DESIGN PREPARATION AND PROPERTIES OF REGULARLY ALTERNATING CONJUGATEDLOW-MOLECULAR-WEIGHT COPOLYMERS BASED ON THIENYLENE-AZOMETHINE MOIETIES

A series of low molecular weight copolymers, composed of a sequence of thienylenic (low energy gap) and phenylenic (high energy gap) residue s linked together by azomethimic moieties, was prepared and extensivel y characterized. The semicrystalline materials, showing a weight loss of about 20% up to 450 degrees C, are soluble in H2SO4 and, when compl exed with GaCl3, in CH3NO2. The molecular structure was derived from F T-IR, viscosity, H-1 NMR and electron spin resonance analyses. The rev ersible complexation with either strong or Lewis acids allowed us to c haracterize the electronic properties of the oligomers in different co nformations (red <----> blue). An approximate structural model consist ent with the experimental data (X-ray diffraction) is presented and di scussed. The energy gaps (close to 2 eV) indicated a fully conjugated structure for the oligomers. Electronic localization effects are detec ted in the terms of the series with the longest thienylenic sequence, therefore indicating the realization of a quantum-dot polymeric struct ure. chi((3)) values observed under resonance conditions are about 10( -9) e.s.u.