Poly anionic initiated

Polyacetaldehyde, a mbbery polymer with an acetal stmcture, was first discovered in 1936 (49,50). More recentiy, it has been shown that a white, nontacky, and highly elastic polymer can be formed by cationic polymerization using BF in Hquid ethylene (51). At temperatures below —75° C using anionic initiators, such as metal alkyls in a hydrocarbon solvent, a crystalline, isotactic polymer is obtained (52). This polymer also has an acetal [poly(oxymethylene)] stmcture. Molecular weights in the range of 800,000—3,000,000 have been reported. Polyacetaldehyde is unstable and depolymerizes in a few days to acetaldehyde. The methods used for stabilizing polyformaldehyde have not been successful with poly acetaldehyde and the polymer has no practical significance (see Acetalresins). 

The addition of living poly(styrene) to AIBN leads finally, especially for high coupling efficiencies, to the elimination of one nitrile group [72]. More recently, Ren et al. [73] have used bis(2-chloroethyl)2,2 -azodiisobu-tyrate (see scheme 19) to terminate anionically initiated poly(butadiene) chains. Since the azo transfer agent possesses two functional groups (Cl) that are able to termi-... 

Anionic polymerization of ethylene oxide by living carbanions of polystyrene was first carried out by Szwarc295. A limited number of methods have been reported in the preparation of A-B and A-B-A copolymers in which B was polystyrene and A was poly(oxyethylene)296-298. The actual procedure was to allow ethylene oxide to polymerize in a vacuum system at 70 °C with the polystyrene anion initiated with cumyl potassium in THF299. The yields of pure block copolymers are usually limited to about 80% because homopolymers are formed300. ... 

Figure I indicates the approach used to synthesize poly(oxyethylene)-b-poly(pivalolactone) telechelomers. An acetal capped anionic initiator, X (13) polymerizes ethylene oxide (EO) to give 2> a potassium alkoxide of a masked polyether, and this "new" initiator is to be used to polymerize pivalolactone (PVL). Since potassium alkoxides are strong nucleophiles, they can randomly attack at both the carbonyl carbon and the 3-methylene carbon in lactones, (Figure 2) such a random attack would result in a pivalolactone segment containing irregularities. Lenz (15), and Hall (16), and Beaman (17) have investigated PVL polymerization and have shown that the less nucleophilic carboxylate anion is preferable in polymerizing PVL smoothly. The weaker carboxylate anion will attack only at the methylene...

Rings Ha, b and c were found to polymerize in bulk with DMSO as an activator and various catalytic amounts of the anionic initiator, potassium poly(dimethylsiloxane)diolate (for polymerization of Ila and b, see (22)). The latter is well known as an efficient initiator of cyclosiloxane polymerization. Thus... 

Hyperbranched polymers have also been prepared via living anionic polymerization. The reaction of poly(4-methylstyrene)-fo-polystyrene lithium with a small amount of divinylbenzene, afforded a star-block copolymer with 4-methylstyrene units in the periphery [200]. The methyl groups were subsequently metalated with s-butyllithium/tetramethylethylenediamine. The produced anions initiated the polymerization of a-methylstyrene (Scheme 109). From the radius of gyration to hydrodynamic radius ratio (0.96-1.1) it was concluded that the second generation polymers behaved like soft spheres. 

A polymerization of a bulky methacrylate ester (e.g. trityl methacrylate) using an optically active anionic initiator can give an isotactic polymer, poly 1-methyl-1-[(trityloxy)carbonyl]ethylene of high optical activity owing to the formation of helical polymer molecules with units of predominantly one chirality sense. 

The synthesis of extremely high molecular weight star polymers has been achieved by another method. First divlnyl-benzene is reacted at very low concentration with an anionic Initiator (sec. BuLi) to yield a suspension of poly-DVB nodules fitted with numerous initiating sites. Then styrene Is added, and each Initiating site should give yield to a branch. However, the polydispersity of the samples obtained is very high. 

TABLE 1. Effect of lithium thioacetal anionic initiators on poly(styrene-co-butadiene) properties. 

Neither the first nor the second step in Scheme (42) has been directly observed, but it has conclusively been shown by studies of the number of the end groups in poly-THF initiated with triflic anhydride that one molecule of the anhydride gives two growing ends of the cationic and/or ester structure in one macxomolecufe. These structures are interconvertible. Recently, Smith separated and characterized two intmnediate products tetramethylene-bis-triflate, resulting from the attack of the anion on the o-methylene carbon atom in salt 42a, and the corresponding dicationic trimer... 

Additional work has shown that it is also possible to induce the ROP of [IJsilaferrocenophanes in solution at ambient temperatures by using anionic initiators (55). For example, the reaction of 13 (R = R = Me) with approximately 10 mol % ferrocenyllithium (FcLi) followed by hydrolytic workup yields a moderate molecular weight poly(ferrocenylsilane) 15 (R = R = Me) with A/ 9500 and Mn 8000. With approximately equimolar... 

Nylon block copolymers were previously synthesized from the anionic polymerization of caprolactam in the presence of polyurethane prepolymers. (11) The prepolymers, prepared from the reaction of diisocyanates with polyether glycols, contained Isocyanate end groups which initiated caprolactam polymerization. Sodium caprolactam was used to catalyze the reaction. This copolymer system is the basis for some current areas of nylon 6 RIM research. (12) NYRIM nylon block copolymers are formed from stoichiometric mixtures of polymeric polyols and caprolactam using poly acyllactam initiation which was described previously. The reactions are as follows ... 

The polymerization of butyl isocyanate and other achiral monomers (74) using optically active anionic initiators 75—81 affords optically active polymers.152 156 The poly-74a (Mn = 9000) obtained using 75 exhibits [a]435 +4 1 6°. The optical activity of the polymers arises from the helical part extending from the chain terminal bearing the chiral group originat-... 

We have been concerned with the precision and accuracy of NMR data of polymers since we first started NMR studies on polymers.1-4 Using continuous-wave (CW) spectrometers, the effects of measurement conditions including temperature, sample concentration and radiofrequency (rf) field strength, were examined using several polymer and copolymer samples. Since our research group have been deeply involved in stereospecific polymerization of methacrylates, one of the main concerns about NMR measurement was the precision of tacticity determination by NMR. The errors in determining the tacticity of poly(methyl methacrylate) (PMMA) and those in the results of polymerization of methyl methacrylate (MMA) by radical and anionic initiators were examined and found to be satisfactorily small.4 Although there... 

A number of poly(dimethylsiloxane) and poly(ferrocenylsilane) copolymers have been prepared using thermal, anionic, and transition metal catalyzed ROP.97,98,121,124-131 Manners et al.132 described the ring-opening of [l]thia- and [l]selenaferrocenophanes using anionic initiators. Electrochemical studies of poly(ferrocenyl sulfide)s prepared by these methods elicited two reversible oxidation processes, indicating that strong Fe-Fe interactions exist in the polymers. 

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