Synthesis and characterization of well‐defined ABC 3‐Miktoarm star‐shaped terpolymers based on poly(styrene), poly(ethylene oxide), and poly(ϵ‐caprolactone) by combination of the “living” anionic polymerization with the ring‐opening polymerization

A series of well‐defined ABC 3‐Miktoarm star‐shaped terpolymers [Poly(styrene)‐Poly(ethylene oxide)‐Poly(ε‐caprolactone)](PS‐PEO‐PCL) with different molecular weight was synthesized by combination of the “living” anionic polymerization with the ring‐opening polymerization (ROP) using macro‐initiator strategy. Firstly, the “living” poly(styryl)lithium (PS^?Li⁺) species were capped by 1‐ethoxyethyl glycidyl ether(EEGE) quantitatively and the PS‐EEGE with an active and an ethoxyethyl‐protected hydroxyl group at the same end was obtained. Then, using PS‐EEGE and diphenylmethylpotassium (DPMK) as coinitiator, the diblock copolymers of (PS‐b‐PEO)_p with the ethoxyethyl‐protected hydroxyl group at the junction point were achieved by the ROP of EO and the subsequent termination with bromoethane. The diblock copolymers of (PS‐b‐PEO)_d with the active hydroxyl group at the junction point were recovered via the cleavage of ethoxyethyl group on (PS‐b‐PEO)_p by acidolysis and saponification successively. Finally, the copolymers (PS‐b‐PEO)_d served as the macro‐initiator for ROP of ε‐CL in the presence of tin(II)‐bis(2‐ethylhexanoate)(Sn(Oct)₂) and the star(PS‐PEO‐PCL) terpolymers were obtained. The target terpolymers and the intermediates were well characterized by ¹H‐NMR, MALDI‐TOF MS, FTIR, and SEC. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1136–1150, 2008     

Preparation of H‐shaped ABCAB terpolymers by atom transfer radical coupling

H‐shaped ABCAB terpolymers composed of polystyrene (PS) (A), poly(ethylene oxide) (PEO) (B), and poly(tert‐butyl acrylate) (PtBA) (C) were prepared by atom transfer radical coupling reaction using ABC star terpolymers as precursors, CuBr and N,N,N′,N″,N″‐pentamethyldiethylenetriamine (PMDETA) as catalysts, and nanosize copper as the reducing agent. The synthesis of 3‐miktoarm star terpolymer PS‐PEO‐(PtBA‐Br) involved following steps: (1) the preparation of PS with an active and an ethoxyethyl‐ptotected hydroxyl group at the same end; (2) the preparation of diblock copolymer PS‐b‐PEO with ethoxyethyl‐protected group at the junction point through the ring‐opening polymerization (ROP) of EO; (3) after de‐protection of ethoxyethyl group and further modification of hydroxyl group, tBA was polymerized by atom transfer radical polymerization using PS‐b‐PEO with 2‐bromoisobutyryl functional group as macroinitiator. The H‐shaped terpolymer could be successfully formed by atom transfer radical coupling reaction in the presence of small quantity of styrene, CuBr/PMDETA, and Cu at 90 °C. The copolymers were characterized by SEC, ¹H NMR, and FTIR in detail. The optimized coupling temperature is 90 °C. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 59–68, 2009     

Synthesis of 4μ‐PS2PEO2, 4μ‐PS2PCL2, 4μ‐PI2PEO2, and 4μ‐PI2PCL2 star‐shaped copolymers by the combination of glaser coupling with living anionic polymerization and ring‐opening polymerization

