The reactions of electron-rich monomers with electrophilic compounds: Methyl tricyanoethylenecarboxylate and trimethylsilyl esters.

Abstract

The experimental results of the current work has three parts. First, the cycloaddition and copolymerization of methyl tricyanoethylenecarboxylate 2 with electron-rich olefins, such as p-methoxystyene, trans-anethole, isobutyl vinyl ether and ethyl cis-propenyl ether are discussed. The nature of the cycloadduct is determined by the orientation of the electrophilic olefins. Copolymerization of 2 with p-methoxystyrene under free-radical initiation gave an alternating copolymer. Second, trimethylsilyl methanesulfonate and trimethylsilyl diphenylphosphate were used as initiators for cationic polymerization. In the presence or absence of hindered pyridine, trimethylsilyl diphenylphosphate and trimethylsilyl methanesulfonate did not initiate the polymerization of p-methoxystyrene, anethole, 4-isopropenylanisole, 1,3-dioxolane or trioxane. Only trimethylsilyl methanesulfonate was able to initiate the cationic polymerization of 1,3-dioxepane in the presence of a hindered base. A model study demonstrates fast desilylation of a carbocation β to a silicon by an oxygen-containing counterion. Finally, block copolydioxepane-polydimethylsiloxane has been synthesized by the "silyl sulfonate approach." In this approach, the nucleophilic macromer, lithium polydimethylsiloxanate, was reacted with chlorodimethylsilane or allylchlorodimethylsilane to produce the corresponding macromers with silylated end groups. They contained a labile substituent, an allyl or a proton, on silicon. These macromers were then converted to electrophilic macropolydimethylsiloxane arylsulfonate by reaction with an aryl or alkyl sulfonic acid. The sulfonate polydisiloxanes can initiate the cationic polymerization of 1,3-dioxepane to yield block polydimethylsiloxane-polydioxepane. This cationic polymerization did proceed in the presence of 2,6-di-t-butylpyridine, which would trap any acid impurities.

The experimental results of the current work has three parts. First, the cycloaddition and copolymerization of methyl tricyanoethylenecarboxylate 2 with electron-rich olefins, such as p-methoxystyene, trans-anethole, isobutyl vinyl ether and ethyl cis-propenyl ether are discussed. The nature of the cycloadduct is determined by the orientation of the electrophilic olefins. Copolymerization of 2 with p-methoxystyrene under free-radical initiation gave an alternating copolymer. Second, trimethylsilyl methanesulfonate and trimethylsilyl diphenylphosphate were used as initiators for cationic polymerization. In the presence or absence of hindered pyridine, trimethylsilyl diphenylphosphate and trimethylsilyl methanesulfonate did not initiate the polymerization of p-methoxystyrene, anethole, 4-isopropenylanisole, 1,3-dioxolane or trioxane. Only trimethylsilyl methanesulfonate was able to initiate the cationic polymerization of 1,3-dioxepane in the presence of a hindered base. A model study demonstrates fast desilylation of a carbocation β to a silicon by an oxygen-containing counterion. Finally, block copolydioxepane-polydimethylsiloxane has been synthesized by the "silyl sulfonate approach." In this approach, the nucleophilic macromer, lithium polydimethylsiloxanate, was reacted with chlorodimethylsilane or allylchlorodimethylsilane to produce the corresponding macromers with silylated end groups. They contained a labile substituent, an allyl or a proton, on silicon. These macromers were then converted to electrophilic macropolydimethylsiloxane arylsulfonate by reaction with an aryl or alkyl sulfonic acid. The sulfonate polydisiloxanes can initiate the cationic polymerization of 1,3-dioxepane to yield block polydimethylsiloxane-polydioxepane. This cationic polymerization did proceed in the presence of 2,6-di-t-butylpyridine, which would trap any acid impurities.

The experimental results of the current work has three parts. First, the cycloaddition and copolymerization of methyl tricyanoethylenecarboxylate 2 with electron-rich olefins, such as p-methoxystyene, trans-anethole, isobutyl vinyl ether and ethyl cis-propenyl ether are discussed. The nature of the cycloadduct is determined by the orientation of the electrophilic olefins. Copolymerization of 2 with p-methoxystyrene under free-radical initiation gave an alternating copolymer. Second, trimethylsilyl methanesulfonate and trimethylsilyl diphenylphosphate were used as initiators for cationic polymerization. In the presence or absence of hindered pyridine, trimethylsilyl diphenylphosphate and trimethylsilyl methanesulfonate did not initiate the polymerization of p-methoxystyrene, anethole, 4-isopropenylanisole, 1,3-dioxolane or trioxane. Only trimethylsilyl methanesulfonate was able to initiate the cationic polymerization of 1,3-dioxepane in the presence of a hindered base. A model study demonstrates fast desilylation of a carbocation β to a silicon by an oxygen-containing counterion. Finally, block copolydioxepane-polydimethylsiloxane has been synthesized by the "silyl sulfonate approach." In this approach, the nucleophilic macromer, lithium polydimethylsiloxanate, was reacted with chlorodimethylsilane or allylchlorodimethylsilane to produce the corresponding macromers with silylated end groups. They contained a labile substituent, an allyl or a proton, on silicon. These macromers were then converted to electrophilic macropolydimethylsiloxane arylsulfonate by reaction with an aryl or alkyl sulfonic acid. The sulfonate polydisiloxanes can initiate the cationic polymerization of 1,3-dioxepane to yield block polydimethylsiloxane-polydioxepane. This cationic polymerization did proceed in the presence of 2,6-di-t-butylpyridine, which would trap any acid impurities.