Self-doped Conjugated Polyelectrolytes for Bioelectronics Applications

Abstract: Self-doped conjugated polyelectrolytes (CPEs) are a class of conducting polymers constituted of a π-conjugated backbone and charged side groups. The ionic groups provide the counterions needed to balance the charged species formed in the CPEs backbones upon oxidation. As a result, addition of external counterions is not required, and the CPEs can be defined as selfdoped. The combination of their unique optical and electrical properties render them the perfect candidates for optoelectronic applications. Additionally, their “soft” nature provide for the mechanical compatibility necessary to interface with biological systems, rendering them promising materials for bioelectronics applications. CPEs solubility, aggregation state, and optoelectronic properties can be easily tuned by different means, such as blending or interaction with oppositely charged species (such as surfactants), in order to produce materials with the desired properties. In this thesis both the strategies have been explored to produce new functional materials that can be deposited to form a thin film and,  therefore, used as an active layer in organic electrochemical transistors (OECTs). Microstructure formation of the films as well as influence on devices operation and performance have been investigated. We also show that these methods can be exploited to produce materials whose uniquecombination of self-doping ability and hydrophobicity allows incorporation into the phospholipid double layer of biomembranes, while retaining their properties. As a result, self-doped CPEs can be used both as sensing elements to probe the physical state of biomembranes, and as functional ones providing them with new functionalities, such as electrical conductivity. Integration of conductive electronic biomembranes into OECTs devices has brought us one step forward on the interface of manmade technologies with biological systems.