SYNTHESIS AND PROCESSING OF HETEROCYCLIC POLYMERS AS ELECTRONIC, OPTOELECTRONIC, AND NONLINEAR OPTICAL-MATERIALS .2. NEW SERIES OF CONJUGATED RIGID-ROD POLYQUINOLINES AND POLYANTHRAZOLINES

A series of 13 new homopolymers and three new copolymers along with six previously known polymers were synthesized and characterized in the class of conjugated polyquinolines and polyanthrazolines. The polymers were designed to systematically vary the pi-electron delocalization along the conjugated polymer backbone and, thereby, to tune the electronic structure and properties in a controlled fashion. The solid polymers, which exhibit a range of light yellow to deep red color in transmitted light, were obtained in high yield, with high intrinsic viscosity and high thermal stability. As a result of the rigid-rod nature of the polymer chains, lyotropic liquid crystalline phases were observed at high concentrations of the polymers in di-m-cresyl phosphate/m-cresol (1:3) solvent. An investigation of the electronic structure of the polymers by optical absorption spectroscopy of the polymer thin films revealed that the structural modifications in the polymers can vary the optical band gap by about 1.0 eV. For example, compared to the biphenyldiyl linked polyquinoline (PBPQ, 2b) which has a band gap (E(g)) of 2.81 eV, the dithienylvinylene linked polyanthrazoline (PBVDA, 3k) exhibited a drastically lower band gap of 2.0 eV. In general, replacement of a phenylene linkage by a thiophene linkage in the polyquinoline or polyanthrazoline backbone produced a significant red shift of lambda(max) by 64-106 nm and a reduction of band gap by 0.3-0.5 eV. The new polymers are expected to have improved electronic, photoelectronic, and nonlinear optical properties for applications and serve as model systems for investigating structure-property relationships in conjugated polymers.