4μ‐A₂B₂ star‐shaped copolymers contained polystyrene (PS), poly(isoprene) (PI), poly(ethylene oxide) (PEO) or poly(ε‐caprolactone) (PCL) arms were synthesized by a combination of Glaser coupling with living anionic polymerization (LAP) and ring‐opening polymerization (ROP). Firstly, the functionalized PS or PI with an alkyne group and a protected hydroxyl group at the same end were synthesized by LAP and then modified by propargyl bromide. Subsequently, the macro‐initiator PS or PI with two active hydroxyl groups at the junction point were synthesized by Glaser coupling in the presence of pyridine/CuBr/N,N,N ′,N ″,N ″‐penta‐methyl diethylenetri‐amine (PMDETA) system and followed by hydrolysis of protected hydroxyl groups. Finally, the ROP of EO and ε‐CL monomers was carried out using diphenylmethyl potassium (DPMK) and tin(II)‐bis(2‐ethylhexanoate) (Sn(Oct)₂) as catalyst for target star‐shaped copolymers, respectively. These copolymers and their intermediates were well characterized by SEC, ¹H NMR, MALDI‐TOF mass spectra and FT‐IR in details. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Synthesis of a novel graft copolymer with hyperbranched poly(glycerol) as core and “Y”‐shaped polystyrene‐b‐poly(ethylene oxide)2 as side chains

The graft copolymers composed of “Y”‐shaped polystyrene‐b‐poly(ethylene oxide)₂ (PS‐b‐PEO₂) as side chains and hyperbranched poly(glycerol) (HPG) as core were synthesized by a combination of “click” chemistry and atom transfer radical polymerization (ATRP) via “graft from” and “graft onto” strategies. Firstly, macroinitiators HPG‐Br were obtained by esterification of hydroxyl groups on HPG with bromoisobutyryl bromide, and then by “graft from” strategy, graft copolymers HPG‐g‐(PS‐Br) were synthesized by ATRP of St and further HPG‐g‐(PS‐N₃) were prepared by azidation with NaN₃. Then, the precursors (Bz‐PEO)₂‐alkyne with a single alkyne group at the junction point and an inert benzyl group at each end was synthesized by sequentially ring‐opening polymerization (ROP) of EO using 3‐[(1‐ethoxyethyl)‐ethoxyethyl]‐1,2‐propanediol (EEPD) and diphenylmethylpotassium (DPMK) as coinitiator, termination of living polymeric species by benzyl bromide, recovery of protected hydroxyl groups by HCl and modification by propargyl bromide. Finally, the “click” chemistry was conducted between HPG‐g‐(PS‐N₃) and (Bz‐PEO)₂‐alkyne in the presence of N,N,N′,N″,N”‐pentamethyl diethylenetriamine (PMDETA)/CuBr system by “graft onto” strategy, and the graft copolymers were characterized by SEC, ¹H NMR and FTIR in details. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Preparation of comb‐like copolymers with amphiphilic poly(ethylene oxide)‐b‐polystyrene graft chains by combination of “graft from” and “graft onto” strategies

A novel method for preparation the comb‐like copolymers with amphihilic poly(ethylene oxide)‐block‐poly(styrene) (PEO‐b‐PS) graft chains by “graft from” and “graft onto” strategies were reported. The ring‐opening copolymerization of ethylene oxide (EO) and ethoxyethyl glycidyl ether (EEGE) was carried out first using α‐methoxyl‐ω‐hydroxyl‐poly(ethylene oxide) (mPEO) and diphenylmethyl potassium (DPMK) as coinitiation system, then the EEGE units on resulting linear copolymer mPEO‐b‐Poly(EO‐co‐EEGE) were hydrolyzed and the recovered hydroxyl groups were reacted with 2‐bromoisobutyryl bromide. The obtained macroinitiator mPEO‐b‐Poly(EO‐co‐BiBGE) can initiate the polymerization of styrene by ATRP via the “Graft from” strategy, and the comb‐like copolymers mPEO‐b‐[Poly(EO‐co‐Gly)‐g‐PS] were obtained. Afterwards, the TEMPO‐PEO was prepared by ring‐opening polymerization (ROP) of EO initiated by 4‐hydroxyl‐2,2,6,6‐tetramethyl piperdinyl‐oxy (HTEMPO) and DPMK, and then coupled with mPEO‐b‐[Poly(EO‐co‐Gly)‐g‐PS] by atom transfer nitroxide radical coupling reaction in the presence of cuprous bromide (CuBr)/N,N,N′,N″,N″‐pentamethyldiethylenetriamine (PMDETA) via “Graft onto” method. The comb‐like block copolymers mPEO‐b‐[Poly(EO‐co‐Gly)‐g‐(PS‐b‐PEO)] were obtained with high efficiency (≥90%). The final product and intermediates were characterized in detail. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1930–1938, 2009     

