Organically modified aluminosilicate mesostructures were synthesized from two metal alkoxides with the use of poly(isoprene-b-ethyleneoxide) block copolymers (PI-b-PEO) as the structure-directing molecules. By increasing the fraction of the inorganic precursors with respect to the polymer, morphologies expected from the phase diagrams of diblock copolymers were obtained. The length scale of the microstructures and the state of alignment were varied using concepts known from the study of block copolymers. These results suggest that the use of higher molecular weight block copolymer mesophases instead of conventional low-molecular weight surfactants may provide a simple, easily controlled pathway for the preparation of various silica-type mesostructures that extends the accessible length scale of these structures by about an order of magnitude.
Communications ADVANCED MATERIALSwithin minutes under static conditions in an oven at 80°C. Deposition was allowed to proceed for a period from 2 h to a day. The films so formed were transferred from the vessel and washed with de-ionized water.Charrrr.ferizatmn: Powder X-ray diffraction patterns (PXRD) were recorded on a Siemens D5000 diffractometer using Ni filtered Cu K a radiation with i = 1.54178A. Samples were mounted onto a home-made low background quarLL plate holder. Scanning electron microscopy (SEM) images and energy dispersive X-ray (EDX) microanalysis were obtained on a Hitachi S-4500 field emission microscope with an acceleration voltage of 2 kV and 20 kV, respectively. All samples were uncoated for direct imaging. Transmission electron microscop) (TEM) images werc recorded for ultrathin cross-sections of the patterned mesoporous silica images on a Philips 430 microscope opcrating at an accelerating voltage of 100 kV. TEM specimens were prepared by cnibedding the sample in epoxy, solidifying the epoxy block at 80 "C' overnight and then ultra-microtoming into sections with a thickness of ca. 300 A.
ert, transparent, and not hazardous to humans or the environment. In addition, the sol-gel coatings show excellent mechanical properties and are stable to humidity, light, and heat. Therefore, sol-gel matrices should also be applicable as reservoir systems, e.g., for the encapsulation of flavors and fragrances, for the long-term aromatization of food, cosmetics, or textile fibers as well as for the long-term impregnation of textiles with insect repellents. An example of the applicability of the sol-gel technique for the preparation of coatings with long-time effect is shown in Figure 5. The liberation of the liquid repellent DETA from impregnated paper can be considerably slowed down by incorporating it into a silica sol. Fig. 5. Evaporation of DETA from cardboard in an airstream (1.25 L/min): a) coated with the composite sol E; b) coated with the same DETA solution but without silica sol. ExperimentalComposite Preparation: To embed the oils within the silica gel matrix, 90 mL tetraethoxysilane, 185 mL ethanol, and 15 mL 0.01 N HCl were stirred together for 20 h at room temperature. 50 mL of this silica sol were mixed with 2.87 g of the OL (Fluka) for composites A±C and E, with 1.84 g OL for sols D and F, and with 1.08 g OL for sol G (see Table 1). One part of this solution was coated onto PETP foil or cardboard. Another portion was neutralized with 1 % aqueous ammonia. After setting, the gel was airdried for 1 h in an exhauster and then for 14 h at 80 C in a drying cupboard. The dry composite powders were ground and sieved to a grain size fraction of between 390 and 500 mm.Composite films with embedded liquids were prepared by coating composite sol E onto 100 mm PETP foil or cardboard (170 g/cm 2 ) using a lab coating device LBM 70 (MABA Wolfen), equipped with a 70 mm slide coating unit and air drying.Characterization: The surface areas and pore size distributions of dried composite gels were determined by N 2 adsorption measurements at 77 K (Ströhlein DEN-AR-mat 1000), see Table 2. Thermal analysis of the dried composite gels was carried out with a TG-DSC system (SETARAM, France). Thermal stability measurements were made at a linear heating rate of 5 K/min. For all the experiments 4 mg samples in open aluminum crucibles were purged with argon gas at a flow rate of 1 L/h. The quantity of liquid liberated was also determined by gas chromatography (HP5890, column HP-5 with a flame ionization detector (FID)) after digestion of thermostated samples of 100 mg of sieved composite powder on 60 cm 2 foil or cardboard (cut into pieces) with 5 mL methanol at 50 C. After three liberation measurements, deviations were smaller than 10 %. A comparison with the calculated quantities reveals that, after digestion, the liquid is nearly completely extracted from the composites. Control of the shape and the size of inorganic materials is an important feature of natural growth phenomena. For biological systems both are the result of long evolutionary
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.