Vermiculite as a useful host for guest cyclic aliphatic amine intercalation, followed by cation adsorption

Two vermiculite hybrids containing aliphatic amines intercalated were synthesized. The amount of guest molecules intercalated resulted in 0.60 and 0.52 mmol g⁻¹ for pyperidine and pyperazine, respectively, which reflect the effectiveness of such kind of reactions. The processes were confirmed by elemental analysis and infrared spectroscopy. X-ray diffraction patterns suggested that the original crystallinity of matrix was maintained, however, the intercalation process is associated with the conformation of the guest molecule and the presence of the compensate cation inside the interlayer cavity. The intercalated inorganic hosts adsorb divalent lead, nickel, copper and cobalt cations, more effectively at basic pH value, from aqueous solution, which content of adsorption is higher than the precursor native vermiculite.     

Photopolymerization of mixed monolayers and black lipid membranes containing gramicidin A and diacetylenic phospholipids

We formed monolayers and black lipid membranes (BLMs) of photopolymerizable lipids mixed with the channel-forming protein gramicidin A to evaluate their miscibility and the potential for improved stability of the BLM scaffold through polymerization. Analyses of surface pressure vs area isotherms indicated that gramicidin A dispersed with three different synthetic, polymerizable, diacetylene-containing phospholipids, 1,2-di-10,12-tricosadiynoyl-sn-glycero-3-phosphocholine (DTPC), 1,2-di-10,12-tricosadiynoyl-sn-glycero-3-phosphoethanolamine (DTPE), and 1-palmitoyl-2,10,12-tricosadiynoyl-sn-glycero-3-phosphoethanolamine (PTPE) to form mixed monolayers at the air-water interface on a Langmuir-Blodgett (LB) trough. Conductance measurements across a diacetylenic lipid-containing BLM confirmed dispersion of the gramicidin channel with the lipid layer and demonstrated gramicidin ion-channel activity before and after UV exposure. Polymerization kinetics of the diacetylenic films were monitored by film pressure changes at constant LB trough area and by UV-vis absorption spectroscopy of polymerized monolayers deposited onto quartz. An initial increase in film pressure of both the pure diacetylene lipid monolayers and mixed films upon exposure to UV light indicated a change in the film structure. Over the time scale of the pressure increase, an absorbance peak indicative of polymerization evolved, suggesting that the structural change in the lipid monolayer was due to polymerization. Film pressure and absorbance kinetics also revealed degradation of the polymerized chains at long exposure times, indicating an optimum time of UV irradiation for maximized polymerization in the lipid layer. Accordingly, exposure of polymerizable lipid-containing black lipid membranes to short increments of UV light led to an increase in the bilayer lifetime.     

Design,synthesis, and characterisation of symmetrical bent-core liquid crystalline dimers with diacetylene spacer

Two new symmetrical bent-core liquid crystalline dimers (B-DA4 and B-DA12) bearing diacetylenes spacer and different terminal alkyl chains were successfully synthesised via Sonagashira coupling reaction. The molecular structures of these dimers were confirmed by ¹H nuclear magnetic resonance (NMR), Fourier transform-infrared spectroscopy (FT-IR), Raman spectroscopy, mass spectrometry, and elemental analysis. Their thermal stability and liquid crystalline properties were characterised by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), polarised light microscopy (PLM), and small-angle X-ray scattering (SAXS). Results showed that the diacetylene group may be thermal polymerised at about 260°C far from thermal decomposition. The dimers exhibited monotropic phase behaviour and typical layered-structure phase with long-range order on a length scale of about 6.3 nm was observed. The results mentioned above offer a promising opportunity to design polydiacetylene nanowires by thermal, UV irradiation, or scanning tunnelling microscope (STM) tip-induced polymerisation.     

