Soluble conjugated one-dimensional nanowires prepared by topochemical polymerization of a butadiynes-containing star-shaped molecule in the xerogel state

Branched Dodecaynes: Synthesis and their Optical Properties

Two homologous branched dodecaynes 1,3,5-{(4-<i>t</i>Bu)[2,3-(RC≡C)₂]Ph(C≡C-C≡C)}₃Ph (<b>2a</b>, R = H; <b>2b</b>, R = Ph) were synthesized and characterized in this work. According to steady-state spectroscopy, their electronic absorption and luminescent behaviors were investigated and compared. Simultaneously, as a typical structure of this class of dodecaynes, the molecular configuration of dodecayne <b>2a</b> was depicted by DFT simulation and the maximal absorption were supported by the subsequent TD-DFT calculations. In addition, the electrochemiluminescence (ECL) emission was also investigated. The experiment results showed that π-extended dodecayne <b>2b</b> with more distorted trigonal-planar possessed strong and stable ECL emission, indicating that it has potential application in ECL and luminescence fields.

Synthesis and Properties of Aromatic-Terminated Diacetylene Organogelators and Their Application to Photopatterning of Polydiacetylenes

A series of simply structured diacetylene-diamide-based gelators (DAGs) with aromatic terminals were synthesized, and their gelation and subsequent photopolymerization abilities were analyzed. DAGs with an adequate spacer length (n) and tolyl terminals (DA-Tn) interacted with aromatic solvents, such as benzene and xylenes, at elevated temperatures. During the subsequent cooling process, the DAGs interacted with each other through CH-π interactions at their terminal positions. They also formed one-dimensional hydrogen bonding arrays through secondary amides, leading to stable organogels. These gels polymerized into π-conjugated polydiacetylenes (PDAs) under ultraviolet irradiation. In the p-xylene gels of DA-Tn, the spacer length exerted characteristic odd-even effects on the photopolymerization rates over a certain range (n = 3-6), which can be explained by periodic changes in the uniformity of the molecular packing modes. When the gelling solvent was changed to cyclohexane, the gelation and photopolymerization abilities were greatly improved because the DA-Tn gel networks became highly crystallized and transparent to ultraviolet light (254 nm). The ultimate conversion to PDA from DA-T8/cyclohexane gels was 45.2 wt %. Applying photolithographic techniques to the DAG with excellent photopolymerizability in the film state, we successfully fabricated microscale photopatterns of PDA. We also established a convenient removal process (development process) of DA monomers in unexposed areas. The resulting PDA patterns were quite stable to ambient light stimuli.

Stimuli responsive dynamic transformations in supramolecular gels

Supramolecular gels are formed by the self-assembly of small molecules under the influence of various non-covalent interactions. As the interactions are individually weak and reversible, it is possible to perturb the gels easily, which in turn enables fine tuning of their properties. Synthetic supramolecular gels are kinetically trapped and usually do not show time variable changes in material properties after formation. However, such materials potentially become switchable when exposed to external stimuli like temperature, pH, light, enzyme, redox, and chemical analytes resulting in reconfiguration of gel matrix into a different type of network. Such transformations allow gel-to-gel transitions while the changes in the molecular aggregation result in alteration of physical and chemical properties of the gel with time. Here, we discuss various methods that have been used to achieve gel-to-gel transitions by modifying a pre-formed gel material through external perturbation. We also describe methods that allow time-dependent autonomous switching of gels into different networks enabling synthesis of next generation functional materials. Dynamic modification of gels allows construction of an array of supramolecular gels with various properties from a single material which eventually extend the limit of applications of the gels. In some cases, gel-to-gel transitions lead to materials that cannot be accessed directly. Finally, we point out the necessity and possibility of further exploration of the field.