Preparation of amphiphilic poly(ethylene oxide)‐block‐polystyrene macrocycles via glaser coupling reaction under CuBr/pyridine system

The amphiphilic cyclic poly(ethylene oxide)‐block‐polystyrene [c‐(PEO‐b‐PS)] was synthesized by cyclization of propargyl‐telechelic poly(ethylene oxide)‐block‐polystyrene‐block‐poly(ethylene oxide) (?? PEO‐b‐PS‐b‐PEO? ?) via the Glaser coupling. The hydroxyl‐telechelic ABA triblock PEO‐b‐PS‐b‐PEO was first prepared by successive living anionic polymerization of styrene and ring‐opening polymerization of ethylene oxide, and then the hydroxyl ends were reacted with propargyl bromide to obtain linear precursors with propargyl terminals. Finally, the intramolecular cyclization was conducted in pyridine under high dilution by Glaser coupling of propargyl ends in the presence of CuBr under ambient temperature, and the c‐(PEO‐b‐PS) was directly obtained by precipitation in petroleum ether with high efficiency. The cyclic products and their corresponding linear precursor ?? PEO‐b‐PS‐b‐PEO? ? were characterized by means of GPC, ¹H NMR, and FTIR. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Preparation of Star‐Shaped ABC Copolymers of Polystyrene‐Poly(ethylene oxide)‐Polyglycidol Using Ethoxyethyl Glycidyl Ether as the Cap Molecule

The 3‐miktoarm star‐shaped ABC copolymers of polystyrene–poly(ethylene oxide)–poly(ethoxyethyl glycidyl ether) (PS‐PEO‐PEEGE) and polystyrene–poly(ethylene oxide)–polyglycidol (PS‐PEO‐PG) with low polydispersity indices (PDI ≤ 1.12) and controlled molecular weight were synthesized by a combination of anionic polymerization with ring‐opening polymerization. The polystyryl lithium (PS⁻Li⁺) was capped by EEGE firstly to form the functionalized polystyrene (PS_A) with both an active ω‐hydroxyl group and an ω′‐ethoxyethyl‐protected hydroxyl group, and then the PS‐b‐PEO block copolymers, star(PS‐PEO‐PEEGE) and star(PS‐PEO‐PG) copolymers were obtained by the ring‐opening polymerization of EO and EEGE respectively via the variation of the functional end group, and then the hydrolysis of the ethoxyethyl group on the PEEGE arm. The obtained star copolymers and intermediates were characterized by ¹H NMR spectroscopy and SEC.

     

Synthesis of amphiphilic tadpole‐shaped copolymers by combination of glaser coupling with living anionic polymerization and ring‐opening polymerization

