Styryl end group

By virtue of the clear initiation mechanism, well-dehned end-functionaUzed polyethers can be synthesized. For example, use of an aluminum porphyrin having a 4-vinylphenolate ligand at the axial position as initiator for the polymerization of 1,2-epoxypropane (11, R = Me) allows formation of a tailored polyether with a polymerizable (styryl) end group (27). ... 

These macromonomers were then copol5unerized with vinyl monomers mainly by free-radical techniques (52) and also other methods as by metallocene catalysts (53) to provide graft copolymers. The reaction of polystyryllithium with p-chlorovinylbenzene at low temperatures affords macromonomers with styryl end groups (eq. 15) (54). 

Let me pass now to some problems of co-polymerization of lithium salts of living polymers. With Dr. Zdenek Laita we studied the rate of cross-over reaction converting lithium poly-styryl into 1,1-diphenyl ethylene", D end-groups in benzene(23). The stoichiometry of the reaction is... 

The introduction of vinylsilyl end groups into a polymer chain has been achieved by several techniques. Since vinylsilyl functions are sensitive to the attack by strong nucleophiles 27), it was considered appropriate to decrease the nucleophilicity of the styryl carbanions by the addition of oxirane before reacting them with either chloromethyldimethylvinylsilane or chlorodimethylvinyl silane 28a). The following structures are formed ... 

Styryl carbanions readily react with carbon dioxide 31) to yield carboxy end groups. These terminal groups are also introduced by reaction with anhydrides 19) whereas the use of oxirane 23) leads to the formation of hydroxy end groups esters and nitriles are used to introduce carbonyl functions at the chain end. These reactions can be carried out at low temperature in THF solution and proceed quantitatively if no deactivation by protons occurs. 

Diene carbanions exhibit a reactivity similar to that of styryl carbanions. Carban-ionic sites of lower reactivity can be functionalized under certain conditions32). Living polymers with alkoxide end groups exhibit the same reactivity as alcoholates with respect to proton-donating substances and activated organic halides. Protonation yields terminal hydroxy groups which are often used in the two-step macromonomer synthesis. 

CAR Carter, S., Hunt, B., and Rimmer, S., Highly branched poly(Y-isopropylacrylamide)s with imidazole end groups prepared by radical polymerization in the presence of a styryl monomer containing a dithioester group. Macromolecules, 38, 4595, 2005. 

It has been reported that poly(styryl) and poly(isoprenyl) anions underwent efficient functionalization reactions with these terminators in THF or THF/heptane (1/1, v/v) even at -78 °C. The polymers were carefully analyzed by SEC, NMR, end-group titration, and TLC-FID, indicating nearly quantitative end functionalizations (>95%). It was also reported that the resulting functionalized polymers exhibited controlled molecular weights and narrow molecular weight distributions. a,co-Difunctionalized polystyrenes were obtained using a,Q)-dianionic polystyrenes. 

Poly(oxazoline) telechelics with hydroxyl, amino, triphenylphosphonium, piperidine, pyrrole, styryl, acrylamide, acrylate, methacrylate, and butadiene end groups were successfully synthesized (377-387). Reaction of methyltosylate (MeOTs) with hisoxazohnes gives rise to the formation of his(oxazoluiium tosy-late) (387). Living polymerization of monofunctional oxazohnes having propagating species at hoth ends can he initiated by the addition of the monomer. 

---