Ethene, functional monomers

The practically most important copolymer is made from ethene and propene. Titanium- and vanadium-based catalysts have been used to synthesize copolymers that have a prevailingly random, block, or alternating structure. Only with Ziegler or single site catalyst, longer-chain a-olefins can be used as comonomer (e.g., propene, 1-butene, 1-hexene, 1-octene). In contrast to this, by radical high-pressure polymerization it is also possible to incorporate functional monomers (e.g., carbon monoxide, vinyl acetate). The polymerization could be carried out in solution, slurry, or gas phase. It is generally accepted [173] that the best way to compare monomer reactivities in a particular polymerization reaction is by comparison of their reactivity ratios in copolymerization reactions. 

Binuclear naphthyloxydiiminato nickel catalysts VIII-1 and VIII-2 activated by [Ni(cod)2] efficiently copolymerize a variety of functionalized monomers from norbomene derivatives [119, 120]. The effective occurrence of eventual cooperative effects in copolymerization of ethene with monomers Nqh> NcooMe> and... 

Nch20h was demonstrated. Activities, as well as incorporation of functionalized monomers, of bimetallic catalysts were three- to fourfold higher than that of the monometallic analogue in identical conditions. Interestingly, the molar masses of copolymers were similar to those of copolymers of ethene with norbomene. Attempts to copolymerize Ncooh faded because the high acidity of the comonomer leads to catalyst deactivation. 

It is self-evident that the concentration of the monomers has an influence on their copolymerization behavior. High concentrations of the nonpolar olefin such as ethene or propene results in higher polymerization activities due to the inaeased incorporation of these monomers. °° Hence, the incorporation level of the polar monomer is accordingly low. To achieve high incorporation rates of the polar comonomer, low concentrations of the nonpolar monomer have to be chosen, which in turn results in low polymerization activities due to the higher stetic demand of the aluminum-protected functionalized monomers. 

Beside these basic reactions with ethene and propene, numerous other monomers can be employed in the co- and terpolymeriza-tions with CO. Due to the huge number of publications, the reader is referred to literature for more information. For example, copolymerization with norbomene, norbomene derivatives, and styrene as well as functionalized monomers such as alcohols, carbonic adds, carbamates, amides, or epoxides is possible. Functionalities are usually required to be separated from the olefin by an alkyl spacer. ... 

Highly branched ethene-methyl acrylate polymers. The cationic palladium diimine complexes are remarkably tolerant towards functional groups, although the rates decrease somewhat when polar molecules are added. In ETM catalysis addition of polar molecules or monomers kills the catalyst and therefore it was very interesting to see what the new palladium catalysts would do in the presence of polar monomers. Indeed, using methyl acrylate a copolymerisation... 

A number of ex situ spectroscopic techniques, multinuclear NMR, IR, EXAFS, UV-vis, have contributed to rationalise the overall mechanism of the copolymerisation as well as specific aspects related to the nature of the unsaturated monomer (ethene, 1-alkenes, vinyl aromatics, cyclic alkenes, allenes). Valuable information on the initiation, propagation and termination steps has been provided by end-group analysis of the polyketone products, by labelling experiments of the catalyst precursors and solvents either with deuterated compounds or with easily identifiable functional groups, by X-ray diffraction analysis of precursors, model compounds and products, and by kinetic and thermodynamic studies of model reactions. The structure of some catalysis resting states and several catalyst deactivation paths have been traced. There is little doubt, however, that the most spectacular mechanistic breakthroughs have been obtained from in situ spectroscopic studies. 

