Star‐shaped polymer PFStODO by atom transfer radical polymerization: Its synthesis,characterization, and fluorescence property

A novel monomer bearing with pyrazoline chromophore, 3‐(4‐fluorophenyl)‐1‐phenyl‐5‐(4‐(4‐vinylbenzyloxy)phenyl‐4,5‐dihydro‐1H‐pyrazole (FStODO), was synthesized, and its atom transfer radical polymerization initiated by a tetrafunctional initiator, pentaerythritol tetrakis(2‐bromoisobutyrate) (4Bri‐Bu), was studied in detail and characterized by ¹H NMR, GPC, and TG‐DSC. The solution, film luminescence of monomer, and its polymer were studied in detail. Compared with that of monomer, both luminescence emission intensity and quantum yield of star‐shaped polymer PFStODO in DMF solution are decreased. However, the two‐photon absorption (TPA) spectra in DMF solution measured by a femtosecond laser show an entirely different result that the maxima TPA cross‐section value of polymer reaches to 203 GM, better than that of the monomer itself (13 GM). More interestingly, the film of polymer shows surprisingly white emission ranging from 400 to 700 nm assigned to the excimer formation. We attribute this formation of excimers to the ordered chromophore aggregates in film, which is further verified by X‐ray diffraction. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Effect of ligand on the synthesis of star polymers by resorcinarene‐based ATRP initiators

The effect of the steric hindrance on the initiating properties of two multifunctional resorcinarene‐based initiators in atom transfer radical polymerization (ATRP) was studied by using Cu(I)‐complexes of three multidentate amine ligands in the polymerization of tert‐butyl acrylate and methyl methacrylate. These ligands are less sterically hindered and have higher activities in the catalysis of ATRP of (meth)acrylates than 2,2′‐bipyridine. The polymerizations were faster and more controlled than with the 2,2′‐bipyridyl catalyst, but the tendency for bimolecular coupling increased. Even though the initiator was octafunctional, the resulting star polymers had only four arms. This indicates that the steric hindrance arising from the conformations of the initiators determines the structure of the polymer, but the ligand noticeably affects the controllability of the polymerization © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3349–3358, 2005     

Amphiphilic polymer electrolytes consisting of PVC‐g‐POEM comb‐like copolymer and LiCF3SO3

An amphiphilic comb‐like copolymer consisting of a poly(vinyl chloride) (PVC) backbone and poly((oxyethylene)₉ methacrylate) (POEM) side chains, PVC‐graft‐POEM was synthesized via atom transfer radical polymerization. This comb copolymer was complexed with LiCF₃SO₃ to form a solid polymer electrolyte. FTIR and FT‐Raman spectroscopy indicate that lithium salts are dissolved in the ion conducting POEM domains of microphase‐separated graft copolymer up to 10 wt % of salt concentration. Microphase‐separated structure of the materials and the selective interaction of lithium ions with POEM domains were revealed by transmission electron microscopy, wide angle X‐ray scattering, and differential scanning calorimetry. The maximum ionic conductivity of 4.4 × 10^?5 S/cm at room temperature was achieved at 10 wt % of salt concentration, above which salts are present as less mobile species such as ion pairs and higher order ionic aggregates, as characterized by FT‐Raman spectroscopy. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1443–1451, 2009     

Synthesis of well‐defined 7‐arm and 21‐arm poly(N‐isopropylacrylamide) star polymers with β‐cyclodextrin cores via click chemistry and their thermal phase transition behavior in aqueous solution

