Presence Of Metallocenes Research Articles

Radical-Initiated (Co)polymerization of Methacrylates in the Presence of Organometallic Iron Complexes

The effect exerted by organometallic iron complexes (ferrocene, tricarbonyl cyclooctatetraene iron, and dimer cyclopentadienyldicarbonyl iron) on the benzoyl peroxide initiated homo- and copolymerization of methyl methacrylate and n-butyl methacrylate was studied. The ligand surrounding in the organometallic complexes influences the shape of the kinetic curves of the methyl methacrylate and n-butyl methacrylate polymerization. In the presence of organometallic iron complexes, the copolymerization constants are close to unity. That is, the azeotropic copolymerization occurs, with the copolymer composition equal to the composition of the monomer mixture and with the random distribution of monomeric units in the copolymer chain. On the other hand, the presence of metallocenes influences the microstructure and molecular-mass characteristics of the copolymers. These changes are due to the formation of macromolecules with the participation of both free radicals and coordination-active polymerization sites formed in the presence of organometallic complexes.

Copolymerization of Methyl Methacrylate and Styrene in Presence of Cyclopentadienyl Complexes of Iron, Titanium, and Manganese

The influence of metallocenes ferrocene, dimer cyclopentadienyl dicarbonyl iron, cyclopentadienyl tricarbonyl manganese, and titanocene dichloride on copolymerization of methyl methacrylate and stryrene initiated by benzoyl peroxide was studied. It was shown that the values of copolymerization constants of monomers and copolymer microstructure change in presence of metallocenes.

Iron Metal Complexes as Catalysts for the Radical-Initiated Homo- and Copolymerization of Methacrylates

The paper presents data on the effect of iron metal complexes (ferrocene and dimer cyclopentadienyldicarbonyl iron) on the homo- and copolymerization of methyl methacrylate and butyl methacrylate initiated by benzoyl peroxide. It was shown that, in the presence of the metal complexes, the shapes of kinetic curves changed, and the compositions of copolymers and the initial mixtures of monomers almost coincided; that is, the resulting copolymer composition corresponded to the azeotropic composition. The copolymerization constants were close to unity. The presence of metallocenes affected the microstructure of the copolymers and their molecular-weight characteristics. These changes were explained by the formation of macromolecules with the participation of both free radicals and coordination active centers formed in the presence of the metal complexes.

Analysis of Curing Rates of Adhesive Compositions Based on Methyl Methacrylate or Styrene and Macroinitiators, Obtained by Radically Initiated Polymerization with the Participation of Metallocenes

Reaction mixtures have been proposed as a basis of adhesive composition for gluing items made of poly(methyl methacrylate) or polystyrene. This composition consists of respective monomers and macroinitiators formed during radically initiated polymerization in the presence of metallocenes. An evaluation of the macroinitiators activity was carried out in postpolymerization of styrene and methyl methacrylate processes (the poly(methyl methacrylate) and polystyrene macroinitiators were considered, they were obtained in two different ways: the first one is during the polymerization with benzoyl peroxide or azobisisobutyronitrile and ferrocene or titanocene dichloride, and the second one is macroinitiators obtained in situ under the influence of UV radiation and in the presence of ferrocene or titanocene dichloride). The optimal methods of preparation and recipe of adhesive compositions were determined from the point of view of the fastest curing rate.

Regularities of postpolymerization in a vinyl monomer-metallocene-radical initiator system

The polymerization of methyl methacrylate in the presence of metallocenes and radical initiators has been shown to proceed as radical-coordination polymerization, with the propagation of some chains following a coordination mechanism involving metallocenes. The polymerization products are capable of initiating monomer polymerization in the absence of an initiator. The catalytic activities of “metallocene” polymers are determined by the history of their synthesis.

Initiation of complex-radical polymerization of methyl methacrylate in the presence of metallocenes

The initiation of radical polymerization of methyl methacrylate in the presence of benzoyl peroxide-metallocene (Cp2Fe, Cp2ZrCl2, and Cp2TiCl2; (C5Me5)2Fe, (C5Me5)2ZrCl2, and (AcC5H4)(C5H5)Fe) systems is studied. It is shown that a metallocene affects the rate of initiation and the initial rate of polymerization. On the basis of quantum-chemical calculations, a new mechanism of the initiation reaction may be advanced: Namely, the decomposition of benzoyl peroxide proceeds via the stage of complexation with a metallocene, while the nature of a metallocene determines the probability of complexation and decomposition.

Effect of metallocenes on the photoinduced postpolymerization of vinyl monomers

The photoinduced postpolymerization of styrene and methyl methacrylate in the presence of metallocenes is studied. It is shown that, after short-term UV irradiation, the polymerization of vinyl monomers mediated by metallocenes continues in the dark regime until the formation of polymer glasses. The process proceeds as a terminationless complex-radical polymerization.

Complex-radical polymerization of methyl methacrylate in the presence of metallocenes

The effects of the nature of metallocene (ferrocene, titanocene dichloride, and zirconocene dichloride) and its content in benzoyl peroxide-metallocene initiating systems on the kinetics of polymerization of methyl methacrylate have been studied. The kinetic features of polymerization and changes in the molecular characteristics of poly(methyl methacrylate) indicate that the process occurs via the complex-radical mechanism. On the basis of quantum-chemical calculations, a scheme describing the formation of complex-radical centers of chain propagation for the benzoyl peroxide-ferrocene system is proposed.

