Ring opening polymerization living anionic

Figure 8 Main mechanistic transformation reactions in living and/or controlled polymerization methods. ATRP, atom transfer radical polymerization RAFT, reversible addition-fragmentation chain transfer NMRP, nitroxide-mediated free radical polymerization CROP, cationic ring-opening polymerization AROP, anionic ring-opening poiymerization.

Priftis D, Sakellariou G, Hadjichristidis N, Penott EK, Lorenzo AT, Muller AJ. Surface modification of multi-walled carbon nanotubes with biocompatible polymers via ring opening and living anionic surface initiated polymerization. Kinetics and crystalhzation behaviour. J Polym Sci A Polym Chem 2009 47(17) 4379-90. 

An alternate way to make block copolymers involving PDMS blocks 124,125) is to have these chains fitted with epoxide functions at chain end, and to react them with a vinylic or dienic polymer carrying terminal COOH functions. Sequential addition of monomers has also been used, the ring opening polymerization of the cyclic trimer (D3) being initiated by the anionic site of a living polymer126). 

As the first, and perhaps the most well-studied form of living polymerizations, anionic procedures have attracted considerable attention both academically and industrially [2, 3], While numerous examples of living procedures have been developed, they can be classified into two main families carbanionic polymerization of vinyl monomers and anionic ring opening polymerizations. 

K. Hashimoto, Ring-Opening Polymerization of Lactams. Living Anionic Polymerization and Its Applications , Prog. Polym. Sci. 2000, 25, 1411-1462. 

Polyethers are prepared by the ring opening polymerization of three, four, five, seven, and higher member cyclic ethers. Polyalkylene oxides from ethylene or propylene oxide and from epichlorohydrin are the most common commercial materials. They seem to be the most reactive alkylene oxides and can be polymerized by cationic, anionic, and coordinated nucleophilic mechanisms. For example, ethylene oxide is polymerized by an alkaline catalyst to generate a living polymer in Figure 1.1. Upon addition of a second alkylene oxide monomer, it is possible to produce a block copolymer (Fig. 1.2). 

Kinetics of anionic ring-opening polymerization has hitherto been quantitatively studied and gave for two monomers, namely ethylene oxide [IS,12] and propylene sulfide [8.20]. Studies on these systems revealed that the living conditions can be achieved, facilitating quantitative determination of rateconstants of propagation on various kinds of ionic growing species. 

Anionic ring-opening polymerization of l,2,3,4-tetramethyl-l,2,3,4-tetraphenylcyclo-tetrasilane is quite effectively initiated by butyllithium or silyl potassium initiators. The process resembles the anionic polymerization of other monomers where solvent effects play an important role. In THF, the reaction takes place very rapidly but mainly cyclic live- and six-membered oligomers are formed. Polymerization is very slow in nonpolar media (toluene, benzene) however, reactions are accelerated by the addition of small amounts of THF or crown ethers. The stereochemical control leading to the formation of syndiotactic, heterotactic or isotactic polymers is poor in all cases. In order to improve the stereoselectivity of the polymerization reaction, more sluggish initiators like silyl cuprates are very effective. A possible reaction mechanism is discussed elsewhere49,52. 

Living anionic ring-opening polymerization, strained metallocenophanes, 12, 326 Living polymerization acetylenes... 

Combination of Living Cationic and Anionic Ring-Opening Polymerization for the Synthesis of Semicrystalline Block Copolymers... 

PMPS-Z -PS and PMPS-/ -Pl were synthesized by the anionic ring-opening polymerization of tetramethyltetraphenylcyclotetrasilane (prepared from commercially available octaphenyltetrasilane) initiated by the living anionic chain ends of polystyrene and polyisoprene [52, 53] (Fig. 4b). 

Fig. 4 Approaches to the synthesis of polysilane block copolymers by living polymerization techniques (a) via anionic polymerization of masked disilenes (b) via anionic ring-opening polymerization of cyclotetrasilanes...

The living polysiloxanes having various densities of vinyl groups were obtained by anionic living ring-opening polymerization of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane (V3) or by copolymerization of this monomer with hexamethylcyclotrisiloxane (D3) or with 2-vinyl-2,4,4,6,6-... 

B-90 and B-91, respectively.390 Another route coupled with cationic ring-opening polymerizations is accomplished for polymer B-92 with the use of a hydroxyl-functionalized initiator with a C—Br terminal, where the OH group initiates the cationic polymerizations of 1,3-dioxepane in the presence of triflic acid.329 Polyethylene oxide)-based block copolymers B-93 are obtained by living anionic polymerization of ethylene oxide and the subsequent transformation of the hydroxyl terminal into a reactive C—Br terminal with 2-bromopropionyl bromide, followed by the copper-catalyzed radical polymerization of styrene.391... 

A blocked, functional initiator is made by reacting p-(N,A-bis(trimethylsilyl)amino)styrene with sec-butyllithium in benzene, and is used for anionically ring-open polymerizing hexamethylcyclotrisilox-ane (D3) in the presence of promoters such as hexamethylphos-phoroamide (HMPA), tetrahydrofuran (THF), or dimethyl sulfoxide (DMSO). The resulting living , monodisperse poly (dimethyl siloxane)... 

Many polymerization techniques have been combined with CRP through site transformation of the active species. These include non-living techniques like condensation (or step) and conventional free radical processes or living methods like anionic, cationic, and ring-opening polymerizations, as well as others. Early examples were undertaken perhaps just to show that two different techniques could be combined, while later examples show how elegant the combinations have become and provide a foundation for controlled synthesis of materials from any type of monomers. These types of reactions are detailed below. 

Homo- and block copolymers from phosphorus-bridged [l]ferrocenophanes were isolated from living anionic ring opening polymerizations.113 Scheme 2.15 shows preparation of borane adducts of poly(ferrocenylphosphine)s by thermal ROP or addition of BX3 (X = H, Cl).114... 

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