Silica Monoliths Templated on L₃ Liquid Crystal

Abstract

Dimensionally stable, optically clear, highly porous (approximately 65% of the apparent volume), and high surface area (up to 1400 m(2)/g) silica monoliths were fabricated as thick disks (0.5 cm) by templating the isotropic liquid crystalline L(3) phase with silica through the hydrolysis and condensation of a silicon alkoxide and then removing the organic constituents by supercritical ethanol extraction. The L(3) liquid crystal is a stable phase formed by the cosurfactants cetylpyridinium chloride monohydrate and hexanol in HCl(aq) solvent. Extracted 0.5 cm thick disks exhibited a low ratio of scattered to transmitted visible light (1.5 x 10(-)(6) at 22 degrees from the surface normal). The degree of silica condensation in the monoliths was high, as determined by (29)Si NMR measurements of Q(3) and Q(4) peak intensities (0.53 and 0.47, respectively). As a result, the extracted and dried monoliths were mechanically robust and did not fracture when infiltrated by organic solvents. Photoactive liquid monomers were infiltrated into extracted silica monoliths and polymerized in situ, demonstrating the possible application of templated silica to optical storage technology.

Effect of Drying Control Agent on Physicochemical and Thermal Properties of Silica Aerogel Derived via Ambient Pressure Drying Process

“…The BET surface area values higher than 1000 m 2 /g were also obtained for only a few aerogels prepared through ambient pressure drying and described by Wu et al (up to 1005 m 2 /g) [26] and Nazriati et al (up to 1113.76 m 2 /g) [64]. Such high specific surface areas are rather typical for supercritical drying systems, e.g., as was presented in the following publications [56][57][58]65]. Based on published data, it was observed that for DMF-modified aerogels with nSi:nDMF molar ratio equal to about 0.65, the increase in surface area values was achieved at about 6.2% [47] and 6.8% [49] levels compared to pure silica samples.…”

“…The FT-IR spectra registered for prepared xerogels: XG1 and XG2 were presented in Figure 2. All IR bands (also for aerogels, see in Figure 3) were assigned based on literature data [52][53][54][55][56][57][58]. Registered FT-IR spectra reveal weak bands at ~2980 cm −1 and ~2931 cm −1 , corresponding to symmetric (νs) and asymmetric (νas) C-H vibrations derived from ethanol residues.…”

Enhanced Resonator Sensitivity with Nanostructured Porous Silica Coatings

“…Use of both the specific surface area and uniformity of the nanostructure to enhance resonator sensitivity is only possible provided the nanostructures within the films are accessible to the target molecules. We anticipate that if L 3 -templated silica films were to be heat treated at higher temperatures to remove the surfactant component and thus create larger specific surface areas, the sensitivity of these films in the low partial pressure regions ( P / P 0 < 0.4) will be higher. , The unique nanostructure of the L 3 -templated silica coating provides this accessibility and thereby demonstrates increased resonator sensitivity relative to the other coatings. This approach, however, is not limited to the detection of water vapor; it should be directly applicable to the sensing of other gases.…”

Silica‐Based, Organically Modified Host Material for Waveguide Structuring by Two‐Photon‐Induced Photopolymerization

“…The basis for the preparation of the host material was the use of the surfactant/solvent template system in the L 3 ‘sponge’ phase. This phase could unambiguously be distinguished from adjacent phases by its water‐like optically clear appearance and low viscosity 16, 24, 25. We used a slightly adapted version of the procedure described by McGrath et al,16 with the modification of using an organically modified co‐precursor, for the production of fully transparent monoliths and thin films.…”