Macromolecules, Vol.31, No.14, 4403-4409, 1998
Chirality induction in cyclocopolymerization. 9. Characterization of chirality induction during the cyclocopolymerizations of (2S,3S)-2,3-butanediyl, (2S,4S)-2,4-pentanediyl, and (2S,5S)-2,5-hexanediyl bis(4-vinylbenzoate)s with styrene
Optically active poly(methyl 4-vinylbenzoate-co-styrene)s (3a-c) were synthesized through the cyclocopolymerizations of (2S,3S)-2,3-butanediyl, (2S,4S)-2,4-pentanediyl, and (2S,5S)-2,5-hexanediyl bis(4-vinylbenzoate)s (1a, 1b, and 1c, respectively) with styrene. The extent of chirality induction increased in the order of 1a congruent to 1c < 1b, and the cyclized units predominately possessed an (R,R)-configuration. The MM2 calculation derived the conformer distributions in which monomers 1a and 1b predominately had a counterclockwise gauche form ("g(-)") and a combination of trans form and clockwise gauche form ("tg(+)"), respectively. Monomer 1c had a nide distribution into "tg(+)g(+)", "g(+)tg(+)", and "ttt" forms because of flexibility. The semiemprical molecular orbital calculations were performed for the model reaction of the radical cyclization. The calculated population difference between (R,R)- and (S,S)-configurations indicated that the template in 1b was more effective for the chirality induction than that in 1a, similar to the experimental results.