Synthesis, structure characterization and ionic conductivity of star-branched organiceinorganic hybrid electrolytes based on cyanuric chloride, diamine-capped poly(oxyalkylene) and alkoxysilane Hao-Yiang Wu a , Diganta Saikia b , Chi-Pin Lin b , Feng-Shien Wu b , George T.K. Fey c , Hsien-Ming Kao b, * a Department of Neurological Surgery, Tri-Service General Hospital, National Defense Medical Center 325, Sec. 2, Cheng-Kung Road, Nei-Hu Dist, Taipei 11490, Taiwan, ROC b Department of Chemistry, National Central University, Chung-Li, Taiwan 32054, Taiwan, ROC c Department of Chemical and Materials Engineering, National Central University, Chung-Li, Taiwan 32054, Taiwan, ROC article info Article history: Received 15 April 2010 Received in revised form 7 July 2010 Accepted 24 July 2010 Available online 30 July 2010 Keywords: Organiceinorganic hybrid electrolytes Cyanuric chloride Ionic conductivity abstract A synthesis route for preparing highly conductive solid organiceinorganic hybrid electrolytes has been developed by using cyanuric chloride as the coupling core to react with diamino-terminated poly(oxy- alkylene) triblock copolymers, followed by cross-linking with an epoxy alkoxysilane 3-glycidyloxypropyl trimethoxysilane via a sol-gel process. The present hybrid electrolyte with a [O]/[Li] ratio of 32 was found to be the most conductive, reaching a maximum lithium ion conductivity of 6.8  10 5 Scm 1 at 30  C. The Li-ion mobility was determined from 7 Li static NMR line width measurements and correlated with their ionic conductivities. The onset of 7 Li line narrowing was closely related to the T g of the hybrid electrolytes as measured by DSC experiments. Thus, the motions of the lithium cations are strongly coupled with the segmental motion of the polymer chains, which is in line with the Vogel-Tamman- Fulcher behavior as observed in ionic conductivity. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Designing new ion-conducting polymer materials has been the subject of intense research due to its promising applications in the fields of Li-ion batteries, supercapacitors, dye-sensitized solar cell, and electrochromic devices [1e5]. The use of polymers in devel- oping electrolyte materials combines the ease of processability, design flexibility, lightweight, shape versatility, safety and lack of toxicity. As Li-ion batteries are considered to be one of the most reliable future energy storage systems, which can provide power ranges from modern electronic devices like cellphone and laptops to electric or hybrid electric vehicles (EV or HEVs), the use of polymer electrolytes in Li-ion batteries offers great promise for the development of low cost, long life and safe lithium-based battery technologies. Solid polymer electrolytes (SPEs) are considered as alternatives to liquid and gel electrolytes because of leakage proof and good mechanical properties. In addition, it is possible to avoid the hazardous chemicals which are used as solvents in liquid and gel polymer electrolytes. The main concern of SPEs is their low ionic conductivity. The ionic conductivity of SPEs is due to the motion of dissolved ionic species (cations and anions) in a polymeric matrix and in most cases occurs in the amorphous phase, above the glass transition temperature, T g , via a liquid like motion of the cations associated with segmental reorientations of the neighboring chains [6]. Although poly(ethylene oxide) (PEO) has been intensively studied as a host matrix to dissolve lithium salts because it contains ether coordination sites and flexible polymer structures, the major disadvantage associated with PEO-based polymer electrolytes is their ionic conductivity at ambient temperature (w10 7 Scm 1 ). This is due to the existence of crystalline domains that interfere with the ion transport and the dependence of the ion transport on the main-chain segmental motions [7]. To overcome this disad- vantage, considerable research efforts have been adopted to increase the volume fraction of the amorphous domain in the polymer host by using polymers with low T g , addition of inorganic sub-micron and nano-sized fillers, synthesis of organiceinorganic hybrid materials, and so on [8e14]. Among these, the organice inorganic hybrid electrolytes are of particular interest because of their highly flexible structures with enhanced segmental mobility as well as high thermal stability. Another advantage is the ease of modifying their properties by a broad choice of different side groups attached to the silicon atoms. In the present work, we investigated the dynamic properties of hyperbranched copolymers made from inorganic siloxane and polyalkylene oxide units connected by using 2,4,6-trichloro-1,3,5- triazine (cyanuric chloride) as the central core linking unit. * Corresponding author. Fax: þ886 3 4227664. E-mail address: hmkao@cc.ncu.edu.tw (H.-M. Kao). Contents lists available at ScienceDirect Polymer journal homepage: www.elsevier.com/locate/polymer 0032-3861/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.polymer.2010.07.039 Polymer 51 (2010) 4351e4361