The tadpole‐shaped copolymers polystyrene (PS)‐b‐[cyclic poly(ethylene oxide) (PEO)] [PS‐b‐(c‐PEO)] contained linear tail chains of PS and cyclic head chains of PEO were synthesized by combination of Glaser coupling with living anionic polymerization (LAP) and ring‐opening polymerization (ROP). First, the functionalized polystyrene‐glycerol (PS‐Gly) with two active hydroxyl groups at ω end was synthesized by LAP of St and the subsequent capping with 1‐ethoxyethyl glycidyl ether and then deprotection of protected hydroxyl group in acid condition. Then, using PS‐Gly as macroinitiator, the ROP of EO was performed using diphenylmethylpotassium as cocatalyst for AB₂ star‐shaped copolymers PS‐b‐(PEO‐OH)₂, and the alkyne group was introduced onto PEO arm end for PS‐b‐(PEO‐Alkyne)₂. Finally, the intramolecular cyclization was performed by Glaser coupling reaction in pyridine/Cu(I)Br/N,N,N′,N″,N″‐pentamethyldiethylenetriamine system under room temperature, and tadpole‐shaped PS‐b‐(c‐PEO) was formed. The target copolymers and their intermediates were well characterized by size‐exclusion chromatography, proton nuclear magnetic resonance spectroscopy, and fourier transform infrared spectroscopy in details. The thermal properties was also determined and compared to investigate the influence of architecture on properties. The results showed that tadpole‐shaped copolymers had lower T_m, T_c, and X_c than that of their precursors of AB₂ star‐shaped copolymers. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis of twin‐tail tadpole‐shaped (cyclic polystyrene)‐ block‐[linear poly (tert‐butyl acrylate)]2 by combination of glaser coupling reaction with living anionic polymerization and atom transfer radical polymerization

The twin‐tail tadpole‐shaped (cyclic polystyrene)‐block‐[linear poly (tert‐butyl acrylate)]₂ [(c‐PS)‐b‐(l‐PtBA)₂] was synthesized by combination of Glaser coupling reaction with atom transfer radical polymerization (ATRP) and living anionic polymerization (LAP). First, the telechelic PS with an active and an ethoxyethyl‐protected hydroxyl groups at both ends was prepared by LAP of St monomers using lithium naphthalenide as initiator and terminated by 1‐ethoxyethyl glycidyl ether. And the alkyne groups were introduced onto each PS end by selectively reaction of active hydroxy group with propargyl bromide in NaH/tetrahydrofuran (THF) system. Then, the intramolecular cyclization was carried out by Glaser coupling reaction in pyridine/Cu(I)Br system in air atmosphere. Finally, the macroinitiator of c‐PS with two bromine groups at the junction point was synthesized via the cleavage of ethoxyethyl group and the subsequent esterification of the deprotected hydroxyl groups with 2‐bromoisobutyryl bromide. The copolymer of (c‐PS)‐b‐(l‐PtBA)₂ was obtained by ATRP of tBA monomers, and the PtBA segment was also hydrolyzed for (cyclic polystyrene)‐block‐(linear polyacrylic acid)₂ [(c‐PS)‐b‐(l‐PAA)₂]. The target copolymers and all intermediates were well characterized by GPC, MALDI‐TOF MS, and ¹H NMR in detail. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Preparation of poly(ethylene oxide)‐block‐poly(isoprene) by nitroxide‐mediated free radical polymerization from PEO macroinitiators

Amphiphilic poly(ethylene oxide)‐block‐poly(isoprene) (PEO‐b‐PI) diblock copolymers were prepared by nitroxide‐mediated polymerization of isoprene from alkoxyamine‐terminal poly(ethylene oxide) (PEO). PEO monomethyl ether (M_n ≈ 5200 g/mol) was functionalized by esterification with 2‐bromopropionyl bromide with subsequent copper‐mediated replacement of the terminal bromine with 2,2,5‐trimethyl‐4‐phenyl‐3‐azahexane‐3‐nitroxide. The resulting PEO‐alkoxyamine macroinitiator was used to initiate polymerization of isoprene in bulk and in solution at 125 °C to yield PEO‐b‐PI block copolymers with narrow molecular weight distributions (M_w/M_n ≤ 1.1). Polymerizations were first order in isoprene through 35% conversion. Micellar aggregates of PEO‐b‐PI in aqueous solution were crosslinked by treatment with a water‐soluble redox initiating system, and persistent micellar structures were observed in the dry state by AFM. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2977–2984, 2005     

Synthesis of dendrimer‐like copolymers based on the star[Polystyrene‐Poly(ethylene oxide)‐Poly(ethoxyethyl glycidyl ether)] terpolymers by click chemistry

