Cyclocopolymerization

In this section wc consider systems where the radical formed by propagation can eyclizc to yield a new propagating radical. Certain 1,4-dicncs undergo cyclocopolymerization with suitable olefins. For example, divinyl ether and MAH are proposed to undergo alternating copolymerization as illustrated in Scheme 4.19.167 These cyclo-copolymerizations can he quantitative only for the case of a strictly alternating copolymer. This can be achieved with certain electron donor-electron acceptor pairs, for example divinyl ether-maleic anhydride. 

The reaction proceeds at the stage of pseudo-cyclocopolymerization involving complex formation between the growing macroradical and the monomer which is responsible for the alternation of monomer units along the macromolecular chain ... 

Cyclopolymerization of Nonconjugated Dienes. Cyclopolymerization is an addition polymerization that leads to introduction of cyclic structures into the main chain of the polymer. Nonconjugated dienes are the most deeply studied monomers for cyclopolymerization and for cyclocopolymerizations with alkene monomers 66 In general, (substituted and unsubstituted) dienes with double bonds that are linked by less than two or more than four atoms cannot undergo efficient cyclization and result in crosslinked materials.12 In fact, efficient cyclopolymerization processes have been described, for instance, for a,oo-dienes like 1,5-hexadiene, 2-methyl-l,5-hexadiene, 1,6-heptadiene, and 1,7-octadiene,67 73 which lead to formation of homopolymers and copolymers containing methylene-1,3-cycloalkane units. 

Cyclocopolymerization is cyclopolymerization of a pair of monomers [Butler, 2000]. An example is the generation of pyran rings by copolymerization between maleic anhydride and the two double bonds of divinyl ether ... 

Butler GB (1992) Cyclopolymerization and cyclocopolymerization, Marcel Dekker, New York... 

There is only one example that fits into this section and it uses a spectacular way to form the crown ether in the polymer that is worth noting (Scheme 22). In contrast to all other procedures that use crown ethers pre-formed in the monomers, this example by Percec forms the crown ether [13]crown-4 during the polymerization reaction [59]. Cationic cyclocopolymerization of l,2-bis(2-ethenyloxyethoxy)ben-zene 37 with the mesogenic cyano biphenyl unit 38 gave copolymer 39 with a 1 1 ratio of 37 38 displaying a smectic phase. 

When a,( -dienes are used as the substrate cyclocopolymerization proceeds if the two double bonds are separated by an adequate distance. Thus, whereas for 1,7-oc-tadiene or l,6-heptadiene-4-ol ring formation was not observed, cyclocopolymerization occurred in fhe case of 1,5-hexadiene and 1,4-pentadiene [128]. Using the (ll,S)-Binaphos catalytic system 66 wifh both substrates results in a regiospecific (Scheme 8.21) but not diastereospecific reaction, since bofh cis- and trons-disubsti-tuted rings are formed at around a 1 1 molar ratio [136]. 

In addition to propylene, other nonconjugated olefins have been copolymerized with CO using enantiopure palladium catalysts. Allylbenzene, 1-butene, 1-heptene, 4-methyl-l-pentene, and cis-2-butene [84,85] as well as hydroxy- and carboxylic acid-functionalized monomers [87] have been polymerized to give optically active polymers. Waymouth, Takaya and Nozaki have recently reported the enantioselective cyclocopolymerization of 1,5-hexadiene and CO [88,89]. 

Studies on the properties of the derived copolymers can thus be helpful in understanding structure-property relationships of copolymers. Furthermore, since nuclear magnetic resonance can be used to characterize the structures of S-MMA copolymers ( 7,8), structural studies on the derived copolymers can provide information about cyclocopolymerization processes. For these reasons, we have developed a procedure for converting styrene-methacrylic anhydride copolymers into styrene-methyl methacrylate copolymers, have developed methods for calculating structural aspects of the derived S-MMA copolymers and, have investigated the 1H-NMR spectra of S/MMA copolymers derived from styrene-methacrylic anhydride copolymers. 

Several theoretical treatments of cyclocopolymerization have been reported previously (8-11). These relate the compositions of cyclocopolymers to monomer feed concentrations and appropriate rate constant ratios. To our knowledge, procedures for calculating sequence distributions for either cyclocopolymers or for copolymers derived from them have not been developed previously. In this paper we show that procedures for calculating sequence distributions of terpolymers can be used for this purpose. Most previous studies on styrene-methacrylic anhydride copolymerizations (10,12,13) have shown that a high proportion of the methacrylic anhydride units are cyclized in these polymers. Cyclization constants were determined from monomer feed concentrations and the content of uncyclized methacrylic anhydride units in the copolymers. These studies invoked simplifying assumptions that enabled the conventional copolymer equation to be used in determinations of monomer reactivity ratios for this copolymerization system. 

Synthesis of Macrocyclic Ring-Containing Polymers Via Cyclopolymerization and Cyclocopolymerization... 

It was the purpose of this investigation to synthesize suitable monomers which could conceivably undergo cyclopolymerization or cyclocopolymerization to lead to large ring-containing polymers. A more specific purpose was to synthesize polymers which would contain ring structures in the polymer backbone which may simulate the properties of the crown ethers (2). Thus a variety of monomers, including l,2-bis(ethenyloxy)benzene, l,2-bis(eth-enyloxy)-4-methylbenzene, 1,2-bis(2-ethenyloxyethoxy)benzene and l,t-butyl-3,4-bis(ethenyloxyethoxy)benzene, as well as model compounds 2,3-dimethyl-1,4-benzodioxane and cis- and trans-2,4-dimethyl -1,5-benzodioxepane, were synthesized and studied. This paper deals with cyclopolymerization studies of the four monomers. 

Monomer 11, a 1,13-diene, undergoes cyclocopolymerization with MA to yield a linear, soluble cyclocopolymer [17] of reasonably high molecular weight, 13,100 (see Table VIII). This cyclocopolymer represents the first example of a structure which includes both monomers in a ring having greater than nine members. All spectral evidence supports a 15-membered ring structure as illustrated in Eq. 9. The polymerization conditions used are summarized in Table VIII. 

Cyclocopolymerization with maleic anhydride and subsequent alcoholysis... 

Scheme 2-1 Schematic representation of the asymmetric cyclocopolymerization of monomer 1 with methyl methacrylate [4].

It is unlikely that the chiral configurations of the linear portions of the chains contribute to the asymmetry of the cavity since no asymmetric cyclocopolymerization is possible for the template monomer 7. With other types of template monomers, though, such contributions of backbone chiral portions of the polymer might be expected (see Section 2.2). 

Butler, G. 1992. Cyclopolymerization and Cyclocopolymerization. New York Marcel Dekker. Rzayev, Z. M., Mamedova, S. G., Yusifov, G. A., and Rustamov, R B. 1988. Complex radical copolymerization of di-n-butyl starmyl butylstannyl dimethacrylate with maleic anhydride. lournal of Polymer Science. Part A Polymer Chemistru 26 849-857. 

Rzaev, Z. M. O. and Salamova, U. 1997. Complex-radical cyclocopolymerization of aUyl-a-(N-maleimido)-acetate with styrene and maleic anhydride. Macromolecular Chemistry and Physics 198 2475-2487. 

MECHANISTIC CONSIDERATIONS OF CYCLOCOPOLYMERIZATION AND SOME PROPERTIES OF TYRAN COPOLYMER... 

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