Hexane cationic polymerization

It has previously been shown that large changes can occur in the rate of a cationic polymerization by using a different solvent and/or different counterion (Sec. 5-2f). The monomer reactivity ratios are also affected by changes in the solvent or counterion. The effects are often complex and difficult to predict since changes in solvent or counterion often result in alterations in the relative amounts of the different types of propagating centers (free ion, ion pair, covalent), each of which may be differently affected by solvent. As many systems do not show an effect as do show an effect of solvent or counterion on r values [Kennedy and Marechal, 1983]. The dramatic effect that solvents can have on monomer reactivity ratios is illustrated by the data in Table 6-10 for isobutylene-p-chlorostyrene. The aluminum bromide-initiated copolymerization shows r — 1.01, r2 = 1.02 in n-hexane but... 

Traditional Ziegler-Natta and metallocene initiators polymerize a variety of monomers, including ethylene and a-olefins such as propene, 1-butene, 4-methyl-1-pentene, vinylcyclo-hexane, and styrene. 1,1-Disubstituted alkenes such as isobutylene are polymerized by some metallocene initiators, but the reaction proceeds by a cationic polymerization [Baird, 2000]. Polymerizations of styrene, 1,2-disubstituted alkenes, and alkynes are discussed in this section polymerization of 1,3-dienes is discussed in Sec. 8-10. The polymerization of polar monomers is discussed in Sec. 8-12. 

Both the monomer and polymer are soluble in the solvent in these reactions. Fairly high polymer concentrations can be obtained by judicious choice of solvent. Solution processes are used in the production of c(5-polybutadiene with butyl lithium catalyst in hexane solvent (Section 9.2.7). The cationic polymerization of isobutene in methyl chloride (Section 9.4.4) is initiated as a homogeneous reaction, but the polymer precipitates as it is formed. Diluents are necessary in these reactions to control the ionic polymerizations. Their use is avoided where possible in free-radical chain growth or in step-growth polymerizations because of the added costs involved in handling and recovering the solvents. 

BF. The anodic oxidation of BF4 yields BF 3 which, as has been postulated by Funt and coworkers105,106-> and by Tidswell and Doughty107 some years ago (see also Ref. 7 pp. 595 and 602) can initiate, in the presence of traces of protic substances, cationic polymerization processes. More recently Mengoli and Vidotto have employed Bu4NBF4 in the electroinitiated polymerization of TRO dispersed in n-hexane and n-heptane81 (see page 21), getting evidence of the formation of acid species of boron, presumably BF 3. 

Polymerization by Transition-Metal Complex Catalysts. Mlly M12, and M13 have been polymerized by Et3Al/TiCl4 catalysts between 50° and 80 °C in n-hexane, the reaction times ranging from a few hours to several days. The polymers obtained have the same structure as those obtained by cationic polymerization. By analogy with mechanisms proposed in the literature (38, 39), the structure shown in Equation 24 may be proposed for the active center. 

It should be noted that the only cationically polymerized butadiene product commercialized is DuPont s Budium , which is an oligomeric resin used for tin-can linings. This product is produced using BF3-(C2H5)20/H20 in hexane at... 

The sulfonation of polyethersulfone with sulfuric and chlorosulfonic acid has been investigated experiments demonstrated that the degree of sulfonation increased with time and temperature. The resultant sulfonated material functions as a polymer electrolyte with an ion-exchange equivalent of 800-5000 gmol . Formaldehyde can be cationically polymerized at low temperatures by strong acids, e.g. chlorosulfonic acid in n-hexane, while trioxan is polymerized to poly(oxymethylene) by heating at 65 °C in the presence of a catalytic amount of chlorosulfonic acid. ... 

Anions of the type [M(C2B9H11)2] (M = Fe, Cp, Ni) were also used as noncoordinating anions with [Cp2ZrMe] +, which are active for the polymerization and copolymerization of ethylene and oc-olefins in non-polar solvents such as toluene and hexane [54]. By using the same anions, cationic actinide complexes have also been prepared [110]. 

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