POLY(2,5-ETHYNYLENETHIOPHENEDIYLETHYNYLENES), RELATED HETEROAROMATIC ANALOGS, AND POLY(THIENO[3,2-B]THIOPHENES) - SYNTHESIS AND THERMAL AND ELECTRICAL-PROPERTIES

The novel class of polymers poly(2,5-ethynylenethiophenediylethynylenes) (la-f) and related materials 2 and 3 undergo a cross-linking reaction at moderate temperatures. The thermal reactivity of the polymers containing a diethynyl moiety provided substantial insight into the solid-state cross-linking reaction of polymeric conjugated diacetylenes. The intrinsic conductivities of the poly(2,5-ethynylenethiophenediylethynylenes) were in the insulating region. Upon doping with strong oxidants such as arsenic pentafluoride or the strong reducing agent sodium naphthalide, the conductivity increased into the semiconducting regime. Unreacted and cross-linked materials exhibit similar electrical conductivities. Investigations of the electrical conductivities of novel polymers, poly(5,5'-ethynylene-2,2'-bithiophenediylethynylene) (2) and poly[2,5-ethynylene (thieno[3,2-b]thiophenediyl)ethynylene] (3), were carried out to afford materials which upon doping were also semiconductive. Very little interaction between the aforementioned polymers la-f, 2, and 3 and the dopants was observed. This result is proposed to be due to a high oxidation potential of the polymers. New syntheses of poly(2,5-thieno[3,2-b]thiopheneylene) (4a,5a) and poly[2,5-(3-methylthieno[3,2-b]thiopheneylene)] (4b,5b) by FeCl3 oxidation and by electrochemical polymerization of the respective monomers afforded conductive materials upon doping.