Nanocomposites and nanomaterials

The influence of relative humidity on the ion (proton) conductivity of the intramolecular polycomplexes
Kunitskaya L., Zheltonozhskaya T., Nesin S., Klepko V.
Institute of Macromolecular Chemistry of the NAS of Ukraine. 48 Kharkivs’ke shosse  St, Kyiv-02160, Ukraine. 
E-mail: larisa_kunitskaya@ukr.net

The problem of the energy crisis is contributing to the increasingly active search for the alternative ways to obtain energy, including fuel cells. A solid polymer electrolytes (SPEs) with high ionic conductivity at room temperature has been an importance subject due to their interest in the all solid-state electrochemical devices development. 
In the present study, block copolymers comprising chemically complementary poly(ethylene oxide)/polyacrylamide have been  evaluated as proton conducting materials. With this aim in mind, two series of block copolymers PAAm-b-PEO (DBC) and PAAm-b-PEO-b-PAAm (TBC) with the variable PEO-block length and also their partially hydrolyzed derivatives (DBChydr and TBChydr respectively) were prepared by using a solution casting technique, and their ion (proton) conductivity was studied at the ambient temperature and at different relative humidity (RH).
 The water absorption data show the rise of the absorbed water as the relative humidity grows in all the samples under study. It has been established that the conductivity of DBC and TBC membranes depends on the content of the adsorbed water and the PEO-block length. The rise in RH from 33% to 98% resulted in the increase in conductivity of DBC and TBC membranes up to 10-4 S∙cm-1.  The study of the kinetics of the water absorption at 98% RH showed that the introduction of –COOH-groups into PAAm chains could accelerate the process of water absorption. The increase in conductivity of DBC and TBC membranes with the PEO-block lengthening has been noticed. 
Thus, block copolymers comprising the interacting polymer components could be considered as potential solid polymer matrices for proton exchange membranes and they open the way for their application in fuel cells. They also demonstrate the possibility of using commercially available, nontoxic solid polymer electrolytes in electrochemical devices. Such polymer electrolytes could be produced at low cost and they are environmentally friendly.