Conducting Pseudopolyrotaxanes: A Chemoresistive Response via Molecular Recognition

Abstract

Pseudorotaxanes are host-guest systems comprised of a cyclic molecule whose cavity is pierced by a compatible linear molecule. In pseudopolyrotaxanes, the polymer chain may function either as thecyclic host or as the linear guest. In both cases, the physical properties of the pseudopolyrotaxane and its parent polymer are dramatically different. In the case of self-assembling ?r-donor/ 7r-acceptor systems, a driving force for this complexation is charge transfer interactions. Although many polyrotaxanes and pseudopolyrotaxanes have been reported, there have been no investigations into pseudopolyrotaxanes derived from conducting polymers. Conducting Tolymers exhibit highly sensitive resistivities and can vary by multiple orders of magnitude as a result of environmental influences.2 This sensitivity allows the design of conducting polymer-based sensory materials wherein the resistivity and or redox potential can vary as a function of stimuli generated from host-guest interactions. Herein we report a novel polythiophene-based conducting pseudopolyrotaxane that exhibits both a reversible attenuation in conductivity and an anodic shift in redox potential in the presence of a 7r-deficient 4,4'-bipyridyl guest. Our design of conducting pseudopolyrotaxanes is based in part on Stoddart's demonstration that bis(p-phenylene)-34-crown10 (BPP) forms self-assembled complexes with ?r-deficient guest molecules such as paraquat (5).3 We therefore synthesized 1,