Intrinsically Stretchable Block Copolymer Based on PEDOT:PSS for Improved Performance in Bioelectronic Applications

Abstract

The conductive polyelectrolyte complex poly­(3,4-ethylenedioxythiophene):poly­(styrenesulfonate) (PEDOT:PSS) is ubiquitous in research dealing with organic electronic devices (e.g., solar cells, wearable and implantable sensors, and electrochemical transistors). In many bioelectronic applications, the applicability of commercially available formulations of PEDOT:PSS (e.g., Clevios) is limited by its poor mechanical properties. Additives can be used to increase the compliance but pose a risk of leaching, which can result in device failure and increased toxicity (in biological settings). Thus, to increase the mechanical compliance of PEDOT:PSS without additives, we synthesized a library of intrinsically stretchable block copolymers. In particular, controlled radical polymerization using a reversible addition–fragmentation transfer process was used to generate block copolymers consisting of a block of PSS (of fixed length) appended to varying blocks of poly­(poly­(ethylene glycol) methyl ether acrylate) (PPEGMEA). These block copolymers (PSS(1)-b-PPEGMEA(x), where x ranges from 1 to 6) were used as scaffolds for oxidative polymerization of PEDOT. By increasing the lengths of the PPEGMEA segments on the PEDOT:[PSS(1)-b-PPEGMEA(1–6)] block copolymers, (“Block-1” to “Block-6”), or by blending these copolymers with PEDOT:PSS, the mechanical and electronic properties of the polymer can be tuned. Our results indicate that the polymer with the longest block of PPEGMEA, Block-6, had the highest fracture strain (75%) and lowest elastic modulus (9.7 MPa), though at the expense of conductivity (0.01 S cm–1). However, blending Block-6 with PEDOT:PSS to compensate for the insulating nature of the PPEGMEA resulted in increased conductivity [2.14 S cm–1 for Blend-6 (2:1)]. Finally, we showed that Block-6 outperforms a commercial formulation of PEDOT:PSS as a dry electrode for surface electromyography due to its favorable mechanical properties and better adhesion to skin.

Preparation of Resilient Organic Electrochemical Transistors Based on Blend Films with Flexible Crosslinkers

“…[46][47][48] A PEG-based crosslinker was selected as the new crosslinker because of its flexibility, which has been incorporated into mixed conductors to improve flexibility. [49][50][51] Some studies have employed PEGDE as a flexible crosslinker for the polymer films of PEDOT: PSS. [52][53][54] Structural analysis revealed that PNIPAM was segregated on the surface and that the PEGDE crosslinker increased the crystallinity of PEDOT.…”

External Measurement of Swallowed Volume During Exercise Enabled by Stretchable Derivatives of PEDOT:PSS, Graphene, Metallic Nanoparticles, and Machine Learning

“…The sEMG electrodes were made using PEDOT:PSS (1) -b-PPEGMEA (6) block copolymer ("Block-6") designed and synthesized with electrical and mechanical properties tuned for measuring electromyography signals on-body (Figure 2). [60] PEDOT:PSS is a conductive polymer used in many different fields of electronics due to its high conductivity with additives and its molecular stability. [61][62][63][64][65] However, the additives used to increase the stretchability and the conductivity tend to be toxic and can leach out over time decreasing the performance of the polymer.…”

Adhesive Properties of Semiconducting Polymers: Poly(3-alkylthiophene) as an Ersatz Glue

“…The mechanical properties of the PEDOT:PSS layer also likely contributed to this observed debonding behavior. P3BT was the only polymer in the series to have an elastic modulus greater than PEDOT:PSS (∼385 MPa), which likely prevented crazing at the PEDOT:PSS/P3BT interface due to elastic mismatch. In contrast, n = 5–7 all delaminated at the PEDOT:PSS/P3AT interface with low measured peel forces (∼60 N m –1 ), which is consistent with findings from the Dauskardt group showing that the PEDOT:PSS/P3HT:PCBM interface is weakest within a device stack. , At n = 8, there was a transition at which the adhesion between the P3AT/tape interface became weak enough such that it becomes the most favorable debonding interface.…”