On the helical motif of the complexes created by association of helix-forming schizophyllan (SPG) and helix-forming polythiophene derivatives.

pi-Conjugated polymers can finely tune their electrical and optical properties in response to their conformational changes. We believe that a deeper understanding of their higher-order structures will stimulate further development of their applications. We had revealed that one helix-forming natural polysaccharide (SPG) and one polythiophene derivative (PT-1) formed a stable one-dimensional complex and in the polythiophene main chain a helical conformation was induced through the dynamic conformational changes. The objective of our present research is to obtain a better mechanistic understanding on the interaction between SPG and polythiophenes. Here we have used particular left- and right-handed helix-forming polythiophene derivatives (D- and L-POWTs, respectively) and studied their influence on the helical motif of the complexes. We observed that SPG interacts with both D- and L-POWTs through their dynamic conformational changes and both D- and L-POWTs form the right-handed co-helical complexes with SPG according to the inherent helical motif of SPG. In addition, it was confirmed that 1) the complexes do not coagulate in aqueous solution, and 2) the exchange in the helical motif can occur only when the polymers experience the denature-renature process. We believe, therefore, that the mechanism of the helical induction of the SPG/POWT complexes is very unique, being different from conventional equilibrium reactions.