Polymers with advanced structural and supramolecular features synthesized through topochemical polymerization

Polymers are an integral part of our daily life. Hence, there are constant efforts towards synthesizing novel polymers with unique properties. As the composition and packing of polymer chains influence polymer's properties, sophisticated control over the molecular and supramolecular structure of the polymer helps tailor its properties as desired. However, such precise control via conventional solution-state synthesis is challenging. Topochemical polymerization (TP), a solvent- and catalyst-free reaction that occurs under the confinement of a crystal lattice, offers profound control over the molecular structure and supramolecular architecture of a polymer and usually results in ordered polymers. In particular, single-crystal-to-single-crystal (SCSC) TP is advantageous as we can correlate the structure and packing of polymer chains with their properties. By designing molecules appended with suitable reactive moieties and utilizing the principles of supramolecular chemistry to align them in a reactive orientation, the synthesis of higher-dimensional polymers and divergent topologies has been achieved via TP. Though there are a few reviews on TP in the literature, an exclusive review showcasing the topochemical synthesis of polymers with advanced structural features is not available. In this perspective, we present selected examples of the topochemical synthesis of organic polymers with sophisticated structures like ladders, tubular polymers, alternating copolymers, polymer blends, and other interesting topologies. We also detail some strategies adopted for obtaining distinct polymers from the same monomer. Finally, we highlight the main challenges and prospects for developing advanced polymers via TP and inspire future directions in this area.

Emerging Bottom-Up Strategies for the Synthesis of Graphene Nanoribbons and Related Structures

The solution-phase synthesis is one of the most promising strategies for the preparation of well-defined graphene nanoribbons (GNRs) in large scale. To prepare high quality, defect-free GNRs, cycloaromatization reactions need to be very efficient, proceed without side reaction and mild enough to accommodate the presence of various functional groups. In this Minireview, we present the latest synthetic approaches for the synthesis of GNRs and related structures, including alkyne benzannulation, photochemical cyclodehydrohalogenation, Mallory and Pd- and Ni-catalyzed reactions.

Topochemical Polymerization of a Nematic Tetraazaporphyrin Derivative To Generate Soluble Polydiacetylene Nanowires

Polydiacetylenes are well-established one-dimensional organic semiconductors that have been generated by photochemical and thermal polymerizations of diacetylenes in single crystals, gel phases, thin films, and membranes. Their formation in mesophases, such as liquid crystals, has been surprisingly little studied although higher-ordered mesophases should support the topochemical polymerization of diacetylenes (1,3-butadiyne groups) and may give access to large domains of uniformly aligned materials. The polymerization of diacetylenes in a mesophase may also increase the stability of the self-assembled supramolecular structure. Here, the dye and discotic mesogen tetraazaporphyrin was decorated with eight diacetylene-containing alkyl chains to probe its mesomorphism and conversion into multifunctional polydiacetylene materials. While the incorporation of diacetylene groups supports columnar mesomorphism, successful photopolymerization required the presence of directing amide groups that suppressed columnar in favor of nematic mesomorphism. Still, the polymerization of the nematic mesophase generated a soluble nematic polydiacetylene of significantly higher molecular weight (M_n = 77 kDa or 25 monomer units by gel permeation chromatography) than what has been obtained in gel phases of related compounds. The formation of polydiacetylene was confirmed by Raman spectroscopy, and its nematic structure was verified by UV-vis spectroscopy, polarized optical microscopy, and X-ray diffraction. Both its nematic structure and the incorporation of eight side chains per discotic unit provide the polydiacetylene with sufficient solubility for casting thin films on substrates. Atomic force microscopy studies of films on silicon wafers revealed a grid-like structure of connected nanofibers. This study demonstrates the requirements for the formation of multifunctional mesomorphic polydiacetylene materials from mesomorphic precursors and their advantages. Optimization of the presented molecular design should give access to other mesophases and, consequently, functional polydiacetylene materials with tunable structures and optoelectronic properties.

