ORIGINAL PAPER Electrical transport study of potato starch-based electrolyte system Tuhina Tiwari & Neelam Srivastava & P.C. Srivastava Received: 19 October 2010 / Revised: 8 December 2010 / Accepted: 21 December 2010 / Published online: 26 January 2011 # Springer-Verlag 2011 Abstract A biopolymer electrolyte system having conduc- tivity ∼1.3×10 −4 S cm −1 has been prepared using potato starch, NaI, glutaraldehyde and poly(ethylene glycol) (PEG; molecular weight=300). High ionic transference numbers (∼0.99) of the material confirmed its electrolytic behaviour. Conductivity and dielectric behaviour as a function of frequency has been studied. Conductivity follows ‘universal power law’ (σ = σ 0 + Aω n ) with exponent ‘n’ varying from 0.94 to 1.18. Cross-linking and plastici- zation increases long pathways motion of charge carriers, comparable to sample dimension. Humidity-independent behaviour (up to 80% relative humidity), of impedance and water intake by the system, indicates the system’ s potenti- ality as a promising candidate for humidity immune device fabrication. The addition of PEG has a twofold effect on the material’ s conductivity. It not only increases conductivity but also improves the material’ s immunity towards humid atmosphere. Keywords Dielectric permittivity and loss . Solid polymer electrolyte . Cross-linker . Plasticizer . Biopolymer . Humidity dependence of impedances . Universal power law Introduction Electrolytes play a key role in electrochemical devices. These have to display high ionic conductivity combined with the properties of electronically insulating separators between electrodes. The current capacity/charging discharg- ing capability etc. of devices are decided by electrolytes; hence, it has received great attention. Due to hard matrix, solid electrolytes have low conductivity, whereas liquid electrolytes are associated with tribulations like packing/ leakage/corrosion etc. These problems could be addressed by a matrix which is physically solid but flexible at atomic/ molecular levels. Hence, polymer electrolytes have received great attention [1–5] since their discovery in 1970s [6]. Amorphous nature and flexible side chains of polymers offer ion movement channels and supporting mechanism; at the same time, polymers can be moulded in thin films/solid pellets etc. Poly(ethylene oxide), poly(propylene oxide), poly(vinyl alcohol), poly(vinyl acetate) [7–10] etc. are some polymers which have been used, as matrix for electrolyte synthesis, either in pure form or modified by plasticizers/cross-linkers/ co-polymerization/blending etc. Many electrochemical devices based on polymer electrolytes are being produced commercially, but synthesized polymers being detrimental to the environment continue to present challenges for scientists. Recently biopolymers have been recognized as a finer option for electrolyte development because they possess properties of polymer matrix and are environmental friendly/biodegradable too. Among the biopolymers, poly- saccharides have received the greatest attention. Starches, chitosan, cellulose, chitin [11–17] etc. are most commonly T. Tiwari : N. Srivastava (*) Physics Department, MMV, Banaras Hindu University, Varanasi 221005, India e-mail: neelamsrivastava_bhu@yahoo.co.in P. Srivastava Physics Department, Banaras Hindu University, Varanasi 221005, India Ionics (2011) 17:353–360 DOI 10.1007/s11581-010-0516-0