Addition polymerization of norbornene catalyzed by palladium(2+) compounds. A polymerization reaction with rare chain transfer and chain termination

1992 ◽  
Vol 25 (16) ◽  
pp. 4226-4228 ◽  
Author(s):  
Christof Mehler ◽  
Wilhelm Risse
Keyword(s):  
Chain Transfer ◽  
Chain Termination ◽  
Polymerization Reaction ◽  
Addition Polymerization

scholarly journals Visible Light-Controlled Living Cationic Polymerization of Methoxystyrene

2021 ◽  
Author(s):  
Lei Wang ◽  
Shaodong Zhang ◽  
Yongfeng Zhou ◽  
Yupo Xu ◽  
Quan Zuo ◽  
...  
Keyword(s):  
Visible Light ◽  
Cationic Polymerization ◽  
Molar Mass ◽  
Chain Transfer ◽  
Polymerization Reaction ◽  
Great Success ◽  
Living Cationic Polymerization ◽  
Green Led ◽  
Polymerization System ◽  
Lytic System

Photo-controlled living polymerization has received great attention in recent years. However, despite the great success therein, the report on photo-controlled living cationic polymerization has been greatly limited. We demonstrate here a novel decolorable, metal-free and visible light-controlled living cationic polymerization system by using tris(2,4-dimethoxyphenyl)methylium tetrafluoroborate as the photocatalyst and phosphate as the chain transfer agent (CTA) for polymerization of 4-methoxystyrene. This polymerization reaction under green LED light irradiation shows clear living characteristics including predictable molar mass, narrow molar-mass dispersity (Đ = 1.25), and sequential polymerization capability. In addition, the photocata-lytic system exits excellent “on-off” photo switchability and shows the longest “off period” of 36 h up to now for photo-controlled cationic polymerization. Furthermore, the residual photo-catalyst is easily deactivated and decolored with addition of a base after the polymerization.

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.

scholarly journals Synthesis of Modified Polycarboxylate and Its Application in Ultra-High Performance Concrete

2021 ◽  
Vol 8 ◽  
Author(s):  
Shuncheng Xiang ◽  
Yansheng Tan ◽  
Yingli Gao
Keyword(s):  
Silica Fume ◽  
High Performance ◽  
Chain Transfer ◽  
High Performance Concrete ◽  
Raw Materials ◽  
Synthesis Method ◽  
Drying Shrinkage ◽  
Polymerization Reaction ◽  
Ultra High Performance Concrete ◽  
Initiation System

Modified polyurethane prepolymer was prepared using the segmental synthesis method. Then, pectiniform polycarboxylate was synthesized at normal temperature in the complex initiation system of H2O2, APS, sodium bisulfite, Vc, and Rongalit according to the free radical polymerization reaction mechanism, using TPEG, AA, and PEG as raw materials and TGA as the chain transfer agent. Compared with commercial Sika polycarboxylate, its flowability, strength, drying shrinkage, and auto-shrinkage were studied. The experimental results show that the synthesized polycarboxylate could be better dispersed. Adding silica fume can enhance the compressive strength of ultra-high performance concrete (UHPC), while slag may decline its strength. By incorporating slag and silica fume, the drying shrinkage of UHPC was reduced, but its auto-shrinkage was increased.

Synthesis and characterization of poly(vinyl chloride-graft-2-vinylpyridine) graft copolymers using a novel macroinitiator by reversible addition-fragmentation chain transfer polymerization

e-Polymers ◽  
2014 ◽  
Vol 14 (1) ◽  
pp. 27-34 ◽  
Author(s):  
Temel Öztürk ◽  
Melahat Göktaş ◽  
Bedrettin Savaş ◽  
Mustafa Işıklar ◽  
Mehmet Nuri Atalar ◽  
...  
Keyword(s):  
Vinyl Chloride ◽  
Chain Transfer ◽  
Raft Polymerization ◽  
Graft Copolymers ◽  
Monomer Concentration ◽  
Polymerization Reaction ◽  
Scanning Calorimetry ◽  
H Nmr ◽  
Poly Vinyl Chloride ◽  
Reversible Addition

AbstractSynthesis of poly(vinyl chloride-graft-2-vinylpyridine) graft copolymers was carried out by reversible addition-fragmentation chain transfer (RAFT) polymerization of 2-vinylpyridine using a novel macroinitiator (RAFT macroinitiator). For this purpose, RAFT macroinitiator was obtained from the potassium salt of ethyl xanthogenate and poly(vinyl chloride) (PVC). Then the graft copolymers were synthesized by using RAFT macroinitiator and 2-vinylpyridine. The principal parameters such as monomer concentration, initiator concentration, and polymerization time that affect the polymerization reaction were studied. The effect of the reaction conditions on the heterogeneity index and molecular weight was also investigated. The block lengths of the graft copolymers were calculated by using 1H nuclear magnetic resonance (1H NMR) spectra. The block lengths of the copolymers could be adjusted by varying the monomer and initiator concentrations. The characterizations of the samples were carried out by using 1H NMR, Fourier-transform infrared spectroscopy, gel-permeation chromatography, thermogravimetric analysis, differential scanning calorimetry, and fractional precipitation (γ value) techniques. RAFT polymerization is used to control the polymerization of 2-vinylpyridine over a broad range of molecular weights.

Synthetic Procedures for Preparing Cross-Linkable Acrylic Comb-Like Copolymers Via Macromonomers

1989 ◽  
Vol 171 ◽  
Author(s):  
Gang-Fung Chen ◽  
Frank N. Jones
Keyword(s):  
Free Radical ◽  
Butyl Acrylate ◽  
Chain Transfer ◽  
Synthetic Route ◽  
Radical Initiation ◽  
The Third ◽  
Addition Polymerization ◽  
Third Stage ◽  
Free Radical Initiation ◽  
Ft Ir

ABSTRACTA versatile procedure was developed for synthesis of acrylic comb-like copolymers in three steps: (1) Hydroxyl terminated oligomers were synthesized from methyl methacrylate, butyl acrylate and glycidyl acrylate by free-radical initiated addition polymerization using a functional chain transfer agent, 2-mercaptoethanol, and very low initiator levels. (2) The oligomers were converted to macromonomers by reaction with isocyanatoethyl methacrylate. (3) The macromonomers were polymerized by free-radical initiation. Conditions during the first stage must be carefully selected to minimize formation of difunctional material which could cause gelation in the third stage. A variety of structures can be made such as comb-like copolymers with homopolymer tines or comb-like homopolymers with copolymer tines. Functional groups can be introduced by copolymerizing glycidyl acrylate into the macromonomer. Assignment of comb-like structures is not rigorously proven but is strongly supported by the synthetic route and by DSC, FT-IR and chromatographic data.

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