Block copolymerization of vinyl

In a recent communication, a microsystem allowing controlled polymerization and block copolymerization of vinyl ethers with triflic acid as the initiator at 25°C has been described.977 The system allows a high level of control on molecular weight distribution. 

In 1985, Rizzardo et al.27 filed a patent for the use of alkoxyamines (Scheme 12) as regulating initiators for the living radical polymerization and block copolymerization of vinyl monomers. R is a group that upon dissociation (Scheme 10) forms a radical that adds to the monomer. The mechanism was disclosed shortly thereafter and involves the reversible dissociations shown in Scheme 11, with the nitroxide radical taking the role of X.28 In a later simulation, the group also revealed the reason for the remarkable absence of the usual terminations and rediscovered the principles of the persistent radical effect 29 As chains undergo termination transient radicals are removed from the system and the concentration of persistent species builds . Further, the authors noted correctly that, in contrast to normal radical polymer-... 

Block Copolymerization of Vinyl Monomers from Living Polyacetals... 

Fig. 7 Flow microreactor system for block copolymerization of vinyl ether initiated by TfOH.

Paik, H.-J., et al. (1999). Block copolymerizations of vinyl acetate by combination of conventional and atom transfer radical polymerization. Macromolecules, 32(21) 7023-7031. 

Imanishi, Y., Tanaka, M., and Bamford, C.H. (1985) Block copolymerization of vinyl compounds by the terminal -group activation of poly(a-amino acids) and the characterization of the block copolymers. International Journal of Biological Macromolecules, 1,89-99. 

Besides condensation reactions, the bifunctional ACPC may also be used for cationic polymerization [52-55] (e.g., of tetrahydrofuran). The polymer obtained by the method depicted in reaction (12) contains exactly one central azo bond [56] and is a suitable macroinitiator for the thermally induced block copolymerization of vinyl monomers. Initiators like ACPC are referred to as transformation agents becaiae they are able to initiate... 

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. 

Hsu T, Tan C (2002) Block copolymerization of carbon dioxide with cyclohexene oxide and 4-vinyl-1-cyclohexene-1,2-epoxide in based poly(propylene carbonate) by yttrium-metal... 

Chemical processes are far more varied and may involve either the formation of radicals or ions along a polymeric backbone. Both cationic processes3 as well as radical processes have been widely used for graft copolymerization of vinyl monomers onto various polymers. Radical graft copolymerization has been reported for many polymers including styrene-butadiene block copolymers, and acrylonitrile-butadiene-styrene terpolymer, ABS.3 7 9... 

Copolymers. Vinyl acetate copolymenzes easily with a few monomers, e g, ethylene, vinyl chloride, and vinyl neodecanoate, which have reactivity ratios close to its own. Block copolymers of vinyl acetate with methyl methacrylate, acrylic acid, acrylonitrile, and vinyl pyrrolidinone have been prepared by copolymerization in viscous conditions, with solvents that are poor solvents for the vinyl acetate macroradical,... 

Star polymers having several PS branches and only one poly(2-vinyl naphthalene), PVN branch were prepared by Takano et al. using anionic polymerization techniques [31]. Sequential anionic block copolymerization of (4-vinyl-phenyl) dimethylvinylsilane (VS) and VN was employed. The double bonds attached to silicon have to remain unaffected during the polymerization of VS. This was ac-... 

Let us now consider situation with 2 0. The dependence of Gibbs energy on composition will exhibit two minima (Fig. 26) with increasing F1 copolymer will pass from the stable range (0 < F2< a) into an unstable one (a < F2 < b) and back into a stable range (F2 > b). The system will have a Tc minimum. Copolymerizations of vinyl and cyclic monomers present examples of such behaviour. The interactions of these compounds are of repulsive character coaddition is difficult to achieve. The product is a block copolymer [214] (for example styrene-/ -propiolactone [215]). At only weakly negative co values, the minimum on the Tc—F2 curve will not occur (see Fig. 27). Two local minima will, however, appear in the AG vs. F2 plot. 

As seen in Scheme 2 (A), the most of the syntheses have been carried out with the HI/I2 and HX/ZnX2 (X = halogen) initiating systems, because these systems can effectively polymerize a large variety of vinyl ethers, including those with pendant functions, into well-defined living polymers [1]. In this way, the sequential living cationic polymerizations of two vinyl ethers are mostly "reversible i.e., both A - B and B - A polymerization sequences are operable. This is in sharp contrast to the block copolymerization of a vinyl ether with a styrene derivative or isobutylene (see below), where such reversibility often fails to work. 