The dendrimer‐like copolymers [PEEGE‐(PS/PEO)]_n (n ≥ 2) based on the star[Polystyrene‐Poly(ethylene oxide)‐Poly(ethoxyethyl glycidyl ether)] [star(PS‐PEO‐(PEEGE‐OH))] terpolymers were synthesized by click chemistry. First, the star‐shaped copolymers star[PS‐PEO‐(PEEGE‐Alkyne)] (also termed as [PEEGE‐(PS/PEO)]₁) were synthesized by the reaction of hydroxyl end group at PEEGE arm (on star[PS‐PEO‐(PEEGE‐OH)]) with propargyl bromide. Then, the small molecule 1,4‐diazidobutane (DAB) with two azide groups and pentaerythritol tetrakis (2‐azidoisobutyrate) (PTAB) with four azide groups were synthesized and reacted with [PEEGE‐(PS/PEO)]₁ by the click chemistry for dendrimer‐like [PEEGE‐(PS/PEO)]₂ and [PEEGE‐(PS/PEO)]₄, respectively. However, in the latter case, only the [PEEGE‐(PS/PEO)]₃ was formed as the main product because of the steric effect. The final dendrimer‐like [PEEGE‐(PS/PEO)]_n copolymers were characterized by SEC and ¹H‐NMR in detail. Comparing with the SEC of their precursor [PEEGE‐(PS/PEO)]₁, the curves of [PEEGE‐(PS/PEO)]₂ was shifted to the shorter elution time, while that of [PEEGE‐(PS/PEO)]_n (n ≥ 3) was shifted to the longer elution time, which was attributed to the different hydrodynamic volume derived from their separate structures and compositions in THF solution. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4800–4810, 2009     

Micelles possessing mixed cores and thermoresponsive shells fabricated from well‐defined amphiphilic ABC miktoarm star terpolymers

Amphiphilic ABC miktoarm star terpolymers consisting of polystyrene, poly(ε‐caprolactone), and poly(N‐isopropylacrylamide) arms, PS(‐b‐PNIPAM)‐b‐PCL, were synthesized via a combination of atom transfer radical polymerization, ring‐opening polymerization (ROP), and click chemistry. Difunctional PS bearing an alkynyl and a primary hydroxyl moiety at the chain end, PS‐alknyl‐OH, was prepared by reacting azido‐terminated PS with an excess of 3,5‐bis(propargyloxy)benzyl alcohol (BPBA) under click conditions. The subsequent ROP of ε‐caprolactone using PS‐alknyl‐OH macroinitiator afforded PS(‐alkynyl)‐b‐PCL copolymer bearing an alkynyl moiety at the diblock junction point. Target PS(‐b‐PNIPAM)‐b‐PCL amphiphilic ABC miktoarm star terpolymers were then prepared via click reaction between PS(‐alkynyl)‐b‐PCL and an excess of azido‐terminated PNIPAM (PNIPAM‐N₃). The removal of excess PNIPAM‐N₃ was accomplished by “clicking” onto alkynyl‐functionalized Wang resin. All the intermediate and final products were characterized by gel permeation chromatography, ¹H NMR, and FTIR. In aqueous solution, the obtained amphiphilic ABC miktoarm star terpolymer self‐assembles into micelles possessing mixed PS/PCL cores and thermoresponsive shells, which were further characterized by dynamic laser light scattering and transmission electron microscopy. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1636–1650, 2009     

One‐pot preparation of ABA‐type block‐graft copolymers via a combination of “click” chemistry with atom transfer nitroxide radical coupling reaction

