Halides terminal

The block copolymer produced by Bamford s metal carbonyl/halide-terminated polymers photoinitiating systems are, therefore, more versatile than those based on anionic polymerization, since a wide range of monomers may be incorporated into the block. Although the mean block length is controllable through the parameters that normally determine the mean kinetic chain length in a free radical polymerization, the molecular weight distributions are, of course, much broader than with ionic polymerization and the polymers are, therefore, less well defined,... 

Controlled synthesis of ABA type poly(2-ethyl-2-oxazoline)-b-PDMS block copolymers was obtained by the melt reaction of a,c -benzyl halide terminated PDMS oligomers and the oxazoline monomer 291 as shown in Reaction Scheme XX. 

A. Cyclizations of halides terminated by hydrogen atom abstraction or halogen atom transfer 1a... 

Coupling of GTP living polymers with halide-terminating agents to form star polymers has been achieved [Hertler, 1996 Webster and Sogah, 1989]. Star polymers are also synthesized by using polyfunctional initiators or by copolymerization with dimethacrylate monomers. 

N. Martinez-Castro, D.L. Morgan, and R.F. Storey, Primary halide-terminated polyisobutylene End-quenching of quasiliving carbocationic polymerization with N-(ru-haIoalkyI)pyrroIe, Macromolecules, 42(14) 4963-4971, July 2009. 

Ionic liquids have been a popular topic of interest in 2002 and a review of the applications of these solvents in organic synthesis has been published (02ACA75>. New, densely functionalized fluoroalkyl-substituted imidazolium ionic liquids have been reported <02TL9497>. An ultrasound-assisted preparation of a series of ambient-temperature ionic liquids, l-alkyl-3-methylimidazolium halides, which proceeds via efficient reactions of 1-methyl imidazole with alkyl halides/terminal dihalides under solvent-free conditions, has been described <02OL3161>. New hydrophilic poly(ethyleneglycol)-ionic liquids have been synthesized from... 

Because acetylide anions are strong nucleophiles, the mechanism of nucleophilic substitution is S 2, and thus the reaction is fastest with CH3X and 1° alkyl halides. Terminal alkynes (Reaction [1]) or internal alkynes (Reaction [2]) can be prepared depending on the identity of the acetylide anion. 

MALDI spectrum of a hydroxyl functional polymer prepared by GTP the level of the impurity is easily seen and the success of this reaction clearly observed. However, this is not a universally applicable technique. Perhaps the most topical living polymerisation at present is transition metal mediated radical polymerization. This typically gives a polymer with a tertiary halide terminal group. This group, as has nitroxide, has been found to be very labile in the mass spectrometer leading to fragmentation. 

Even at threshold laser intensity for tertiary halide terminated polymers there is evidence for cleavage of the carbon halogen bond. The peak at 1045.7... 

Two related procedures have been developed to effect this transformation. Both Involve the Initial synthesis of mono- or dlfunctlonal living anionic polymers of styrene, butadiene, or block copolymers of both. They are then reacted via Grlgnard Intermediates (7 ) with either excess bromine or with excess m-xylylyl dlbromlde (8-10) to yield polymers with reactive halide terminal groups (benzyllc or allyllc depending upon the polymer and terminating agent). The reactions for polystyrene are shown In equations 2 and 3. 

Higher alkynes can be synthesized fhom acetylene by reacting with NaNH followed by treatment with the appropriate alkyl halide.Terminal alkynes can be deprotonated using strong bases such as sodium amide. Hydroxides or alkoxides are not strong enough to deprotonate an acetylenic hydrogen. 

The Inifer process developed by Kennedy can be used to functionalize vinyl monomers via a cationic route by initiating a polymerization with an alkyl halide-boron trichloride mixture R BCl. The termination by transfer to an alkyl halide leaves a halide-terminated polymer. This can be transformed to a hydroxyl terminal unit via the sequence (1) dehydrohalogenation, (2) hydroboration, and (3) oxidation and hydrolysis (Equation 5.24). These co-functional blocks may be coupled to form diblock copolymers using standard reaction techniques, e.g., diisocyanate will couple cohydroxy and co-amine blocks together. Direct reactions can also occur, and co-acid chlorides combine readily with co-hydroxy units. 

Since there is no known "living" carbenium ion system, block copolymer synthesis by sequential addition is unknown. Block copolymers have, however, been produced by cationic polymerization. The preparation is based on Kennedy s discovery that certain alkyl-aluminum compounds (Et2AlCl for example) will initiate the cationic polymerization of certain active vinyl monomers in the presence of alkyl halides. By this technique, a halide terminated polymer can, in the presence of Et2AlCl, initiate polymerization of a second monomer to form a block copolymer. 

Sharghi, H., Khalifeh, R., and Doroodmand, M. M. 2009b. Copper nanoparticles on charcoal for multicomponent catalytic synthesis of 1,2,3-triazole derivatives from benzyl halides or alkyl halides, terminal alkynes and sodium azide in water as a green solvent. Adv. Synth. Catal. 351(l-2) 207-218. 

In ATRP a transition-metal catalyst is used to reversibly activate halide-terminated dormant chains. The principal mechanism is outlined in equation 2. 

A broad variety of difunctional allylic olefins have been used for the synthesis of amino-, carboxyl-, and halide-terminated polybutadienes by means of the Grubbs catalyst I (396-398). With the same catalyst, commercially interesting hydroxy telechelic polybutadienes could be obtained by the cleavage of the acetyl end-capped polymer or the copolymer, as depicted in Figure 14 (399,400). 

As in the other polycondensation reactions, competition between linear polymerization and ring formation also occurs here and it is strongly dependent on the structure of both the dihalide and inor nic polysulfide. CycUc monosulfides are favoured when the dihalide monomer has four or five carbon atoms between the halide terminals [18]. 

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