Methacrylate macromonomers chain transfer

Chain transfer to methacrylate and similar maeromonomers has been discussed in Section 6.2.3.4. The first papers on the use of this process to achieve some of the characteristics of living polymerization appeared in 1995.380 The structure of macromonomer RAFT agents (163) is shown in Figure 9.3. An idealized reaction scheme for the case of a MMA terminated macromonomer is shown in Scheme 9.36. 

ESI mass spectrometry ive mass spectrometry ESR spectroscopy set EPR spectroscopy ethyl acetate, chain transfer to 295 ethyl acrylate (EA) polymerizalion, transfer constants, to macromonomers 307 ethyl methacrylate (EMA) polymerization combination v.v disproportionation 255, 262 kinetic parameters 219 tacticity, solvent effects 428 thermodynamics 215 ethyl radicals... 

Pentadienyl-terminated poly(methyl methacrylate) (PMMA) as well as PSt, 12, have been prepared by radical polymerization via addition-fragmentation chain transfer mechanism, and radically copolymerized with St and MMA, respectively, to give PSt-g-PMMA and PMMA-g-PSt [17, 18]. Metal-free anionic polymerization of tert-butyl acrylate (TBA) initiated with a carbanion from diethyl 2-vinyloxyethylmalonate produced vinyl ether-functionalized PTBA macromonomer, 13 [19]. 

Acrylic Macromonomers. Acrylic-methacrylic macromonomers prepared by catalytic chain transfer using cobalt(II) chelates afford polymer chains, each with an olefinic endgroup (18, 24). Such macromonomers can be polymerized or copolymerized to produce graft polymers that are useful in coatings, fibers, films, and composite materials applications (24). Moreover, one is able to synthesize macromonomers containing several alkylmethacrylates, alkylacrylates, and styrene (IS). 

Using SEC-ESIMS we studied the products of a macromonomer synthesis in which MMA (2) and BA (3) MS were loaded in an 80 20 (wt/wt) weight ratio. The details of the synthesis are reported in Experimental Details. The SEC-ESIMS data will allow us to profile the chemical composition distribution across the MWD. From these data we should be able to measure the relative efficiency of our chain-transfer agent for methacrylates versus acrylates. 

In a more specific example, macromonomer composed of n-butyl methacrylate and methacrylic acid prepared by CCT was copolymerized with n-butyl acrylate containing a small portion of methyl methacrylate.341 Comparison to the equivalent copolymer made with a macromonomer prepared with a thiol chain-transfer agent demonstrated that the CCT macromonomer formed a copolymer while the thiol macromonomer did not. When these compositions were cured using trifunctional isocyanates, they were useful as both clear and pigmented automotive finishes. 

CCT of benzyl methacrylate leads to a mixture of poly(benzyl methacrylate) macromonomers from which the dimer macromonomer could be isolated.516 When the benzyl dimer is used as a RAFT chain-transfer agent, PMMA with a- and co-terminal benzyl methacrylate units is obtained. Catalytic hydrogenation of the a,co-benzyl terminal methyl methacrylate polymer results in the evolution of toluene and formation of a,co-dicarboxyl functional telechelic PMMA. 

PMMA macromonomers have been prepared by several methods. The most common involves the use of thioglycolic acid, as a chain transfer agent for the preparation of polymers with carboxyl end groups, followed by the reaction with glycidyl methacrylate (GMA) to introduce a methacrylate terminal group [8] (Scheme 42). 

Lauryl Methacrylate (LMA)-Hethacrylic Acid MAA/MMA The macromonomer of lauryl methacrylate was prepared by using thioglycolic acid as a chain transfer agent. The Cg value was around 0,25/ 0.30. The copolymerization proceeds homogeneously in THF by using MMA as a third monomer. Some of the results are shown in Table IV and Figure 4. 

Poly(methyl methacrylate) (PMMA) macromonomers have been prepared using thioglycolic acid as a chain-transfer agent, followed by reaction with glycidyl methacrylate (82) (eq. 21). 

Here, the CTC agent acts as a chain transfer terminator but does not initiate new chain in the classical manner. Similarly, Haddleton and co-workers (129) used methyl(2-bromomethyl)acrylate in transition-metal-mediated controlled radical polymerization to replace the -halogen end group via addition-fragmentation to yield a methacrylate-based macromonomer. 

With thioglycolic acid as a chain-transfer agent, macromonomers are prepared from dimethylaminoethyl methacrylate and other acrylate and methacrylate derivatives (539). lodoacetic acid is used as the transfer agent for polystyrene macromonomers (540). 

Segmented terpolymers of poly(alkyl methacrylate)-g-poly(D-lactide)/poly(dimethylsiloxane) (PLA/PDMS) were prepared by combination of a grafting through technique (macromonomer method) and controlled/living radical polymerization such as atom transfer radical polymerization (ATRP) or reversible addition-fragmentation chain transfer polymerization. In a single-step approach, the low molecular weight methacrylate monomer (methyl methacrylate... 

Macro monomers (7, X = CH2, R = polymer chain) can react by a RAFT mechanism as shown in Scheme 16 for MAA trimef (63). The product (65) is also a macromonomef, thus chain transfer is reversible and degenerate. " " These chain transfer agents are frequently called macromonomers even when used as transfer agents. This may appear to be a misnomer, since, when used in this context, they should not behave as macromonomers. Copolymerization when it occurs is a side reaction. The most reported transfer agents of this class are the methacrylate macromonomers (e.g., 66-68) and... 

As macromonomers act as CTAs when copolymerized with methacrylic monomers, it results in a reduction in the molecular weight of the product. The macro monomer acts as a CTA by an AFCT mechanism (Figure 10), with a measurable chain transfer constant. ... 

As stated in section I, the termination mode of the particular monomer determines the number of functionalities per macromolecular chain. Most monomers undergo both unimolecular and bimolecular termination reactions. It is often observed that both respective monofunctional and bifunctional polymers are formed and well-defined functional polymers cannot be prepared. The use of allylmalonic acid diethylester in free-radical polymerization has been proposed to overcome the problems associated with the aforementioned functionality. In the presence of the allyl compound, the free-radical polymerization of monomers, regardless of their termination mode, proceeds entirely with the unimolecular termination mechanism, as shown in Scheme 9. Because allyl compounds lead to degradative chain transfer, the resulting allyl radical is quite stable due to the allyl resonance. Monofunctional polystyrene, polyvinylacetate, and poly(t-butyl methacrylate) were prepared by using this approach [33]. Subsequently, various macromonomers were derived from these polymers. 

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