Dielectric Characterization of Polyceram Films
- PDF / 323,510 Bytes
- 6 Pages / 420.48 x 639 pts Page_size
- 40 Downloads / 221 Views
DIELECTRIC CHARACTERIZATION OF POLYCERAM FILMS G. Teowee, J.M. Boulton, H.H. Fox, A. Koussa, T. Gudgel and D.R. Uhlmann Department of Materials Science and Engineering, University of Arizona, Tucson, AZ 85721. ABSTRACT Polycerams are an emergent class of hybrid, multifunctional materials which combine the properties of organic and inorganic materials. Films have been prepared from silicon alkoxides and reactive, functionalized polymers such as triethoxysilyl polybutadiene (MPBD), (N-triethoxysilylpropyl)Omodified polyethylene oxide urethane (MPEOU) and trimethoxysilylpropyl Characterization of substituted polyethyleneimine (MPEI). dielectric constant and tan 6 of the films has been carried out over a range of frequency from 500 Hz to 100 kHz; and the results are used to consider the potential of Polycerams as dielectric materials. INTRODUCTION Many desirable properties can be obtained by incorporating organic polymers in inorganic gels. In particular, the unique drying behavior of Polycerams allows the simple fabrication of monoliths and thick films without the cracking problems associated with conventional sol-gel derived alkoxide gels. A wide range of synthetic routes can be used to prepare these materials [1,2 e.g.]. One attractive method, which was chosen in this work, is to incorporate reactive functionalized polymers into the forming gel network. Previous examples of reactive polymers include silanol terminated polydimethylsiloxanes (3,4, e.g.] and triethoxysilyl terminated polytetramethylene oxide (5]. Schmidt has reported a dielectric constant of approximately 2-3 and a surface resistivity of 10 16f for organically modified coatings [6,7]; however, no other electrical characterization of Polycerams has been published. EXPERIMENTAL Details of precursor materials can be found in an accompanying paper (8]. In initial experiments for MPBD [triethoxysilyl modified 1,2- polybutadiene) and MPEOU [(N-triethoxysilylpropyl) 0-polyethylene oxide urethane] -modified silica, tetramethoxysilane (TMOS) was directly hydrolyzed with H20 resulting in an exothermic reaction and the formation of a clear solution. The water was acidified to 0.15M HCl, and a molar ratio of 1 TMOS: 4 H20 was used. The solution was stirred at room temperature for 10 min and the polymer was added in THF (1 g TMOS: 6 ml THF) to give a wgt ratio of 2 TMOS: 1 polymer. The resulting solution was stirred for 30 min prior to coating. This reaction scheme was unsuitable for MPEI [thriethoxysilylpropyl substituted polyethyleneimine], as the basic polymer solution (pH 9.4) resulted in rapid gelation. Therefore tetraethoxysilane (TEOS) was hydrolyzed with 0.15M HCl at a molar ratio of 1 TEOS: 2 H20 in THF (I g TEOS: 4.38 ml THF). The solution was refluxed for 15 mins and cooled; polymer was added and then directly used for coating. Mat. Res. Soc. Symp. Proc. Vol. 180. @1990 Materials Research Society
408
Coatings of each solution were applied to Pt-coated Si substrates at 2000 rpm for 20 secs. Films of neat polymer and silica were prepared by similar meth
