Control of helical sense and tightness of amino acid-based poly(N-propargylamide) by temperature and solvents

Poly(N-(alpha-tert-butoxycarbonyl)-L-aspartic acid beta-cyclohexyl ester N'-propargylamide) [poly(1)] was synthesized by the polymerization of the corresponding monomer 1 catalyzed by (nbd)Rh+ [eta(6)-C6H5B-(C6H5)(3)] in CH2Cl2 at 30 degrees C for 2 h. Poly(1) was soluble in CH2Cl2, CHCl3, THF, and partly soluble in DMF. The specific rotation, CD, and UV-vis spectroscopic data revealed that poly(1) exists in a helical structure in CH2Cl2, CHCl3, CHCl3/DMF, and CHCl3/ MeOH. Poly(1) underwent thermo- and solvent-driven switch of helical sense, accompanying the change of tightness.