Synthetic Approaches to Star-Shaped Molecules with 1,3,5-Trisubstituted Aromatic Cores

Herein, we summarize the synthetic approaches that have been developed for the synthesis of star-shaped molecules. Typically, to design such highly functionalized molecules, simple building blocks are first assembled through trimerization reactions, starting from commercially available starting materials. Then, these building blocks are synthetically manipulated to generate extended star-shaped molecules. We also discuss the syntheses of star-shaped molecules that contain 2,4,6-trisubstituted 1,3,5-triazine or 1,3,5-trisubstituted benzene rings as a central core and diverse substituted styrene, phenyl, and fluorene derivatives at their periphery, which endows these molecules with extended conjugation. A variety of metal-catalyzed reactions, such as Suzuki, Buchwald-Hartwig, Sonogashira, Heck, and Negishi cross-coupling reactions, as well as metathesis, have been employed to functionalize a range of star-shaped molecules. The methods described herein will be helpful for designing a wide range of intricate compounds that are highly valuable in the fields of supramolecular chemistry and materials science. Owing to space limitations, we will not cover all of the publications on this topic. Instead, we will focus on examples that were reported by our research group and other relevant recent literature. Apart from the trimerization sequence, this Minireview has been structured based on the key reactions that were used to prepare the star-shaped molecules and other higher analogues. Finally, some examples that do not fit into this classification are discussed.

Covalent Cross-Linking of Diketopyrrolopyrrole-Based Organogels with Polydiacetylenes

A new strategy toward functional materials with novel properties and well-defined structures has been developed through the topochemical polymerization of diacetylene-containing diketopyrrolopyrrole (DPP) derivatives. In order to enable the efficient photopolymerization and cross-linking of the materials, a rational design of DPP-based derivatives has been performed to incorporate amide moieties, thus enabling the formation of intermolecular hydrogen bonds and the formation of an organogel. The new materials showed good gelation properties in aromatic solvents, resulting in the formation of a dense fibrous network in the gel state. Upon UV irradiation, the supramolecular self-assemblies obtained were shown to be efficiently cross-linked through the conversion of diacetylene into polydiacetylene. A detailed investigation of new resulting materials was performed by a combination of morphological characterization tools, including X-ray diffraction, Raman spectroscopy, and atomic force microscopy. Our results demonstrate that the topochemical polymerization of diacetylene-containing DPP-based compounds is a promising strategy toward new electroactive and well-defined materials, without the use of catalysts or additives, thus creating new opportunities for the preparation and processing of π-conjugated materials.

Reversibly Thermochromic Cyclic Dipeptide Nanotubes

Owing to their capability of forming extensive hydrogen bondings and the facile introduction of chirality, cyclic dipeptides (CDPs) have gained great attention as scaffolds for functional supramolecules. Surprisingly, introduction of a photopolymerizable diacetylene (DA) moiety to the CDP afforded nanotubular structures with enhanced stability and reversible thermochromism. A series of CDP-containing DAs (CDP-DAs) are prepared by coupling 10,12-pentacosadiynoic acid with CDPs, cyclo(-Gly-Ser) and cis/trans cyclo(-Ser-Ser). Fabrication of CDP-DA self-assemblies in a polar chloroform and methanol solvent mixture affords nanotubes comprising single-wall and multiwall structures. The self-assembly behavior and morphology characteristic are examined by scanning electron microscopy and transmission electron microscopy. Next, X-ray diffraction analysis confirms well-ordered lamellar structures with a perfect agreement with the bilayer formation leading to the tubular structure via lamellar scrolling behavior. Upon UV irradiation, monomeric CDP-DA tubular assemblies result in the blue-colored CDP/polydiacetylene (PDA) nanotubes. Interestingly, CDP/PDA nanotubes exhibit a reversible blue-to-red color change for over 10 consecutive thermal cycles. The CDP-DA/PDA supramolecular system demonstrates potential applications in developing stimulus-responsive functional materials.

