**3. Effect of 2-propanol concentration in electrolyte solution on polypyrrole actuator performance**

### **3.1 Introduction**

Recently, it has been reported that some PPy actuators exhibit strains of more than 10%, and that some of those even achieved strains of up to 40% (Hara et al., 2004). The improved strain has been mostly achieved using an electrolyte of tetra-n-butylammonium bis(trifluoromethansulfonyl)imide (TBATFSI) during PPy electropolymerization. These actuators generally function under a low potential voltage range less than 1 V.

Hara et al. reported that their TFSI-doped porous PPy films exhibited increased deformation when their aqueous lithium bis(trifluoromethansulfonyl)imide (LiTFSI) electrolyte solutions contained propylene carbonate (Hara et al., 2004). They attributed those effects to the swelling of the PPy film caused by the penetration of propylene carbonate. The swelled PPy film could more easily pass TFSI anions. We also immersed TFSI-doped PPy films into several organic chemicals, and found that the PPy films showed notable swelling in 2 propanol (Hoshino et al., 2011). Therefore, it was interesting to investigate whether the PPy actuators show improved deformation behaviors in aqueous LiTFSI solutions containing 2 propanol. In this section, the electrochemical deformation characteristics of TFSI-doped PPy soft actuators in aqueous LiTFSI solutions with different 2-propanol concentrations are reported.
