Controlling the electro-mechanical performance of polypyrrole through 3- and 3,4-methyl substituted copolymers

Abstract

Conducting polymers such as polypyrrole are biocompatible materials used in bioelectronic applications and microactuators for mechanobiology and soft microrobotics. The materials are commonly electrochemically synthesised from an electrolyte solution comprising pyrrole monomers and a salt, which is incorporated as the counter ion. This electrosynthesis results in polypyrrole forming a threedimensional network with extensive cross-linking in both the alpha and beta positions, which impacts the electro-mechanical performance. In this study we adopt a 'blocking strategy' to restrict and control cross-linking and chain branching through beta substitution of the monomer to investigate the effect of crosslinking on the electroactive properties. Methyl groups where used as blocking groups to minimise the impact on the pyrrole ring system. Pyrrole, 3-and 3,4-methyl substituted pyrrole monomers were electro-polymerised both as homo-polymers and as a series of co-polymer films. The electroactive performance of the films was characterised by measuring their electrochemical responses and their reversible and non-reversible film thickness changes. This showed that altering the degree of crosslinking through this blocking strategy had a large impact on the reversible and irreversible volume change. These results elaborate the importance of the polymer structure in the actuator performance, an aspect that has hitherto received little attention.

Label-free impedimetric biosensor for Salmonella Typhimurium detection based on poly [pyrrole-co-3-carboxyl-pyrrole] copolymer supported aptamer

“…48 Immunological assays such as ELISA can detect Salmonella at level of 10 4 -10 5 cells mL -1 ; and 49 lower detection levels can be achieved by coupling ELISA methods with an enrichment step that Among CPs, polypyrrole has found widespread application due to properties such as ease of 67 synthesis in different solvents and at room temperature, good chemical stability and high 68 conductivity. Even more interestingly, polypyrrole can be fabricated via electrochemical 69 approaches, giving a high degree of control over thickness, shape, morphology and hydrophobicity polypyrrole suffers from the absence of functional groups and so copolymerisation of pyrrole with 72 modified monomers has been explored as a possible route to provide polypyrrole films with new 73 functionalities (Melling et al 2015). 74 Copolymers such as poly[pyrrole-co-4-(3-pyrrolyl] butanoic acid, have been used for the 75 fabrication of DNA hybridisation biosensors (Peng et al 2005).…”

Covalently linked nanocomposites of polypyrrole with graphene: Strategic design toward optimized properties

“…Also, due to the cross‐linked Ppy structures, movement of charge carriers (polarons) along the main chain of PPy can be restricted. This should lead to a reduction in the electrochemical stability, as observed . Likewise, the non‐covalently linked nanocomposite rGO‐Ppy also shows low stability, although slightly higher than neat Ppy and a depression of redox activity of Ppy.…”

“…Overall, the polymerization in this method can occur by the α‐position and β‐position of pyrrole. This could lead to a cross‐linked PPy covalently linked on the planar surface of graphene sheet, as represented in Figure . For the non‐covalent composites, the polymer formed is favorably surrounding the GO surface due to π–π‐stacking and hydrogen bonding, but the polymer growth is not so controlled and homogeneously distributed such as observed for the covalently formed composites .…”

Switchable presentation of cytokines on electroactive polypyrrole surfaces for hematopoietic stem and progenitor cells

“…The ratio of monomers in the film is not the same as the ratio in solution and unpredictable due to the different reactivity of the monomers. 32 Also, such modified conjugated polymers result in low conductive films. 33,34 Therefore, we have chosen to covalently attach the cytokines to dopants instead.…”