Responsive Nanoporous Smectic Liquid Crystal Polymer Networks as Efficient and Selective Adsorbents

Abstract

5045www.MaterialsViews.com wileyonlinelibrary.com capacities were found for materials based on functionalized biological waste [ 13 ] or clay-polymer composites, [ 14 ] but these materials were not selective. Recently, a charge-selective supramolecular hydrogel [ 15 ] with high adsorption capacity was published, but the adsorption process was slow. Materials which show high selectivity as well as high capacity in combination with a fast adsorption process are practically unavailable.We have previously reported a fabrication process for nanoporous membranes based on the self-organization of reactive thermotropic hydrogen-bonded smectic liquid crystals (LCs). [ 16,17 ] The membranes were created by photo-polymerization to lock the smectic structure into a network followed by an alkaline treatment to break the hydrogen bonds. Minute interstices are formed and the smectic nature of the material results in pores with a two-dimensional geometry. Transmission electron microscopy revealed that the width of the straight pores is around 1 nm. A dye was used to measure the local pH in the pores and to prove the porosity. Furthermore, these pores could be fi lled with silver ions, and subsequently reduced to silver nanoparticles. The diameter and orientation of these nanoparticles were controlled by the pore size and shape of the material. [ 18 ] This nanoporous material is expected to be a good candidate for an adsorbent material due to the well-organized structure with high surface area and permeability, which promote the adsorption capacity and kinetics. Furthermore, the confi ned pore interior will be benefi cial for selective adsorption. Nanoporous, LC networks have been studied earlier for use as nanoporous membranes, [19][20][21] in host-guest chemistry, [ 22 ] molecular imprinting, and chiral recognition. To our knowledge, however, nanoporous materials based on reactive thermotropic liquid crystals have never been considered as selective and fast adsorbents with a high capacity. Results and Discussion Preparation and Characterization of a Smectic Liquid Crystalline NetworkThe LC mixture with 4-(6-acryloyloxylhexyloxy)benzoic acid (6OBA) and 1,4-phenylene bis(4-(6-(acryloyloxy)hexyloxy) Responsive Nanoporous Smectic Liquid Crystal Polymer Networks as Effi cient and Selective AdsorbentsHuub P. C. van Kuringen , Geert M. Eikelboom , Ivelina K. Shishmanova , Dirk J. Broer, * and Albertus P. H. J. Schenning * An effi cient and selective porous nanostructured polymer adsorbent is prepared from smectic liquid crystals. The adsorption study is performed by using hydrophilic dyes as water pollutants. The anionic pore interior of the nanoporous polymer is able to selectively adsorb cationic methylene blue over anionic methyl orange. Even zwitter ionic rhodamine B could hardly be adsorbed due to the presence of the anionic group in this dye. The confi ned pore dimensions allow size selective adsorption; a 4 th generation cationic dendrimer is not able to diffuse into the nanometer sized pores. The porous nature of the polymer p...

On the Dimensional Control of 2 D Hybrid Nanomaterials

“…C6 has the same length of the 6OBA dimer. It should be noted that the C6 containing nanoporous material has already been partially characterized previously …”

Hydrogen Bonding in Supramolecular Nanoporous Materials

“…The H-bonds in this material play a crucial role; only the material where the H-bonds were broken was able to adsorb the dye (Fig. 2.19) [76]. The adsorption rate constant was competitive too.…”

“…The membranes were created by photopolymerization to lock the smectic structure into a network followed by an alkaline treatment to create the pores (Fig. 2.17a) [76]. The H-bonds were formed between two benzoic acid monomers and after deprotonating of the acid moieties the H-bonds break and a carboxylate pore interior was created.…”

“…This material exhibits appealing adsorption behavior [76]. The adsorption study was performed with dyes as model compounds.…”

Selective Absorption of Hydrophobic Cations in Nanostructured Porous Materials from Crosslinked Hydrogen‐Bonded Columnar Liquid Crystals

“…There are several examples of porous materials made from LCs, however, only a few have been reported from hydrogenbonded LCs. [10][11][12][13][14][15][16][17][18][19][20][21] A class of LCs which is even less commonly investigated for its thermotropic LC properties is that of hydrogen-bonded discotic or columnar LCs. One example is of Ishida and co-workers , who demonstrate the template assisted self-assembly of columnar LCs via orthogonal ionic interactions.…”