The syntheses of well‐defined 7‐arm and 21‐arm poly(N‐isopropylacrylamide) (PNIPAM) star polymers possessing β‐cyclodextrin (β‐CD) cores were achieved via the combination of atom transfer radical polymerization (ATRP) and click reactions. Heptakis(6‐deoxy‐6‐azido)‐β‐cyclodextrin and heptakis[2,3,6‐tri‐O‐(2‐azidopropionyl)]‐β‐cyclodextrin, β‐CD‐(N₃)₇ and β‐CD‐(N₃)₂₁, precursors were prepared and thoroughly characterized by nuclear magnetic resonance and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry. A series of alkynyl terminally functionalized PNIPAM (alkyne‐PNIPAM) linear precursors with varying degrees of polymerization (DP) were synthesized via atom transfer radical polymerization (ATRP) of N‐isopropylacrylamide using propargyl 2‐chloropropionate as the initiator. The subsequent click reactions of alkyne‐PNIPAM with β‐CD‐(N₃)₇ and β‐CD‐(N₃)₂₁ led to the facile preparation of well‐defined 7‐arm and 21‐arm star polymers, namely β‐CD‐(PNIPAM)₇ and β‐CD‐(PNIPAM)₂₁. The thermal phase transition behavior of 7‐arm and 21‐arm star polymers with varying molecular weights were examined by temperature‐dependent turbidity and micro‐differential scanning calorimetry, and the results were compared to those of linear PNIPAM precursors. The anchoring of PNIPAM chain terminal to β‐CD cores and high local chain density for star polymers contributed to their considerably lower critical phase separation temperatures (T_c) and enthalpy changes during phase transition as compared with that of linear precursors. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 404–419, 2009     

Resorcinarene‐based ATRP initiators for star polymers

Two novel multifunctional initiators for atom transfer radical polymerization (ATRP) were synthesized by derivatization of tetraethylresorcinarene. The derivatization induced a change in the conformation of the resorcinarene ring, which was confirmed by NMR spectroscopy. The initiators were used in ATRP of tert‐butyl acrylate and methyl methacrylate, producing star polymers with controlled molar masses and low polydispersities. Instead of the expected star polymers with eight arms, polymers with four arms were obtained. Conformational studies on the initiators by rotating‐frame nuclear Overhauser and exchange spectroscopy NMR and molecular modeling suggested that of eight initiator functional groups on tetraethylresorcinarene, four are too close to each other to be able to initiate the chain growth. Starlike poly(tert‐butyl acrylate) macroinitiators were used further in the block copolymerization of methyl methacrylate. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4189–4201, 2004     

Synthesis of multiarmed poly(3‐hexyl thiophene) star polymer with microgel core by GRIM and ATRP methods

Regioregular poly(3‐hexyl thiophene) (rr‐P3HT)‐based star polymers were synthesized by a crosslinking reaction of the linear rr‐P3HT macroinitiator and ethylene glycol dimethacrylate (EGDMA) crosslinker through Ru‐based atom transfer radical polymerization (ATRP), where the rr‐P3HT macroinitiator was prepared by Grignard metathesis method (GRIM) followed by end functionalization of the ATRP initiator with chlorophenylacetate (CPA) to the rr‐P3HT. Relatively high molecular weight of the star polymers were obtained (M_p = 8,988,000 g/mol), which consisted of large numbers of the rr‐P3HT arm chains radiating from the EGDMA‐based microgel core. The yield of the star polymers were strongly affected by the added amount of the EGDMA crosslinker. The crystalline structure of the rr‐P3HT by intermolecular π‐π stacking interaction gradually decreased as the star polymer formed, which was confirmed by differential scanning calorimeter (DSC), atomic force microscopy (AFM), and electro‐optical analyses. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Facile synthesis of AB2‐type miktoarm star polymers through the combination of atom transfer radical polymerization and ring‐opening polymerization

A novel miktofunctional initiator ( 1 ), 2‐hydroxyethyl 3‐[(2‐bromopropanoyl)oxy]‐2‐{[(2‐bromopropanoyl)oxy]methyl}‐2‐methyl‐propanoate, possessing one initiating site for ring‐opening polymerization (ROP) and two initiating sites for atom transfer radical polymerization (ATRP), was synthesized in a three‐step reaction sequence. This initiator was first used in the ROP of ?‐caprolactone, and this led to a corresponding polymer with secondary bromide end groups. The obtained poly(?‐caprolactone) (PCL) was then used as a macroinitiator for the ATRP of tert‐butyl acrylate or methyl methacrylate, and this resulted in AB₂‐type PCL–[poly(tert‐butyl acrylate)]₂ or PCL–[poly(methyl methacrylate)]₂ miktoarm star polymers with controlled molecular weights and low polydispersities (weight‐average molecular weight/number‐average molecular weight < 1.23) via the ROP–ATRP sequence. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2313–2320, 2004     