Preparation of poly(propylene carbonate)/organo-vermiculite nanocomposites via direct melt intercalation

Intercalated nanocomposites comprised of poly(propylene carbonate) (PPC) and organo-vermiculite (OVMT) was first prepared via direct melt compounding of the alkali-vermiculite intercalated host with PPC in a twin rotary mixer. The dispersion and morphologies of OVMT within PPC were investigated by X-ray diffraction and transmission electron microscopic techniques. The results revealed the formation of intercalated-exfoliated vermiculite sheets in the PPC matrix. Because of the thermally sensitive nature of PPC, thermal degradation occurred during the melt compounding. The degradation led to a deterioration of the mechanical properties of the nanocomposites. Tensile test showed that the yield strength and modulus of the nanocomposites decrease with increasing vermiculite content. The degradation mechanism was discussed according to the results of GPC and TGA measurements.     

Synthese, 13C-NMR-Spektren und räumliche Struktur von ‘Push-Pull’-Diacetylenen

Synthesis, ¹³C-NMR Spectra, and X-Ray Investigation of ‘Push-Pull’ Diacetylenes Phenyl-substituted ‘push-pull’ diacetylenes 1f and 1g have been prepared by acetylation and benzoylation of the appropriate lithiodiynylamines 4 (Scheme 2). ¹³C-NMR spectra of diacetylenes 1a–g (Table 1) are discussed with respect to the expected polarisation of the diacetylene unit by ‘push’ and ‘pull’ substituents. X-Ray investigations of 1c , 1e , and 1f have been performed in view of the planned solid-state polymerisation of ‘push-pull’ diacetylenes. In the crystalline state, diacetylenes 1c and 1f are stacked, however, the stacking parameters do not allow a solid-state polymerisation.     

Single-crystal-to-single-crystal topochemical polymerizations of a terminal diacetylene: two remarkable transformations give the same conjugated polymer

Host-guest chemistry was used to prepare a cocrystal of a dipyridyl substituted oxalamide host and a resorcinol derivative of a terminal diacetylene. X-ray crystallography revealed that the molecules assemble into a triple-helix with the diacetylene functionalities aligned in the center of the helix. Upon heating, the diacetylenes polymerize to give the corresponding polymer. In a second experiment, the X-ray structure of the crystalline hydrate of the same diacetylene also showed a suitable alignment of the diacetylene functionalities. These crystals polymerize at only 50 degrees C with the C1 carbon end of the diacetylene undergoing an unprecedented 2.4 A inward swinging movement. This results in a remarkable 9% increase in crystal density. These are the first structurally characterized polymerizations of any terminal diacetylene. A detailed comparison of the two sets of structural changes offers an interesting insight into the precise trajectories of polymerization reactions.     

Structure and properties of polyamide‐6/vermiculite nanocomposites prepared by direct melt compounding

Polyamide‐6 (PA6)/vermiculite nanocomposites were fabricated through the direct melt compounding of maleic anhydride‐modified vermiculite (MAV) with PA6 in a twin‐screw extruder followed by injection molding. The structure and morphology of the nanocomposites were determined by X‐ray diffraction and scanning and transmission electron microscopy techniques. The results revealed the formation of intercalated and exfoliated vermiculite platelets in the PA6 matrix. Tensile measurement showed that the tensile modulus and strength of the nanocomposites tended to increase with increasing vermiculite content. The thermal properties of the nanocomposites were determined by dynamic mechanical analysis, differential scanning calorimetry, and thermogravimetry measurements. The storage modulus of the PA6–MAV nanocomposites increased to almost twice that of the neat PA6. The thermal stability of the nanocomposites increased dramatically, and this was associated with the addition of vermiculite. The effect of the addition of maleic anhydride on the formation of the PA6–vermiculite nanocomposites was examined. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2860–2870, 2002     

TG and DSC as tools for confirming hybrid vermiculites derived from intercalation

Vermiculite was prepared to react with aliphatic diamines (ethylene-, trimethylene-, tetramethylene- and hexamethylene-) diamine. The products were characterized by elemental analysis, infrared spectroscopy and X-ray diffraction. The amounts of diamines adsorbed were 0.89, 0.86, 0.79 and 0.68 mmol g^–1, respectively for NH₂(CH₂)⋅nNH₂ where n=2, 3, 4, 6. The basal spacings of the intercalated vermiculites varied between 1300 and 1470 pm. Thermogravimetry and DSC data confirmed intercalation of diamines in gallery space of vermiculite.     