Copolymerization of Ethylene with 2,7‐Octadienyl Methyl Ether in the Presence of Metallocene and Nickel Diimine Catalysts

AbstractIn this work, copolymers of ethylene with 2,7‐octadienyl methyl ether have been synthesized in the presence of three single‐site catalysts. The obtained copolymers not only have a polar ether function but also a double bond in the side chains that is useful for secondary reactions. The polymers were characterized by GPC, EA, DSC, NMR, and FT‐IR. The catalytic activity depends on the kind of catalysts, the concentration of the polar monomer, and the concentration of the protecting agent. Up to 7.3 wt.‐% of MODE could be incorporated by the metallocene catalyst. These are in average 120 functional side groups in a polymer molecule with a molecular mass of 230 000.magnified image

Photoinduced Postpolymerization of vinyl monomers in the presence of metallocenes

Photoinduced Postpolymerization of vinyl monomers in the presence of metallocenes

Zielona chemia polimerow

The article is a review of the newest literature data (159 references) concerning the application of the rules of green and sustainable chemistry in chemistry of polymers. The processes (being in agreement with these rules) of manufacturing of intermediate products for polymers syntheses, coming from oil or renewable resources, as well as the polymerization carried out in the presence of metallocene or enzymatic catalysts were described. Alternate media of polymerization reactions, such as supercritical carbon dioxide, ionic liquids and water, were characterized. Special attention has been paid to biodegradable polymers, feedstock recycling and energy recovery from polymeric materials used, especially in the presence of supercritical liquids.

Homo-and copolymerization of vinylcyclohexane with α-olefins in the presence of heterogeneous and homogeneous catalytic systems

The polymerization and copolymerization of vinylcyclohexane with α-olefins in the presence of several heterogeneous and homogeneous catalytic systems were studied. It was shown that, with respect to activity in the polymerization of vinylcyclohexane, the tested catalysts can be arranged in the following order: α-TiCl3 < titanium-magnesium catalyst < metallocene catalyst. Poly(vinylcyclohexane) prepared with heterogeneous catalytic systems is a solid semicrystalline polymer. The properties of polymers synthesized with homogeneous systems differ substantially depending on the type of the metallocene used. In the presence of metallocenes with a C2 symmetry, crystalline powderlike products arise, while in the case of metallocenes with C1 and C s symmetries, polymerization yields amorphous viscous products. Molecular-mass distributions of poly(vinylcyclohexane) samples prepared using both heterogeneous titanium-magnesium catalysts and homogeneous metallocene complexes show a bimodal pattern, indicating the heterogeneity of active centers of these catalysts. Upon introduction of a comonomer (ethylene, propylene, and 1-hexene) into the reaction mixture, the activity of all studied catalytic systems increases. When Me2C(3-Me-Cp)(Flu)ZrCl2 and rac-Me2SiInd2ZrCl2 are used as catalysts, the degree of crystallinity of the copolymers grows owing to the presence of ethylene or propylene units in poly(vinylcyclohexane) chains.

Radical Copolymerization of Methyl Methacrylate and Styrene in the Presence of Metallocenes

The effect of ferrocene and zirconocene dichloride on the rate and constants of copolymerization of methyl methacrylate with styrene was studied. The results obtained suggest that the metallocenes in the elementary steps of the reaction.

C1-symmetric metallocenes for olefin polymerisation, 1. Catalytic performance of [Me2C(3-tertBuCp)(Flu)]ZrCl2in ethene/norbornene copolymerisation

The mechanism of the alternating ethene/norbornene copolymerisation using [Me2C(3-tertBuCp)(Flu)]ZrCl2 with methylaluminoxane as catalyst is investigated. Copolymerisation models to describe the copolymerisation behavior in the presence of metallocenes with heterotopic sites for monomer coordination are given and applied. It is shown that the microstructure of the copolymers produced at 30°C is the result of a chain migratory insertion mechanism (alternating mechanism) and the sterical hindrance for norbornene insertion at one of the two heterotopic sites of the metallocene. Further investigations on the influence of the reaction parameters showed that an increase in temperature (to 60°C) causes deviations from the alternating mechanism.

Molecular Sieve Synthesis using Metallocenes as Structure Directing Agents

ABSTRACTWe have been exploring molecular sieve synthesis using metal complexes as templates. Our objectives were to affect the crystallization of new structures as well as prepare bifunctional catalysts via the encapsulation of metal complexes during synthesis. In this paper the results for the synthesis of SiO2, AlPO4and SAPO molecular sieves in the presence of metallocenes will be presented. In particular, Cobalticinium ion, Cp2Co+, was found to be a template for Nonasil, AlPO4−5, AlPO4−16, SAPO−16 and CoAPO−16 which are known phases but require templates. The larger decamethyl derivative, CP*2Co+has produced a novel high silica zeolite molecular sieve, UTD-1 as well as a new SAPO phase UTD-2 which appear to be large pore materials. In all cases, the metal complex is occluded intact and cannot be extracted. Aspects of the synthesis and characterization of these microporous materials are presented below.