Ratios of Weight and Number Average Molecular Weights to be Expected in Ionic Polymerization with Chain Termination but No Chain Transfer

1979 ◽  
Vol 12 (3) ◽  
pp. 532-533 ◽  
Author(s):  
Herbert Morawetz
Keyword(s):  
Chain Transfer ◽  
Chain Termination ◽  
Molecular Weights

Synthesis and characterization of a naphthalimide–dye end-labeled copolymer by reversible addition–fragmentation chain transfer (RAFT) polymerization

2011 ◽  
Vol 89 (3) ◽  
pp. 317-325 ◽  
Author(s):  
Binxin Li ◽  
Daniel Majonis ◽  
Peng Liu ◽  
Mitchell A. Winnik
Keyword(s):  
Chain Transfer ◽  
Raft Polymerization ◽  
Polymer Composition ◽  
Cooh Group ◽  
Agent Based ◽  
Molecular Weights ◽  
Reversible Addition ◽  
Raft Agent ◽  
End Use ◽  
Naphthalimide Dye

We describe the synthesis of an end-functionalized copolymer of N-(2-hydroxypropyl)methacrylamide (HPMA) and N-hydroxysuccinimide methacrylate (NMS) by reversible addition–fragmentation chain transfer (RAFT) polymerization. To control the polymer composition, the faster reacting monomer (NMS) was added slowly to the reaction mixture beginning 30 min after initating the polymerization (ca. 16% HPMA conversion). One RAFT agent, based on azocyanopentanoic acid, introduced a –COOH group to the chain at one end. Use of a different RAFT agent containing a 4-amino-1,8-naphthalimide dye introduced a UV–vis absorbing and fluorescent group at this chain end. The polymers obtained had molecular weights of 30 000 and 20 000, respectively, and contained about 30 mol% NMS active ester groups.

scholarly journals Redox-Initiated Reversible Addition–Fragmentation Chain Transfer (RAFT) Polymerization

2019 ◽  
Vol 72 (7) ◽  
pp. 479 ◽  
Author(s):  
Amin Reyhani ◽  
Thomas G. McKenzie ◽  
Qiang Fu ◽  
Greg G. Qiao
Keyword(s):  
Redox Reactions ◽  
Chain Transfer ◽  
Raft Polymerization ◽  
Molecular Structures ◽  
Biologically Relevant ◽  
Molecular Weights ◽  
Polymeric Biomaterials ◽  
Reversible Addition ◽  
Wide Range ◽  
Metal Catalyzed

Reversible addition–fragmentation chain transfer (RAFT) polymerization initiated by a radical-forming redox reaction between a reducing and an oxidizing agent (i.e. ‘redox RAFT’) represents a simple, versatile, and highly useful platform for controlled polymer synthesis. Herein, the potency of a wide range of redox initiation systems including enzyme-mediated redox reactions, the Fenton reaction, peroxide-based reactions, and metal-catalyzed redox reactions, and their application in initiating RAFT polymerization, are reviewed. These redox-RAFT polymerization methods have been widely studied for synthesizing a broad range of homo- and co-polymers with tailored molecular weights, compositions, and (macro)molecular structures. It has been demonstrated that redox-RAFT polymerization holds particular promise due to its excellent performance under mild conditions, typically operating at room temperature. Redox-RAFT polymerization is therefore an important and core part of the RAFT methodology handbook and may be of particular importance going forward for the fabrication of polymeric biomaterials under biologically relevant conditions or in biological systems, in which naturally occurring redox reactions are prevalent.

Self-assembly in the solutions of poly(methyl methacrylates) end-capped with fluorophenyl groups

e-Polymers ◽  
2009 ◽  
Vol 9 (1) ◽  
Author(s):  
Ekaterina R. Gasilova ◽  
Olga G. Zakharova ◽  
Sergey D. Zaitsev ◽  
Yury D. Semchikov
Keyword(s):  
Self Assembly ◽  
Chain Transfer ◽  
Photon Correlation Spectroscopy ◽  
Correlation Spectroscopy ◽  
Selective Solvent ◽  
Photon Correlation ◽  
Molecular Weights ◽  
Methyl Methacrylates ◽  
A Chain ◽  
Strong Segregation

AbstractSelf-assembly of poly(methyl methacrylates) end-capped with -Ge(C6F5)3 groups (PMMA-F) has been studied in a selective solvent (acetone) by means of photon correlation spectroscopy and static light scattering. PMMA-F’s of different molecular weights (MW), were obtained by radical polymerization in the presence of a chain transfer agent, HGe(C6F5)3. At MW>130 000 conformational and hydrodynamic properties of PMMA-F’s is shown to be the same as of PMMA. At MW less than130 000 an aggregation starts: additional fraction of large scatterers appears in PCS. Large aggregates of Rh=200 - 300 nm are likely to be formed by bridged micellar clusters. Presence of large aggregates indicates a super strong segregation limit predicted in the work of Semenov et al.