Modified cubic spherosilicates as macroinitiators for the synthesis of inorganic–organic starlike polymers

Modified cubic spherosilicate cages of the type [Si₈O₂₀]^8? were used as rigid, inorganic cores for the synthesis of macroinitiators for thermal and photoinduced free radical and controlled radical polymerizations. Two different routes to these macroinitiators were investigated: the direct modification of the octaanion with chlorosilane‐functionalized initiators and the hydrosilation of SiH‐substituted cages. The latter synthesis of the macroinitiators resulted in more defined reaction products. With these compounds, the polymerizations of styrene and methyl methacrylate were carried out. The free radical polymerizations showed broad polydispersities based on coupling reactions, whereas the copper‐mediated atom transfer radical polymerizations (ATRP) revealed that good polymerization control could be achieved with the prepared initiators. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3858–3872, 2002     

Synthesis of mikto‐topology star polymer containing one cyclic arm

Well‐defined mikto‐topology star polystyrene composed of one cyclic arm and four linear arms was synthesized by a combination of atom transfer radical polymerization (ATRP) and Cu‐catalyzed azide‐alkyne cycloaddition (CuAAC) click reaction. First, the bromine‐alkyne α,ω‐linear polystyrenes containing four hydroxyl groups protected with acetone‐based ketal groups were synthesized by ATRP of styrene using a designed initiator. Then, the bromine end‐group was converted to the azide and the linear polystyrene was cyclized intra‐molecularly by the CuAAC reaction. The four hydroxyl groups were released by deprotection and then esterified with 2‐bromoisobutyryl bromide to produce a cyclic polymer bearing four ATRP initiating units. By subsequent ATRP of styrene to grow linear polymers with the cyclic polystyrene as a macroinitiator, the mikto‐topology star polymers were prepared. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Efficient water‐soluble drag reducing star polymers with improved mechanical stability

We describe here the first example of the synthesis of 4‐arm star poly(acrylic acid) for use as a water‐soluble drag reducing agent, by applying Cu(0)‐mediated polymerization technique. High molecular weight 4‐arm star poly(tert‐butyl acrylate) (M_n = 3.0–9.0 × 10⁵ g mol^?1) was first synthesized using 4,4′‐oxybis(3,3‐bis(2‐bromopropionate)butane as an initiator and a simple Cu(0)/TREN catalyst system. Then, 4‐arm star poly(tert‐butyl acrylate) were subjected to hydrolysis using trifluoroacetic acid resulting in water‐soluble 4‐arm star poly(acrylic acid). Drag reduction test rig analysis showed 4‐arm star poly(acrylic acid) to be effective as a drag reducing agent with drag reduction of 24.3%. Moreover, 4‐arm star poly(acrylic acid) exhibited superior mechanical stability when compared with a linear poly(acrylic acid) and commercially available drag reducing polymers; Praestol and poly(ethylene oxide). The linear poly(acrylic acid), Praestol, and poly(ethylene oxide) all showed a large decrease in drag reduction of 8–12% when cycled 30 times through the drag reduction test rig while, in contrast, 4‐arm star poly(acrylic acid) demonstrated much higher mechanical stability. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 335–344     