Enhanced circular dichroism at elevated temperatures through complexation-induced transformation of a three-layer cyclophane with dualistic dynamic helicity

When two planes stacked one above the other are twisted, they provide a dynamic pair of helical conformations with (M)- or (P)-helicity. We designed a three-layer cyclophane that consists of two such dynamic pairs: the top and middle planes, and the middle and bottom planes. Hence, several global conformations could be created for the overall molecule, e.g., double-helical forms with a pair with the same helicity [(M,M) or (P,P)], and a meso-like form with a pair with a different helicity (M,P). These conformations dynamically interconvert to each other in solution. Chiroptical properties were given by the helical-sense preference of the double-helical forms, which was brought about through complexation with a chiral hydrogen-bonding guest. In terms of the conformational energy in a complexed state, when a desirable relationship between double-helical and meso-like forms was attained, complexation-induced circular dichroism was enhanced at elevated temperatures and decreased at lowered temperatures.

Gels with sense: supramolecular materials that respond to heat, light and sound

Advances in the field of supramolecular chemistry have made it possible, in many situations, to reliably engineer soft materials to address a specific technological problem. Particularly exciting are "smart" gels that undergo reversible physical changes on exposure to remote, non-invasive environmental stimuli. This review explores the development of gels which are transformed by heat, light and ultrasound, as well as other mechanical inputs, applied voltages and magnetic fields. Focusing on small-molecule gelators, but with reference to organic polymers and metal-organic systems, we examine how the structures of gelator assemblies influence the physical and chemical mechanisms leading to thermo-, photo- and mechano-switchable behaviour. In addition, we evaluate how the unique and versatile properties of smart materials may be exploited in a wide range of applications, including catalysis, crystal growth, ion sensing, drug delivery, data storage and biomaterial replacement.

Recent progress in the stabilization of supramolecular assemblies with functional polydiacetylenes

This minireview covers the most recent examples of covalent rigidification of supramolecular self-assemblies through the photopolymerization of diacetylene moieties.

Polymerizable Supramolecular Approach to Highly Conductive PEDOT:PSS Patterns

Owing to its high conductivity, solution processability, mechanical flexibility, and transparency, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) has been extensively explored for use in functional devices including solar cells, sensors, light-emitting diodes, and supercapacitors. The ability to fabricate patterned PEDOT:PSS on a solid substrate is of significant importance to develop practical applications of this conducting polymer. Herein, we describe a new approach to obtain PEDOT:PSS patterns that are based on a polymerizable supramolecular concept. Specifically, we found that UV irradiation of a photopolymerizable diacetylene containing PEDOT:PSS film followed by development in deionized water and subsequent treatment with sulfuric acid (glass and silicon wafer) or formic acid (PET) produces micron-sized PEDOT:PSS patterns on solid substrates. The newly designed photolithographic method, which can be employed to generate highly conductive (>1000 S/cm) PEDOT:PSS patterns, has many advantages including the use of aqueous process conditions, a reduced number of process steps, and no requirement for plasma etching procedures.

Templating for hierarchical structure control in carbon materials

Carbon-based materials show a remarkable variety of physical properties. For this reason, they have recently been explored for many advanced applications and emerging technologies. In the absence of actual "chemical" functionalities in these materials, tailoring these physical properties requires control on all levels of the structural hierarchy, from the atomic structure (carbon connectivity, defects, impurities), to the supramolecular level (domain orientations), nanoscopic length scale (domain sizes, porosity), microscopic structure (morphology), and macroscopic aspects (shape, surface chemistry). When preparing carbon materials, all these features can be tailored through the use of hard, soft, or molecular templates. Based on such templating approaches or through their combination, tremendous progress towards hierarchically structured carbon materials has recently been accomplished. Novel carbon nanomaterials such as brick-walled carbon tubes, carbon nanotube forests, coral-like carbon monoliths, or functional carbon nanosheets have become available, some of which exhibit unusual combinations of electronic, mechanical, and chemical properties. This review aims to discuss how the different templating approaches allow the control of structure formation on various length scales, how hierarchical structure formation can be realized, and which challenges remain, such as the detailed control over the carbon connectivity or the surface chemistry.

