Group transfer copolymerizations

P. F. W. Simon and A. H. E. Muller, Synthesis of hyperbranched and highly branched methacrylates by self-condensing group transfer copolymerization . Macromolecules, 2001,34, 6206-13. 

Tacticity measurements can be correlated with reaction mechanisms and physical properties. For example, the incorporation of an electron donor into the polymerization catalyst formulation has been found to increase isotacticity in a propylene-1-butene copolymer [123], and the distribution of propylene and 1-butene contents as a function of molecular weight varied, depending on donor type. External donors, such as dimethox-ysilane, decrease the butene content more than internal electron donors (in this case, di-n-butyl phthalate). Mechanisms of new polymerization reactions, such as the group-transfer copolymerization of methyl methacrylate and lauryl methacrylate, can be elucidated by comparing NMR-derived structural details [124]. The presence of unanticipated peaks in the spectrum of poly(ethylene-co-norbomene) suggest the occurrence of epimerization... 

Most of the methods for synthesizing block copolymers were described previously. Block copolymers are obtained by step copolymerization of polymers with functional end groups capable of reacting with each other (Sec. 2-13c-2). Sequential polymerization methods by living radical, anionic, cationic, and group transfer propagation were described in Secs. 3-15b-4, 5-4a, and 7-12e. The use of telechelic polymers, coupling and transformations reactions were described in Secs. 5-4b, 5-4c, and 5-4d. A few methods not previously described are considered here. 

The most efficient transfer agents are the mercaptans. Practially every —SH group is used for transfer, and does not retard polymerization [4]. Molecules with several mercaptan groups are copolymerizing cross-linking agents of a well-defined reaction mode [25]... 

After synthesis, the methacryloxy-terminated PDMS macromonomers were purified, and the macromonomers were copolymerized with methyl methacrylate using free-radical, anionic, and group transfer polymerization. Detailed descriptions of the polymerization are provided by DeSimone (1990) and Hellstern (1989). In addition to well-defined graft copolymers, there is... 

Haddleton, D. M., et al. (1997). Identifying the nature of the active species in the polymerization of methacrylates inhibition of methyl methacrylate homopolymerizations and reactivity ratios for copolymerization of methyl methacrylate/n-butyl methacrylate in classical anionic, alkyUithium/trialkylaluminum-initiated, group transfer polymerization, atom transfer radical polymerization, catalytic chain transfer, and classical free radical polymerization. Macromolecules, 30(14) 3992-3998. 

Block copolymers can be obtained by copolymerization of cycloolefins of entirely different reactivities or by applying adequate sequential addition of the monomer. They also arise from cycloolefins and vinylic monomers, including linear olefins, in the presence of Ziegler-Natta catalysts [5] [Eq. (3)] or of metathesis catalysts. In the latter case it is usual to change the reaction mechanism to Ziegler Natta [6] and group transfer polymerization [7] or from anionic-coordina-tive to metathesis polymerization [8] [Eq. (4)]. 

Block copolymers from cyclooolelins have been prepared by various experimental techniques [52]. Some interesting methods use living ROMP catalysts, which allow ready synthesis of new products having controllable structures and properties. Other methods apply cross-metathesis between unsaturated polymers and/or polyalkenamers [3], polymerization of cycloolelins in the presence of unsaturated polymers [4], polymerization of two or more cycloolelins of quite different reactivities with classical ROMP catalysts [4], and copolymerization of cycloolefins with other monomers, effected by changing the polymerization mechanism from ROMP to anionic, cationic, Ziegler Natta, and group transfer, and vice versa [6-8, 52]. 

Alternating copolymers by zwitterionic mechanism were also formed in group-transfer alternating copolymerization of 2-phenyl-1,3,2-dioxaphosphorinane (67) with trimethylsilyl 3-(acryloyloxy)propanoate. 

The reactivity ratios, which are very sensitive to the nature of the active centers, are nearly identical to those reported for conventional radical copolymerization of the same monomers but are different from those observed for anionic, group transfer, and cationic systems. " ... 

The term acrylic apphes to a family of copolymers of monomers that are polymerized by a chain growth mechanism. Most often, the mechanism of polymerization is by free radical initiation. Other mechanisms of polymerization, such as ionic and group transfer polymerization, are possible but will not be discussed in this publication. For a description of other polymerization mechanisms, polymer textbooks are available (5,6). Technically, acrylic monomers are derivatives of acrylic or methacrylic acid. These derivatives are nonfunctional esters (methyl methacrylate, butyl acrylate, etc.), amides (acrylamide), nitrile (acrylonitrile), and esters that contain functional groups (hydroxyethyl acrylate, glycidyl methacrylate, dimethylaminoethyl acrylate). Other monomers that are not acryhc derivatives are often included as components of acryhc resins because they are readily copolymerized with the acryhc derivatives. Styrene is often used in significant quantities in acryhc copolymers. 

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