Practical,high-yield synthesis of thiol-terminated diacetylenes for formation of conductive monolayers

Self-assembled monolayers of thiol terminated conjugated diacetylenes can be cross-linked using ultraviolet light to form highly conjugated polydiacetylenic conductive monolayers [1]; however, the reported syntheses of the diacetylene monomers present numerous problems that prevent the wide spread application of these in functional materials. We report a redesigned four-step synthesis that proceeds in 75–80% overall yields and allows gram scale production of an array of thiol terminated conjugated diacetylenes, thereby allowing examination and application of these low-dimensional conductive materials.     

Alternating diacetylene copolymer utilizing perfluorophenyl-phenyl interactions

The symmetric diacetylenes, 2,4-hexadiynylene dibenzoate 4 and 2,4-hexadiynylene bis(pentafluorobenzoate) 5, as well as the unsymmetric 6-(pentafluorobenzoyloxy)hexa-2,4-diynyl benzoate 6 were prepared and investigated with respect to their reactivity toward topochemical polymerization in the crystalline state. The 1:1 cocrystal 4.5 was successfully polymerized to the corresponding poly(diacetylene) copolymer 7, as evidenced by solid-state (13)C NMR and Raman spectroscopy, as well as single-crystal structure analysis of the monomer-polymer cocrystal. Thus, perfluorophenyl-phenyl interactions were utilized as complementary supramolecular synthons in the cocrystallization of two different diacetylene monomers and their unprecedented conversion into a strictly alternating diacetylene copolymer.     

Polymerization of diacetylenes in multilayers

A series of amphiphilic diacetylene monocarbonic acids was synthesized, and their ability to form monolayers at the air–water interphase was investigated. Acids with total number of C atoms ≥20 and mp >45°C form surface states suitable to be used for buildup of multilayers by the Langmuir–Blodgett technique. Using the LB technique, multilayers of defined thickness were built up on quartz substrates. The multilayers were polymerized by exposure to a UV light source according to the mechanism of solid-state polymerization of diacetylenes without destruction of the layer structure and with retention of the packing in the individual layers. Thus well-defined polymer multilayers were obtained. The monomer and polymer multilayers were characterized by UV spectra, x-ray small-angle diffraction, and interference microscopic and electron microscopic techniques. The polyconjugated backbones of the polymer chains are all stretched out in the plane of the substrate but not over macroscopic dimensions because the multilayers have a crystalline domain structure. The polymer multilayer films are quite stable under ambient conditions.     

Deposition and photopolymerization of phase-separated perfluorotetradecanoic acid-10,12-pentacosadiynoic acid Langmuir-Blodgett monolayer films

Mixed monolayer surfactant films of perfluorotetradecanoic acid and the photopolymerizable diacetylene molecule 10,12-pentacosadiynoic acid were prepared at the air-water interface and transferred onto solid supports via Langmuir-Blodgett (LB) deposition. The addition of the perfluoroacid to the diacetylene surfactant results in enhanced stabilization of the monolayer in comparison with the pure diacetylene alone, allowing film transfer onto a solid substrate without resorting to addition of cations in the subphase or photopolymerization prior to deposition. The resulting LB films consisted of well-defined phase-separated domains of the two film components, and the films were characterized by a combination of atomic force microscope (AFM) imaging and fluorescence emission microscopy both before and after photopolymerization into the highly emissive "red form" of the polydiacetylene. Photopolymerization of the monolayer films resulted in the formation of diacetylene bilayers, which were highly fluorescent, with the apparent rate of photopolymerization and the fluorescence emission of the films being largely unaffected by the presence of the perfluoroacid.     

