Abstract
Organic bioelectronic devices, particularly electrolyte-gated organic field-effect transistors (EGOFETs), demand receptor layers that combine high charge-carrier mobility with specific biorecognition ability. The [1]benzothieno[3,2-b][1]benzothiophene (BTBT) core is widely recognized for its excellent self‑organization and transport properties, whereas biotin provides a universal anchor for streptavidin‑based immobilisation of various bioreceptors. However, the integration of both moieties into a single polymer matrix with controlled architecture remains a challenging taski. In this work, we report two complementary synthetic strategies yielding novel copolymers with grafted BTBTii and biotin side groups. The first and main approach focuses on styrene‑based copolymers. The synthesis begins with a Wittig reaction to introduce the BTBT‑containing substituent into a styrenic monomer, followed by radical copolymerisation with styrene to afford a polymer backbone with pendant BTBT units. Subsequently, the biotin moiety is attached via an azide–alkyne cycloaddition (click reaction) to alkyne‑functionalised comonomer units pre‑introduced in the copolymer. This sequence (Wittig → copolymerisation → click) provides precise control over the BTBT/biotin ratio and yields processable materials with good film‑forming properties. The second route involves siloxane‑based copolymers prepared by polymer‑analogous transformations of a poly(methylhydride‑dimethyl)siloxane backbone. Here, BTBT groups are grafted via hydrosilylation, then the remaining groups are converted through Williamson etherification, and finally biotin is attached by a separate azide–alkyne cycloaddition. Both families of copolymers were thoroughly characterised with respect to phase behaviour, thermal stability, and self‑assembly. Langmuir–Schaefer technique demonstrated pronounced self‑organisation of the copolymers at the air–water interface, allowing the formation of highly ordered receptor layers. The polymeric nature of the receptor layer substantially improved the reproducibility of measurements, which is a critical advantage for practical biosensing. Among the two types, the styrene‑based copolymers showed fine film uniformity and easier processing, making them particularly attractive for large‑area sensor arrays. Overall, specifically the developed styrene based copolymers represent a versatile platform for the fabrication of highly sensitive and reproducible EGOFET biosensors.