1,2-dichloroethane, cationic polymerization

Sakurada, I., Y. Tanaka, and N. Ise Cationic polymerization of a-methylstyrene catalyzed by boron trifluoride etherate in 1,2-dichloroethans under an electric field. J. Polymer Sci. A-l 6, 1463 (1968). 

Cationic polymerization of thiiranes CMT (9-(thiiran-2-ylmethyl)-9//-carbazole) 217 and PMT (10-(thiiran-2ylmethyl)-1077-phenothiazine) 218 was studied by a Lithuanian group <2002JPH63>. Initiators were di-(/-butylphenyl)iodonium tetrafluoroborate (BPIT), diphenyliodonium tetrafluoroborate, cyclopropyldiphenylsulfonium tetrafluoroborate, and ( 7 -2,4-cyclopentadien-1 -yl) [1,2,3,4,5,6- )-( 1 -methylethyl)benzene]-iron(- -)-hexafluorophosphate(—1). The influences of temperature and initiator concentration on the polymerization rate and the conversion limit were determined. The values of initiator exponent and activation energy for the photopolymerization of CMT and PMT initiated with BPIT in 1,2-dichloroethane was established. 

Following an interesting article on the influence of electric fields on the cationic polymerization of vinyl monomers by iodine in 1,2-dichloroethane solutions116, Giusti and coworkers published a basic research on the electrochemical activation of tetraalkylammonium iodide and triiodide in chlorinated organic solvents117, in the absence of the monomer. The electrodic reactions are ... 

In a solution of 1,2-dichloroethane at 60°C, iV-vinylcarbazole has been cationically polymerized with ethyl l-cyano-2-(p-methoxyphenyl)cyclopropane-carboxylate as initiator. The polymers obtained had a bimodal distibution of their molecular weights. It was postulated that the propagation steps of the process proceeded by both free-ion and an ion-pair steps. At low temperatures, low monomer concentrations, higher initiator concentrations, lower conversion, and in more polar solvents, the free-ion propagation was favored [61]. 

Trifluoromethanesulfonic acid (TfOH) is an effedive initiator for cationic polymerization. For example, TfOH-initiated polymerization of isobutyl vinyl ether (IBVE) in 1,2-dichloroethane using a macroscale batch system (20 mL scale) [46] is complete within lOsat—25°C. The molecular weight distribution is, however, rather broad and Mw/Mn ranges from 2.73 to 4.71, presumably because of chain transfer readions due to the high readivity of the polymer ends. 

Interesting effects were observed if cationic polymerization was carried out under an electric field [91,92]. Depending on the solvent, the degree of ion separation is decreased under the influence of the electrical field. However, if toluene is applied, the effect is small due to the low value of the solvent. In the range of intermediate values of (dichloroethane) the highest changes in rate are observed. In nitrobenzene, a solvent with high values, the ion separation is almost complete. Therefore, application of an... 

The cation [NSO(NPCl2)2] (14.11) is the proposed intermediate in this ring-opening polymerization process. This cation is extremely reactive, as illustrated by the isolation of the solvent-derived product 14.12 when it is generated by halide abstraction from the cyclic precursor with AICI3 in l,2-dichloroethane. °... 

In 1,1-dichloroethane no polymer forms with tetrabutylammonium bromide (TBAB) and tetrabutylammonium tetraphenylboron (TBAPB) whereas with tetrabutylammonium boronfluoride (TBABF) cationic and free-radical polymerization proceed where anionic chain growth is hindered (Table 4). Thus, by changing the solvent the polymerization mechanism may altered from a cationic to an anionic one. 

Furthermore, with [Ni(Ci2Hi9)]PF6 as catalyst it has been found that, if the cation-anion interaction is enhanced by addition of NEt4PF6 to the reaction solution in dichloroethane, the degree of polymerization n can be increased [79]. Presumably the electrophilicity of the nickel(II) and thence the tendency toward )9-hydride elimination can be decreased in this way, opening an additional possibility for molecular weight regulation which is of practical importance in the case of the technical nickel catalyst. 

Problem 8.28 Consider styrene polymerization by triflic (trifluoroethanesul-fonic) acid in 1,2-dichloroethane at 20°C where is 4.2x10 mol/L (23]. For experiments performed (using stopped-flow rapid scan spectroscopy) at a styrene concentration of 0.397 M and acid concentration of 4.7x10 M at 20°C, the maximum concentration of cationic ends (both free ions and ion pairs) was found [23] to be 1.4x10 M, indicating that the initiator efficiency is 0.030. At 20°C, kf / is reported [23] to be 12. 

Monomers 1, 2, and 4 are very insoluUe in almost all organic solvent. Thus we had to explore non-traditional solvent systems to effect our electropolymerization. 1, 2, and 4 were found to be soluble in CH2CI2 and 1,2 dichloroethane with small amounts (<5% v v) of TFA. Trifluoroacetic acid and TEA in CH2CI2 have been shown to stabilize radical cations formed during oxidation (34). Since die conductivity of this solution was low, we added 0.1 M TBAPF6, and subsequent excursions to oxidative potentials showed no clear oxidation peaks nor any products precipitating onto the electrodes. We reasoned that PFe maybe acid labile, so we synthesized triethylammonium trifluoroacetate as a supporting electrolyte and added TFA to solubilize the monomer. This solvent electrolyte system provided an excellent media for die electrooxidative polymerization of 1,2, and 4. 

Other cationic systems studied include the polymerization of indene using tetrabutylammonium hexachloroantimonate in either dichloroethane or nitrobenzene. The antimonate was found to be more efficient and it was shown that polymerization occurred as a result of both direct oxidation of the monomer and by interaction with HSbCl, and HCIO4 produced electrochemically. Cerrai et al., investigating the polymerization of cyclohexyl vinyl ether, report that in dichloroethane with tetrabutylammonium perchlorate, only 0.05 mA was required to produce polymer by direct oxidation of the monomer. The same school, using cyclic voltammetry, rotating electrode voltammetry, and chromo-amperometry, report that the oxidation of anethole proceeds by an ECE mechanism with an intermediate chemical step of moderate velocity. 

Porous silica-supported polymeric catalysts were prepared by sulfonation of divinylbenzene (DVB) or styrene-DVB copolymers with chlorosulfonic acid. The resultant acidic polymers had an ion-exchange capacity of up to 0.41 mequiv. g. ° Treatment of the styrene-divinylbenzene copolymer (one part) with chlorosulfonic acid (three to four parts) in 1,2-dichloroethane at 10-25 afforded the cation-exchange resin. ... 

Figure 13 Time course of the formation of polystyryl cation and monomer conversion. Polymerization conditions 10°C 1,2-dichloroethane solvent [CF3S03H]o = 2.4mmol [styrene]o = 0.391 molM. ...

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