UNUSUALLY LOW-ENERGY ELECTRONIC-TRANSITIONS IN POLY(DIACETYLENE) SOLUTIONS - SOLVATOCHROMIC AND THERMOCHROMIC BEHAVIOR OF POLY(1,4-BIS(3-QUINOLYL)BUTA-1,3-DIYNE)

Solutions of poly(1,4-bis(3-quinolyl)buta-1,3-diyne) (PDQ) have shown the lowest energy electronic transitions of all the reported poly(diacetylene)s. Unusual solvato- and thermochromic behavior of PDQ in various polar and nonpolar environments is discussed. The role of hydrogen bonding appears crucial to the solution and chromic behavior in these solutions. pi-Conjugation between the polymer backbone and the cross-conjugated heteroaromatic side groups appears to lead to chain segments with unusually extensive electron delocalization. Stable (over a period of 2 years), dark green, true solutions in phenol-acetonitrile (nonsolvent) (lambda(max) = 733 nm) are obtained. The stability of charged and rigid rod-like PDQ macromolecules is explained in terms of screening of interchain Coulombic interactions.