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Carbon dioxide (CO2) capturefrom point sources likecoal-fired power plants is a potential solution for stabilizing atmosphericCO2content to avoid global warming. Sorbents with highand reversible CO2uptake, high CO2selectivity,good chemical and thermal stability, and low cost are desired forthe separation of CO2from N2in flue or naturalgas. We report here, for the first time, on the synthesis of new microporouspolyimide (PI) networks from the condensation of perylene-3,4,9,10-tetracarboxylicdianhydride (PTCDA) and 1,3,5-triazine-2,4,6-triamine (melamine) usinga Lewis acid catalyst zinc acetate/imidazole complex. These PI networkmaterials, prepared in the absence and presence of dimethyl sulfoxide(DMSO) as weak solvent template, exhibit strong fluorescence. Nitrogen-containingcarbons can be accessed from our PI networks via a simple thermalpyrolysis route. The successful construction of new microporous PInetworks and derived N-containing carbons is shown here to providepromising CO2sorbents with high uptake capacities (15wt %) combined with exceptional selectivities over N2(240),while their fluorescent properties can be exploited for simple sensing. [ABSTRACT FROM AUTHOR]

The self-assembly of well-defined organic–organometallic polystyrene-b-poly(ferrocenylmethyl(dimethylaminopropynylsilane)) (PS-b-PFAMS) diblock copolymers has been systematically investigated by varying the volume fraction of the organometallic block (PFAMS). Quaternization of the PFAMS block yielded PS-b-qPFAMS, which was ionically complexed to the anionic surfactants sodium bis(2-ethylhexyl) sulfosuccinate (AOT) and sodium bis(2,2,3,3,4,4,5,5,5-nonafluoropentyl) sulfosuccinate (AOTF). The self-assembly of the block copolymer-surfactant complexes was also studied in bulk and thin films and produced materials with structural hierarchy over multiple length scales as shown by AFM, TEM, and SAXS studies. [ABSTRACT FROM AUTHOR]

A series of four hydrophobically modified, diphenylazo-based organic salts have been prepared and characterized. To achieve this a Cx(x= 4, 6, 8, or 10) hydrocarbon chain was inserted between the diphenylazo moiety and the quaternary ammonium headgroup of the salt. The absorption of each of the four modified organic salts into anionic microgel particles of poly(N-isopropylacrylamide-co-acrylic acid) has been studied at pH 8. In addition, the hydrodynamic diameters and electrophoretic mobilities of the microgel particles have been studied as a function of the organic salt concentration, also at pH 8. In addition to the electrostatic attraction between the quaternary ammonium head groups of the organic salts and the anionic groups within the microgel particles, hydrophobic association between the chains of the organic salts within the microgel particles plays a role, with this effect increasing strongly from x= 4 to 10. Desorption of the x= 4 and 6 organic salts occurs readily on changing, in situ, the pH from 8 to 2.5 (and thereby eliminating the electrostatic interaction) but is only partially achieved for the x= 8 and 10 organic salts. Indeed, for the x= 10 organic salt, only about 80% of the organic salt is desorbed upon dilution of the microgel particles into a large excess of water. [ABSTRACT FROM AUTHOR]

This work describes the solid-state conformational and structural properties of self-assembled polypeptide−surfactant complexes with double-tailed surfactants. Poly(l-lysine) was complexed with three dialkyl esters of phosphoric acid (i.e., phosphodiester surfactants), where the surfactant tail branching and length was varied to tune the supramolecular architecture in a facile way. After complexation with the branched surfactant bis(2-ethylhexyl) phosphate in an aqueous solution, the polypeptide chains adopted an α-helical conformation. These rod-like helices self-assembled into cylindrical phases with the amorphous alkyl tails pointing outward. In complexes with dioctyl phosphate and didodecyl phosphate, which have two linear n-octyl or n-dodecyl tails, respectively, the polypeptide formed antiparallel β-sheets separated by alkyl layers, resulting in well-ordered lamellar self-assemblies. By heating, it was possible to trigger a partial opening of the β-sheets and disruption of the lamellar phase. After repeated heating/cooling, all of these complexes also showed a glass transition between 37 and 50 °C. Organic solvent treatment and plasticization by overstoichiometric amount of surfactant led to structure modification in poly(l-lysine)−dioctyl phosphate complexes, PLL(diC8)x(x= 1.0−3.0). Here, the α-helical PLL is surrounded by the surfactants and these bottle-brush-like chains self-assemble in a hexagonal cylindrical morphology. As xis increased, the materials are clearly plasticized and the degree of ordering is improved: The stiff α-helical backbones in a softened surfactant matrix give rise to thermotropic liquid-crystalline phases. The complexes were examined by Fourier transform infrared spectroscopy, small- and wide-angle X-ray scattering, transmission electron microscopy, differential scanning calorimetry, polarized optical microscopy, and circular dichroism. [ABSTRACT FROM AUTHOR]

We study the photoresponsive behavior of thin films of supramolecular 4-nitro-4′-hydroxyazobenzene−poly(4-vinylpyridine) complexes. Hydrogen bonding between the phenol and pyridine moieties allows attaching a chromophore to essentially each repeat unit of the polymer, thereby suppressing macroscopic phase separation and crystallization. Moreover, the noncooperative nature of hydrogen bonding leads to random complexation of the chromophores to the polymer backbone, which enables a systematic study of the effect of chromophore concentration on the photo-orientation of the complexes. Two regimes are observed: Photoinduced birefringence increases linearly with the chromophore concentration until nominally every third polymer repeat unit is occupied. Beyond that concentration, a new regime is observed with a drastically steeper slope of increase. The latter regime is connected to the interplay between the formation of a hydrogen-bonded supramolecular complex and intermolecular interactions between the mesogenic chromophores. Such a behavior significantly enhances the birefringence at high concentrations and also leads to high remnant birefringence. Hence, the supramolecular approach yields a superior optical performance compared to guest−host polymers and even surpasses the properties of many covalently functionalized polymers, while still allowing modular tunability of the materials properties. [ABSTRACT FROM AUTHOR]

A surfactant featuring a polymerizable pyrrole head group (dodecyl-dimethyl-(2-pyrrol-1-yl-ethyl)-ammonium bromide, DDPABr) was synthesized. The thermotropic behavior of the surfactant was investigated by differential scanning calorimetry (DSC) and X-ray scattering techniques, with small-angle X-ray scattering (SAXS) analysis revealing a highly ordered lamellar bilayer structure. After full characterization, DDPABr was used in the preparation of mesostructured SiO2nanocomposite thin films via evaporation-induced self-assembly (EISA). Resulting thin SiO2−DDPABr films were studied by 1D and 2D small-angle X-ray scattering (SAXS) techniques, indicating a lamellar nanocomposite structure. Suitable theoretical SAXS models were applied to fit the experimental 1D SAXS data. The surfactant could be chemically polymerized within the lamellar domains. [ABSTRACT FROM AUTHOR]