Ionic liquids polymerisable

By the end of 2004 ring-opening polymerisation in ionic liquids has been reported in only one paper, using complexes 35a, 35b or 36 as catalysts.[33] A biphasic system comprised of [C4CiCiim][PF6] and toluene in a 1 4 ratio was used to minimise catalyst loss during product isolation and the polymer could be obtained almost quantitatively by simple decantation. The activity of ionic liquid solutions of 35a drop markedly after the first cycle and become inactive in the third cycle, whereas 35b and 36 could be used for three and five cycles, respectively, with very good conversions, as shown in Scheme 7.5. 

A summary of polymerisation reactions in ionic liquids, which also covers non-metal catalysed reactions, is available[33] and ring-opening polymerisation (ROMP) was described in Chapter 6. 

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... 

An important benefit of performing the polymerisation of acrylates in [C4Ciim][PF6] is that the number of undesirable side-reactions is considerably reduced. This observation correlates with the fraction of active macromolecules found in the reaction mixture, which was much higher in the ionic liquid relative to the solvent-free reaction, see Table 8.2.[43] Especially towards the end of a polymerisation reaction, when the monomer concentration is low, side-reactions such as irreversible chain termination become increasingly important. 

Irreversible termination of growing macromolecules during the final stages of ATRP are particularly disadvantageous if the synthesis of block co-polymers by sequential polymerisation is attempted. Due to different solubilities of catalyst, monomer and polymer in the ionic liquid phase, a larger amount of active molecules may be observed in the presence of an ionic liquid. 

Block co-polymers have been synthesised in [C4Ciim][PF6] by ATRP of butylacrylate and acrylate monomer.[62] The outcome of the reaction depends significantly on the order of substrate addition. If, for example, methyl acrylate was added to a two-phase system of poly-butylacrylate and ionic liquid, the resulting copolymer has a narrow polydispersity and is essentially free of homopolymer. A markedly higher amount of homopolymer was formed when butyl acrylate was added to a solution of poly-methyl acrylate and the degree depended on the stage of the MA polymerisation. Below 70% conversion, copolymer without homopolymer was formed, while above 90% conversion, practically no co-polymer was produced. 

Ethylene may also be polymerised in [C4Ciim]Cl-AlCl3-AlCl2Et (1 1 0.32) in the presence of the nickel(II) bisimine complex, 43, and toluene as co-solvent.1" After the reaction, the upper toluene layer contains the product while the catalyst remains in the ionic liquid. After decantation, the second run was initiated by introducing a new batch of ethylene-saturated... 

Polymerisation of ethylene was also attempted in [C4Ciim][PF6] or [Cspy][Tf2N], employing the palladium compound 45 together with either Ag[SbF6] or Na[BARF] to activate the complex.1681 However, the best activity obtained in these ionic liquids was one order of magnitude lower compared to using dichloromethane as solvent. 

A series of ionic liquids have been tested for the polymerisation of phenylacetylene with the pyrazolylborate rhodium complexes 46 and 47, shown in Scheme 8.13.[701 Complex 46 afforded higher molecular weights and lower polydispersity at comparable activity in the ionic liquid relative to dichloromethane. The addition of small amounts of methanol to the ionic liquid was found to have a positive effect on the catalytic activity. With complex 47 best results were obtained in [C4Ciim]Cl, giving 64% yield after 2 hours at 65°C. Molecular weights were usually lower with 46 than those obtained with either 47a or 47b as catalyst. 

The related system 31 has been prepared by thionation of the diketone 32 with P4S10 or Lawesson s reagent. Furthermore, dithieno[2,3-6 2 ,3 -c( thiophene 31 was also submitted to electrochemical polymerisation <04TL3405>. Lawesson s reagent has also been used to effect conversion of several 1,4-diketones to thiophenes employing a new reusable catalytic system consisting of Bi(OTf)3 and the ionic liquid [bmim]BF4 (l-butyl-3-methylimidazolium tetrafluoroborate) <04TL5873>. 

For structuring, the IL has to be immobilised. This can be done using i.e. zeolitic structures or molecular sieves. It is obvious that with increasing surface area of the solid phase, the motion of the liquid and the proton transport will be hindered. From polymerisation experiments it is known that the stiffening of polymers by cross-linking can be compared with the polymer-surface interaction. Electrode surfaces and solids such as silica, carbon black or cathode powder also stiffen the polymer [52]. This can be explained by different transport properties at the interfaces. As a consequence it must be expected that at the surface of the added particles the ionic liquid will behave in a different way than in the immobilised liquid phase. 

Bon SAF, Carmichael AJ, Haddleton DM, Seddon KR. 2000. Copper(I) mediated living radical polymerisation in an ionic liquid. Chem Commun 74 1237-1238. 

Enzymatic ROP of other cyclic monomers, l,4-dioxan-2-one, [56-58], 3(S)-isopropylmorpholine-2,5-dione and its derivatives have been studied [59, 60]. Out of 12 enzymes (7 lipases, 2 esterases and 3 proteases) studied, immobilised lipase from C. antarctica gave the best results. In a recent study [58], the activity of CALB was improved by coating with an ionic liquid, 1-butyl-3-methylimidazolium hexafluorophoshphate, which protected the bound water layer surrounding the lipase. Poly(l,4-dioxan-2-one) (PPDO) with a MW of 182,100 g/mol was obtained via this method. The thermodynamics and kinetics of CALB [57] showed that the polymerisation of l,4-dioxan-2-one reached equilibrium after 12 h at 60 C in the presence of 5wt% lipase, and the ROP kinetics of PPDO was of the first order with regards to the monomer concentration. 

LA is currently an important six-membered lactone used as a starting monomer for the production of PLA, a type of green plastic. LA polymerisation was first reported in 1997 [88] at temperatures between 80 and 130 °C to produce PLA with MW up to 1.26 X 10. The lipase-catalysed polymerisations of L-lactide were also carried out in four types of ionic liquids. [C4mim][BF4] was suitable to obtain higher MW polylactides and higher polymer yield at lower lipase content [89]. 

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