13C?13C coupling constants in diacetylene (1,3-butadiyne) and its bis(triethylsilyl) derivative

Completely ¹³C-labelled diacetylene and its bis(triethylsilyl) derivative have been synthesized and all the possible spin–spin couplings between the acetylenic carbon nuclei have been determined from their Fourier transform ¹³C NMR spectra. J(CC) values in diacetylene have been also computed by means of the finite perturbation INDO method. Carbon–proton coupling constants in diacetylene have been determined from the spectrum at natural abundance. It has been established that J(CC) values across the triple bond in diacetylene and bis(triethylsilyl)diacetylene are greater than in acetylene and triethylsilylacetylene, respectively. The increase is interpreted in terms of σ- and π-electronic changes which occur with the coupling of two isolated triple bonds into a dimer-like system. All CC coupling constants are greater in diacetylene than in bis(triethylsilyl)diacetylene, which indicates that strong (p→d)π interaction takes place in the latter compound.     

Synthesis and characterization of mono- and bis(pentafluorosulfur)diacetylene

The synthesis of novel, high density, diacetylene monomers has been achieved by the preparation of mono- and bis(pentafluorosulfur) diacetylene. The derivatives are readily prepared by the addition of pentafluorosulfur bromide (SF₅Br) to diacetylene (C₄H₂) and subsequent dehydrobromination. Details of the synthesis and properties of these compounds are discussed.     

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.     

Oligo(octithienylene-diethynylene)s as unprecedentedly long conjugated nanomolecules

[reaction: see text] A series of oligo(octithienylene-diethynylene)s alternately composed of octithiophene and diacetylene units have been prepared by a random Eglinton coupling reaction among mono- and diethynyloctithiophenes. The largest compound isolated in the oligomeric series is comprised of twelve octithiophene units and eleven diacetylene units, and its molecular length reaches ca. 43 nm, which is the longest among single-component conjugated nanomolecules.     

Studies on diacetylenic vinyl compounds. VI. ESR studies on the polymerization of diacetylene containing acrylate and methacrylates

A number of diacetylene containing acrylate and methacrylates have been synthesized and the interaction between their propagating radicals and the diacetylene groups was studied by ESR spectroscopy. In the case of polymerization at 70°C using AIBN as an initiator, the propagating radicals of methacrylates are temporarily trapped with the diacetylenes with rapid exchange of the electron, thus showing strong signals of the propagating radicals. Gamma irradiation of the frozen state produces a blue color in samples, and the ESR signals were found to be those of uninteracted acrylate and methacrylates. From a comparison of spectral widths, there seems to exist an intramolecular interaction between the radicals and the diacetylene group at the frozen state. © 1992 John Wiley & Sons, Inc.     

Pressure dependence of phase transitions in two diacetylene crystals

The phase transitions which occur in a diacetylene polymer crystal (PTS) at 195 K and a diacetylene monomer crystal (DCH) at 142 K have been studied as a function of pressure. For the second-order phase transition in PTS the pressure dependence of the transition temperature was found to be less than 0.05 K MPa^?1; for the first-order transition in DCH it was 0.63 ± 0.08 K MPa^?1.     

Synthesis and properties of diacetylene azides

A three-stage method was developed for the synthesis of diacetylene azides from diacetylene alcohols prepared by Cadiot-Chodkiewicz reaction. By their bromination the corresponding diacetylene bromides were obtained whose azidation resulted in the target diacetylene azides. The attempt was performed to prepare azides of triacetylene series, but the low stability of the synthesized triacetylene alcohols prevented their conversion into the corresponding bromides.     

Phase separation and fractal domain formation in phospholipid/diacetylene-supported lipid bilayers

Phase separation in lipid bilayers is a phenomenon dependent on many environmental parameters such as pH, temperature, ionic strength, and pressure. Its importance in biological systems is reflected by the fact that it has been implicated in the spatial reorganization of plasma membranes, which leads to signaling and stimulation. Here, we present the study of phase separation, domain formation, and domain morphology of supported lipid bilayers composed of mixtures of diacetylene lipids and phospholipids. We have used high-resolution fluorescence and atomic force microscopy to characterize the phase separation between these lipids, and have found that at temperatures below 40 degrees C diacetylene molecules form fractal-like domains. These molecules aggregate in tetralayer stacks with an average monolayer thickness of 3 nm. Boundary and area fractal dimensions were calculated to quantify the domain growth and morphology. A transition from dendritic to dense branching growth was observed as the relative diacetylene concentration was increased. The ability to tailor the growth pattern by changing the relative amount of diacetylene molecules makes this a useful model system for the study of nonequilibrium growth phenomena. In addition, we have explored the possibility of promoting diacetylene domain nucleation through the use of nanostructured surfaces. We found that nanoscale perturbations acted as nucleation sites and modified the growth pattern of diacetylene domains. Phase separation induced by nanometer-scale perturbations could prove useful in selectively positioning lipid patches with specific compositions.     

