Homo- and R/S-copolymerizations of chiral methylpropargyl esters carrying pyrene moieties, and optical properties of the formed polymers

Pyrene-functionalized chiral methylpropargyl esters, (R)-3-butyn-2-yl-1-pyrenebutyrate (R)-1], (S)-3-butyn-2-yl-1-pyrenebutyrate (S)-1], (R)-3-butyn-2-yl-1-pyrenecarboxylate (R)-2], and 3-butyn-2-yl-1-pyrenecarboxylate (R,S)-2] were polymerized with (nbd)Rh⁺η⁶-C₆H₅B⁻(C₆H₅)₃] to obtain the corresponding polymers with moderate molecular weights (M_n: 10?500-66?500) in good yields (82-97%). All the polymers were soluble in CHCl₃, CH₂Cl₂, and THF. The polarimetric and CD spectroscopic data indicated that poly(R)-1], poly(S)-1], and poly(R)-2] existed in a helical structure with predominantly one-handed screw sense in these solvents. The helical structure of poly(R)-1] and poly(S)-1] was stable upon heating and addition of MeOH, while that of poly(R)-2] changed upon MeOH addition. The copolymerization of (R)-1 with (S)-1 was also conducted to obtain the copolymers satisfactorily. Poly(R)-1], poly(S)-1], and poly(R)-2] emitted fluorescence smaller than the corresponding racemic copolymers. The fluorescence intensity was tuned by the addition of MeOH to THF solutions of the polymers.