The defect structure of sol–gel-derived silica/polytetrahydrofuran hybrid films by FTIR

Abstract The structural perturbations induced by polytetrahydrofuran (PTHF) on sol–gel hybrid films were identified by Fourier-transform infrared (FTIR) spectroscopy. The films were prepared by spin-coating, from aged solutions containing tetraethylorthosilicate (TEOS) as the inorganic precursor and different concentrations of PTHF. All the spectra reveal a set of bands that may be associated with structural defects of the silica network. The hybrid films show an additional `defect' band at 560 cm −1 , assigned to a skeletal vibration of 4-fold siloxane rings, whose intensity grows as the polymer content or molecular weight increases. The relative intensity of two components of the νasSi–O–Si mode (resolved by deconvolution of the band at ∼ 1080 cm −1 ) grow accordingly. They were thus assigned to the longitudinal (LO) and transverse optical (TO) modes of that vibration in 4-fold siloxane rings. Simultaneously, the bands assigned to the νSi–O− mode and to the νSi–O(H) mode of unreacted silanol groups (obtained by deconvolution of the band at ∼ 950 cm −1 ) increase. These conjugated observations lead to the conclusion that the polymer hinders the condensation reactions, being responsible for a more porous structure, with retention of a larger proportion of 4-fold siloxane rings. For high concentrations of high molecular weight PTHF, the defect structure of the films indicates that a partial segregation of the polymer occurs.

[1]  Helmut Schmidt,et al.  Investigation of Ion-Conducting Ormolytes: Structure-Property Relationships , 1994 .

[2]  Katsuhisa Tanaka,et al.  Thermal evolution of gels derived from CH3Si(OC2H5)3 by the sol-gel method , 1990 .

[3]  L. Hench,et al.  The sol-gel process , 1990 .

[4]  C. Brinker,et al.  Sol-Gel Science: The Physics and Chemistry of Sol-Gel Processing , 1990 .

[5]  T. Yoko,et al.  Hydrolysis and condensation reactions of Si(OC2H5)4 related to silica fiber drawing , 1988 .

[6]  Lesile Glasser.  The chemistry of silica: By Ralph K. Iller. Pp. vii+ 866. Wiley, Chichester. 1979, £39.50 , 1980 .

[7]  H. Nasu,et al.  X-ray diffraction of silica gels made by sol–gel method under different conditions , 1998 .

[8]  W. A. Pliskin.  Comparison of properties of dielectric films deposited by various methods , 1977 .

[9]  L. Hench,et al.  Quantum chemistry of sol-gel silica clusters☆ , 1990 .

[10]  L. Ilharco,et al.  Hybrid Silica Gel-Polytetrahydrofuran Thin Films , 1998 .

[11]  S. Katayama,et al.  Processing and optical properties of patternable inorganic–organic hybrid films , 1999 .

[12]  L. Matějka,et al.  Structure evolution in epoxy–silica hybrids: sol–gel process , 1998 .

[13]  S. Sakka,et al.  Influence of the type of alkyl group on hydrolysis and polycondensation of tetraalkoxysilane , 1988 .

[14]  R. Mcdonald.  Surface Functionality of Amorphous Silica by Infrared Spectroscopy , 1958 .

[15]  D. Wood,et al.  Study of Alkoxide Silica Gels by Infrared Spectroscopy , 1989 .

[16]  M. A. Morelli,et al.  Raman and infrared spectra on silica gel evolving toward glass , 1982 .

[17]  R. W. Hendricks,et al.  Neutron irradiation effects and structure of noncrystalline SiO2 , 1974 .

[18]  L. Ilharco,et al.  The Structure of Hybrid Gels by Drift and NMR Spectroscopies , 2000 .

[19]  H. Nasu,et al.  IR study on the structural evolution of sol-gel derived SiO2 gels in the early stage of conversion to glasses , 1990 .

[20]  T. Parrill.  Transmission infrared study of acid-catalyzed sol-gel silica coatings during room ambient drying , 1992 .

[21]  J. Zink,et al.  Effects of organic and inorganic network development on the opticalproperties of ORMOSILs , 1997 .

[22]  L. Hench,et al.  AM1 study on infra-red spectra of silica clusters modified by fluorine , 2000 .

[23]  H. Kozuka,et al.  Stability of solutions, gels and glasses in the sol-gel glass synthesis , 1988 .

[24]  F. L. Galeener,et al.  Planar rings in vitreous silica , 1982 .

[25]  Rui M. Almeida,et al.  Characterization of silica gels by infrared reflection spectroscopy , 1990 .

[26]  A. Chmel,et al.  Vibrational spectra and deffect structure of silica prepared by non-organic sol-gel process , 1990 .

[27]  E. Knözinger,et al.  Novel aspects of mid and far IR Fourier spectroscopy applied to surface and adsorption studies on SiO2 , 1987 .

[28]  J. E. Mark.  The Sol–Gel Route to Inorganic‐Organic Composites , 1996 .

[29]  David Avnir,et al.  Organic Chemistry within Ceramic Matrixes: Doped Sol-Gel Materials , 1995 .

[30]  F. L. Galeener,et al.  Band limits and the vibrational spectra of tetrahedral glasses , 1979 .

[31]  Rui M. Almeida,et al.  Structural investigation of silica gel films by infrared spectroscopy , 1990 .