Z. Guan, Control of polymer topology through late‐transition‐metal catalysis, <i>J Polym Sci Part A: Polym Chem (2003), 41(22), 3680–3692</i>

Guan, Zhibin

doi:10.1002/pola.11084

Cited by 35 publications

(61 citation statements)

References 57 publications

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“…[1][2][3] For example, hyperbranched polymers exhibit several unique properties, including low solution and melt viscosities, enhanced solubility, and the presence of a large number of functional end groups for further modification [4][5][6][7][8][9][10][11][12][13][14][15][16][17] as compared to linear analogs. However, the application of hyperbranched polymers as conventional structural materials is limited due to inadequate mechanical strength, which is attributed to a lack of chain entanglements among the low molar mass branches.…”

Section: Introductionmentioning

confidence: 99%

“…[1,[18][19][20][21][22] However, there has been less progress in the control of branch length in step-growth Summary: Branched poly(arylene ether)s were prepared in an oligomeric A 2 þ B 3 polymerization of phenol endcapped telechelic poly(arylene ether sulfone) oligomers as A 2 and TFPPO as trifunctional monomer B 3 . The molar mass of the A 2 oligomer significantly influenced the onset of gelation and the DB.…”

Section: Introductionmentioning

confidence: 99%

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Highly Branched Poly(arylene ether)s via Oligomeric A₂ + B₃ Strategies

Qin¹,

Ünal

Fornof

et al. 2006

Macro Chemistry & Physics

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Summary: Branched poly(arylene ether)s were prepared in an oligomeric A2 + B3 polymerization of phenol endcapped telechelic poly(arylene ether sulfone) oligomers as A2 and TFPPO as trifunctional monomer B3. The molar mass of the A2 oligomer significantly influenced the onset of gelation and the DB. A high level of cyclization during polymerization of low molar mass A2 oligomers (U3 = 660 and U6 = 1 200 g · mol−1) led to a high conversion of functional groups in the absence of gelation, and the level of cyclization reactions in the polymerization decreased as the molar mass of the A2 oligomer was increased. The pronounced steric effect in the polymerization of higher molar mass A2 oligomers (U8 = 1 800 and U16 = 3 400 g · mol−1) resulted in low reactivity of the third aryl fluoride in the B3 monomer. As a result, only slightly branched (U8 = 1 800 g · mol−1) or nearly linear (U16 = 3 400 g · mol−1) high molar mass products were obtained with higher molar mass A2 oligomers. The branched polymers exhibited lower Mark‐Houwink exponents and [η] relative to linear analogs, and differences between the branched polymers and linear analogs were less significant as the molar mass of the A2 oligomers was increased due to a decrease in the overall DB. magnified image

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Highly Branched Poly(arylene ether)s via Oligomeric A₂ + B₃ Strategies

Qin¹,

Ünal

Fornof

et al. 2006

Macro Chemistry & Physics

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“…[5] Whereas these catalysts exhibit excellent properties as described, one limitation is their relatively high sensitivity to temperature. The catalysts decompose rapidly at 50 8C for Pd II -a-diimine [6] and at 70 8C for Ni II -a-diimine systems.…”

mentioning

confidence: 98%

Cyclophane‐Based Highly Active Late‐Transition‐Metal Catalysts for Ethylene Polymerization

