Preparation of nanostructured organic/inorganic polymer hybrids and their humidity sensing properties Hung-Jie Liou a , Gobalakrishnan Suyambrakasam b , Te-Chin Tsai a , Ren-Jang Wu a,b, *, Murthy Chavali a,b, ** a Department of Applied Chemistry, Providence University, Taichung 433, Taiwan b Department of Nanotechnology, School of Interdisciplinary Courses, Noorul Islam Centre for Higher Education (Noorul Islam University), Kumaracoil, 629 180 Tamilnadu, India 1. Introduction Humidity is the one of the most important parameter in our environment, especially in storage, preservation and transport operations. Measurement and control of humidity are important not only for human comfort but also for a broad spectrum of industries and technologies. Sensing humidity is extremely significant in agricultural, food, medical and other industrial production fields. For measuring relative humidity (RH) involve infrared hygrometers, aspirated psychrometers and capacitive or resistive type sensors. Materials that have been studied for humidity sensing include organic polymers (Sakai et al., 1996), ceramics (Cantalini and Perlino, 1992), hybrid polymer/inorganic systems (Su and Tsai, 2004) and composites (Wu et al., 2006), have been investigated and used as humidity sensors, by detecting changes in capacitance or resistance; each of them have their own merits and specific conditions of application (Kulwicki, 1991; Yamazoe and Shimizu, 1986). The RH detection mechanism of polymers has also been based on fluorescence intensity (Zhu et al., 1989), colorimetric absorbance (Zanjanchi and Sohrabnezhad, 2005), SAW devices (Bruno et al., 2004) and optical detection (Bariain et al., 1998) by means of changes in effective refractive index (m). Most of them show intrinsic shortcomings of instability at high humidity and large hysteresis (Sager et al., 1994), so that they should be modified to improve the sensing characteristics. In the past 20 years, organic– inorganic nanocomposite materials have been regarded as a new class of materials for many new electronic, optic or magnetic applications, since many bulk properties can be improved compared with those of base polymers (Novak, 1993). In need to solve many shortcomings, hybrid material systems, which are one of the most interesting type towards better humidity-sensitive characteristics, such as reliability, ease of processing and low fabrication cost. Many research groups have demonstrated that, monolithic transparent hybrid materials can be prepared by controlling properly the conditions of hydrolysis and condensation of sol–gel materials such as tetraethoxysilane (TEOS) (Tong et al., 2002) either by bonding chemically or by physical mixing. A significant feature to enhance compatibility in hybrid materials is the formation of covalent bonding between organic–inorganic poly- mers and inorganic components (Ershad et al., 1997). Hybrid inorganic–organic (nanocomposite) offer a variety of advanta- geous properties in various applications such as optical materials with high reflective indices, colored glasses, hard coatings, and corrosion protection coatings on the aluminum surfaces, porous materials for chromatography and catalyst supports, and aerogel. Journal of the Taiwan Institute of Chemical Engineers xxx (2011) xxx–xxx ARTICLE INFO Article history: Received 17 August 2010 Received in revised form 16 December 2010 Accepted 2 January 2011 Keywords: HPMC TEOS Microwave Nanostructured hybrids Humidity sensing ABSTRACT Humidity sensitive nanostructured hybrid films were synthesized from hydroxyl propyl methyl cellulose (HPMC) and tetra ethoxy ortho silicate (TEOS) via sol–gel route by microwave assistance method. HPMC and TEOS were used as organic and inorganic precursors, respectively. FT-IR spectra of the hybrid material revealed the formation of organic–inorganic networks between HPMC and TEOS. XRD spectra and micrographs showed the formation of HPMC/TEOS amorphous nano hybrids film like structures. Surface roughness was measured using an AFM was 120 nm and measured film thicknesses were between 20 and 24 mm. Hybrid films have showed better linear sensor response, lower hysteresis (<1% RH), faster response (5 s) and recovery time (10 s), and short-term stability (30 min at least). Using Material Studio 3.2 Software, the adsorption phenomena were explained to that of humidity sensing property. ß 2011 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved. * Corresponding author at: Department of Applied Chemistry, Providence University, 200 Chungchi Road, Shalu, Taichung 433, Taiwan. Tel.: +886 4 26328001 15212; fax: +886 4 26327554. ** Corresponding author at: Department of Nanotechnology, School of Interdisci- plinary Courses, Noorul Islam Centre for Higher Education (Noorul Islam University), Kumaracoil, 629 180 Tamilnadu, India. Tel.: +91 9789 232 232; fax: +91 4651 257 266/250 266. E-mail addresses: rjwu@pu.edu.tw (R.-J. Wu), ChavaliM@gmail.com (M. Chavali). G Model JTICE-301; No. of Pages 6 Please cite this article in press as: Liou, H.-J., et al., Preparation of nanostructured organic/inorganic polymer hybrids and their humidity sensing properties. J. Taiwan Inst. Chem. Eng. (2011), doi:10.1016/j.jtice.2011.01.001 Contents lists available at ScienceDirect Journal of the Taiwan Institute of Chemical Engineers journal homepage: www.elsevier.com/locate/jtice 1876-1070/$ – see front matter ß 2011 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.jtice.2011.01.001