Tetrabutylammonium bromide polymerization

In an extension of this work, the reuse of the polymeric catalyst was addressed and several new PE-poly(alkene) glycol copolymers were prepared [68]. Commercially available oxidized polyethylene (CO2H terminated, both high and low molecular weight) was converted to the acid chloride and reacted with Jeffamine D or Jeffamine EDR, and subsequently converted to the tributylammonium bromide salt with butyl bromide. These new quaternary salts were shown to catalyze the nucleophihc substitution of 1,6-dibromohexane with sodium cyanide or sodium iodide. While none of the polymeric quaternary salts catalyzed the reaction as well as tetrabutylammonium bromide, the temperature-dependent solubility of the polymers allowed removal of the polymer by simple filtration. 

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. 

Imidazole or pyridine mediated silylation of l,2-0-[l-exo-ethoxy )ethylidene]-oc-D-glucopyranose failed to give a high yield of the 6-silyl ether due to some polymerization and side reactions. Activation of hydroxyl groups via a tributylstannyl intermediate followed by the tetrabutylammonium bromide catalyzed reaction with tert-butyl-chlorodiphenylsilane was more successful [231], the 6-0-silyl derivative being isolated in 87 % yield.. The lability of this protecting group under benzylation with benzyl bromide and sodium hydride at 0 °C has been observed [449]. 

Instead of acryloyl chloride or methacryloyl chloride, the glycidyl esters are used for functionalization with polymerizable compounds. Such a compound is 2-[2-hydroxy-4-alkoxy-(2-oxypropyl methacrylate)phenyl]-2H-4-methoxybenzotriazoIe, as shown in Figure 9.9. It is prepared by the reaction of 4-(5-methoxy-2H-benzotriazole-2-yl)resorcinol with glycidyl methacrylate. Tetrabutylammonium bromide is used as a catalyst and hy-droquinone is used as a polymerization inhibitor. 

In some systems it is necessary to add a large amount of salts to obtain polymers with low polydispersities. This happens when salts participate in ligand/anion exchange (special salt effect) and when they enhance ionization of covalent compounds through the increase of ionic strength. The special salt effect may either reduce or enhance ionization. Strong rate increases observed in the polymerization of isobutyl vinyl ether initiated by an alkyl iodide in the presence of tetrabutylammonium perchlorate or triflate can be explained by the special salt effect [109]. The reduction in polymerization rate of cyclohexyl vinyl ether initiated by its HI adduct in the presence of ammonium bromide and chloride can be also ascribed to the special salt effect [33]. The breadth of MWD depends on the relative rate of conversion of ion pairs to covalent species and is affected by the structure of the counterions. 

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