**2.7.1 Advantages of plasticizers**

The effect of plasticizers on the polymer electrolytes entirely depends on the specific characteristics of the plasticizer, for example, viscosity, dielectric constant, the interaction between polymer and plasticizer, and the coordinative bond between ion and plasticizer (Rajendran and Sivakumar, 2008b). The incorporation of plasticizer not only enhances the salt solvating power, but it also provides sufficient mobility of ions with a better contact between polymer electrolytes and electrodes (Ramesh and Arof, 2001; Rajendran et al., 2004). Apart from that, plasticizer is an attractive additive due to its superior miscibility with polymer, high dielectric constant and low viscosity (Ramesh and Chao, 2011b). Inclusion of plasticizer is the most successful skill to enhance the ionic conductivity without compromising the thermal, electrochemical and dimensional stabilities (Ganesan et al., 2008). Plasticizer are expected to improve the ionic conductivity through some important intrinsic modifications such as significant changes in local structure, enhancement of amorphous fraction and changes in local electric field distribution in the polymer matrix.