In block copolymerizations with vinyl ethers, as seen in this example, a styrene derivative should be polymerized after the first-stage polymerization of a vinyl ether component, and an additional dose of a Lewis acid (activator) is usually needed to accelerate the second-phase polymerization. The reverse polymerization sequence (from a styrene derivative to a vinyl ether) often results in a mixture of block copolymers and homo-... 

An azo bromoester bifunctional compound FI-43 induces a living polymerization of nBA with a highly active catalytic system (CuBr/L-32) at 30 °C from the latter function alone.338 The low temperature allows the azo group to elude concurrent thermal dissociation (<0.5%). The obtained polymers of narrow MWDs were employed for block copolymerization with vinyl acetate at 90 °C. 

The NIR in situ process also allowed for the determination of intermediate sequence distribution in styrene/isoprene copolymers, poly(diene) stereochemistry quantification, and identification of complete monomer conversion. The classic one-step, anionic, tapered block copolymerization of isoprene and styrene in hydrocarbon solvents is shown in Figure 4. The ultimate sequence distribution is defined using four rate constants involving the two monomers. NIR was successfully utilized to monitor monomer conversion during conventional, anionic solution polymerization. The conversion of the vinyl protons in the monomer to methylene protons in the polymer was easily monitored under conventional (10-20% solids) solution polymerization conditions. Despite the presence of the NIR probe, the living nature of the polymerizations was maintained in... 

Previously, Hogen-Esch reported the successful synthesis of block copolymers composed of poly(acetylene) (PA) segments (PS-b-PA), by the living anionic block copolymerization of styrene and phenyl vinyl sulfoxide, followed by thermal treatment [158]. In this way, poly(phenyl vinyl sulfoxide) was completely converted to a PA segment A similar block copolymer was obtained by the reaction of chain-end-amine-fimctionaHzed poly(4-methylphenyl vinyl sulfoxide) with chain-end-COOH-functionaHzed PS via ionic interaction, followed by thermal treatment [215]. 

Sequential block copolymerization of IB with more reactive monomers such as aMeSt, p-MeSt, IBVE, or methyl vinyl ether (MeVE) as a second monomer invariably leads to a mixture of block copolymer and PIB homopolymer. To overcome the difficulty in the crossover step, a general methodology has been developed for the synthesis of block copolymers when the second monomer is more reactive than the first one. It involves the intermediate capping reaction with non(homo)polymerizable monomers such as diarylethylenes and 2-substituted furans. 

The first and simplest method has been successfully employed in the block copolymerization of IB with ctMeSt [186], p-MeSt [66], MeVE [187, 188]. tBuVE [97], t-butyldimethylsilyl vinyl ether [189], CHVE [190], and p-tert-butyldimethylsiloxystyrene (tBDMSt) [191]. 

Yuan, J.Y. and Pan, C.Y. (2002) Block copolymerization of 5,6-benzo-2-methylene-13 dioxepane with conventional vinyl monomers by AXRP method. Eur. Pdym. J, 38, 1565. 

Block copolymerization of IBVE and n-butyl vinyl ether (NBVE) can also be successfully achieved using a microflow system consisting of two micromixers... 

KOU 09] Koumura K., Satoh K., Kamig.aito M., Mn2(CO)io-induced controlled/living radical copolymerization of vinyl acetate and methyl aciylate Spontaneous formation of block copolymers consisting of gradient and homopolymer segments , Journal of Polymer Science Part A Polymer Chemistry, vol. 47, pp. 1343-1353, 2009. 

Beginning from the 1990s, MSCBs have been primarily used for anionic copolymerization with monomers of other types, most frequently vinyl monomers, mainly styrene in most cases, block copolymers were prepared at low temperatures in polar media (e.g., —78°C, THE). As an example, the scheme of the block copolymerization of 1,1-dimethyl-1-silacyclobutane with styrene under conditions more acceptable for formation of living chains (—48°C, THE hexane = l l(v/v), without HMPA [38]) is presented below. 

Pittman and coworkers reported a number of ferrocene-functionalized polymers in the 1960s and 1970s that not only included the synthesis but also the properties of these polymers. " In particular, the bulk and solution polymerization of vinylferrocene along with the physical, chemical, and electrical properties of many polymers and copolymers were studied. The copolymerization of vinyl-ferrocene with styrene was reported by Frey and co-workers in 1999, using living radical initiator 2,2,6,6-tetramethyl-l-pyperidinyl-l-oxy (TEMPO). The polymers obtained by this method were block copolymers with narrow polydis-persities. 

Extending controlled radical polymerization methods to the block copolymerization of cyclic vinyl ethers using commercially available monomers is of... 

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