Backbone functionalisation of conjugated polymers is crucial to their performance in many applications, from electronic displays to nanoparticle biosensors, yet there are limited approaches to introduce functionality. To address this challenge we have developed a method for the direct modification of the aromatic backbone of a conjugated polymer, post-polymerisation. This is achieved via a quantitative nucleophilic aromatic substitution (SNAr) reaction on a range of fluorinated electron-deficient comonomers. The method allows for facile tuning of the physical and optoelectronic properties within a batch of consistent molecular weight and dispersity. It also enables the introduction of multiple different functional groups onto the polymer backbone in a controlled manner. To demonstrate the versatility of this reaction, we designed and synthesised a range of emissive poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT)-based polymers for the creation of mono and multifunctional semiconducting polymer nanoparticles (SPNs) capable of two orthogonal bioconjugation reactions on the same surface.

Conjugated polymers exhibit interesting material and optoelectronic properties that make them well‐suited to the development of biointerfaces. Their biologically relevant mechanical characteristics, ability to be chemically modified, and mixed electronic and ionic charge transport are captured within the diverse field of organic bioelectronics. Conjugated polymers are used in a wide range of device architectures, and cell and tissue scaffolds. These devices enable biosensing of many biomolecules, such as metabolites, nucleic acids, and more. Devices can be used to both stimulate and sense the behavior of cells and tissues. Similarly, tissue interfaces permit interaction with complex organs, aiding both fundamental biological understanding and providing new opportunities for stimulating regenerative behaviors and bioelectronic based therapeutics. Applications of these materials are broad, and much continues to be uncovered about their fundamental properties. This report covers the current understanding of the fundamentals of conjugated polymer biointerfaces and their interactions with biomolecules, cells, and tissues in the human body. An overview of current materials and devices is presented, along with highlighted major in vivo and in vitro applications. Finally, open research questions and opportunities are discussed.

A simple route to the preparation of alkylamine, thioalkyl, and alkoxy monofunctionalized 4,7-di(thiophen-2yl)-2,1,3-benzothiadiazole) based monomers is reported from a common fluorinated precursor. Copolymerization with a carbazole comonomer under Suzuki conditions yielded a series of analogous donor−acceptor copolymers in which the only difference was the nature of the heteroatom (N, O, or S) on the benzothiadiazole core. This was shown to have a significant impact on the wavelength and intensity of the intramolecular charge transfer (ICT) absorption peak due to a combination of electronic and steric factors. Substantial differences were also observed in the solar cell performance of blends with PC 71 BM, with the octylamino substituted polymer exhibiting significantly lower performance than the other two polymers. This polymer also exhibited a reversible change in the optical spectra upon exposure to acid, suggesting potential as a sensing material.

The unique electrochemical properties of the conductive polymer poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) make it an attractive material for use in neural tissue engineering applications. However, inadequate mechanical properties, and difficulties in processing and lack of biodegradability have hindered progress in this field. Here, the functionality of PEDOT:PSS for neural tissue engineering is improved by incorporating 3,4-ethylenedioxythiophene (EDOT) oligomers, synthesized using a novel end-capping strategy, into block co-polymers. By exploiting end-functionalized oligoEDOT constructs as macroinitiators for the polymerization of poly(caprolactone), a block co-polymer is produced that is electroactive, processable, and bio-compatible. By combining these properties, electroactive fibrous mats are produced for neuronal culture via solution electrospinning and melt electrospinning writing. Importantly, it is also shown that neurite length and branching of neural stem cells can be enhanced on the materials under electrical stimulation, demonstrating the promise of these scaffolds for neural tissue engineering.

This method therefore allows an easy way to modulate the wettability and solubility of CP materials for a diverse series of applications.

The influence of the carborane isomer and double bond geometry on the optoelectronic properties for a series of side chain functionalised polythiophenes is reported.

Modification of functional groups attached to conjugated polymer backbones can drastically alter the material properties. Oxidation of electron-donating thioalkyl substituents to electron-withdrawing sulfoxides or sulfones is a particularly effective modification. However, so far, this reaction has not been studied for the modification of conjugated polymers used in organic electronics. Crucial questions regarding selectivity and reaction time waited to be addressed. Here, we show that the reaction is highly selective and complete within just a few minutes when using dimethyldioxirane (DMDO) for the oxidation of thioalkyl substituents attached to the well-investigated conjugated polymers poly(9-(1-octylnonyl)carbazole-alt-4,7-dithienylbenzothiadiazole) (PCDTBT) and poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT). The selectivity was confirmed by comparison with polymers obtained from pre-oxidized monomers and by control experiments using related polymers without thioalkyl substituents. Using DMDO, the oxidation yields acetone as the only side-product, which reduces the work-up to mere evaporation of solvents and excessive reagent. Our results show that this oxidation is an exciting method for the preparation of electron-deficient conjugated polymers. It may even allow the preparation of electron acceptors for solar cells directly from the electron donors.

Semiconducting polymer nanoparticles (SPNs) are explored for applications in cancer theranostics because of their high absorption coefficients, photostability, and biocompatibility. However, SPNs are susceptible to aggregation and protein fouling in physiological conditions, which can be detrimental for in vivo applications. Here, a method for achieving colloidally stable and low‐fouling SPNs is described by grafting poly(ethylene glycol) (PEG) onto the backbone of the fluorescent semiconducting polymer, poly(9,9′‐dioctylfluorene‐5‐fluoro‐2,1,3‐benzothiadiazole), in a simple one‐step substitution reaction, postpolymerization. Further, by utilizing azide‐functionalized PEG, anti‐human epidermal growth factor receptor 2 (HER2) antibodies, antibody fragments, or affibodies are site‐specifically “clicked” onto the SPN surface, which allows the functionalized SPNs to specifically target HER2‐positive cancer cells. In vivo, the PEGylated SPNs are found to have excellent circulation efficiencies in zebrafish embryos for up to seven days postinjection. SPNs functionalized with affibodies are then shown to be able to target HER2 expressing cancer cells in a zebrafish xenograft model. The covalent PEGylated SPN system described herein shows great potential for cancer theranostics.