A new strategy for the one‐pot preparation of ABA‐type block‐graft copolymers via a combination of Cu‐catalyzed azide‐alkyne cycloaddition (CuAAC) “click” chemistry with atom transfer nitroxide radical coupling (ATNRC) reaction was reported. First, sequential ring‐opening polymerization of 4‐glycidyloxy‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl (GTEMPO) and 1‐ethoxyethyl glycidyl ether provided a backbone with pendant TEMPO and ethoxyethyl‐protected hydroxyl groups, the hydroxyl groups could be recovered by hydrolysis and then esterified with 2‐bromoisobutyryl bromide, the bromide groups were converted into azide groups via treatment with NaN₃. Subsequently, bromine‐containing poly(tert‐butyl acrylate) (PtBA‐Br) was synthesized by atom transfer radical polymerization. Alkyne‐containing polystyrene (PS‐alkyne) was prepared by capping polystyryl‐lithium with ethylene oxide and subsequent modification by propargyl bromide. Finally, the CuAAC and ATNRC reaction proceeded simultaneously between backbone and PtBA‐Br, PS‐alkyne. The effects of catalyst systems on one‐pot reaction were discussed. The block‐graft copolymers and intermediates were characterized by size‐exclusion chromatography, ¹H NMR, and FT‐IR in detail. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Synthesis of amphiphilic poly(methyl methacrylate‐ b‐ethylene oxide) copolymers from monohydroxy telechelic poly(methyl methacrylate) as macroinitiator

The synthesis of well‐defined poly(methyl methacrylate)‐block‐poly(ethylene oxide) (PMMA‐b‐PEO) dibock copolymer through anionic polymerization using monohydroxy telechelic PMMA as macroinitiator is described. Living anionic polymerization of methyl methacrylate was performed using initiators derived from the adduct of diphenylethylene and a suitable alkyllithium, either of which contains a hydroxyl group protected with tert‐butyldimethylsilyl moiety in tetrahydrofuran (THF) at ?78 °C in the presence of LiClO₄. The synthesized telechelic PMMAs had good control of molecular weight with narrow molecular weight distribution (MWD). The ¹H NMR and MALDI‐TOF MS analysis confirmed quantitative functionalization of chain‐ends. Block copolymerization of ethylene oxide was carried out using the terminal hydroxyl group of PMMA as initiator in the presence of potassium counter ion in THF at 35 °C. The PMMA‐b‐PEO diblock copolymers had moderate control of molecular weight with narrow MWD. The ¹H NMR results confirm the absence of trans‐esterification reaction of propagating PEO anions onto the ester pendants of PMMA. The micellation behavior of PMMA‐b‐PEO diblock copolymer was examined in water using ¹H NMR and dynamic light scattering. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2132–2144, 2008     

Synthesis of ABCD 4‐miktoarm star polymers by combination of RAFT,ROP, and “Click Chemistry”

The ABCD 4‐miktoarm star polymers based on polystyrene (PS), poly(ε‐caprolactone) (PCL), poly(methyl acrylate) (PMA), and poly(ethylene oxide) (PEO) were synthesized and characterized successfully. Using the mechanism transformation strategy, PS with three different functional groups (i.e., hydroxyl, alkyne, and trithiocarbonate), PS‐HEPPA‐SC(S)SC₁₂H₂₅, was synthesized by the reaction of the trithiocarbonate‐terminated PS with 2‐hydroxyethyl‐3‐(4‐(prop‐2‐ynyloxy)phenyl) acrylate (HEPPA) in tetrahydrofuran (THF) solution. Subsequently, the ring‐opening polymerization (ROP) of ε‐caprolactone (CL) was carried out in the presence of stannous(II) 2‐ethylhexanoate and PS‐HEPPA‐SC(S)SC₁₂H₂₅, and then the PS‐HEPPA(PCL)‐SC(S)SC₁₂H₂₅ obtained was used in reversible addition‐fragmentation chain transfer (RAFT) polymerization of methyl acrylate (MA) to produce the ABC 3‐miktoarm star polymer, S(PS)(PCL)(PMA) carrying an alkyne group. The ABCD 4‐miktoarm star polymer, S(PS)(PCL)(PMA)(PEO) was successfully prepared by click reaction of the alkyne group on the HEPPA unit with azide‐terminated PEO (PEO‐N₃). The target polymer and intermediates were characterized by NMR, FTIR, GPC, and DSC. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6641–6653, 2008     

