Copolymerization block copolymers

Polyaddition reactions based on isocyanate-terminated poly(ethylene glycol)s and subsequent block copolymerization with styrene monomer were utilized for the impregnation of wood [54]. Hazer [55] prepared block copolymers containing poly(ethylene adipate) and po-ly(peroxy carbamate) by an addition of the respective isocyanate-terminated prepolymers to polyazoesters. By both bulk and solution polymerization and subsequent thermal polymerization in the presence of a vinyl monomer, multiblock copolymers could be formed. 

Block copolymers have been synthesized on an industrial scale mainly by anionic or cationic polymerization, although monomers for block components are limited to ones capable of the process. Intensive academic and technological interest in radical block copolymerization using macroinitiators is growing. This process can be implemented in plants with easier handling of materials, milder conditions of operation, and a variety of materials to give various kinds of block copolymers to develop a wide application area [1-3]. 

As it was shown in73, 74), methods that can be used to synthesize these copolymers of PAN are those of radical AN block copolymerization in the presence of an oxidation-reduction system in which the hydroxyl end groups of polyethylene oxide) (PEO)73) and polypropylene oxide) (PPO)74- oligomers serve as the reducing agents and tetravalent cerium salts as the oxidizing agents. 

When PAN block copolymers are synthesized with the help of such method the reaction is conducted during a period of time (20—30 min) shorter than the induction period of AN polymerization (45 min) in the presence of cerium ions. When the mechanism and the laws governing the reaction of AN copolymerization with PEO and PPO were studied, it was established that the initiation of the block copolymerization proceeds in accordance with the following scheme ... 

Anionic polymerization of polystyrene takes place very rapidly- much faster than free radical polymerization. When practiced on a large scale, this gives rise to heat transfer problems and limits its commercial practice to special cases, such as block copolymerization by living reactions. We employ anionic polymerization to make tri-block copolymer rubbers such as polystyrene-polybutadiene-polystyrene. This type of synthetic rubber is widely used in the handles of power tools, the soft grips of pens, and the elastic side panels of disposable diapers. 

We commonly copolymerize styrene to produce random and block copolymers. The most common random copolymers are styrene-co-acrylonitrile and styrene-co-butadiene, which is a synthetic rubber. Block copolymerization yields tough or rubbery products. 

Water soluble block copolymers consisting of N-isopropylacrylamidc, NIPA, and the zwitterionic monomer 3-[N-(3-methacrylamidopropyl)-N,N-dimethyl]ammoniopropane sulfonate, SPP, were prepared via the RAFT process [82] (Scheme 31). NIPA was polymerized first using AIBN as the initiator and benzyl dithiobenzoate as the chain transfer agent. To avoid the problem of incomplete end group functionalization the polymerization yield was kept very low (less than 30%). The block copolymerization was then performed... 

As described in Section 9.1.2.2.3, several lanthanocene alkyls are known to be ethylene polymerization catalysts.221,226-229 Both (188) and (190) have been reported to catalyze the block copolymerization of ethylene with MMA (as well as with other polar monomers including MA, EA and lactones).229 The reaction is only successful if the olefin is polymerized first reversing the order of monomer addition, i.e., polymerizing MMA first, then adding ethylene only affords PMMA homopolymer. In order to keep the PE block soluble the Mn of the prepolymer is restricted to <12,000. Several other lanthanide complexes have also been reported to catalyze the preparation of PE-b-PMMA,474 76 as well as the copolymer of MMA with higher olefins such as 1-hexene.477... 

Well-defined nanoclusters (w 10-100 A diameter) of several metals have been prepared via the polymerization of metal-containing monomers. The synthetic approach involves the block copolymerization of a metallated norbornene with a hydrocarbon co-monomer which is used to form an inert matrix. Subsequent decomposition of the confined metal complex affords small clusters of metal atoms. For example, palladium and platinum nanoclusters may be generated from the block copolymerization of methyl tetracyclododecane (223) with monomers (224) and (225) respectively. 10,611 Clusters of PbS have also been prepared by treating the block copolymer of (223) and (226) with H2S.612 A similar approach was adopted to synthesize embedded clusters of Zn and ZnS 613,614... 

Anionic block copolymerizations of MM A with lactones proceeded smoothly to give copolymers with Mw/Mn = 1.11-1.23 when the monomers were added in this order. However, when the order of addition was reversed, no copolymerization took place [3c], i.e., no addition of MMA to the polylactone active end group occurred (Scheme 12). 