CO, CH4, CO2, acetone, ketene. ethene. propene. 1-butene, benzene, toluene, xylene, cydopentene, methyl ethyl ketone, diethyl ketone, methyl-n-propyl ketone, di-n-propyl ketone, methyl vinyl ketone, methyl Isopropenyl ketone, methyl isopropyl ketone, ethyl vinyl ketone, trace amounts of methyl-n-bulyl ketone, cyclopentanone, cydohexanone. acrolein, ethanal. butanal. chain fragments, some monomer CO. CH4, COj, ketene, 1-butene, propene, acetone, methyl ethyl ketone, methyl n-propyl ketone, 1,4-cyclohexadiene. toluene, l-methy. l.3-cydohexadlene, 2-hexanone, cydopentene, 1-methyl cydopentene. mesityl oxide, xylenes, benzene, ethene, cyclopentanone, 1.3-cyclopentad iene, diethyl ketone, short chain fragments, traces of monomer CO, CH4, COi, ketene, 1-butene, propene, acetone, methyl ethyl ketone, methyl isopropyl ketone, methyl-n-propyl ketone, diethyl ketone, methyl propenyl ketone, 3-hexanone. toluene, 2-hexanone. 1,3-cydopentadiene, cyclopentanone, 2-melhylcydopenlanone, mesityl oxide, xylenes, benzene, propionaldehyde, acrolein, acetaldehyde ethene, short chain fragments, traces of monomer CO, COj, H2O, CH4. acetone, ketene, ethene, propylene, 1-butene, methyl vinyl ketone, benzene, acrylic add, toluene, xylene, short chain fragments such as dimer to octamer with unsaturated and anhydride functionalities... 

The same complex will induce anionic growth of ethene, and while one research school proposes that the propagating species is a lithium alkyl derivative intimately involving TMEDA, another suggests the action of the base is purely to release monomer Bu"Li from its hexameric form in hexane solution, and that this then acts as the initiator. More recent work has established that a Bu"Li/TMEDA complex in a 1 1 stoicheiometry is the active species, and that N,A, NW -tetraethylethylenediamine and pentamethyldi-ethylenetriamine are more effective than TMEDA. Furthermore the living polymer obtained has been terminally functionalized by reaction with CO2. 

What is fhe implication of our work wifh respect to the metal-catalyzed polymerization of polar vinyl monomers FirsL for fhe late metal compounds, fhe polar vinyl monomers can clearly outcompete efhene and simple 1-alkenes wifh respect to insertion. However, fhe ground-state destabilization of the alkene complex that favors the migratory insertion of fhe polar vinyl monomers is a two-edged sword because it biases the alkene coordination towards ethene and l-alkenes. Indeed, we have observed fhe near quantitative displacement of vinyl bromide by propene to form 7 from 3 (Scheme 9.1). Thus, the extent of incorporation of fhe polar vinyl monomer in fhe polymer will depend on the opposing trends in alkene coordination and migratory insertion. The above discussion does not take into account the problem of functional group coordination for acrylates or halide abstraction for vinyl hahdes. 

Choi et a/.182 have used a perturbed Hartree-Fock method with the PM3 Hamiltonian to analyse the dynamic a, ft and response functions of thiophene, furan, pyrrole, 1,2,4-triazole, 1,3,4-oxadiazole and 1,2,4-thiadiazole monomers and oligomers. The PM3 method is also the basis of a study of the static a and response functions of tetrakis(phenylethynyl)ethene.183... 

Figure 4.6-5 Rate parameter jt,Oi iis a function of monomer conversion measured via SP-PLP during ethene homopolymerizations at 230 °C and 2550 bar [31].

Fig. 5 The specific rate of ethene polymerization at steady state as a function of the monomer concentration with MgCl2/Di/TiCl4/Al(C2H5)3 at 50°C [26]...

As an alternative approach, polycarbosilanes 2.31 bearing pendant zirconocene moieties have also been prepared by ring-opening polymerization of the spirocyc-lic monomer 2.30 (Eq. 2.13) [62], In this case, the materials were structurally characterized, but the soluble fraction was of low molecular weight (M < ca. 3000) and the high molecular weight fraction was insoluble in organic solvents. In the presence of activators, both fractions functioned as ethene polymerization catalysts with moderate activity [62]. 

In this paper, we review continuous thermodynamics as applied to copolymer systems. Special attention is focused on liquid-liquid equilibria and thermodynamic stability. Equilibria in solutions of random copolymers, blends of random copolymers with homo- or copolymers, and also the high pressure phase equihbrium in the mixture of copoly(ethene vinylacetate) with its monomers are also discussed. A special examination of polydispersity effects in solutions with block copolymers is made. Thus, the paper reviews in a comprehensive way how to build up continuous thermodynamics with multivariate distribution functions and how to derive relations necessary for solving special problems. Some short remarks on possible future prospects will round up the paper. 

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