Synthesis of inverse star block copolymer by combination of ATRP,ring opening polymerization,and “click chemistry”

The inverse star block copolymer, (poly(ε‐caprolactone)‐b‐polystyrene)₂‐core‐(poly(ε‐caprolactone)‐b‐polystyrene)₂, [(PCL‐PS)₂‐core‐(PCL‐PS)₂] has been successfully prepared by combination of atom transfer radical polymerization (ATRP), ring opening polymerization (ROP), and “Click Chemistry.” The synthesis includes the following five steps: (1) synthesis of a heterofunctional initiator with two ATRP initiating groups and two hydroxyl groups; (2) formation of (Br‐PS)₂‐core‐(OH)₂ via ATRP of styrene; (3) preparation of the (PCL‐PS)₂‐core‐(OH)₂ through “click” reaction of the α‐propargyl, ω‐acetyl terminated PCL with (N₃‐PS)₂‐core‐(OH)₂ which was prepared by transformation of the terminal bromine groups in (Br‐PS)₂‐core‐(OH)₂ into azide groups; (4) the ROP of CL using (PCL‐PS)₂‐core‐(OH)₂ as macroinitiator to form (PCL‐PS)₂‐core‐(PCL‐OH)₂; and (5) preparation of the (PCL‐PS)₂‐core‐(PCL‐PS)₂ through the ATRP of styrene using (PCL‐PS)₂‐core‐(PCL‐Br)₂ as macroinitiator which was prepared by reaction of the terminal hydroxyl groups at the end of the PCL chains with 2‐bromoisobutyryl bromide. The characterization data support structures of the inverse star block copolymer and the intermediates. The differential scanning calorimeter results and polarized optical microscope observation showed that the intricate structure of the inverse star block copolymer greatly restricted the movement of the PS segments and PCL segments, resulted in the increase of the glass transition temperature of PS segments and the decrease of crystallization ability of PCL segments. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7757–7772, 2008     

Synthesis of amphiphilic ABC triblock copolymers by single electron transfer nitroxide radical coupling reaction in tetrahydrofuran

A series of ABC triblock copolymers, that is, polyisoprene‐block‐polystyrene‐block‐poly(ethylene oxide) (PI‐PS‐PEO), PI‐block‐poly(tert‐butyl acrylate)‐block‐PEO (PI‐PtBA‐PEO), and PI‐block‐poly(acrylic acide)‐block‐PEO (PI‐PAA‐PEO) were obtained by combination of anionic technique, atom transfer radical polymerization (ATRP), and single electron transfer nitroxide coupling (SETNRC) reaction. Anionic polymerization of isoprene followed by end capping with ethylene oxide yielded hydroxyl‐terminated PI. After esterification, PI with Br end group was used as a macroinitiator to initiate the polymerization of styrene and tBA by ATRP that was then trapped by 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO) group in PEO by SETNRC reaction rapidly with high efficiency in tetrahydrofuran at room temperature. The effect of reaction time and polymer chain length on SETNRC reaction was discussed in detail. In the presence of Cu⁰/tris[2‐(dimethylamino)ethyl]amine, SETNRC between PI‐PS‐Br and PEO‐TEMPO was carried out with the efficiency of up to 91.6% in 2 h. With the increase in polymer chain length, the efficiency decreased fleetly. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Polymerization of n‐hexyl isocyanate with CpTiCl2(OR) (R = functional group or macromolecular chain): A route to ω‐functionalized and block copolymers and terpolymers of n‐hexyl isocyanate

