Macromers macromonomers

Active centres and their residues (in non-stationary polymerizations) are always a source of unwanted reactions of macromolecules during further operations. On an industrial scale, radical centres are terminated by inhibitors. Even the inhibiting effect of atmospheric oxygen is exploited. 

The effectiveness of such cheap termination by oxygen is, of course, low. In high-pressure polyethylene, polyvinyl chloride, polytetrafluoroethylene, etc., a large amount of frozen radicals was detected by ESR [126]. Actually, even after oxygen addition to a radical, the resulting ROO is sufficiently unstable. Research in this direction could lead to an acceptably cheap and efficient deactivation. 

Decay of ionic and coordination centres always leads to the formation of some end groups and centre residues. The centres usually lose their polymerizing activity on contact with atmospheric humidity. A residue of very active centres, which are rare, is usually not removed from the polymer (e.g. of the order of one ppm of the transition metal in low-pressure polyethylene). Larger residues have to be washed out (some types of polypropylene are still washed at the present time). 

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Macroinitiators 56 Macromers see Macromonomers Macromolecular monomers 157 Macromolecules, at-co difunctional 151 Macromonomers 21-23, 54-56, 155. 157... 

Note 3 Macromonomers are also sometimes referred to as macromers . The use of the term macromer is strongly discouraged. 

A second test was done by using butyl acrylate as the comonomer as shown in Figure 11. The reactivity ratios in this case are such that the methacrylate functionality would react slower with acrylates than with vinyl chloride. As predicted the butyl acrylate is at 62% conversion before the MACROMER peak is significantly diminished. These data add validity to the hypothesis that the placement of side chains in the backbone is dependent on the terminal group of the macromonomer and the relative reactivity of its comonomer. 

Another early attempt to prepare low molecular weight co-unsaturated polymers (the terms Macromer 1 and macromonomer were not used until 1978 6y) was made by Greber et al. 8) by means of anionic deactivation. A living m-carbanionic poly-... 

When a macrom nomer is polymerized, the determination of the conversion requires a quant. tative separation of the unreacted macromonomer which is in some cases rather difficult and requires fractionation. GPC can be very helpful to evaluate the amount of unreacted macromonomer and to check the accuracy of the fractionation. 

If LCB arises from macromonomer (usually shortened "macromer") insertion, then one might expect the LCB level in the polymer to drop when the ethylene concentration in the reactor is raised. Because macromer insertion competes with ethylene insertion, the degree of macromer incorporation should vary inversely with ethylene concentration in the reactor, as it does with any other comonomer. This relationship, well known with metallocenes, is sometimes also observed with chromium catalysts. An example is shown in Figure 79. Polymers were made with... 

An alternate route to graft copolymers is by synthesis of macromolecules possessing exactly one polymerizable group in the chain and their subsequent polymerization, i.e. grafting through. Such reactive polymers are macromolecular monomers, i.e. Macromers as abbreviated by Milkovitch 159), who was the first to call the attention of the scientific community to the importance of this field although macromonomers have been prepared and copolymerized as early as 1962 160). 

Macromolecular monomers, called macromonomers or macromers, are a relatively new category of functionalized polymer materials having a molecular weight range of 10 -10" and possessing one or more reactive polymerizable end groups [81] of those described in Table 3.2. The... 

LCB results from the copolymerization of ethylene or propene with vinyl-terminated polymer formed during the polymerization. Since vinyl double bonds are more reactive in copolymerization than other types of double-bond end groups, LCB is increased under conditions that generate higher vinyl contents. This can be accomplished by choice of initiator and reaction conditions. Tandem polymerization is also useful, such as by using two initiators, one of which produces a vinyl-terminated oligomer (referred to as a macromonomer or macromer) [Komon and Bazan, 2001 Quijada et al., 2001 Wang et al., 2000]. 

Living polymerization created the idea of Macromer (proposed by R. Milkovich, generic term is macromonomer) for synthesizing a graft copolymer of well-controlled structure. We reported the synthesis of polydimethylsiloxane (PDMS)... 

Another method, namely the macromonomer (macromer) technique, has also been reported. In this method, the macromer is initially prepared by the reaction of hydroxyl-containing oil specimens with a vinyl monomer such as acrylic acid and methyl methacrylate (Rg. 8.7). This macromer is then homopolymerised and copolymerised with styrene. It is also possible to obtain the macromer by transesterification of linseed oil and castor oil. It may subsequently be homo- and copolymerised by the same method. 

Copolymerisation of acrylated vegetable oil with styrene by a macromonomer (macromer) technique. 

The functionality of the end group itself is important. When such groups are hifimctional (eg, vinyl groups) they can participate in polymerization reactions, 5delding graft copol5uners or networks such telechelic polymers are called macromolecular monomers, macromonomers, or macromers. 

Macromolecular monomers, called macromonomers or macromers, can be defined as oligomers or polymers with a polymerizable end group. Such groups may be... 

The ability to incorporate long-chain branches appears reasonably common among metallocene catalysts. Experimental results for LCB formation with both CGC and conventional metallocene-catalyzed polymerizations are in line with an in situ copolymerization mechanism. For copolymerization of vinyl-terminated polyethylene molecules to occur, the first requirement is the presence of termination mechanisms producing vinyl-terminated macromonomers. Secondly, the catalyst must able to incorporate these macromonomers into a growing chain. Macromers probably do not move from one active site to another, but instead insertion of macromer to another chain takes place at same site where it was formed in a intramolecular incorporation manner. 

Cordova and co-workers [106] prepared macromonomers using Candida antarctica lipase B as catalyst. Ring opening polymerisation of e-CL was initiated by alcohols which included 9-decenol, cinnamyl alcohol, 2-(4-hydroxyphenyl) ethanol and 2-(3-hydroxyphenyl) ethanol. In another approach acids and esters which included n-decanoic acid, octadecanoic acid, oleic acid, linoleic acid, 2-(3-hydroxyphenyl)acetic acid, 2-(4-hydroxyphenyl)acetic acid and 3-(4-hydroxyphenyl)propanoic acid were added to the prepolymerised e-CL. Consequently, acid terminated PCL was formed. In the first approach 9-decenol-initiated PCL was formed (24 hours, 99% conversion of e-CL) with an average MW of 1,980 Da. In the second approach linoleic acid terminated PCL was formed with an average MW of 2,400 Da (51 hours, 99% conversion). In an effort to simultaneously control both the hydroxyl and carboxyl end groups of macromers, esters, e.g., 9-decenyl oleate, 2-... 

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