Reversible Chain Transfer Catalyzed Polymerization of Methyl Methacrylate with In-Situ Formed Alkyl Iodide Initiator

2009 ◽  
Vol 62 (11) ◽  
pp. 1492 ◽  
Author(s):  
Atsushi Goto ◽  
Koji Nagasawa ◽  
Ayaka Shinjo ◽  
Yoshinobu Tsujii ◽  
Takeshi Fukuda
Keyword(s):  
Methyl Methacrylate ◽  
Chain Transfer ◽  
Alkyl Iodide ◽  
Nitrogen And Phosphorus ◽  
Molecular Weights ◽  
Living Radical Polymerizations ◽  
Low Mass ◽  
Reversible Chain Transfer ◽  
Catalyzed Polymerization

A method utilizing generation of an alkyl iodide (low-mass dormant species) in situ formed in polymerization was adopted to reversible chain transfer catalyzed polymerizations (RTCP) (living radical polymerizations) with several nitrogen and phosphorus catalysts. The polymerization of methyl methacrylate afforded low-polydispersity polymers (Mw/Mn ~1.2–1.4), with Mn values predicted to high conversions; where Mn and Mw are the number- and weight-average molecular weights respectively. This method is robust and would enhance the utility of RTCP.

THE POLYMERIZATION OF ISOPRENE AND 2, 3-DIMETHYLBUTADIENE AND COPOLYMERIZATION WITH STYRENE AT −18 °C. IN EMULSION

1952 ◽  
Vol 30 (2) ◽  
pp. 108-123 ◽  
Author(s):  
R. J. Orr ◽  
H. Leverne Williams
Keyword(s):  
Transfer Reaction ◽  
Chain Transfer ◽  
Price Equation ◽  
Side Reactions ◽  
Polymerization Temperature ◽  
Reactivity Ratios ◽  
Molecular Weights ◽  
Rate Of Polymerization ◽  
Chain Transfer Reaction ◽  
Cyclic Compounds

The rate of polymerization increased with purification of the monomers. It was possible that the dienes formed cyclic compounds or dimers in side reactions. The 1,2 addition of the monomer decreased with decreasing polymerization temperature. A study was made of the copolymerization of isoprene and dimethylbutadiene with styrene at −18° C. From analyses of bound diene in the product at various conversions and initial diene to styrene ratios the reactivity ratios for these diene-styrene systems were calculated to be r1 = 1.30 ± 0.02 and r2 = 0.48 ± 0.01 for isoprene and styrene and r1 = 0.92 ± 0.02, r2 = 0.42 ± 0.02 for dimethylbutadiene and styrene (styrene always being considered monomer 2). Q and e values from the Alfrey-Price equation were calculated as Q = 119 and e = −0.112 for isoprene and Q = 1.09 and e = −0.181 for dimethylbutadiene relative to Q = 1.0 and e = −0.8 for styrene. Fom these and the values previously determined for butadiene, reactivity ratios for all combinations of the three dienes were calculated. The chain transfer reaction between dienyl radicals and mixed tertiary mercaptans was studied and it was found that isoprenyl and dimethylbutadienyl radicals were much more reactive than butadienyl. The effect of this was illustrated by number and viscosity average molecular weights. Intrinsic viscosities of homo- and copolymers formed in a mercaptan-free recipe were measured and compared.

scholarly journals Synthesis of Poly(3-vinylpyridine)-Block-Polystyrene Diblock Copolymers via Surfactant-Free RAFT Emulsion Polymerization

Materials ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3145 ◽  
Author(s):  
Katharina Nieswandt ◽  
Prokopios Georgopanos ◽  
Clarissa Abetz ◽  
Volkan Filiz ◽  
Volker Abetz
Keyword(s):  
Emulsion Polymerization ◽  
Self Assembly ◽  
Diblock Copolymers ◽  
Chain Transfer ◽  
Raft Polymerization ◽  
Free Water ◽  
Monomer Conversion ◽  
Molecular Weights ◽  
Reversible Addition

In this work, we present a novel synthetic route to diblock copolymers based on styrene and 3-vinylpyridine monomers. Surfactant-free water-based reversible addition–fragmentation chain transfer (RAFT) emulsion polymerization of styrene in the presence of the macroRAFT agent poly(3-vinylpyridine) (P3VP) is used to synthesize diblock copolymers with molecular weights of around 60 kDa. The proposed mechanism for the poly(3-vinylpyridine)-block-poly(styrene) (P3VP-b-PS) synthesis is the polymerization-induced self-assembly (PISA) which involves the in situ formation of well-defined micellar nanoscale objects consisting of a PS core and a stabilizing P3VP macroRAFT agent corona. The presented approach shows a well-controlled RAFT polymerization, allowing for the synthesis of diblock copolymers with high monomer conversion. The obtained diblock copolymers display microphase-separated structures according to their composition.

