Alternating copolymerisation

Finally where both reactivity ratios take the value of zero, the monomers do not react at all, with growing polymer chains terminated in their own kind of monomer unit. This results in alternating copolymerisation. A few typical monomer reactivity ratios are given in Table 2.2. 

Ever since their original discoveries, Ziegler Natta catalysts and Phillips catalysts have been used for both the homopolymerisation and the copolymerisation of olefins. Moreover, Ziegler-Natta catalysts also allowed the copolymerisation of olefins with vinylaromatic monomers, conjugated dienes and cycloolefins. Other coordination catalysts such as group 8 metal compounds, especially cationic Pd(II) complexes, enabled the alternating copolymerisation of olefins and carbon monoxide [2,29,30,37,43,46,241,448 450],... 

Under most conditions, only the simple polypropylene ketone) is formed in propylene/carbon monoxide alternating copolymerisation. Isomerisation of poly(ketone) to poly(spiroketal) can occur, and it may be assisted by cationic palladium species and protonic acids. It must be emphasised that a low reaction temperature favours the formation of a spiroketal structure [107]. At a temperature above the ceiling temperature, the poly(spiroketal) depolymerises to the more flexible and entropically favoured poly (ketone) [481]. 

Stereospecific Alternating Copolymerisation of Styrene and Carbon Monoxide... 

A valuable ligand for the highly isotactic alternating copolymerisation of styrene and / -methylstyrene with carbon monoxide appeared to be Ch-symmet-ric (4S, 4,iS)-(-)-4,4,5,5,-tetrahydro-4,4,-bis(l-methylethyl)-2,2 -bioxazole coordinated to Pd(II) in the cationic complex [135] ... 

A scheme for the alternating copolymerisation of conjugated dienes and a-olefins has been proposed in the case of isoprene/propylene copolymerisation with V-based Ziegler-Natta catalysts [209] ... 

Heck-type step-growth condensation polymerisation involves mainly palladium-based catalysts, although nickel-based catalysts are also effective. It is worth noting that this polycondensation requires a change in the oxidation state of the metal (e.g. Pd) [schemes (30) and (31)] [71], which is in contrast to chain growth polymerisation, such as ethylene/carbon monoxide alternating copolymerisation promoted by Pd-based catalysts [schemes (82) and (83) in Chapter 3], for which the preservation of the oxidation state of palladium, Pd(II), is typical [83-85] ... 

However, organotin-based catalyst systems such as BU2S11I2 or BU3S11I—PBU3, PPI13 or NEt3 have been found to promote the alternating copolymerisation of oxetane and carbon dioxide to yield poly(trimethylene carbonate) ... 

This insight is strikingly illustrated by the observation of alternating copolymerisation. The radical-initiated polymerisation of a 1 1 mixture of dimethyl fumarate 7.3 and vinyl acetate 7.5 takes place largely to give a polymer in which the fragments derived from the two monomers alternate along the chain. In this case... 

The alternating copolymerisation of methyl methacrylate and styrene in the presence of borontrichloride proceeds in the homopolymerisation of a ternary molecular complex composed of all three 68... 

Hardacre C, Holbrey J D, Katdare S P, et al. Alternating copolymerisation of styrene and carbon monoxide in ionic liquids. Green Chem. 

Copolymerisation is another approach to improve the mechanical behaviour of polymers, especially their ductility. In copolymerisation, different monomers are used to form the chain molecules. There are several possibilities to arrange the monomers, shown in figure 8.26. The monomers can alternate alternating copolymerisation) or can be arranged irregularly random copolymerisation). In block copolymers, there are longer chain segments of one type... 

In this context a particularly interesting and unique example of the alternating copolymerisation of enantiomers was demonstrate in the polymerisation of 1-methylnorbornene with the ReCl j catalyst [63,75]. The analysis relied on the fact that the hydrogenated forms of these polymers (but see more recent work, p. 52), unlike their unsaturated precursors, exhibited fine structure due to the presence of ring dyad units of different tacticities. 

Hardacre, C., Holbrey, J.D., Katdare, S.P. Seddon, K.R. (2002). Alternating Copolymerisation of Styrene and Carbon Monoxide in Ionic Liquids, Green Chem., 4, pp. 143-146... 

Alternating copolymerisation. This occurs if r = t2 = 0, that is, each radical reacts exclusively with the other monomer, not with its own (Figure 2.5). In this case d[Mi]/d[M2] = 1 and for each monomer feed composition = in = 1- An example is the copolymerisation of vinyl acetate (Mi) with maleic anhydride (M2), for which n = 0.055, f2 = 0.003 and r r2 = 0.00017. Alternating copolymers can crystallise only if the copolymers are purely alternating and if the product is stereoregular or if the monomers are symmetrical. 

A new route to a controlled synthesis of heavily aromatic substituted polyesters has been investigated. The method involves an alternating copolymerisation of an aldehyde and a ketene. PEK and MBA can be copolymerised under /THF/nBuLi/ — 20°C/LiCl/CH3OH/ conditions to obtain an alternating PEK/ MBA copolymer MJM = 1.15, = 5.1 kg/mol). The alternating structure... 

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