Soot Formation in the Isothermal Pyrolysis of a Mixture of Acetylene with Diacetylene

Soot formation from acetylene–diacetylene mixtures was experimentally studied under isothermal conditions. It was found that new soot particles were formed only from diacetylene, whereas acetylene was consumed only in particle growth. Thus, diacetylene exhibited a higher activity in the formation of new soot particles, as compared with acetylene, which is a soot-forming agent in mixtures with other hydrocarbons.     

Polydiacetylene–inorganic clay nanocomposites

Two new diacetylenes, 14-amino-10,12-tetradiynoic acid (a diacetylenic aminoacid) and 10,12-docosadiyndiamine (diacetylenic diamine), were successfully synthesized via Eglinton and Cadiot–Chodkiewicz coupling. These two diacetylenes and 10,12-pentacosadiynyl amine (monoamine) were intercalated in mica-type layered silicates, montmorillonite and vermiculite, via a cationic exchange reaction. The intercalation process was confirmed by X-ray diffraction and Fourier transform infrared spectroscopy. The interlayer spacing and polymerizability of the intercalated diacetylene were found to depend upon the length of the diacetylene molecule, the layer charge density of the clay and the solvent treatment. The X-ray diffraction pattern of vermiculite–diacetylene showed evidence of the in-plane packing of the diacetylene. The polymerization of the intercalated diacetylene was confirmed by Raman spectra. © 1998 John Wiley & Sons, Ltd.     

Excited states of the polyacetylenes. Analysis of the near ultraviolet spectra of diacetylene and triacetylene

The 2000–2800 Å system of diacetylene and the 2300–3000 Å system of triacetylene have been investigated. Analysis of the vibrational structure indicates that we observe transitions to a ¹Δ_u upper electronic state for both molecules and transitions to a ¹Σ^?_u state for diacetylene.     

Soluble poly(diacetylene)s using the perfluorophenyl-phenyl motif as a supramolecular synthon

A series of diacetylene monomers with benzoyl, 4-hexylbenzoyl, 4-dodecylbenzoyl, and perfluorobenzoyl substituents were synthesized and investigated with respect to their crystal structures and polymerizability. In the absence of perfluorophenyl-phenyl interactions, the crystal structures of related alkylated and nonalkylated derivatives were substantially different and dominated by the phase segregation between the alkylated side chains and the diaryl-substituted diacetylene cores. By contrast, the perfluorophenyl-phenyl interactions served as a reliable supramolecular synthon in that they persisted in the crystal structures of different alkylated and nonalkylated derivatives. The packing of the diacetylene functions was appropriate for a topochemical polymerization in these cases, and the perfluorophenyl-phenyl interaction determined the polymerization direction. As a result, soluble alternating diacetylene copolymers were obtained which were further characterized with solution phase methods.     

琼脂糖基类丁二炔凝胶剂量计的辐照响应行为

将类丁二炔(10, 12-二十五碳二炔酸)囊泡固载于琼脂糖凝胶制备出了新型辐射变色凝胶复合凝胶材料。利用γ射线辐照研究了所制备凝胶的辐照响应行为,结果显示:当γ辐射剂量在500-2000 Gy内,随着剂量增加,凝胶由无色逐渐变为蓝色,颜色不断加深,采用紫外-可见光分光光度计测试其吸收光谱,发现其主要吸收峰值在660 nm附近,且辐照前后凝胶的吸光度差值与剂量有良好线性关系(相关系数R² =0.9942)。进一步研究表明:所制备的凝胶材料对γ射线和电子束辐照有相同的剂量响应,且无明显的能量和剂量率依赖性;凝胶的辐射后效应较弱,辐照后24 h,吸光度基本恒定;分次辐照对凝胶剂量计准确性的影响极小;凝胶在0-30℃范围内的响应性基本保持稳定;在辐照后48 h内,并未观察到囊泡有明显扩散效应,显示出良好的稳定性。此外,琼脂糖具有价廉、无毒且易制备为任意形状凝胶的优点,因此该凝胶剂量计有望应用于真实场景的三维剂量分布测定。     

