²/s (colistin), which are two orders of magnitude less than those in pure PEG gels where diffusion is controlled purely by gel tortuosity. The release and hindered diffusion can be understood based on the partial shielding of the charged groups within the loaded gel, and they have a significant effect on the antimicrobial properties of these gels. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 64–72     

Synthesis and photoresponsive behavior of azobenzene‐containing side‐chain liquid crystalline diblock polymers with polypeptide block

Well‐defined azobenzene‐containing side‐chain liquid crystalline diblock copolymers composed of poly[6‐(4‐methoxy‐azobenzene‐4′‐oxy) hexyl methacrylate] (PMMAZO) and poly(γ‐benzyl‐L ‐glutamate) (PBLG) were synthesized by click reaction from alkyne‐ and azide‐functionalized homopolymers. The alkyne‐terminated PMMAZO homopolymers were synthesized by copper‐mediated atom transfer radical polymerization with a bromine‐containing alkyne bifunctional initiator, and the azido‐terminated PBLG homopolymers were synthesized by ring‐opening polymerization of γ‐benzyl‐L ‐glutamate‐N‐carboxyanhydride in DMF at room temperature using an amine‐containing azide initiator. The thermotropic phase behavior of PMMAZO‐b‐PBLG diblock copolymers in bulk were investigated using differential scanning calorimetry and polarized light microscopy. The PMMAZO‐b‐PBLG diblock copolymers exhibited a smectic phase and a nematic phase when the weight fraction of PMMAZO block was more than 50%. Photoisomerization behavior of PMMAZO‐b‐PBLG diblock copolymers and the corresponding PMMAZO homopolymers in solid film and in solution were investigated using UV–vis. In solution, trans–cis isomerization of diblock copolymers was slower than that of the corresponding PMMAZO homopolymers. These results may provide guidelines for the design of effective photoresponsive anisotropic materials. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Preparation and properties of poly(N‐isopropylacrylamide)/poly(N‐isopropylacrylamide) interpenetrating polymer networks for drug delivery

A novel poly(N‐isopropylacrylamide) (PNIPA)/PNIPA interpenetrating polymer network (IPN) was synthesized and characterized. In comparison with conventional PNIPA hydrogels, the shrinking rate of the IPN hydrogel increased when gels, swollen at 20 °C, were immersed in 50 °C water. The phase‐transition temperature of the IPN gel remained unchangeable because of the same chemical constituent in the PNIPA gel. The reswelling kinetics were slower than those of the PNIPA hydrogel because of the higher crosslinking density of the IPN hydrogel. The IPN hydrogel had better mechanical strength because of its higher crosslinking density and polymer volume fraction. The release behavior of 5‐fluorouracil (5‐Fu) from the IPN hydrogel showed that, at a lower temperature, the release of 5‐Fu was controlled by the diffusion of water molecules in the gel network. At a higher temperature, 5‐Fu inside the gel could not diffuse into the medium after a burst release caused by the release of the drug on the surface of the gel. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1249–1254, 2004     

Heterograft copolymers via double click reactions using one‐pot technique

The double click reactions (Cu catalyzed Huisgen and Diels–Alder reactions) were used as a new strategy for the preparation of well‐defined heterograft copolymers in one‐pot technique. The synthetic strategy to the various stages of this work is outlined: (i) preparing random copolymers of styrene (St) and p‐chloromethylstyrene (CMS) (which is a functionalizable monomer) via nitroxide mediated radical polymerization (NMP); (ii) attachment of anthracene functionality to the preformed copolymer by the o‐etherification procedure and then conversion of the remaining ? CH₂Cl into azide functionality; (iii) by using double click reactions in one‐pot technique, maleimide end‐functionalized poly(methyl methacrylate) (PMMA‐MI) via atom transfer radical polymerization (ATRP) of MMA and alkyne end‐functionalized poly (ethylene glycol) (PEG‐alkyne) were introduced onto the copolymer bearing pendant anthryl and azide moieties. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6969–6977, 2008     

A route toward multifunctional polyurethanes using triple click reactions

The aliphatic polyurethane with pendant alkyne, perfluorophenyl, and anthracene moieties (PU‐anthracene) was prepared from polycondensation of anthracene, alkyne, and perfluorophenyl functional‐diols with hexamethylenediisocyanate in the presence of dibutyltindilaurate (DBTL) in CH₂Cl₂ at room temperature for 10 days. Thereafter, the PU‐(anthracene‐co‐alkyne‐co‐perfluorophenyl) (M_n,GPC = 15,400 g/mol, M_w/M_n= 1.37, relative to PS standards) was sequentially clicked with benzyl azide, octylamine, and 4‐(2‐hydroxyethyl)?10‐oxa‐4‐azatricyclo[5.2.1.02,6]dec‐8‐ene‐3,5‐dione (adduct alcohol) via copper‐catalyzed azide‐alkyne cycloaddition, active ester substitution and Diels–Alder reactions, respectively, to finally yield PU‐(hydroxyl‐co‐benzyltriazole‐co‐octylamine). The PUs were characterized using ¹H NMR, GPC, and DSC. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 480–486     

