This paper provides a review of the recent advances made in the field of electroactive polymers and composites for biomedical applications.

Photo-dimerisation reactions that can be reversed upon application of an appropriate wavelength of light have generated a considerable interest in the development of new photo-responsive polymeric systems for diverse applications. The incorporation of photo-dimerisable moieties into polymers allows the fabrication of various polymer architectures with an added advantage of reversibility. This review focuses on polymeric systems that exploit photo-reversible dimerisation reactions and their applications.

Recently conducting and electroactive polymers have received the attention of researchers to explore their potential in biomedical applications. Polyurethanes (PUs) are of particular interest to make conductive polymer composites by the incorporation of conductive particles because of their inherent biocompatibility, biostability, excellent processability and good mechanical properties. In the present work, conductive composites of graphene and a siloxane polyurethane (Elast-Eon™) were prepared. The graphene/Elast-Eon™ composites were prepared using different methods i.e. solution mixing, melt processing and in situ polymerisation in order to compare the effect of the processing method on the conductivity of resulting composites. The composites were prepared with varying content of graphene and the electrical conductivity of the resulting composites was determined using a two point probe method. In order to improve the conductivity, effect of cooling rate during compression moulding as well as annealing of composite films was examined. Both of these approaches were found to significantly improve the conductivity of composites with lower graphene content (≤5 wt%). A conductivity of 1.12 × 10⁻³ S cm⁻¹ was achieved with 5 wt% loading of graphene and a maximum conductivity of 5.96 × 10⁻² S cm⁻¹ was achieved with 15 wt% of graphene content. The composites were further characterised using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and tensile testing methods. The tensile and TGA results showed that the composites have good mechanical properties and showed that composites retain the thermal properties of parent PU material. Furthermore, the cytotoxicity assay tests found that composites were not cytotoxic to living cells in vitro and potentially useful in biomedical applications.

Electrically conductive polymeric materials have recently garnered significant interest from researchers due to their potential applications in the biomedical field, including medical implants, tissue engineering, flexible electronic devices, and biosensors. Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is considered the most successful conducting polymer due to its higher electrical conductivity and chemical stability, but it suffers from limited solubility in common organic solvents, poor mechanical properties, and low biocompatibility. An area of tremendous interest is in combining PEDOT:PSS with another polymer to form a blend or composite material in order to access the beneficial properties of both materials. However, the hydrophilic nature of PEDOT:PSS makes it difficult to produce composites with non-polar polymers. In order to overcome these problems, we have specifically designed and synthesized two new sulfonated polyurethanes (PUS) with high sulfonic acid functionality. The two polyurethanes, one water-soluble (PUS1) and one water-insoluble (PUS2), were used to make blends with two commercially available PEDOT:PSS formulations (Clevios^TM FET and PH1000). Solvent cast films on glass substrates were made from water-soluble PEDOT:PSS/PUS1 blends while free-standing films of PEDOT:PSS/PUS2 blends were fabricated by compression-moulding. Ethylene glycol was used as conductivity enhancer, which showed an increase in the conductivity by several orders of magnitude in most of the compositions investigated. The highest conductivity of 438 S cm⁻¹ was achieved for the blend with 80 wt% of PEDOT:PSS (PH1000) in PUS1.