联二炔囊泡的光致聚合、热致变色及应用

物理化学实验为各大高校本科化学教学的主干实验课程之一。虽然各高校的物理化学实验内容已十分丰富,但仍然缺乏将不同章节知识点融会贯通以及与学科前沿密切联系的综合型实验内容。我们根据南开大学郭东升教授课题组发表的一篇有关联二炔程序性响应检测胆碱酯酶的工作设计了“联二炔囊泡的光致聚合、热致变色及应用”的物理化学实验,涉及到联二炔缔合胶体的制备、联二炔的紫外光致聚合反应和聚联二炔的热致变色,进而显示其在防伪领域的潜在应用价值。希望通过此实验,使学生对物理化学中的缔合胶体、光化学、热力学、动力学等章节有更深一步的贯通性掌握,并了解自组装、光聚合、变色材料和防伪等相关研究领域的前沿动态。     

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.     

Supramolecular assembly of fluorescent phasmidic diacetylene and its photopolymerization

The closed micellar triclinic structure of a fluorescent phasmidic diacetylene (PhDO) has been fixed by topochemical photopolymerization which induced fluorescence quenching to offer a novel method of image photopatterning.     

Photosensitized Solid-state Polymerization of Diacetylenes in Nanoporous TiO2 Structures

In situ topochemical polymerization of two diacetylene monomers within nanoporous TiO₂ thin films was carried out under visible light irradiation. One of the monomers used contains a carboxylic acid group, which could help to link the monomer onto the TiO₂ surface covalently. UV-Vis absorption and Raman studies showed that both monomers were successfully photopolymerized. These results suggest that the covalent linkage of the diacetylene to the nanoparticle through the carboxylic acid group is not needed. Since photopolymerization of diacetylene is typically induced by excitation of the monomer at λ< 300 nm, the observed red shift of the photopolymerization wavelength is attributed to the photosensitization effect of TiO₂. The morphological study of the polydiacetylene/TiO₂ nanocomposite revealed that the diacetylene monomers were polymerized in the vicinity of the TiO₂ nanoparticles. This is attributed to the fact that the electron-transfer process occurs at the interface of nanocrystalline TiO₂ (nc-TiO₂) and the diacetylene monomer and the polymerization is expected to be initiated near the nc-TiO₂ surface. Photopolymerization of the carboxylated diacetylene monomer with other oxides nanoparticles, such as ZnO and SiO₂ was also investigated.     

Reactions of diacetylene radical cation with ethylene

Ion-molecule reactions and energy-resolved mass spectrometry have been used to determine the structures of the products formed in the reaction of diacetylene radical cation with ethylene in a flowing afterglow-triple quadrupole instrument. The structure of the adduct ion, C(6)H(6)(.+), has been determined to be that of singly ionized benzene. The reaction thus presents a first example of the ability of diacetylene radical cation to undergo an aromatic ring forming reaction. The other products formed in the reaction are m/z 52, C(4)H(4)(.+), and m/z 39, C(3)H(3)(+). Isotopic labeling studies show that C(4)H(4)(.+) and C(3)H(3)(+) are formed with nearly statistical hydrogen incorporation, indicating a complex mechanism that scrambles all protons.     

双炔酸多层LB膜的光敏聚合研究

选用(口恶)花菁染料为光敏剂,将其镶嵌到双炔酸LB膜中,利用Ar~+离子激光514.5 nm照射LB膜,观察到双炔酸LB膜的光敏聚合及(口恶)花菁染料荧光的猝灭,对其光敏聚合机理进行了讨论。     

Synthesis and self-assembling properties of diacetylene-containing glycolipids

Diacetylene-containing glycolipids are interesting molecules that have many potential applications. The polydiacetylenes formed by the cross-linking of the diacetylene lipids are new stimuli-responsive materials. In particular, diacetylene lipids that can form gels in aqueous solution are of great interest in designing functional biocompatible materials. We have synthesized a series of diacetylene-containing sugar lipids with different chain lengths, substituents, and positions of diyne and studied their self-assembling properties in several solvents including hexane, ethanol, and ethanol/water mixture. Among the 24 diacetylene-containing glycolipids synthesized, many of them exhibited excellent gelation properties in ethanol or ethanol/water mixture. Typically very long chain diacetylene lipids formed gels in ethanol and hexane. Shorter chain diacetylene lipids and compounds with one free hydroxyl group can form gels in aqueous solution. The position of the diyne and chain length affect the self-assembling properties significantly. The systematic study of the gelation properties for diacetylene lipids with different lipid chains can help us to understand the structure requirement for the desired physical properties. Optical microscopy studies showed that the molecules form interesting architectures such as tubules, rods, sheets, and belts. The resulting organogels can also be cross-linked and give different colored polymerized gels depending on their structures.