Camacho¹,

Salo²,

Ziller³

et al. 2004

Angew Chem Int Ed

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307

186

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Cyclophane chemistry has evolved into an exciting research area stemming from simple curiosity of the syntheses and structures to the exploitation of physical properties of cyclophanes for various applications including molecular recognition, supramolecular chemistry, and biomimics.[1] A plethora of literature describing cyclophane-metal host-guest chemistry indicates the potential application of cyclophanes as ligands in metal-catalyzed transformations.[1] One major research effort in our group is to explore the use of cyclophanes as ligands for olefin polymerization catalysis. In our ligand design, we strategically position metal binding sites at the core of cyclophanes to chelate transition metals. The cyclophane framework shields all directions of the catalytic metal center except leaving two cis coordination sites open in the front: one for monomer coordination and the other for the growing polymer chain. The well-defined cavity and sterically hindered microenvironment of cyclophanes should offer great opportunities for fine-tuning the catalytic properties. The rigid cyclophane framework may also enhance the stability of transition-metal complexes. Despite these promises, however, the use of cyclophanes as ligands for transition-metal polymerization catalysis remains mostly unexplored.[2]Herein, we report the first cyclophane-based late-transitionmetal catalyst that shows high activity and thermal stability for ethylene polymerization.Late-transition-metal olefin polymerization catalysts have received much attention recently because they can produce polyolefins with interesting new branching topologies and have better tolerance to functional groups.[3] One noteworthy example is the Ni II -and Pd II -a-diimine complexes reported by Brookhart and co-workers.[4] The Ni II systems were shown to have comparable activities to those of the early-transitionmetal catalysts in polymerizing ethylene into high molecular weight (MW) polyethylenes (PEs) and the Pd II systems were shown to be able tolerate and incorporate polar olefins such as methyl acrylate.[4] The branching topology of the PEs formed by the Pd II -a-diimine catalysts can easily be tuned from linear to hyperbranched to dendritic by simply varying ethylene pressure.[5] Whereas these catalysts exhibit excellent properties as described, one limitation is their relatively high sensitivity to temperature. The catalysts decompose rapidly at 50 8C for Pd II -a-diimine [6] and at 70 8C for Ni II -a-diimine systems.[7] The MW of the PEs formed by Ni II catalysts also decreases precipitously as the temperature of polymerization is raised. [7] These issues hindered the commercialization of these catalysts since gas-phase olefin polymerizations typically operate at temperatures as high as 80-100 8C.[8] Herein, we report novel Pd II and Ni II -a-diimine catalysts containing a cyclophane ligand moiety that demonstrate improved thermal stability and produce high MW PEs at temperature ranges suitable for industrial gas-phase olefin polymerization.In the acyclic catalyst...

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“…[4][5][6][7][8][9] The fluoropolymers have been synthesized homogeneously in ScCO 2 by free radical methods. 7,8,[10][11][12][13][14] Unfortunately, most industrially important hydrocarbon-based polymers are relatively insoluble in ScCO 2 . Therefore, polymerization has to be heterogeneous when hydrocarbon-based polymers are produced in ScCO 2 .…”

Section: Introductionmentioning

confidence: 99%

Dispersion copolymerization of acrylonitrile‐vinyl acetate in supercritical carbon dioxide

Yang

Qi-wu

Wang

et al. 2006

J of Applied Polymer Sci

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Dispersion copolymerization of acrylonitrilevinyl acetate (AN-VAc) had been successfully performed in supercritical carbon dioxide (ScCO 2 ) with 2,2-azobisisobutyronitrile (AIBN) as a initiator and a series of lipophilic/ CO 2 -philic diblock copolymers, such as poly(styrene-r-acrylonitrile)-b-poly(1,1,2,2-tetrahydroperfluorooctyl methacrylate) (PSAN-b-PFOMA), as steric stabilizers. In dispersion copolymerization, poly(acrylonitrile-r-vinyl acetate) (PAVAc) was emulsified in ScCO 2 effectively using PSAN-b-PFOMA as a stabilizer. Compared with the precipitation polymerization (absence of stabilizer), the products prepared by dispersion polymerization possessed of higher yield and higher molecular weight. In addition, the particle morphology of precipitation polymerization was irregular, but the particle morphology of dispersion polymerization was uniform spherical particles. In this study, the effects of the initial concentrations of monomer and the stabilizer and the initiator, and the reaction pressure on the yield and the molecular weight and the resulting size and particle morphology of the colloidal particles were investigated.

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Z. Guan, Control of polymer topology through late‐transition‐metal catalysis, J Polym Sci Part A: Polym Chem (2003), 41(22), 3680–3692

Cited by 35 publications

References 57 publications

Highly Branched Poly(arylene ether)s via Oligomeric A₂ + B₃ Strategies

Highly Branched Poly(arylene ether)s via Oligomeric A₂ + B₃ Strategies

Cyclophane‐Based Highly Active Late‐Transition‐Metal Catalysts for Ethylene Polymerization

Dispersion copolymerization of acrylonitrile‐vinyl acetate in supercritical carbon dioxide

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Z. Guan, Control of polymer topology through late‐transition‐metal catalysis, J Polym Sci Part A: Polym Chem (2003), 41(22), 3680–3692

Cited by 35 publications

References 57 publications

Highly Branched Poly(arylene ether)s via Oligomeric A2 + B3 Strategies

Highly Branched Poly(arylene ether)s via Oligomeric A2 + B3 Strategies

Cyclophane‐Based Highly Active Late‐Transition‐Metal Catalysts for Ethylene Polymerization

Dispersion copolymerization of acrylonitrile‐vinyl acetate in supercritical carbon dioxide

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Highly Branched Poly(arylene ether)s via Oligomeric A₂ + B₃ Strategies

Highly Branched Poly(arylene ether)s via Oligomeric A₂ + B₃ Strategies