POLY(N-(3-THIENYL)ALKANESULFONATES) - SYNTHESIS, REGIOREGULARITY, MORPHOLOGY, AND PHOTOCHEMISTRY

Poly(n-(3-thienyl)alkanesulfonates) (P3TAS's) containing propanesulfon ate, hexanesulfonate, and octanesulfonate substituents have been prepa red by oxidative coupling using ferric chloride. The ratio of head-to- tail dyads to head-to-head dyads is 4:1. The extent of pi-conjugation in the polymers, as determined by UV-vis spectroscopy, is relatively i ndependent of:whether the polymers are in solution or in the solid sta te. Polymer films of the sodium salt and sulfonic acid forms are amorp hous in contrast to non-sulfonated analogs, i.e., the poly(3-alkylthio phenes), which self-organize into semicrystalline solids. Morphologica l differences between alkane and alkanesulfonate derivatives of polyth iophenes are explained on the basis of ion aggregation which prevents polymer chains from achieving the coplanar conformation required for c rystallization. Remarkably, the acid form of the polymers, termed ''se lf-doped'', exhibit electronic conductivities in the range 5 x 10(-2)- 10(-1) S/cm even though they too are amorphous and devoid of long rang e order. The photochemistry of P3TAS's, in both their sodium salt and ''self-doped'' form, was investigated. The primary photochemical proce ss is photosensitization and reaction of singlet oxygen, which leads t o photobleaching, In oxygenated solutions, P3TAS's are much more photo stable than their non-sulfonated analogs due to quenching of photosens itized singlet oxygen by water. Films of P3TAS's take up atmospheric m oisture in ambient air and, as a result, exhibit enhanced photostabili ty compared td their non-sulfonated analogs exposed to ambient conditi ons. Anhydrous films,. however, exhibit rates of photobleaching which are comparable to the poly(3-alkylthiophenes). The acid form of the po lymers is found to be more photostable than their corresponding sodium salts. Unlike their non-sulfonated analogs, irradiated films of P3TAS 's exposed to ambient atmosphere do not cross-link to form insoluble P olymer upon irradiation due to the presence of residual moisture. Howe ver, photolithography can be performed on polymer films oxidized with ferric chloride. Anhydrous films of P3TAS's are rendered insoluble upo n exposure to UV or visible irradiation, thus affording the deposition of negative polymer images.