Organosoluble and optically active polyamides based on axially asymmetric 9,9′-spirobifluorene moieties

Abstract

Optically active polyamides containing axially asymmetric 9,9′-spirobifluorene units in the main chain were synthesized for the first time by low-temperature solution polycondensation of (R)-2,2′-bis(4-amino-2-trifluoromethylphenoxy)-9,9′-spirobifluorene with various diacyl chlorides. All these polymers were obtained in quantitative yields with inherent viscosities of 0.28–0.43 dL g⁻¹. These polyamides were amorphous and readily soluble in many organic solvents such as N-methyl-2-pyrolidone, N, N-dimethylacetamide (DMAc), dimethyl sulfoxide, and tetrahydrofuran. The glass transition temperatures of these polyamides were recorded in the range of 199–261°C by differential scanning calorimetry, and the 10% weight loss temperatures were over 410°C both under nitrogen and in air atmospheres. The specific rotations of these chiral polyamides oscillated between 65.0° and 127.8° depending on the structures of the diacid chlorides. All the optically active polymers exhibited high chiral stability in solid state or in DMAc solvent at high temperature due to incorporation of chiral spirobifluorone unit in polymer backbones. The ultraviolet–visible and circular dichroism spectroscopic properties of these chiral polyamides in solutions were also studied.