Apolar monomer

In some cases, due to the highly polar character of the sulfate radicals, peroxydisulfate initiators can provide slow polymerization rates with some apolar monomers since the polar sulfate radicals cannot easily penetrate into the swollen micelle structures containing apolar monomers. The use of mercaptans together with the peroxydisulfate type initiators is another method to obtain higher polymerization rates [43]. The mercaptyl radicals are more apolar relative to the free sulfate radicals and can easily interact with the apolar monomers to provide higher polymerization rates. 

Some typical dispersion polymerization recipes and the electron micrograph of the uniform polymeric particles with Recipe I are given in Table 5 and Fig. 10, respectively. As seen in Table 5, the alcohols or alcohol-water mixtures are usually utilized as the dispersion media for the dispersion polymerization of apolar monomers. In order to achieve the monodispersity in the final product, a costabilizer can be used together with a primary steric stabilizer, which is usually in the polymeric form as in... 

With some limitations. Single-stage soapless emulsion polymerization can be used for the direct copolymerization of a relatively apolar monomer with a polar... 

The rate of polymerization of living anionic polymerizations depends not only on the molar concentrations of monomer and initiator, but also on the relative proportions of free ions, ion pairs, and ion associates. Very complicated kinetic expressions are obtained for the general case. Fortunately, almost all anionic polymerizations fall within two limiting cases. One of the limiting cases consists of the polymerization of apolar monomers in apolar solvents ion pairs and their associates only occur in this case with free ions being absent. The other limiting case consists of the polymerization of polar monomers in polar solvents. Ion associates need not be considered here, but the equilibrium between free ions and the various kinds of ion pairs must be considered. 

Anionic polymerizations of polar monomers in polar solvents are only poorly stereospecific, whereas, according to conditions, the anionic polymerization of apolar monomers in apolar solvents can be strongly stereo-controlled. All possible levels of stereocontrol lie within the two extremes. 

The polymerization probably results from an insertion mechanism, as would be expected particularly in the case of polymerization of apolar monomers in hydrocarbons (see Section 19.1). This mechanism explains why only limited branching can occur and why the same catalyst system leads to isotactic products in the higher a-olefins, as was first discovered by Natta for the polymerization of propylene with Ziegler catalysts. 

Inoue Y, Watanabe J, Takai M, Yusa S, Ishihara K. Synthesis of sequence-controlled copolymers from extremely polar and apolar monomers by hving radical polymerization and their phase-separated structures. J Polym Sci A Polym Chem 2005 43 6073-6083. 

In early investigations, hydrogen peroxide has been used as an initiator for the photoinduced free-radical polymerization of acrylonitrile [89-91]. However, hydrogen peroxide only absorbs weakly, and solubility problems are unavoidable, especially if apolar monomers are to be polymerized. 

AS )) the function to be minimized is exp (-AS p/R)/ [36]. A quantitative expression for AS can be found by noting that the A monomers in an unstrained loop (N > 4) have essentially two possible confonnations, pointing either inwards or outwards. For loops smaller than a critical size the inward ones are in an apolar environment, since the enclosed water no longer has bulk properties, and the outward ones are in polar bulk water hence the electrostatic charges on... 

The monomers that are apolar relative to the continuous media are usually used in the dispersion polymerization... 

Highly monodisperse reversed micelles are formed by sodium bis(2-ethylhexyl) sul-fosuccinate (AOT) dissolved in hydrocarbons that are in equilibrium with monomers whose concentration (cmc) is 4 X 10 M, have a mean aggregation number of about 23, a radius of 15 A, exchange monomers with the bulk in a time scale of 10 s, and dissolve completely in a time scale of 10 s [1,2,4,14], Other very interesting surfactants able to form reversed micelles in a variety of apolar solvents have been derived from this salt by simple replacing the sodium counterion with many other cations [15,16],... 

At infinite dilution, 1-pentanol monomers distribute between AOT-reversed micelles and the continuous organic phase, whereas at finite alcohol concentration, given the ability of alcohol to self-assemble in the apolar organic solvent, a coexistence between reversed micelles (solubilizing 1-pentanol) and alcoholic aggregates (incorporating AOT molecules) is realized [25],... 

For example, a proline-based chiral ligand was attached to a vinyl-substituted monomer (Fig. 42.15) by reacting vinylbenzoyl chloride with the amine functionality of the ligand [106]. As mentioned previously, the apolar Merrifield resin as a support is not swollen in polar solvents. Hence, in order to match the polarity of the resin with that of the typically used substrates in enantioselective hydrogenation, the functionalized monomer was copolymerized with polar units of methacrylic acid 2-hydroxyethyl ester. 

Polymers of 4(5)-vinylimidazole and copolymers containing this monomer are usually studied with ethanol-buffer mixtures as solvent because of their insolubility in water. Overberger and Smith (82) found that poly(l-Me-5-vinylimidazole) was soluble in water. Negatively charged substrates with long apolar side chains were bound very strongly to this polymer. A rate enhancement of 106 over the monomeric analog, 1,5-dimethylimidazole, was observed. 

In order to keep polyamides soluble in relatively apolar solvents, the use of flexible (macro)monomers such as a, co-(diaminopropyl)polydimethylsiloxane [52] or oligoethyleneglycol-based diamines [53, 54] has been proven to be a successful approach (Fig. 10). Poly condensations of dimethyl adipate with a variety of diamines were successful in bulk and at moderate temperatures between 60 and 100 °C (reaction A in Fig. 10). The low temperatures (60-100 °C) that suffice in these polymerizations also allow the use of monomers that are thermally instable, such as diethyl fumarate [53]. Moreover, multifunctional amines could be regioselectively polymerized up to molecular weights of 9 kDa, making lipase catalysts a valuable tool for the preparation of well-defined polyamides that can be further functionalized with active groups. 

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