Dialkoxy-Substituted, C1-Symmetric Metallocenes: Synthesis and Catalytic Behavior in the Propylene Polymerization Reaction

2004 ◽  
Vol 59 (2) ◽  
pp. 233-240 ◽  
Author(s):  
Martin Schlögl ◽  
Bernhard Rieger
Keyword(s):  
Chain Transfer ◽  
Active Catalyst ◽  
Propylene Polymerization ◽  
Polymerization Reaction ◽  
Catalytic Behavior ◽  
Molecular Weights ◽  
Hydrocarbon Solvents ◽  
In Situ Activation ◽  
Reversible Chain Transfer

The synthesis of a series of C1-symmetric metallocene complexes rac-[1-(5,6-dialkoxy-2-methyl- 1-η5-indenyl)-2-(9-η5-fluorenyl)ethane]zirconium dichlorides (alkyl: n-butyl, n-hexyl, n-octyl, n-decyl) is described. These complexes are versatile catalysts in the polymerization of propylene after in situ activation with triisobutylaluminum (TIBA) and Ph3C[B(C6F5)4] in toluene and heptane solution. All catalysts show higher solubility and improved polymerization properties in industrially used hydrocarbon solvents (e.g. heptane). However, the molecular weights and isotacticity values of the resulting polypropylene materials are decreased compared to the ethoxy-bridged analogue rac- [1-(5,6-ethylenedioxy-2-methyl-η5-indenyl)-2-(9-η5-fluorenyl)ethane]zirconium dichloride. A possible explanation is based on enhanced interaction of the active catalyst centers with Al(III) scavenger molecules even at low Al : Zr ratios, leading to reversible chain transfer.

Reversible addition fragmentation chain transfer (RAFT) polymerization of styrene in fluid CO2

e-Polymers ◽  
2004 ◽  
Vol 4 (1) ◽  
Author(s):  
Toshihiko Arita ◽  
Sabine Beuermann ◽  
Michael Buback ◽  
Philipp Vana
Keyword(s):  
Chain Transfer ◽  
Raft Polymerization ◽  
Molecular Weights ◽  
Reversible Addition ◽  
Significant Difference ◽  
Raft Agent ◽  
Successful Control ◽  
A Minor ◽  
Peak Widths

Abstract Reversible addition fragmentation chain transfer (RAFT) polymerizations of styrene in fluid CO2 have been carried out at 80°C and 300 bar using cumyl dithiobenzoate as the controlling agent in the concentration range of 3.5·10-3 to 2.1·10-2 mol/L. This is the first report on RAFT polymerization in fluid CO2. The polymerization rates were retarded depending on the employed RAFT agent concentration with no significant difference between the RAFT polymerization performed in fluid CO2 and in toluene. Full chain length distributions were analyzed with respect to peak molecular weights, indicating the successful control of radical polymerization in fluid CO2. A characterization of the peak widths may suggest a minor influence of fluid CO2 on the addition reaction of macroradicals on the dithiobenzoate group.

scholarly journals Facile synthesis of fluorescent ABA type amphiphilic triblock copolymers via RAFT polymerization and their aggregation behavior in a selective solvent

e-Polymers ◽  
2009 ◽  
Vol 9 (1) ◽  
Author(s):  
Junwei Fu ◽  
Zhenping Cheng ◽  
Nianchen Zhou ◽  
Jian Zhu ◽  
Wei Zhang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Chain Transfer ◽  
Uv Light ◽  
Triblock Copolymers ◽  
Raft Polymerization ◽  
Facile Synthesis ◽  
Selective Solvent ◽  
Molecular Weights ◽  
Aggregation Behaviour ◽  
Transmission Electron

AbstractWell-defined naphthalene end-capped poly(styrene)-block-poly(Nisopropyl- acrylamide)-block-poly(styrene) (PS-b-PNIPAM-b-PS) amphiphilic triblock copolymers with different molecular weights and block copolymer compositions were successfully prepared via consecutive reversible additionfragmentation chain transfer (RAFT) polymerizations using a novel RAFT reagent, S,S'-bis(1-naphthylmethyl) trithiocarbonate (BNTTC). The aggregation behaviour of the prepared PS-b-PNIPAM-b-PS in water/DMF mixture was studied by transmission electron microscopy (TEM). The effect of the copolymer concentration, PNIPAM block length and the irradiation of UV-light on the sizes and morphologies of micelles were also investigated.

Enhanced ionic polymerization of styrene induced by radiation

1964 ◽  
Vol 281 (1386) ◽  
pp. 392-400 ◽  
Keyword(s):  
Low Temperature ◽  
Chain Transfer ◽  
Small Difference ◽  
Silica Powder ◽  
Molecular Weights ◽  
Temperature Irradiation ◽  
Methylene Dichloride ◽  
Powder Analysis

The yield of polymer formed by low-temperature irradiation of styrene in methylene dichloride has been measured at various concentrations of monomer and at different intensities. Corresponding yields were also determined when polymerization occurred in the presence of Aerosil (fine silica powder). Analysis of the results by means of a Mayo type of plot shows that the increased yield with Aerosil is due to a reduction in the termination step. Chain transfer during propagation is found to explain the relatively small difference in measured molecular weights. Over much of the range studied the intensity exponent is about 1 without and 0.5 with Aerosil. The former agrees with the usual kinetics involving a termination by the original gegenion, whereas the latter requires termination by a species produced in a separate ionizing event.

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