Solvent styrene with methyl acrylate

Substituted terpyridine, 4,4, 4"-tris(5-nonyl)-2,2 <5, 2"-terpyridine (tNtpy), is a planar tridentate ligand that was successfully used in homogeneous ATRP of methyl acrylate and styrene [79]. Polymerization of both monomers was controlled and the resulting polymers had relatively low polydispersities (MJMn < 1.2). Similarly to PMDETA, the typical ligand to copper halide ratio used in the polymerization was 1 1. Terpyridine and its derivatives are expected to form tetra-coordinated complexes with copper in which the fourth coordination sphere is occupied by a monodentate ligand (Br-, Cl , solvent, monomer, etc.). Although,... 

For the addition of ethylene, EtOAc as solvent was particularly advantageous and gave 418 in 60% yield (Scheme 6.86). The monosubstituted ethylenes 1-hexene, vinylcyclohexane, allyltrimethylsilane, allyl alcohol, ethyl vinyl ether, vinyl acetate and N-vinyl-2-pyrrolidone furnished [2 + 2]-cycloadducts of the type 419 in yields of 54—100%. Mixtures of [2 + 2]-cycloadducts of the types 419 and 420 were formed with vinylcyclopropane, styrene and derivatives substituted at the phenyl group, acrylonitrile, methyl acrylate and phenyl vinyl thioether (yields of 56-76%), in which the diastereomers 419 predominated up to a ratio of 2.5 1 except in the case of the styrenes, where this ratio was 1 1. The Hammett p value for the addition of the styrenes to 417 turned out to be -0.54, suggesting that there is little charge separation in the transition state [155]. In the case of 6, the p value was determined as +0.79 (see Section 6.3.1) and indicates a slight polarization in the opposite direction. This astounding variety of substrates for 417 is contrasted by only a few monosubstituted ethylenes whose addition products with 417 could not be observed or were formed in only small amounts phenyl vinyl ether, vinyl bromide, (perfluorobutyl)-ethylene, phenyl vinyl sulfoxide and sulfone, methyl vinyl ketone and the vinylpyri-dines. 

Table 1. TLC developments of styrene-methyl acrylate copolymers with single solvents...

This technique allows the formation of many different types of block copolymers. Lithium metal can be used to initiate polymerizations in solvents of varying polarity. Monomers, like styrene, a-methylstyrene, methyl methacrylate, butyl methacrylate, 2-vinylpyridine, 4 vinylpyridine, acrylonitrile, or methyl acrylate, can be used. The mechanism of initiation depends upon the formation of ion radicals through reactions of lithium with the double bonds ... 

Radical-solvent complexes are more difficult to detect spectroscopically however, they do provide a plausible explanation for many of the solvent effects observed in free-radical homopolymerization—particularly those involving unstable radical intermediates (such as vinyl acetate) where complexation can lead to stabilization. For instance, Kamachi (50) observed that the homopropagation rate of vinyl acetate in a variety of aromatic solvents was correlated with the calculated delocalization stabilization energy for complexes between the radical and solvent. If such solvent effects are detected in the homopolymerization of one or both of the comonomers, then they are likely to be present in the copolymerization systems as well. Indeed, radical-complex models have been invoked to explain solvent effects in the copolymerization of vinyl acetate with acrylic acid (51). Radical-solvent complexes are probably not restricted merely to systems with highly unstable propagating radicals. In fact, radical-solvent complexes have even been proposed to explain the effects of some solvents (such as benzyl alcohol, A7 / 7 -dimethyl for-mamide, and acetonitrile) on the homo- and/or copolymerizations of styrene and methyl methacrylate (52-54). Certainly, radical-solvent complexes should be considered in systems where there is a demonstrable solvent effect in the copolymerizations and/or in the respective homopolymerizations. 

In many cases, azobis(isobutyronitrile) (AIBN) is employed as radical initiator. The polymerization conditions, in particular solvent, depend mainly on both, solubility of the starting sf monomers and choice of comonomer. To give just a few examples, copolymers of dodecafluoroheptyl methacrylate with methacrylic acid could be synthesized in dioxane due to the solubilizing effect of methacrylic acid [66], copolymers of sfMA-H2F8 and sfMA-H2F4 with styrene could be prepared in toluene [35], and copolymerizations of i/methacrylates with butyl acrylate, hydroxy-butyl acrylate, and styrene were performed using tert-butyl peroxyacetate as initiator in methyl amyl ketone [31]. 

Zhou and coworkers [67] prepared Pd nanoparticles in situ in the H O/TX-lOO/ [bmim][PFg] microemulsion and used this microemulsion system to catalyze the Heck reaction of butyl acrylate with iodobenzene. The reaction time was decreased compared with conventional solvent system. Other Heck reactions relating to the coupling of iodobenzene and methyl acrylate, ethyl acrylate and styrene were also investigated with high yields. All the results indicated that the HjO/TX-100/[bmim] [PF ] microemulsion containing Pd nanoparticles was a very efficient catalyst system for the ligand-free Heck reaction. 

Parallel approaches have been described for the preparation of polyacrylate-protease conjugates [396-400]. Acryloylation of subtilisin and a-chymotrypsin, followed by mixed polymerization with methyl methacrylate, vinyl acetate, styrene, or ethylvinyl ether, provides insoluble, doped polymethyl methacrylate, polyvinyl acetate, polystyrene, and polyethyl vinyl ether polymers [396]. These biocatalytic plastics perform especially well in hydrophilic and hydrophobic solvents, and have been used for peptide synthesis and the regioselective acylation of sugars and nucleosides. Similarly, modification of subtilisin and thermolysin with PEG monomethacrylate, then copolymerization with methyl methacrylate and trimethylolpropane trimethacrylate furnishes protease-polymethyl methacrylate plastics, which show good activities and stabilities in aqueous, mixed, and low-water and anhydrous organic media [397-400]. The protein-acrylate composites are unique in that they enable catalytic densities as high as 50% w/w. 

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