Anionic polymerization difunctional polymers

The earliest SIS block copolymers used in PSAs were nominally 15 wt% styrene, with an overall molecular weight on the order of 200,000 Da. The preparation by living anionic polymerization starts with the formation of polystyryl lithium, followed by isoprene addition to form the diblock anion, which is then coupled with a difunctional agent, such as 1,2-dibromoethane to form the triblock (Fig. 5a, path i). Some diblock material is inherently present in the final polymer due to inefficient coupling. The diblock is compatible with the triblock and acts... 

The preparation of ABA triblock polymers requires use of a telechelie bisthiol prepared by termination of anionic polymerization initiated by a difunctional initiator. The relative yields of homopolymer, di- and triblock obtained in these experiments depend critically on conversion.273... 

Acrolein is a very reactive monomer with a high tendency to polymerize. Free-radical and cationic polymerizations lead to Insoluble polymers even if the conversions are low. On the other hand, anionic polymerization gives soluble polyacroleins under well-adapted conditions. Because of the difunctional nature of this monomer, the chains of polyacroleins contain different types of units ... 

Anionic polymerization has also been used to make telechelic polymers (Greek telos, end, and chele, claw), i.e., polymers with reactive terminal groups.We coined the term, telechelic in 1957 and it has been accepted ever since in technical as well as patent literature. Liquid carboxy- and hydroxy telechelic polybutadienes initiated with difunctional organolithium initiators are commercially produced since 1962. Some of the physical properties,production details and uses as in solid rockets... 

Most interesting from the standpoint of commercial development is the formation of block copolymers by the living polymer method. Sequential addition of monomers to a living anionic polymerization system is at present the most useful method of synthesizing well-defined block copolymers. Depending on whether monofunctional or difunctional initiators are used, one or both chain ends remain active after monomer A has completely reacted. Monomer B is then added, and its polymerization is initiated by the living polymeric carbanion of polymer A. This method of sequential monomer addition can be used to produce block copolymers of several different types. 

Polymer Preparation. Two bifunctional (telechelic) polymers were used in this study. Carboxy-telechelic polybutadiene (PB) is commercially available from B. F. Goodrich (Hycar CTB 2000X156) with molecular characteristics of Mn=4,600, Mw/Mn= 1.8, functionality 2.00 and cis/trans/vinyl ratio of 20/65/15. Carboxy-telechelic polyisoprene (PIP) was prepared by anionic polymerization in THF at -78°C with a-methylstyrene tetramer as a difunctional initiator. The living macrodianions were deactivated by anhydrous carbon dioxide. Five polymers werejjrepared with Mn=6,000 10,000, 24,000, 30,000 and 37,000 having Mw/Mn=sl.l5 a microstructure ratio of 3, 4/1, 2 of 65/35, respectively, and a functionality >1.95. 

Anionic polymerization of 4-vinylpyridine by Ba[CMe2Ph]2 occurs in THF, giving a non-stereospecific polymer 2-vinylpyridine is also polymerized by Ba[CMe2Ph]2 or difunctional initiator Ba[Ph2CCH2CH2CPh2], giving >50% isotactic linkages. ... 

The production of liquid short-chain difunctional polymers by anionic polymerization is of considerable technological interest and importance, and has attracted much attention in recent years, since it offers an analogous... 

The production of liquid short-chain difunctional polymers by anionic polymerization is of considerable technological interest and importance, and has attracted much attention in recent years, since it offers an analogous technology to that of the polyethers and polyesters used in urethane polymers. Such liquid telechelic polydienes could thus lead, by means of chain extension and crosslinking reactions, directly to castable polydiene networks [161,162]. 

As in the case of anionic living polymerization, the ATRP polymerization allows the synthesis of polymer networks by the end linking process [303]. A difunctional initiator (bis(2-bromopropionyloxy)ethane) allowed the preparation of difunctional polymer precursors that can be used to prepare polymer networks with divinylbenzene-end linking. Divinylbenzene also gives access to a self condensing TEMPO functionalized AB monomer [304]. 

Linear pentablock terpolymers PBLL-Z -PBLG-Z -PS-Z -PBLG-Z -PBLL (BLL r -butylox-ycarbonyl-L-lysine, PS polystyrene) were recently synthesized by Karatzas et al. (2008) using a,co-diamino-PS. This polymer was prepared by anionic polymerization of styrene with sodium/naphthalene (difunctional initiator) and termination with l-(3-bromo-propyl)-2,2,5,5-tetramethyl-aza-2,5-disilacyclopentane, and of deprotection by successive... 

The synthesis of low molecular weight difunctional carboxyl-terminated butadiene-based polymers via either free radical or anionic polymerization is well established. Teyssie and co-workers have converted such carboxyl-terminated polymers to salt forms, which they refer to as halato-telechelic polymers, by neutralization with metal alkoxides in appropriate solvents. The quantitative removal of low molecular weight reaction products is necessary to drive the reaction to completion and fully realize the ionomeric properties of these materials. 

Aromatic radical anions, such as lithium naphthalene or sodium naphthalene, are efficient difunctional initiators (eqs. 6,7) (3,20,64). However, the necessity of using polar solvents for their formation and use limits their utility for diene polymerization, since the unique abiUty of lithium to provide high 1,4-polydiene microstmcture is lost in polar media (1,33,34,57,63,64). Consequentiy, a significant research challenge has been to discover a hydrocarbon-soluble dilithium initiator which would initiate the polymerization of styrene and diene monomers to form monomodal a, CO-dianionic polymers at rates which are faster or comparable to the rates of polymerization, ie, to form narrow molecular weight distribution polymers (61,65,66). 

Stars with high arm numbers are commonly prepared by the arm-first method. This procedure involves the synthesis of living precursor arms which are then used to initiate the polymerization of a small amount of a difunctional monomer, i.e., for linking. The difunctional monomer produces a crosslinked microgel (nodule), the core for the arms. The number of arms is a complex function of reaction variables. The arm-first method has been widely used in anionic [3-6,32-34], cationic [35-40], and group transfer polymerizations [41] to prepare star polymers having varying arm numbers and compositions. 

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