Mojca Fir,^a Jelica Vince,^a Angela Šurca Vuk,^a Aljaž Vilčnik,^a Vasko Jovanovski,^a Gregor Mali,^a Boris Orel,^a,* Barbara Simončič^b

^aNational Institute of Chemistry, Hajdrihova 19, SI-1000 Ljubljana, Slovenia.
Tel: +38614760276;
Fax: +38614760300,
E-mail: boris.orel@ki.si
^bUniversity of Ljubljana, Faculty of Natural Sciences and Engineering, Aškerčeva 12, SI-1000 Ljubljana, Slovenia

Abstract
A novel organic-inorganic sol-gel hybrid precursor, di-ureapropyltriethoxysilyl [bis(aminopropyl)terminated-polydimethylsiloxane (1000)] (PDMSU), was synthesized and tested as a hydrophobic impregnation for cotton fabrics. Hydrolysis of the precursor was performed with 0.1 mol L^–1 HCl and for deposition 4% sols of PDMSU in EtOH were used. Contact angle measurements revealed the hydrophobicity of the coatings, either on Al substrate (Θ > 100°) or on cotton (Θ ≈ 130°). IR attenuated total reflection (ATR) spectroscopy showed that urea groups participate in PDMSU/cotton interface bonding, while “free” urea groups (1725, 1691 cm^–1) were noted in the spectra of PDMSU/Al and PDMSU/xerogel samples. The stability of the coatings was determined by repetitive washing. Degradation of the coatings was evidenced from the decrease in contact angle values and the relaxation of the urea-urea associations, leading to the appearance of the new Amide II band (1541 cm^–1) in the IR ATR spectra.

Keywords: cotton, impregnation, hydrophobic, sol-gel, IR spectroscopy