Solid-state polymerization of diacetylene: 1,11,13,23-tetracosatetrayne

The solid-state polymerization of a diacetylene, 1,11,13,23-tetracosatetrayne, was studied using x-ray powder diffraction and electron diffraction. It is shown that the material exhibits polymorphism. Thermochromic transitions, which are generally observed for diacetylenes, are related to the particular crystalline phase using x-ray powder diffraction. The unit cell dimensions and space group of one polymorph were determined by electron diffraction analysis: a = 20.83 Å, b = 4.84 Å, c = 10.08 Å, β = 92.4°, space group: P2₁/n. © 1995 John Wiley & Sons, Inc.     

Enantioselective recognition between polydiacetylene nucleolipid monolayers and complementary oligonucleotides

A two-dimensional bio/synthetic hybrid system at the air-solution interface made of a polymerized diacetylene Langmuir film with nucleobase modified headgroups is presented. The polymerized film presents a crystalline array of nucleobases, capable of specific binding of complementary mononucleoside or oligonucleotide sequences. Mixed monolayers of the linear polyconjugated polydiacetylene (PDA) films derivatized with cytosine (10,12-pentacosadiyne-cytidyl, PDC) monomers and alcohol-terminated diacetylene lipid (10,12-pentacosadiynol, PDOH) at a 3:1 ratio (PDC 75%) were compressed and polymerized at the air-water interface with circular polarized light (CPL) or nonpolarized UV light. Here we report a grazing incidence X-ray diffraction (GIXD) investigation of PDC films polymerized to different chirality and hybridized with complementary ssDNA strands. We have demonstrated enantioselective interactions on synthetic structured interfaces produced by Langmuir surface compression followed by polymerization with circular polarized UV light (CPL). The left- and right-CPL polymerized light exhibit the same well-defined crystalline structure. The observed difference between left- and right-CPL polymerized PDC 75% Langmuir films compressed over the complementary mononucleotide guanosine or hybridized with fully complementary ssG(12)T(5) oligonucleotide in the subphase suggests that they are indeed enantiomeric structures, capable of enantioselective binding of their natural ligand, guanosine, solely as a result of surface induced asymmetry in "left" but not in "right" form. This observation may also be related to the intriguing question of chiral selection during the early period of "Origin of Life". We show that achiral compounds, as a result of irradiation with circular polarized light, can organize in chiral surface structures capable of amplification of biopolymer binding of particular handedness.     

Functionalized diacetylenes for nonlinear optical applications: Synthesis,characterization, and the properties of their monolayers

Synthesis and characterization of DA(8/1)OMe (14-{4′-[(methoxy)methoxy] biphenyl}-10,12-tetradecadiynoic acid) and DA(8/1)NBP (14-{4′-[(nitro)methoxy] biphenyl}-10,12-tetradecadiynoic acid ) are presented. Monolayers of DA(8/1)OMe at gas-water interface were investigated. It does not form a stable monolayer nor does it undergo polymerization at the gas-water interface. However, the Ba²⁺ and Cd²⁺ salts formed stable monolayer that polymerized. Polymerization was confirmed by Raman spectroscopy. The diacetylene analog with the more polar tail group, DA(8/1)NBP, does not form a monolayer and undergo polymerization regardless of the subphase condition. A mixed monolayer of DA(8/1)OMe and DA(8/1)NBP forms a true monolayer if the composition of DA(8/1)NBP is 50% or less. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1771–1779, 1999     

Synthesis and cytotoxic activity of a series of diacetylenic compounds related to falcarindiol

The synthesis of a series of diacetylenic compounds related to the natural product falcarindiol has been carried out. Unsymmetrical diacetylenes were prepared by a modification of the Cadiot-Chodkiewicz coupling reaction, while a Glaser coupling was used to prepare symmetrical diacetylenes. These compounds have been tested for in vitro cytotoxic activity against Hep-G2, and H-4-II-E cell lines. Diacetylenes with additional unsaturation at C-1, 2, appended with hydroxyl groups at C-3 and C-8, or with long hydrophobic chains, exhibited IC50 values in the micromolar range.     

