Polymerization exclusive

The presence of halogen atoms appears to exert little, if any, effect on catalyst activity, but it can influence the course of the metathesis reaction. Vinylic halides are unreactive, as exemplified by the ring-opening polymerization of l-chloro-l,5-cyclooctadiene, which afforded a perfectly alternating copolymer of butadiene and chloroprene (7/2) via polymerization exclusively through the unsubstituted double bond. 

Strongly electrophilic or nucleophilic monomers will polymerize exclusively by anionic or cationic mechanisms. However, monomers that are neither strongly electrophilic nor nucleophilic generally polymerize by ionic and free radical processes. The contrast between anionic, cationic, and free radical methods of addition copolymerization is clearly illustrated by the results of copolymerization utilizing the three modes of initiation (Figure 7.1). Such results illustrate the variations of reactivities and copolymer composition that are possible from employing the different initiation modes. The free radical tie-line resides near the middle since free radical polymerizations are less dependent on the electronic nature of the comonomers relative to the ionic modes of chain propagation. 

The dependence of the conversion and polymer-composition on the reaction time is shown in Figure 1 for the copolymerization of St with AA at f = 0.4, pH 9.0 and 70°C. The polymerization course was found to consist of three stages At first AA polymerizes preferentially but the preference decreases rapidly with increasing conversion (0 - 1.0 hr) St polymerizes exclusively (1.0 - 1.5 hrs) and again AA polymerizes preferentially (1.5 hrs - end). A similar copolymerization mode was observed in an aqueous copolym-... 

Cyclic acetals polymerize exclusively by cationic mechanism it should be noted, however, that polyoxymethylene may be obtained also by anionic polymerization of formaldehyde. Both processes are used in industry. 

The lack of specificity is thus related to similar ring strain of both fused rings. 1,6-Anhydrosugars, in contrast, polymerize exclusively with opening of 5-membered ring because the 6-membered ring, being in more favorable conformation, is essentially strainless [153]. 

The polymerization of aldehydes is initiated by ionic initiators and the polymerization proceeds by ionic propagation. No radical polymerization of aldehydes has been documented yet. In the case of anionic polymerizations the growing ion is an alkoxide ion. The cationic polymerization has as the propagating species an oxonium ion. Most recent experimental results have shown that haloaldehydes, such as chloral polymerize exclusively by an anionic mechanism. 

Since polymerization in inclusion compounds is restricted to only a few monomers with small substituent groups, it seemed worthwhile to search for other systems where butadiene derivatives are able to polymerize exclusively according to a 1,4-addition mechanism. In the following, our recent investigations (JJl-ii.) on the polymerization behavior of 1,4-disubstituted butadienes in various layered structures will be reviewed. Polymerization has been investigated... 

Oxetanes, 4-membered cyclic ethers, polymerize exclusively by cationic mechanism 1 3), although coordinative anionic homopolymerization and copolymerization with C02 was claimed 4 5) for the unsubstituted oxetane. 

It was demonstrated that DBO polymerizes with Lewis acids as initiators. BF3 OEt SbCl5 and PFS were used and the best results were obtained with PFS however, no systematic studies of the kinetics of polymerization or molecular weights have been published yet. The stereochemistry of DBO polymerization was investigated in detail, and it was shown that DBO polymerizes exclusively through opening of the 5-membered ring ... 

The above listed monomers polymerize exclusively by cationic ring-opening polymerization. Polymerization of cyclic imino ethers has been reviewed by Saegusa1,4,). In this section we follow mostly the conclusions of the Kyoto group summarizing the applied synthetic methods. Subsequently we describe initiating systems, peculiarities of chain growth, side reactions, copolymerization systems and possible applications, in this order. 

Pentafluorovinylcyclopropane (34, Scheme 4.24) undergoes facile ring-opening polymerization exclusively as shown iranx double bond). ... 

Concerning grafting techniques, in GTP acrylates are much more reactive than methacrylates. Thus 2-methacryloxyethyl acrylate in the presence of ZnBr2 is polymerized exclusively to a polymer with pendant methacrylate groups capable of radical and GTP grafting from polymerizations [73]. Irradiation teehniques have often been employed... 

The stereochemistry of the ring-opening polymerization of 1, -bridged bicyclic ethers derived from cyclohexane have been studied. The endo- and exo-2-methyl-T oxabicyclo[2.2.l]heptane (5) were found to polymerize exclusively through nucleophilic attack at the bridge head carbon in the Sj 2 propagation step leading... 

Thus, in the cationic process the (usually) strained onium ion is attacked, whereas in the anionic polymerization the neutral cyclic species is attacked, which is less prone to ring opening. There are a few monomers that are able to polymerize exclusively by cationic mechanism (cyclic amines, phospha-zenes) and all monomers polymerizing anionically are also able to polymerize cationically (Table 10). 

Among cyclic ethers, three-membered ring epoxides - with the exception of some four-membered ring oxetanes - are the only ones that can be polymerized by an anionic or a related nucleophilic polymerization mechanism. Larger cyclic ethers polymerize exclusively by a cationic or electrophilic ring-opening mechanism. 

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