Poly halogen terminated

Most of the block copolymers consisting of methacrylates and acrylates (B-8 to B-12) have been prepared via macroinitiator methods. AB- and BA-type block copolymers of MMA and MA (B-876 135,359 and B-9359) were prepared with nickel, copper, and iron catalysts. Due to the higher activity of the carbon—halogen terminals in poly(methacrylate) s than in poly(acrylate)s, block copolymerization from PMMA is successfully performed via both sequential and macroinitiator methods, where the controllability seems better in the copper-based system. Similar... 

The ABA-type block copolymers B-86 to B-88 were synthesized via termination of telechelic living poly-(THF) with sodium 2-bromoisopropionate followed by the copper-catalyzed radical polymerizations.387 A similar method has also been utilized for the synthesis of 4-arm star block polymers (arm B-82), where the transformation is done with /3-bromoacyl chloride and the hydroxyl terminal of poly(THF).388 The BAB-type block copolymers where polystyrene is the midsegment were prepared by copper-catalyzed radical polymerization of styrene from bifunctional initiators, followed by the transformation of the halogen terminal into a cationic species with silver perchlorate the resulting cation was for living cationic polymerization of THF.389 A similar transformation with Ph2I+PF6- was carried out for halogen-capped polystyrene and poly(/>methoxystyrene), and the resultant cationic species subsequently initiated cationic polymerization of cyclohexene oxide to produce... 

Many mono- and poly(N-alkoxyamines) have been synthesized and investigated in NMP reactions (161,173-185). Halogen-terminated polymers have been converted into alkoxyamine macroinitiators (186). 

Polysilanes are connected with carbon polymers to form A-B and A-B-A type block pol5uners. Reaction of Li-terminated polyst5Tene with cyclotetrasilanes (73) or halogen-terminated polysilanes (74), photolysis of polysilanes in carbon monomers (methacrylic monomers) (75), or reaction of halogen-ended polysilanes with poly(ethylene glycol) affords A-B and/or A-B-A type Block Copolymers (qv) (76) (Fig. 8). Comb-like Graft Copolymers (qv) have also been prepared by reaction of triflate-substituted poly(methylphenylsilane) with THF, 2-methyl-2-oxazoline, or isobutyl vinyl ether (77). 

The mechanism exhibited in Fig. 7 is also applicable to the sMMO-catalyzed oxygenation of terminal olefins. The formation of primary alcohol and epoxide from terminal olefin is reasonably explained by applying the reaction mechanism for the poly halogenated ethene as shown in Scheme 5. Formation of a carbonium cation at the tertiary carbon must be predominant, because a carbonium cation at the primary carbon is very unstable. The predominant intermediate gives both primary alcohol and epoxide. The minor intermediate, a carbonium cation at the primary carbon, gives only epoxide. Secondary alcohol having a terminal olefin can not be formed via these intermediates. Therefore, this mechanism explains the formation of the primary alcohol from terminal olefins better than the radical mechanism. 

Controlled radical polymerization of MMA followed by n-BuMA produces linear AB diblock copolymer LB-1 with a narrow molecular weight distribution (MWD, M /Mn = 1.2), which can be extended further into ABA triblock copolymer LB-2 with a similarly narrow MWD (M ,/Mn = 1.2) [21]. The block copolymers of MMA and MA, LB-3 and LB-4, were prepared using catalysts based on nickel, copper or iron complexes. Due to the higher activity of the carbon halogen terminal bonds in poly(methacrylate)s than in poly(acrylate)s, the block copolymerization of MA using a PMMA macroini-... 

The second approach for creating halogen-terminated polymers involves quenching living anionic polymerization by a-methylstyrene (aMSt), followed by addition of liquid bromine [130], Similarly, poly(isoprene)- >-PSt (PI-6-PSt) block copolymers may be prepared by quenching the living anionic polymerization of isoprene with l-(9-phenonthryl)-l-phenylethylene followed by addition of excess a, a -dibromo-p-xylene, which leaves a C-Br terminal moiety effective for the copper-catalyzed radical polymerization of St [131]. 

Recommended initiators for methacrylate polymerizations are 1-24 (X = Br) and 1-25 (X = Cl), both of which are unimer and dimer models of poly(methacry-late) dormant terminals, respectively. For example, PMMA with precisely controlled molecular weights, very narrow MWDs (MJMn — 1.1), and nearly perfect end-capping with halogen was obtained with the 1-25 (X = Cl)/Ru-5/Al(0-7-Pr)3 initiating system.60 197 Alternatively, arenesulfonyl chlorides can lead to well-controlled poly (methacrylate) s with narrow MWDs (MJMn = 1.1 —1.2) in combination with copper catalysts.126176... 

Almost all metal-catalyzed living polymerizations give polymers capped with halogens that are stable after the usual workup. These terminal halogens would be undesirable, because they may lower the polymer s thermal stability. Dehalogenation by tribu-tyltin hydride (EC-15) is of importance in this respect and effectively works for the bromide terminals in polystyrene, PMMA, and poly(MA) in the presence of copper catalysts.277... 

In ATRP, the nature of the halogen end group can play an important role. The initiation of MMA polymerization by a Cl-terminated poly(methyl acrylate) macroinitiator is poor, but is much faster if a Br-terminated poly(methyl acrylate) is used. In general, efficient block copolymer formation occurs when the rate of... 

Researchers van der Broeke and coworkers[" created perfluoro-functionalized poly(propyleneimine) dendrimers (23 Fig. 4) and demonstrated their potential as phase-transfer catalysts in supercritical carbon-dioxide-water mixtures and as anionic species extractants. The dendrimers were accessed via reaction of perfluorinated, linear alkyl acid chlorides with the terminal amines. Extraction of perinanganate or dichromate from aqueous to CO2 solution was described as rather low, whereas their use as phase-transfer catalysts in a halogen exchange reaction [benzyl chloride to benzyi bromide (24)] resulted in high rates of conversion. 

Shaver and coworkers [319] investigated the mechanism of bis(imino)pyridine ligand framework for transition metal systems-mediated polymerization of vinyl acetate. Initiation using azobisisobu-tyronitrile at 120°C results in excellent control over poly(vinyl acetate) molecular weights and polymer dispersities. The reaction yields vanadium-terminated polymer chains which can be readily converted to both proton-terminated poly(vinyl acetate) or poly(vinyl alcohol). Irreversible halogen transfer from the parent complex to a radical derived from azobisisobutyronitrile generates the active species. 

Morris and others reacted a poly (oxyalky-lene) glycol with an alkali metal in dispersion, and treated the alcoholate with a halogenated organic compound, and then reacting further with a sulfur containing compound and, finally, hydrolyzing with an alkali metal to yield the mercaptan terminated polyether. 

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