Thermal and optical studies on hexa-2,4-diyne-1,6-diyl-bis(4-n-hexoxybenzoate)

As part of a programme investigating mesogenic diacetylenes a symmetrically disubstituted diacetylene has been synthesized and polymerized. Thermal, thermo-optical and IR studies have been carried out to investigate the different crystalline forms of the diacetylene.     

Molecular aggregation of disklike benzenetricarboxamides containing diacetylenic groups in bulk and organic solvents

We prepared disklike tris(4-alkylbutadiynylphenyl)-1,3,5-benzenetricarboxamide and tris[4-(4-alkyloxyphenyl)butadiynylphenyl]-1,3,5-benzenetricarboxamide, where three phenyl diacetylenic and diphenyl diacetylenic groups are connected to a benzene ring through amide linkages, respectively. The structures of self-assembled substances were investigated by using transmission electron microscopy, scanning electron microscopy, and X-ray diffraction techniques. All the compounds were highly viscous in melt states, and only compound 9 having three phenyl diacetylenic groups and hexyl tails showed a thermotropic mesophase on cooling. The compound with three diphenyl diacetylenic groups and dodecyloxy tails (13) formed a stable gel in THF/cyclohexane. The IR and X-ray analyses showed that in the gel state molecules were assembled into a rectangular columnar lattice and held each other by hydrogen bondings between amide groups. The compound with tetradecyloxy tails (14) formed stable colloidal particles in cyclohexane. The UV irradiation of 13 in a gel and 14 in a colloidal particle did not result in a long conjugated polymer because of the inappropriate alignment of diacetylenic groups for the topochemical polymerization.     

Preparation and structure/property relationships of polyesters containing conjugated diacetylene groups

A series of novel polyesters containing conjugated diacetylenes (DA‐polyesters) were prepared from various diacetylene diols with/without methyl side groups and isomers of aromatic acid chlorides via an interfacial condensation. A fully aliphatic DA‐polyester was also prepared for comparison. All synthesised DA‐polyesters are soluble in m‐cresol, and the intrinsic viscosities were measured. In addition, compact and coherent films and sheets can be obtained from some of the polymers via solution or melt casting. The structure, morphology, and properties were characterized using spectroscopic methods, including FTIR, Raman, and WAXD and thermal analysis including TGA, DSC techniques. DMA was carried out on the solution‐cast thin films and melt‐processed samples. Close correlation was found between the structure and properties in these DA‐polyesters. In particular, through analysis using isothermal DSC and Raman spectroscopy, the solid‐state reactivity of the diacetylene groups in these polyesters was found related to the interchain spacings, which are, in turn, controlled by the molecular structure of the polymers. Results have shown that the aliphatic DA‐polyester behaves very differently compared to the aromatic ones. Distinct differences were also observed among meta‐ and para‐disubstituted isomers of the DA‐polyesters. Furthermore, the introduction of methyl side groups has dramatically affected the thermal and thermal mechanical behavior by altering the interchain spacing of the polymers. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 965–974, 1999     

Phospholipid/protein cones

The presence of protein in tubule-forming solutions of the diacetylenic phospholipid 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine results in the formation of hollow cones rather than the expected hollow cylinders. Differential phase-contrast video microscopy reveals that cones grow from proteinaceous nodules in a fashion similar to cylindrical tubule growth from spherical vesicles. Spatially resolved electron-beam energy-dispersive X-ray fluorescence spectroscopy shows the protein to be associated with the cone wall. Small-angle X-ray scattering shows that, like the protein-free cylinders, the cones are multilamellar with essentially identical interlamellar spacing.