Lactose-Modied Triethoxysilane for the Surface Modication of Clay Nanocomposites
All reagents were used as supplied from Sigma-Aldrich unless otherwise stated. DMF was puried by reuxing with ninhydrin and distilled. Microwave reactions were conducted using Biotage Initiator Microwave Synthesizer under normal absorption level. After workup, the organic layers were dried over anhydrous Na2SO4. Reactions were monitored by analytical thin-layer chromatography using silica gel 60 F254-precoated plates (E. Merck). The visualization of spots was performed by soaking in (1) charring solution (sulfuric acid/methanol/water: 5/45/45 v/v/v) and (2) oxidizing solution of molybdate (prepared from 25 g of ammonium molybdate and 10 g of ceric sulfate dissolved in 900 mL of water and 100 mL of concentrated sulfuric acid), followed by heating to 300°C. Preparative chromatography was performed using silica gel from Silicycle Inc. (Quebec, Canada) (60 Å, 40-63 μm) with the indicated eluent. The solvents employed for the chromatography were High Performance Liquid Chromatography (HPLC) quality. They were evaporated under reduced pressure (rotary evaporator under vacuum generated by a system of glass lter pump). Optical rotations were measured with a JASCO P-1010 polarimeter. NMR spectra were recorded for solutions in CDCl3 with a Bruker Avance III HD 600 MHz spectrometer. Proton and carbon chemical shifts are reported in ppm (δ) relative to the signal of CDCl3 (δ 7.27 and 77.23 ppm for 1H-and 13C, respectively). Coupling constants (J) are reported in hertz (Hz), and the following abbreviations are used for signal multiplicities: singlet (s), doublet (d), doublet of doublets (dd), and multiplet (m). Analysis and assignments were made by COSY and HSQC experiments. The superscripts (I and II) in the 1H NMR assignments refer to the Glc and Gal residues, respectively. High-resolution mass spectra (HRMS) were measured with an LC-MS-TOF (liquid chromatography-mass spectrometry time of ight) (Agilent Technologies) in positive and/or negative electrospray mode by the analytical platform of UQAM.