Poly living anionic polymer

Reactions of Living Anionic Polymers With Living Poly THF... 

Anionic polymerization frequently has been used to prepare well-defined living polymers such as polystyrene, poly(a-methylstyrene), polydienes, which may be transformed by two methods into block copolymers with cationically polymerizable monomers. When a living anionic polymer is mixed with a stoichiometric amount of a living cationic polymer the cationic and anionic species may couple. For example, anionic living polystyrene (St) or poly (a-methylstyrene) (MSt) were reacted with living cationic polytetrahydrofuran (THF). In the latter system the coupling efficiency was low, probably because of proton or hydride transfer 132) ... 

The hydrosilylation reaction has also been employed in the reverse way. A poly(dimethyl-siloxane) backbone exhibiting a number of silane (Si-H) functions is reacted with a polystyrene or a poly(methyl methacrylate) fitted at its chain end with allyloxy groups. The latter species can be obtained readily by reacting a living anionic polymer first with oxirane and then with allyl bromide. The hydrosilylation reaction yields poly(dimethylsiloxane- ra/t-styrene) or poly(dimethylsiloxane-graft-mQthyl methacrylate), which have been characterized as such. They exhibit typical behavior of thermoplastic elastomers over a rather broad range of compositions. ... 

Grafting of other living anionic polymers has also been reported and it was found that the maximum number of grafted chains depends on the nucleophiUdty of the terminal carbanion [51]. This behavior is not unexpected as the reactivity of the fuUerene decreases with each addition. For ejample, for the carbanions isoprenyl and 1,3-cyclohexadienyl, which have about the same reactivity as the carbanion styryl, a maximum of six polyisoprene (PI) or poly(l,3reaction with, respectively, polyisoprenyUith-ium (PILi) [51, 70] and poly 1,3-cyclohexadienyllithium [71] in a non-polar solvent Some other factors like steric effects or stability of the carbanion may interfere in this latter case, and a recent publication concluded that only four arms are attached, based on a ratio = 4.37 [72]. However, these molar masses were deter-... 

This saturation of the C o already attached to one or x chains (x < 6) by a living anionic polymer can be used in many cases. For example, respectively, five, four and two additional PS chains have been grafted on poly(methyl methacrylate) C,so, (PS)2Cbo and (PS)4Cbo prepared by atom transfer radical addition. 

A radical initiator based on the oxidation adduct of an alkyl-9-BBN (47) has been utilized to produce poly(methylmethacrylate) (48) (Fig. 31) from methylmethacrylate monomer by a living anionic polymerization route that does not require the mediation of a metal catalyst. The relatively broad molecular weight distribution (PDI = (MJM ) 2.5) compared with those in living anionic polymerization cases was attributed to the slow initiation of the polymerization.69 A similar radical polymerization route aided by 47 was utilized in the synthesis of functionalized syndiotactic polystyrene (PS) polymers by the copolymerization of styrene.70 The borane groups in the functionalized syndiotactic polystyrenes were transformed into free-radical initiators for the in situ free-radical graft polymerization to prepare s-PS-g-PMMA graft copolymers. 

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. 

Based on this approach Schouten et al. [254] attached a silane-functionalized styrene derivative (4-trichlorosilylstyrene) on colloidal silica as well as on flat glass substrates and silicon wafers and added a five-fold excess BuLi to create the active surface sites for LASIP in toluene as the solvent. With THF as the reaction medium, the BuLi was found to react not only with the vinyl groups of the styrene derivative but also with the siloxane groups of the substrate. It was found that even under optimized reaction conditions, LASIP from silica and especially from flat surfaces could not be performed in a reproducible manner. Free silanol groups at the surface as well as the ever-present impurities adsorbed on silica, impaired the anionic polymerization. However, living anionic polymerization behavior was found and the polymer load increased linearly with the polymerization time. Polystyrene homopolymer brushes as well as block copolymers of poly(styrene-f)lock-MMA) and poly(styrene-block-isoprene) could be prepared. 

The simplest examples of this class are the quenching living cationic polymers with living anionic or nucleophilic polymers. Namely, living poly(vi-nyl ethers) derived from the HI/ZnI2 system are allowed to react with living anionic polystyrene with the lithium counterion [115], poly(methyl methacrylate) with a silyl ketene acetal terminal by group transfer po-... 

In a reversed way, cationically prepared end-functional polymers are used to quench other living polymers. For example, living anionic polystyrene may be terminated by polyisobutenes with silylchloride terminals [119,120] or epoxide ends [121,122] and by poly(vinyl ethers) with acetal terminals [123], The former case is reported to give H-shaped, tetraarmed block copolymers. 

The anionic polymerization of masked disilenes proceeds via living anions, and therefore block copolymerization with a conventional vinyl monomer is possible. Recently, interesting hydrophobic block copolymer of PMHS with poly(2-hydroxyethyl methacrylate) (PHEMA) and poly(methacrylic acid) (PMMA) have been prepared (Scheme 11). These polymers can be self-assembled and are transformed into polysilane micelles, shell cross-linked micelles (SCM), and nanometer-sized hollow particles. ... 

The reverse strategy consists of coupling a living polymer onto a second polymer that contains pendant electrophiles. This approach was used by Pitsikalis and coworkers, who synthesized PS-grq/f-PtBuMA (86) by treatment of poly(p-bromomethylstyrene) (84) with living anionic PtBuMA (85) (equation 66) °. The graft copolymer was purified by selective precipitation with hot methanol. Indeed, the graft copolymer was insoluble in this solvent, whereas the PtBuMA arms were soluble . ... 

Examples of organometallic polymers containing both phosphorus atoms and transition metals in the backbone include polyferrocenylphosphines 8 (and the corresponding phosphine sulfides 9), which are accessible via the thermal ROP of phosphorus-bridged [1] ferrocenophanes [16,17]. Polymers of this type have been previously prepared by condensation routes and the catalytic potential of some of their transition metal derivatives has already been noted [18]. Living anionic ROP of phosphorus-bridged [l]ferrocenophanes has recently been demonstrated and provides a route to block copolymers such as 10 (PI = poly-isoprene) [19] ... 

We have also observed that, at elevated temperature (50°C), DPE could effectively cap the living anionic polyferrocenylsilane directly.30 Therefore, the addition of DMSB to pump up the activity of PFS anionic chain ends can potentially be omitted, but the yield of the isolated PFS- -PMMA is significantly reduced.31 The living DPE-capped PFS polymers also can react with chloromethyl functionalities of poly(styrene-co-chloromethylstyrene) (PS-co-PCMS), leading to the first PS-g-PFS graft copolymers (see Scheme 3.10).30... 

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