Yasuda et al. [122] extended the above work to the block copolymerization of ethylene with lactones. 5-Valerolactone and s-caprolactone were combined with the growing polyethylene end at ambient temperature and the expected AB-type copolymers (100 1 to 100 89) were obtained at high yield. Reversed addition of the monomers (first MMA or lactones and then ethylene) induced no block copolymerization at all, even in the presence of excess ethylene, and only homo-poly(MMA) and homo-poly(lactone) were produced. 

Block copolymerization was carried out in the bulk polymerization of St using 18 as the polymeric iniferter. The block copolymer was isolated with 63-72 % yield by solvent extraction. In contrast with the polymerization of MMA with 6, the St polymerization with 18 as the polymeric iniferter does not proceed via the livingradical polymerization mechanism,because the co-chain end of the block copolymer 19 in Eq. (22) has the penta-substituted ethane structure, of which the C-C bond will dissociate less frequently than the C-C bond of hexa-substituted ethanes, e.g., the co-chain end of 18. This result agrees with the fact that the polymerization of St with 6 does not proceed through a living radical polymerization mechanism. Therefore, 18 is suitably used for the block copolymerization of 1,1-diubstituted ethylenes such as methacrylonitrile and alkyl methacrylates [83]. 

It was confirmed that the resulting polymers obtained from the St polymerization with 13 induced further photopolymerization of MMA to produce a block copolymer, and the yield and molecular weight increased as a function of the polymerization time, similar to the results for the polymerization of MMA with 13, indicating that this block copolymerization also proceeds via a living radical polymerization mechanism [64]. Similar results were also obtained for the photoblock copolymerization of VAc. Thus, various kinds of two- or three-component block copolymers were prepared [157,158]. 

The results of the block copolymerization of St, MMA, AA, and VAc with the polymers obtained by 7 and 8 are shown in Table 3. The yields of the block copolymers with 42 and 43 were as high as 70-90%. These block copolymer syntheses are advantageous for the synthesis of the polymer consisting of many kinds of vinyl monomer units, especially polar and functional monomers. 

Block coal, 6 705 Block copolyamide, 79 739 Block copolymerization, 79 762 Block copolymers, 7 645-650 70 436 23 367... 

The trick used in asyrmnetric inclusion polymerization is to perform the reaction in a rigid and chiral environment. With more specific reference to chirality transmission, the choice between the two extreme hypotheses, influence of the starting radical (which is chiral because it comes from a PHTP molecule), or influence of the chirality of the channel (in which the monomers and the growing chain are included), was made in favor of the second by means of an experiment of block copolymerization. This reaction was conducted so as to interpose between the starting chiral radical and the chiral polypentadiene block a long nonchiral polymer block (formed of isoprene units) (352), 93. The iso-prene-pentadiene block copolymer so obtained is still optically active and the... 

NMP is as successful as RAFT polymerization for the construction of block copolymers. A small library of block copolymers comprised of poly(styrene) (PSt) and poly(ferf-butyl acrylate) (FYBA) was designed and the schematic representation of the reaction is depicted in Scheme 10 [49]. Prior to the block copolymerization, the optimization reactions for the homopolymerization of St and f-BA were performed as discussed in this chapter (e.g., see Sect. 2.1.2). Based on these results,... 

The GPC profile provided a unimodal, sharp elution pattern for the finally obtained polymer, in which the peak due to the prepolymer of MMA was not observed, showing that a MMA-MAN block copolymer was produced quantitatively [Fig. 20 (II)]. The Mn of the polymer, as estimated by GPC, was 20,800 (Mw/Mn=I.I7), which is close to that (16,700) expected from the initial MAN-to-2 mole ratio. Successful block copolymerization indicates that all the molecules of the growing PMMA (2) produced in the first stage participated in initiating the second-stage polymerization of MAN. 

The purpose of this contribution is to show how the design of a new dianionic species can lead to interesting advances in block copolymerization and especially to original PA(P0)2 starshaped block copolymers. PA is a hydrophobic block polystyrene, polytertiarybutylstyrene (PTBS) or polyisoprene (Pi). The surface activity of this novel and well mastered molecular architecture is considered and compared as far as possible with the behavior of the corresponding PA-PO diblock copolymers. 

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