Transformation of Helical Sense of Poly(N-propargylamides) Controlled by Competition between Structurally Different Enantiomeric Amino Acids

Copolymerizations of structurally different chiral amino acid-based N -propargylamides, N- ( tert -butoxycarbonyl)- d -alanine- N -propargylamide (DA) with either N - (tert -butoxycarbonyl)- l -valine- N -propargylamide (LV) or N -( tert -butoxycarbonyl)- l -phenylalanine- N -propargylamide (LF), were conducted with (nbd)Rh + [ η 6 -C 6 H 5 B - (C 6 H 5 ) 3 ] as a catalyst to obtain the corresponding copolymers with moderate molecular weights in good yields. The specific rotation, CD, and UV−vis spectra showed that some of the copolymers underwent a helix−helix transition driven by temperature change. The transition of helix of poly(LV- co -DA) was much more obvious than that of poly(LF- co -DA). Poly(LV 50 - co -DA 50 ) underwent a solvent-induced helix−helix transition via random coil.