One‐pot preparation of 3‐miktoarm star terpolymers via click [3 + 2] reaction

The preparation of 3‐miktoarm star terpolymers using nitroxide mediated radical polymerization (NMP), ring opening polymerization (ROP), and click reaction [3 + 2] are carried out by applying two types of one‐pot technique. In the first one‐pot technique, NMP of styrene (St), ROP of ε‐caprolactone (ε‐CL), and [3 + 2] click reaction (between azide end‐functionalized poly(ethylene glycol) (PEG‐N₃)/or azide end‐functionalized poly(methyl methacrylate) (PMMA‐N₃) and alkyne) are carried out in the presence of 2‐(hydroxymethyl)‐2‐methyl‐3‐oxo‐3‐(2‐phenyl‐2‐(2,2,6,6‐tetramethylpiperidin‐1‐yloxy)ethoxy) propyl pent‐4‐ynoate, 2 , as an initiator for 48 h at 125 °C (one‐pot/one‐step). As a second technique, NMP of St and ROP of ε‐CL were conducted using 2 as an initiator for 20 h at 125 °C, and subsequently PEG‐N₃ or azide end‐functionalized poly(tert‐butyl acrylate (PtBA‐N₃) was added to the polymerization mixture, followed by a click reaction [3 + 2] for 24 h at room temperature (one‐pot/two‐step). The 3‐miktoarm star terpolymers, PEG‐poly(ε‐caprolactone)(PCL)‐PS, PtBA‐PCL‐PS and PMMA‐PCL‐PS, were recovered by a simple precipitation in methanol without further purification. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3588–3598, 2007     

Novel,environmentally friendly crosslinking system of an epoxy using an amino acid: Tryptophan‐cured diglycidyl ether of bisphenol A epoxy

Tryptophan, an amino acid, has been used as a novel, environmentally friendly curing agent instead of toxic curing agents to crosslink the diglycidyl ether of bisphenol A (DGEBA) epoxy resin. The curing reaction of tryptophan/DGEBA mixtures of different ratios and the effect of the imidazole catalyst on the reaction have been evaluated. The optimum reaction ratio of DGEBA to tryptophan has been determined to be 3:1 with 1 wt % catalyst, and the curing mechanism of the novel reaction system has been studied and elucidated. In situ Fourier transform infrared spectra indicate that with the extraction of a hydrogen from NH₃⁺ in zwitterions from tryptophan, the formed nucleophilic primary amine and carboxylate anions of the tryptophan can readily participate in the ring‐opening reaction with epoxy. The secondary amine, formed from the primary amine, can further participate in the ring‐opening reaction with epoxy and form the crosslinked network. The crosslinked structure exhibits a reasonably high glass‐transition temperature and thermal stability. A catalyst‐initiated chain reaction mechanism is proposed for the curing reaction of the epoxy with zwitterion amino acid hardeners. The replacement of toxic curing agents with this novel, environmentally friendly curing agent is an important step toward a next‐generation green electronics industry. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 181–190, 2007     

Novel poly(N‐isopropylacrylamide)/clay/poly(acrylamide) IPN hydrogels with the response rate and drug release controlled by clay content

Novel interpenetrating network (IPN) hydrogels (PNIPAAm/clay/PAAm hydrogels) based on poly(N‐isopropylacrylamide) (PNIPAAm) crosslinked by inorganic clay and poly(acrylamide) (PAAm) crosslinked by organic crosslinker were prepared in situ by ultraviolet (UV) irradiation polymerization. The effects of clay content on temperature dependence of equilibrium swelling ratio, deswelling behavior, thermal behavior, and the interior morphology of resultant IPN hydrogels were investigated with the help of Fourier transform infrared spectroscopy, differential scanning calorimeter (DSC), scanning electron microscope (SEM). Study on temperature dependence of equilibrium swelling ratio showed that all IPN hydrogels exhibited temperature‐sensitivity. DSC further revealed that the temperature‐sensitivity was weakened with increasing amount of clay. Study on deswelling behavior revealed that IPN hydrogels had much faster response rate when comparing with PNIPAAm/clay hydrogels, and the response rate of IPN hydrogels could be controlled by clay content. SEM revealed that there existed difference in the interior morphology of IPN hydrogels between 20 [below lower critical solution temperature (LCST)] and 50 °C (above LCST), and this difference would become obvious with a decrease in clay content. For the standpoint of applications, oscillating swelling/deswelling behavior was investigated to determine whether properties of IPN hydrogels would be stable for potential applications. Bovine serum albumin (BSA) was used as model drug for in vitro experiment, the release data suggested that the controlled drug release could be achieved by modulating clay content. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 96–106, 2009     

