Tailoring Pore Size and Chemical Interior of near 1 nm Sized Pores in a Nanoporous Polymer Based on a Discotic Liquid Crystal

Abstract

A triazine based disc shaped molecule with two hydrolyzable units, imine and ester groups, was polymerized via acyclic diene metathesis in the columnar hexagonal (Colhex) LC phase. Fabrication of a cationic nanoporous polymer (pore diameter ∼1.3 nm) lined with ammonium groups at the pore surface was achieved by hydrolysis of the imine linkage. Size selective aldehyde uptake by the cationic porous polymer was demonstrated. The anilinium groups in the pores were converted to azide as well as phenyl groups by further chemical treatment, leading to porous polymers with neutral functional groups in the pores. The pores were enlarged by further hydrolysis of the ester groups to create ∼2.6 nm pores lined with −COONa surface groups. The same pores could be obtained in a single step without first hydrolyzing the imine linkage. XRD studies demonstrated that the Colhex order of the monomer was preserved after polymerization as well as in both the nanoporous polymers. The porous anionic polymer lined with −COOH groups was further converted to the −COOLi, −COONa, −COOK, −COOCs, and −COONH4 salts. The porous polymer lined with −COONa groups selectively adsorbs a cationic dye, methylene blue, over an anionic dye.

Functional Liquid Crystals towards the Next Generation of Materials

“…TheL Cn anopores selectively adsorb molecules and ions which are of as uitable size and charge.T he adsorption properties of the pores can be tuned by modifying the wall surfaces of the pores by chemical reaction with chemically active groups. [157] Thep reparation of nanoporous films with 2D smectic structures and their molecular sieving properties were reported by Broer and co-workers (Figure 6c). [158][159][160] The networks are composed of apolyacrylate containing abenzoic acid in the side-chain.…”

“…Polymer materials with LC nanopores can be also used as adsorbents at the molecular level as well as in filtration membranes.Inaddition, the size of pores in LC polymer films can be tuned by post-modification procedures.P olymerizable host molecules and non-polymerizable content were combined using non-covalent bonding [153][154][155][156] and dynamic covalent bonding. [157] Formation of the LC state and subsequent in situ polymerization for example by photopolymerization [153][154][155] or acyclicd iene metathesis (ADMET) polymerization [156,157] gives polymer films with nanochannels filled with non-polymerized small compounds.T he LC nanopores were obtained by removal of the non-polymerized small molecules in the nanochannels (Figure 6b). TheL Cn anopores selectively adsorb molecules and ions which are of as uitable size and charge.T he adsorption properties of the pores can be tuned by modifying the wall surfaces of the pores by chemical reaction with chemically active groups.…”

Polymeric fibers and microporous films by photo‐crosslinking of triphenylene‐derived liquid crystals

“…Gin et al polymerized LC molecules to prepare a hexagonally ordered polymer nanocomposite . Recently fixation of well‐ordered columnar LC molecules collects further interests of many researchers and highly functional polymer materials have been prepared by various reactions like photo‐initiated radical polymerization 12 γ‐irradiation, thiol‐ene reaction, ring‐opening reaction, and metathesis …”

“…We have worked on the development of several discotic LCs and studied their thermal, mesomorphic, and charge transport properties . Considering the structural features and the applicability of the columnar LCs, the next challenge is to fix the oriented discotic molecules in the structure and enhance their properties as reported previously . If the ordered columns are covalently connected along the molecular axis and plane, polymeric fibers or films should be formed depending on the macroscopic shape, and they could be applied as polymeric conducting wires or layers.…”

Functional liquid-crystalline polymers and supramolecular liquid crystals

“…One strategy to overcome this problem is polymerization and crosslinking of the self-organized LC molecules into LC networks with preserving the periodic nanostructures. 30,49,[181][182][183][184][185][186][187] This process certainly reduces the mobility and dynamic nature of the LC arrays, but drastically improves the mechanical properties of the samples and their thermal stability. There are some important processes for transforming nanosegregated liquid crystals into nanostructured LC networks ( Figure 9): (1) introduction of polymerizable group into LC molecules; (2) spontaneous self-organization of the LC monomers; (3) alignment of LC domains in a macroscopic scale if necessary; and (4) in situ polymerization.…”