Photoresponsive Nanoporous Smectic Liquid Crystalline Polymer Networks: Changing the Number of Binding Sites and Pore Dimensions in Polymer Adsorbents by Light

Abstract

Photoresponsive nanoporous polymer films have been fabricated by adding a photoresponsive azobenzene cross-linker to a hydrogen-bonded smectic liquid crystalline polymer network. A base treatment resulted in the nanoporous material which has been fully characterized. Upon exposure to UV light a decrease in the smectic layer spacing is observed, suggesting a decrease in pore size. In addition, the binding sites in the material could be changed with light, leading to light-induced adsorption of cations and cationic dyes. Finally, light could also be used to create nanoporous channels in the polymer film.

Nematic DNA Thermotropic Liquid Crystals with Photoresponsive Mechanical Properties

“…Based on the analysis of the two sharp first order reflection peaks at q = 1.64 nm −1 and q = 1.83 nm −1 ( d = 2π/ q 1 ), the smectic layer spacing of the two isomers can be determined to 3.82 nm for the E ‐ and 3.43 nm for the Z ‐isomer, respectively, approximately corresponding to the molecular dimensions of the AZO isomers. We note that the layer spacing difference of ≈0.39 nm of the two isomers also corresponds to the length change of about 0.35 nm from E‐ to Z‐ azobenzene . Moreover, after irradiation with UV‐light overnight, the sample was remeasured by SAXS at room temperature.…”

Macroscopically Oriented Porous Materials with Periodic Ordered Structures: From Zeolites and Metal–Organic Frameworks to Liquid‐Crystal‐Templated Mesoporous Materials

“…In a rotating magnetic field, the target nanoscale object is aligned so that the least magnetically susceptible axis (“hard” axis) becomes parallel to the axis of rotation of the magnetic field (Figure c) . leading to an oriented structure that is difficult or impossible to obtain by using a static field (see Section and ) …”

“…This progress report presents an overview of recent studies on the synthesis, properties, and applications of porous materials with macroscopically oriented structures ( Table 1 ). The scope of this report is limited to porous materials with nano‐ or mesoscale periodic channels constructed by supramolecular self‐assembly of atomic and/or molecular components, such as zeolites (Section ), MOFs (Section ), mesoporous oxides (Section ), and polymers based on liquid crystals (LCs) (Section ) . In other words, porous materials produced by physical processes, such as anodic aluminum oxides or porous silicones, are beyond the scope of this report.…”

Light‐Responsive Polymer Membranes

“…Photochromic molecules have been applied in liquid crystal (LC) compounds and polymers to add photoresponsiveness to LC self‐organization . Photochromic LCs are generally obtained by physical addition of small amounts of photochromic molecules or by incorporation of photochromic groups in polymer structures …”

“…LC polymers can be tailored with a desired uniform nanometer pore size, which favors molecular adsorption . In order to control the capture, transport, and release of chemical species in nanoporous materials by light, van Kuringen et al reported on a free‐standing photoresponsive nanoporous LC polymer film incorporating Azo cross‐linkers (a mixture in the molar ratio 5: 95 of A6MA, a photoresponsive Azo diacrylate cross‐linker, and 6OBA, a hydrogen‐bonded dimer diacrylate) in a smectic hydrogen‐bonded polymer network . The polymer network was treated with an alkaline solution in order to break H bonds and create nanopores.…”