Double network hydrogels with controlled shape deformation: A mini review

Double network hydrogels (DN gels), consisting of two networks with strongly asymmetric network structures and properties, are one of most investigated high strength hydrogels. In most cases, the first network of DN gels is rigid, brittle and tightly crosslinked, while the second network is soft, ductile and loosely crosslinked. Because of the tunable and diverse network structures, DN gels with controlled shape deformation have attracted great attention in recent years. The shape deformation of DN gels can be controlled by first network, second network, or both networks. In this mini review, the shape deformation of DN gels via different networks will be summarized, and the application and future perspectives also are discussed. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 1351–1362     

Synthesis of organic‐inorganic hybrid gels by means of thiol‐ene and azide‐alkene reactions

Organic–inorganic hybrid gels have been synthesized from a multi‐vinyl functional cyclic siloxane, 1,3,5,7‐tetravinyltetramethylcyclotetrasiloxane (TVMCTS), or a cubic silsesquioxane, octavinyloctasilasesquioxane (PVOSS), and α,ω‐dithiol compounds, 1,6‐hexanedithiol (HDT), 1,10‐decanedithiol (DDT), using thiol‐ene reaction in toluene. The network structure of the resulting gels, mesh size and mesh size distribution, was quantitatively characterized by means of a scanning microscopic light scattering (SMILS). The gels obtained from TVMCTS‐HDT formed homogeneous network structure with 1.5–1.6 nm mesh. Relaxation peaks derived from large clusters and/or micro gels were detected in the SMILS analysis of the TVMCTS‐DDT, PVOSS‐HDT, and PVOSS‐DDT gels besides those from the small meshes. The organic–inorganic hybrid gels were also synthesized from TVMCTS, PVOSS with α,ω‐diazide compounds, 1,6‐hexanediazide (HDA), 1,10‐decanediazide (DDA), using azide‐alkene reaction in toluene. All the gels obtained with the azide‐alkene reaction formed the homogeneous network structure. Enthalpy relaxation at the glass transition of the dried samples was detected by differential scanning calorimetry to study the network uniformity of the original gels. The gels synthesized by the azide‐alkene reaction showed larger enthalpy than the gels synthesized by the thiol‐ene reaction, indicating homogeneous network structure in the former gels. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2229–2238     

ROMP‐NMP‐ATRP combination for the preparation of 3‐miktoarm star terpolymer via click chemistry

A combination of ring opening metathesis polymerization (ROMP) and click chemistry approach is first time utilized in the preparation of 3‐miktoarm star terpolymer. The bromide end‐functionality of monotelechelic poly(N‐butyl oxanorbornene imide) (PNBONI‐Br) is first transformed to azide and then reacted with polystyrene‐b‐poly(methyl methacrylate) copolymer with alkyne at the junction point (PS‐b‐PMMA‐alkyne) via click chemistry strategy, producing PS‐PMMA‐PNBONI 3‐miktoarm star terpolymer. PNBONI‐Br was prepared by ROMP of N‐butyl oxanorbornene imide (NBONI) 1 in the presence of (Z)‐but‐2‐ene‐1,4‐diyl bis(2‐bromopropanoate) 2 as terminating agent. PS‐b‐PMMA‐alkyne copolymer was prepared successively via nitroxide‐mediated radical polymerization (NMP) of St and atom transfer radical polymerization (ATRP) of MMA. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 497–504, 2009     

Synthesis of well‐defined macromonomers by the combination of atom transfer radical polymerization and a click reaction

This article presents a new strategy for synthesizing a series of well‐defined macromonomers. Bromine‐terminated polystyrene and poly(t‐butyl acrylate) with predetermined molecular weights and narrow distributions were prepared through the atom transfer radical polymerization of styrene and t‐butyl acrylate initiated with ethyl 2‐bromoisobutyrate. Then, azido‐terminated polymers were obtained through the bromine substitution reaction with sodium azide. Catalyzed by CuBr/N,N,N′,N″,N″‐pentamethyldiethylenetriamine, the azido end group reacted with propargyl methacrylate via a 1,3‐dipolar cycloaddition reaction, and ω‐methacryloyl‐functionalized macromonomers were thus obtained. The end‐group transformation yields were rather high, as characterized by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectra and ¹H NMR analysis. By this effective and facile approach, some novel macromonomers that otherwise are difficult to achieve, such as poly(ethylene oxide)‐block‐polystyrene, were easily prepared. Radical homopolymerizations of these macromonomers were performed, and a series of comb polymers were prepared. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6103–6113, 2006