Well‐defined ω‐cholesteryl poly(n‐hexyl isocyanate) (PHIC–Chol), as well as diblock copolymers of n‐hexyl isocyanate (HIC) with styrene, PS‐b‐PHIC [PS = polystyrene; PHIC = poly(n‐hexyl isocyanate)], and triblock terpolymers with styrene and isoprene, PS‐b‐PI‐b‐PHIC and PI‐b‐PS‐b‐PHIC (PI = polyisoprene), were synthesized with CpTiCl₂(OR) (R = cholesteryl group, PS, or PS‐b‐PI) complexes. The synthetic strategy involved the reaction of the precursor complex CpTiCl₃ with cholesterol or the suitable ω‐hydroxy homopolymer or block copolymer, followed by the polymerization of HIC. The ω‐hydroxy polymers were prepared by the anionic polymerization of the corresponding monomers and the reaction of the living chains with ethylene oxide. The reaction sequence was monitored by size exclusion chromatography, and the final products were characterized by size exclusion chromatography (light scattering and refractive‐index detectors), nuclear magnetic resonance spectroscopy, and, in the case of PHIC–Chol, differential scanning calorimetry. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6503–6514, 2005     

One‐pot synthesis of ABC miktoarm star terpolymers by coupling ATRP,ROP, and click chemistry techniques

We report on the one‐pot synthesis of well‐defined ABC miktoarm star terpolymers consisting of poly(2‐(dimethylamino)ethyl methacrylate), poly(ε‐caprolactone), and polystyrene or poly(ethylene oxide) arms, PS(‐b‐PCL)‐b‐PDMA and PEO (‐b‐PCL)‐b‐PDMA, taking advantage of the compatibility and mutual tolerability of reaction conditions (catalysts and monomers) employed for atom transfer radical polymerization (ATRP), ring‐opening polymerization (ROP), and click reactions. At first, a novel trifunctional core molecule bearing alkynyl, hydroxyl group, and bromine moieties, alkynyl(? OH)? Br, was synthesized via the esterification reaction of 5‐ethyl‐5‐hydroxymethyl‐2,2‐dimethyl‐1,3‐dioxane with 4‐oxo‐4‐(prop‐2‐ynyloxy)butanoic acid, followed by deprotection and monoesterification of alkynyl(? OH)₂ with 2‐bromoisobutyryl bromide. In the presence of trifunctional core molecule, alkynyl(? OH)? Br, and CuBr/PMDETA/Sn(Oct)₂ catalytic mixtures, target ABC miktoarm star terpolymers, PS(‐b‐PCL)‐b‐PDMA and PEO(‐b‐PCL)‐b‐PDMA, were successfully synthesized in a one‐pot manner by simultaneously conducting the ATRP of 2‐(dimethylamino)ethyl methacrylate (DMA), ROP of ε‐caprolactone (ε‐CL), and the click reaction with azido‐terminated PS (PS‐N₃) or azido‐terminated PEO (PEO‐N₃). Considering the excellent tolerability of ATRP to a variety of monomers and the fast expansion of click chemistry in the design and synthesis of polymeric and biorelated materials, it is quite anticipated that the one‐pot concept can be applied to the preparation of well‐defined polymeric materials with more complex chain architectures. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3066–3077, 2009     

ABCD 4‐miktoarm star quarterpolymers using click [3 + 2] reaction strategy

Two samples of ABCD 4‐miktoarm star quarterpolymer with A = polystyrene (PS), B = poly(ε‐caprolactone) (PCL), C = poly(methyl methacrylate) (PMMA) or poly(tert‐butyl acrylate) (PtBA), and D = poly(ethylene glycol) (PEG) were prepared using click reaction strategy (Cu(I)‐catalyzed Huisgen [3 + 2] reaction). Thus, first, predefined block copolymers of different polymerization routes, PS‐b‐PCL with azide and PMMA‐b‐PEG and PtBA‐b‐PEG copolymers with alkyne functionality, were synthesized and then these blocks were combined together in the presence of Cu(I)/N,N,N′,N″,N″‐pentamethyldiethylenetriamine as a catalyst in DMF at room temperature to give the target 4‐miktoarm star quarterpolymers. The obtained miktoarm star quarter polymers were characterized by GPC, NMR, and DSC measurements. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1218–1228, 2008