Protection and polymerization of functional monomers. 29. Syntheses of well-defined poly[(4-vinylphenyl)acetic acid], poly[3-(4-vinylphenyl)propionic acid], and poly(3-vinylbenzoic acid) by means of anionic living polymerizations of protected monomers bearing bicyclic ortho ester moieties

Anionic polymerizations of four styrenes protected with bicyclic ortho este r moieties, 1-(4-vinylphenyl)methyl-4-methyl-2,6,7-trioxabicyclo[2.2.2]octa ne (1), 1-[2-(4-vinylphenyl)ethyl]-4-methyl-2,6,7-trioxabicyclo[2.2.2]octan e (2), 1-(3-vinylphenyl)-4-methyl-2,6,7-trioxabicyclo[2.2.2] (3), and 1-(4- vinylphenyl)-4-methyl-2,6,7-trioxabicyclo[2.2.2]octane (4), were carried ou t in THF at -78 degrees C for 0.5 h with oligo(alpha-methylstyryL)lithium a nd -dipotassium and potassium naphthalenide. Poly(1)-(3) were quantitativel y obtained, and the resulting polymers possessed the predicted molecular we ights based on the molar ratios of monomers to initiators and narrow molecu lar weight distributions (MWDs, M-w/M-n < 1.1). By contrast, polymerization of 4 did not go to completion and gave insoluble polymeric product in low yield due to the side reactions under the similar conditions. The substitue nt position in the monomer was very important for the success of the polyme rization, although the bicyclic ortho ester was found to be stable under th e polymerization conditions of 1-3. Well-defined block copolymers of 1 and 2 with styrene were synthesized by the sequential block copolymerizations r egardless of the order of addition of the monomers. Hydrolyses of bicyclic ortho ester moieties of the resulting polymers were performed at room tempe rature by treating with 6 N HCl in THF/MeOH for 1 h and subsequently with 1 0% NaOH(aq) in THF/MeOH for 12 h. Deprotections of poly(1), poly(2), and po ly(3) quantitatively proceeded to afford poly[(4-vinylphenyl)acetic acid], poly[3-(4-vinylphenyl)propionic acid], and poly(3-vinylbenzoic acid) having tailored chain structures, respectively.