Simple route for synthesis of H‐shaped copolymers

The H‐shaped copolymers, [poly(L ‐lactide)]₂polystyrene [poly(L ‐lactide)]₂, [(PLLA)₂PSt(PLLA)₂] have been synthesized by combination of atom transfer radical polymerization (ATRP) with cationic ring‐opening polymerization (CROP). The first step of the synthesis is ATRP of St using α,α′‐dibromo‐p‐xylene/CuBr/2,2′‐bipyridine as initiating system, and then the PSt with two bromine groups at both chain ends (Br–PSt–Br) were transformed to four terminal hydroxyl groups via the reaction of Br–PSt–Br with diethanolamine in N,N‐dimethylformamide. The H‐shaped copolymers were produced by CROP of LLA, using PSt with four terminal hydroxyl groups as macroinitiator and Sn(Oct)₂ as catalyst. The copolymers obtained were characterized by ¹H NMR spectroscopy and gel permeation chromatography. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2794–2801, 2006     

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     

Synthesis and characterization of 4‐arm star side‐chain liquid crystalline polymers containing azobenzene with different terminal substituents via ATRP

4‐Arm star side‐chain liquid crystalline (LC) polymers containing azobenzene with different terminal substituents were synthesized by atom transfer radical polymerization (ATRP). Tetrafunctional initiator prepared by the esterification between pentaerythritol and 2‐bromoisobutyryl bromide was utilized to initiate the polymerization of 6‐[4‐(4‐methoxyphenylazo)phenoxy]hexyl methacrylate (MMAzo) and 6‐[4‐(4‐ethoxyphenylazo)phenoxy]hexyl methacrylate (EMAzo), respectively. The 4‐arm star side‐chain LC polymer with p‐methoxyazobenzene moieties exhibits a smectic and a nematic phase, while that with p‐ethoxyazobenzene moieties shows only a nematic phase, which derives of different terminal substituents. The star polymers have similar LC behavior to the corresponding linear homopolymers, whereas transition temperatures decrease slightly. Both star polymers show photoresponsive isomerization under the irradiation with UV–vis light. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3342–3348, 2007     

Thermoregulated phase‐transfer catalysis via PEG‐armed Ru(II)‐bearing microgel core star polymers: Efficient and reusable Ru(II) catalysts for aqueous transfer hydrogenation of ketones

Thermoregulated phase‐transfer catalysis for the transfer hydrogenation of 2‐octanone in 2‐propanol/H₂O biphasic media was achieved with ruthenium‐bearing microgel‐core star polymers with amphiphilic, thermosensitive poly(ethylene glycol) (PEG) arms [Ru(II)‐PEG star], which were directly prepared by the ruthenium‐catalyzed living radical polymerization in conjunction with a phosphine ligand‐carrying styrene derivative. The star polymers were first placed in the aqueous (lower) layer at room temperature and immediately moved into the organic (upper) layer at 100 °C, and once again, moved down to the aqueous layer (lower) upon cooling the solution to room temperature. The Ru(II)‐PEG star catalyst was clearly superior to the original Ru(II) catalyst and related non‐microgel catalysts [Ru(II)‐PEG block] in terms of activity and recovery/recycle, due to the unique designer structure of the microgel‐core star polymers. Other substrates (less hydrophobic alkyl ketones and aromatic ketone) were also efficiently hydrogenated into the corresponding sec‐alcohols with the star catalyst in aqueous media. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 373–379, 2010     

Well‐defined polymers containing high density of pendant viologen groups

Atom transfer radical polymerization (ATRP) of a viologen‐containing methacrylate, 1‐propyl‐1′‐[2‐(methacryloyloxy)ethyl]‐4,4′‐bipyridinium dihexafluorophosphate, is reported. To achieve good polymerization control, it was essential to use the viologen‐based monomer with a hexafluorophosphate instead of halide counterion, and 2,2′‐bipyridine as the ligand for the Cu‐based ATRP catalyst. The solubility of produced cationic polymers could be tuned by anion metathesis: the polymers with hexafluorophosphate counterions were soluble in organic solvents (e.g., acetone, DMF), and those with chloride counterions were water‐soluble. In aqueous solutions, the polymers (chloride salts) formed large aggregates, the sizes of which ranged from about 200 to about 400 nm (based on dynamic light scattering measurements) depending on the molecular weight. Upon addition of electrolytes (e.g., NaCl), the aggregates underwent dissociation. The apparent diffusion coefficients of the aggregates existing in aqueous solutions and the products of their electrolyte‐induced dissociation were measured by diffusion‐ordered NMR spectroscopy. The association–dissociation processes were also studied by fluorescence spectroscopy: the aqueous polymer solutions, which were originally fluorescent (λ _em = 402 nm at λ _ex = 350 nm), lost their fluorescence in the presence of NaCl. The addition of small amounts of the viologen‐containing polyelectrolytes to solutions of inorganic salts (NaCl) altered the crystal morphology of the salts due to interaction of the multiple charged pendant groups with small ions. In the presence of reducing agents, the pendant viologen groups were converted to viologen radical‐cations, which are prone to dimerize reversibly in aqueous solutions. Indeed, marked dimerization of viologen radical cations (with absorbance maxima at 520 and 870 nm) was observed in relatively dilute aqueous solutions (4 mg mL^?1) upon addition of reducing agents (hydrazine). © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 55 , 1173–1182     

