In Depth Study on Solution-State Structure of Poly(lactic acid) by Vibrational Circular Dichroism

Polyesters are biodegradable analogues of polypeptides, but their biochemical applications have been hampered by the lack of a method to analyze polyester conformation in a solution state. We have demonstrated that vibrational circular dichroism (VCD) spectroscopy can conveniently and accurately elucidate the conformation of polyesters through the studies on poly( l -lactic acid) (PLLA), PLLA-amylose complex, and oligo( l -lactic acid). The analysis of VCD exciton couplet of these molecules has clarified the stable left-handed helical structure of PLLA, while density functional theory calculations of oligo( l -lactic acid) have revealed its detailed structural nature.