Polymerisation transition-metal-catalysed

T. J. PuUukat, M. Shida, and R. E. Hoff, ia R. P. Quirk, ed.. Transition Metal Catalysed Polymerisations Mlkenes and Dienes, Harwood Academic Pubhshers, New York, 1983, p. 697. 

The alkene metathesis reaction arose serendipitously from the exploration of transition-metal-catalysed alkene polymerisation. Due to the complexity of the polymeric products, the metathetic nature of the reaction seems to have been overlooked in early reports. However, in 1964, Banks and Bailey reported on what was described as the olefin disproportionation of acyclic alkenes where exchange was evident due to the monomeric nature of the products [8]. The reaction was actually a combination of isomerisation and metathesis, leading to complex mixtures, but by 1966 Calderon and co-workers had reported on the preparation of a homogeneous W/Al-based catalyst system that effected extraordinarily rapid alkylidene... 

To conclude this section, an example is given of the application of statistical models to examine double bond sequences in polymers with unsaturated backbones. The presence of backbone unsaturation leads to the occurrence of cisitrans isomerism and this can be treated entirely analogously to comonomer sequence. Ivin [42] and others have used NMR spectroscopy extensively to study the microstructure of polymers prepared by transition metal catalysed ring-opening metathesis polymerisation (ROMP) such as polynorbornene (PNB). 

Transition metal catalysed ATRP is one of the most efficient methods to control radical polymerisation [13]. ATRP is based on the reversible formation of radicals from alkyl halides in the presence of transition metal complexes, and is a direct extension to polymers of the Kharasch reaction, ATRA, (Scheme 4). Among the plethora of catalysts (or precatalysts) described in the literature for ATRP, the copper systems developed by Matyjaszewski [3, 14] and the ruthenium complexes introduced by Sawamoto [15] play a most prominent role and set the standards in the field (Scheme 5). 

Mention has already been made in this chapter of metallocene-catalysed polyethylene (see also Chapter 2). Such metallocene catalysts are transition metal compounds, usually zirconium or titanium. Incorporated into a cyclopentadiene-based structure. During the late 1990s several systems were developed where the new catalysts could be employed in existing polymerisation processes for producing LLDPE-type polymers. These include high pressure autoclave and... 

In this chapter we will discuss a few topics in the area of alkene polymerisations catalysed by homogeneous complexes of early and late transition metals (ETM, LTM). One of the main research themes for the ETM catalysts has been the polymerisation of propene, while industries have also paid a lot of attention to metallocenes giving LLDPE (linear low-density polyethylene, for thinner plastic bags). In less than a decade a completely new family of catalysts has been developed which enables one to synthesise regioselective and stereoselective polymers of a wide variety of monomers. These new catalysts are starting to find application on industrial scale, but as yet only reports on commercialisation of (branched) polyethylene and polystyrene have appeared. 

Coordination polymerisation was first proposed in 1956 for the unusual, at that time, low-pressure polymerisation of ethylene and polymerisation of propylene with the transition metal catalysts discovered by Ziegler in 1953 [1], and for the ferric chloride catalysed ring-opening polymerisation of propylene oxide to crystalline polymer reported by Pruitt et al. in a Dow patent [2]. 

In contrast to heterogeneous Ziegler-Natta catalysts, homogeneous catalysts based on biscyclopentadienyl derivatives of group 4 transition metals, which contain cationic metallocene species of formally d° 14-electronic structure, hardly promote the polymerisation of conjugated dienes, since the diene can act as a donor of four electrons rather than of two electrons as in monoolefin polymerisation (let us recall that the polymerisation of conjugated dienes is catalysed by half-sandwich metallocene-based catalysts). However, it has been reported [162] that statistical copolymers of ethylene and butadiene were obtained with the Cp2ZrCl2— [Al(Me)0]x catalyst. 

Polymerisation reactions in ionic liquids have so far focused on processes that do not involve a transition metal catalyst. Examples include acid-catalysed/34"361 free-radical,[37 50] electrochemical19,51"551 and laser1561 induced polymerisation reactions and a review is available on the topic.1571... 

Atom radical transfer polymerisation (ATRP) has its roots in atom transfer radical addition (ATRA), which involves the formation of 1 1 adducts of alkyl halides and alkenes, and is also catalysed by transition metal complexes. ATRP is a modification of the Kharasch addition reaction (Kharasch et al. 1945) although there may be some differences (Minisci 1975). A general mechanism for ATRP is shown in Scheme 10.5. In ATRP the radicals or the active species are generated through a reversible redox process catalysed by a transition metal complex (Mtn-L/... 

The use of multifunctional monomers in anaerobics leads to a highly crosslinked thermoset polymer that is heat-resistant and has excellent resistance to oil and solvents. Anaerobics cure very quickly on clean surfaces made of iron, steel or brass where transition metal ions catalyse the initiation of polymerisation. However, they cure at a slower rate on plated surfaces, on oily surfaces, or in the presence of certain rust-inhibiting chemicals such as chromates. For very inactive surfaces or for fixing on plastics, surface primer solutions (usually amines or copper salts) can be used. 

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