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Propagation cyclopolymerization

Diene monomers with suitably disposed double bonds may undergo intramolecular ring-closure in competition with propagation (Scheme 4.12). The term cyclopolymcrization was coined to cover such systems. Many systems which give cyclopolymerization to the exclusion of normal propagation and crosslinking are now known. The subject is reviewed in a series of works by Butler.98 102... [Pg.185]

Propagation in cyclopolymerization may be substantially faster than for analogous monoene monomers.15" The various theories put forward to account for this observation are summarized in Butler s review.98 A recent theoretical study by Ttiziin et al.u3 looks at the effects of substituents on the rate of the cyclization step. [Pg.191]

Geometric considerations would seem to dictate that 1,4- and 1,5-dicncs should not undergo cyclopolymerization readily. However, in the case of 1,4-dienes, a 5-hexenyl system is formed after one propagation step. Cyclization via 1,5-backbiling generates a second 5-hexenyl system. Homopolymerization of divinyl ether (22) is thought to involve such a bicyclization. The polymer contains a mixture of structures including that formed by the pathway shown in Scheme 4.18. [Pg.192]

Diallyl monomers find significant use in cyclopolymerization (Section 4.4.1). Transfer to monomer is of greater importance in polymerizations of allyl than it is in diallyl monomers.184 This might, in part, reflect differences in the nature of the propagating species [e.g. a secondary alkyl (115) v.v a primary alkyl radical (116)]. Electronic factors may also play a role,185... [Pg.319]

To explain the formation of non-crosslinked polymers from the diallyl quaternary ammonium system, Butler and Angelo proposed a chain growth mechanism which involved a series of intra- and inter-molecular propagation steps (15). This type of polymerization was subsequently shown to occur in a wide variety of symmetrical diene systems which cyclize to form five or six-membered ring structures. This mode of propagation of a non-conjugated diene with subsequent ring formation was later called cyclopolymerization. [Pg.128]

Recent advances in the development of well-defined homogeneous metallocene-type catalysts have facilitated mechanistic studies of the processes involved in initiation, propagation, and chain transfer reactions occurring in olefins coordi-native polyaddition. As a result, end-functional polyolefin chains have been made available [103].For instance, Waymouth et al.have reported about the formation of hydroxy-terminated poly(methylene-l,3-cyclopentane) (PMCP-OH) via selective chain transfer to the aluminum atoms of methylaluminoxane (MAO) in the cyclopolymerization of 1,5-hexadiene catalyzed by di(pentameth-ylcyclopentadienyl) zirconium dichloride (Scheme 37). Subsequent equimolar reaction of the hydroxyl extremity with AlEt3 afforded an aluminum alkoxide macroinitiator for the coordinative ROP of sCL and consecutively a novel po-ly(MCP-b-CL) block copolymer [104]. The diblock structure of the copolymer... [Pg.44]

The importance of intramolecular cyclization was emphasized when Butler and coworkers found that the radical polymerization of N, N, N, /V-diallyldimethylammonium chloride (DADMAC) gave soluble, uncrosslinked polymers with little or no unsaturation (Eq. 6-101) [Butler and Angelo, 1957 Butler and Ingley, 1951 Wandrey et al., 1999]. There is a very low tendency for radical IV to propagate intermolecularly and undergo crosslinking. The predominant reaction is intramolecular cyclization, and the product is a linear product with cyclic structures in the backbone. The reaction is referred to as alternating intra/intermolecular polymerization or cyclopolymerization. [Pg.525]

The reason these so-called cyclopolymerization reactions occur is not known with certainty. Perhaps the best explanation that seems to fit most of the experimental results is that the two alkenic groups are associated in the ground state. Intramolecular cyclopolymerization is thus favored over intermolecular polymerization even before attack by a radical, and the overall cyclization process, from attack by the radical to formation of the propagating cyclic radical, is concerted. [Pg.293]