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 and properties of comb polymers with semirigid mesogen‐jacketed polymers as side chains

A series of novel comb polymers, poly{2,5‐bis[(4‐methoxyphenyl)oxycarbonyl]styrene}‐g‐polystyrene (PMPCS‐g‐PS), with mesogen‐jacketed rigid side chains were synthesized by the “grafting onto” method from α‐yne‐terminated PMPCS (side chain) and poly(vinylbenzyl azide) (backbone) by Cu(I)‐catalyzed 1,3‐dipolar cycloaddition click reaction. The α‐yne‐terminated PMPCS was synthesized by Cu(I)‐catalyzed atom transfer radical polymerization initiated by a yne‐functional initiator. Poly(vinylbenzyl azide) was prepared by polymerizing vinylbenzyl chloride using nitroxide mediated radical polymerization to obtain poly(vinylbenzyl chloride) as the precursor which was then converted to the azide derivative. The chemical structure and architectures of PMPCS comb polymers were confirmed by ¹H NMR, gel permeation chromatography, and multiangle laser light scattering. Both surface morphologies and solution behaviors were investigated. Surface morphologies of PMPCS combs on different surfaces were investigated by scanning probe microscopy. PMPCS combs showed different aggregation morphologies when depositing on silicon wafers with/without chemical modification. The PMPCS comb polymers transferred to polymer‐modified silicon wafers using the Langmuir‐Blodgett technique showed a worm‐like chain conformation. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Modification of carboxyl‐functionalized single‐walled carbon nanotubes with biocompatible,water‐soluble phosphorylcholine and sugar‐based polymers: Bioinspired nanorods

We report here the successful functionalization of single‐walled carbon nanotubes with bioinspired sugar and phosphocholine polymeric structures via surface‐initiated atom transfer radical polymerization. The surface‐polymer‐coated carbon nanotubes have been systematically analyzed by Raman, infrared, ultraviolet–visible, and nuclear magnetic resonance spectroscopy and high‐resolution transmission electron microscopy, which give strong evidence of successful functionalization. The successful aqueous dispersion of the functionalized carbon nanotubes also indicates that functionalization has been achieved. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6558–6568, 2006     

利用原子转移自由基聚合方法制备一种新型聚合物整体柱固相萃取材料初探

利用两步原子转移自由基聚合(ATRP)方法,初步建立了新型聚合物整体柱固相萃取(SPE)材料制备的新方法。首先利用ATRP方法,以乙二醇二甲基丙烯酸酯（EDMA）为交联剂,在室温条件下,在滤头中原位快速聚合制备得到负载有聚合物整体柱的萃取装置;然后采用表面诱导的电子转移活化再生原子转移自由基聚合(ARGET ATRP)方法进行表面修饰,得到了聚(二甲基氨基乙基甲基丙烯酸酯)(PDMAEMA)修饰的柱体;进一步将此整体柱用作萃取材料,实现了对激素类药物的富集分析。本研究表明:ATRP有望作为一种简单、有效及反应条件温和的聚合方法用于整体柱的制备,且该方法有潜力实现固相萃取材料在不同装置中的制备。