Following the findings of Butler et al. [5], that diallyl quaternary ammonium halides form water soluble polymers, the structures of polymers produced via a ring-closing mechanism have been the subject of intensive research. A cyclic structure was elucidated and the mechanism was defined as an alternating intra-intermolecular chain propagation, later termed cyclopolymerization [3]. Based on the general scheme presented in Fig. 6 the chemical structure of PDADMAC is determined by... [Pg.132]

Kossler et al. (349] described the cyclopolymerization of isoprene in the presence of EtAlCl2. They postulate simple diene addition to the propagating ladder chain... [Pg.351]

The hypotheses considered so far share the attempt of explaining the ease of formation of the ring structures in cyclopolymerization taking into account only the relative ability of the double bond pendant from the active chain end, and of the double bonds of an unreacted monomer molecule, to reach the reaction site. No attention is paid to the fact that the intramolecular and intermolecular chain propagation reactions are basically different, in the sense that the former involves an entropy decrease due to the loss of some rotational degrees of freedom at the end of the active chain, whereas the latter involves an entropy decrease... [Pg.17]

Table V - Calculated A AS and experimental AAS for the chain propagation reactions in the free radical cyclopolymerization of some monomers. Table V - Calculated A AS and experimental AAS for the chain propagation reactions in the free radical cyclopolymerization of some monomers.
The radical polymerization of acrylic anhydride(AA) as a typical 1,6-diene has been investigated in detail in terms of cyclopolymerization. Thus, in 1958 Crawshaw and Butler(31) and Jones(32) have independently demonstrated that AA could be polymerized in solution by an alternating intramolecular-intermolecular chain propagation or cyclopolymerization, leading to the formation of saturated, linear polymers consisting exclusively of six-membered ring anhydride structure. Later, Mercier and Smets(33)... [Pg.35]

Other workers have reported the homopolymerization of certain substituted bismaleimides in solution by successive 2+2 cycloaddition reactions, and they have appropriately defined this type of process as a true photopolymerization i.e. a polymerization in which every chain-propagating step involves a photochemical reaction. Another such example is the solid-phase 2+2 cyclopolymerization of divinyl monomers.— By contrast, the polymers described above result from a combination of photocycloadditions and Diels-Alder cycloadditions. [Pg.75]

Propagation reactions of unconjugated dienes can proceed by an intra-intermolecular process. This usually results in ring formation or in cyclopolymerization. It can be illustrated as follows ... [Pg.51]

The authors proposed a mechanism for the radical polymerization of VPA based on the analysis of and NMR spectra of the polymer. They assumed that the polymerization occurs via cyclopolymerization of the vinylphosphonic anhydride, which may be present in equilibrium with the free acid in water at the polymerization temperature (Scheme 4.9). The formation of anhydrides of phosphonic acids in water at higher temperature is already known.By intramolecular propagation can be formed the six-membered ring, generating the pattern of head-to-tail addition and formation of a... [Pg.72]

The homopolymerization of aliphatic diisocyanates across their C=N bond is limited to aliphatic 1,2- and 1,3-diisocyanates and cyclohexane-1,2 and 1,3-diisocyanate (3). These diisocyanates are cyclopolymerized by an alternating, intermolecular-intramolecular propagation mechanism, using sodium cyanide as the catalyst. The cyclopolymers obtained in this manner are listed in Table 5. [Pg.4151]


See other pages where Propagation cyclopolymerization is mentioned: [Pg.5]    [Pg.612]    [Pg.238]    [Pg.350]    [Pg.556]    [Pg.53]    [Pg.56]    [Pg.350]    [Pg.12]    [Pg.16]    [Pg.34]    [Pg.35]    [Pg.38]    [Pg.41]    [Pg.144]    [Pg.205]    [Pg.464]    [Pg.5]    [Pg.185]    [Pg.191]    [Pg.44]    [Pg.73]    [Pg.245]    [Pg.235]    [Pg.97]    [Pg.20]   


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Cyclopolymerization

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