Fabrication of Helical Nanoribbon Polydiacetylene via Supramolecular Gelation: Circularly Polarized Luminescence and Novel Diagnostic Chiroptical Signals for Sensing

Four kinds of commercially available diacetylene (DA) monomers with different chain length, diacetylene positions were fabricated into the organogels via mixing with a chaperone gelator, an amphiphilic l-histidine ester derivative LHC18 that can help the nongelator to form gels. Upon photo irradiation with a 254 nm UV light, the white gels underwent topochemical reaction and turned into red or blue gels, depending on the DA monomer structures. Through the gel formation, the molecular chirality of LHC18 can be transferred to the polydiacetylene (PDA) and helical nanoribbon structures were obtained. The blue gels showed a clear response to stimuli such as pH variation, heating, mechanical force and organic solvents, and turned into red gels. Interestingly, the blue gel showed strong supramolecular chirality, which could be turned off or changed into red phase CD signals. Such changes in chiroptical signals depended on the external heating and various organic solvents. In the case of heating, the blue gel changed into red one, which showed both strong CD signals and circularly polarized luminescence. In the case of organic solvents, although all the tested solvents made the blue gel to red, only some of them could keep the CD signals, thus providing additional sensing capacity of the PDA system. So far, the blue-to-red color change and the "fluorescence on" was widely used as colorimetric and fluorogenic diagnostic signals for PDA, here we showed an additional chiroptical diagnostic signal for a more precise sensing by using the helical PDA.

Fluorometric Measurement of Individual Stomata Activity and Transpiration via a "Brush-on", Water-Responsive Polymer

Much of atmospheric water originates from transpiration, the process by which plants release H2O from pores, known as stomata, that simultaneously intake CO2 for photosynthesis. Controlling stomatal aperture can regulate the extent of water transport in response to dynamic environmental factors including osmotic stress, temperature, light, and wind. While larger leaf regions are often examined, the extent of water vapor release from individual stomata remains unexplored. Using a "brush-on" sensing material, we can now assess transpiration using a water-responsive, polydiacetylene-based coating on the leaves surfaces. By eliciting a fluorometric signal to passing water vapor, we obtained information regarding the activity of individual stomata. In this demonstration, our results prove that this coating can identify the proportion of active stomata and the extent of transpirational diffusion of water in response to different conditions.

Construction of Covalent Organic Nanotubes by Light-Induced Cross-Linking of Diacetylene-Based Helical Polymers

Organic nanotubes (ONTs) are tubular nanostructures composed of small molecules or macromolecules that have found various applications including ion sensor/channels, gas absorption, and photovoltaics. While most ONTs are constructed by self-assembly processes based on weak noncovalent interactions, this unique property gives rise to the inherent instability of their tubular structures. Herein, we report a simple "helix-to-tube" strategy to construct robust, covalent ONTs from easily accessible poly(m-phenylene diethynylene)s (poly-PDEs) possessing chiral amide side chains that can adopt a helical conformation through hydrogen-bonding interactions. The helically folded poly-PDEs subsequently undergo light-induced cross-linking at longitudinally aligned 1,3-butadiyne moieties across the whole helix to form covalent tubes (ONTs) both in solution and solid phases. The structures of poly-PDEs and covalent ONTs were characterized by spectroscopic analyses, diffraction analysis, and microscopic analyses. We envisage that this simple yet powerful "helix-to-tube" strategy will generate a range of ONT-based materials by introducing functional moieties into a monomer.

Hydrochromic Approaches to Mapping Human Sweat Pores

Hydrochromic materials, which undergo changes in their light absorption and/or emission properties in response to water, have been extensively investigated as humidity sensors. Recent advances in the design of these materials have led to novel applications, including monitoring the water content of organic solvents, water-jet-based rewritable printing on paper, and hydrochromic mapping of human sweat pores. Our interest in this area has focused on the design of hydrochromic materials for human sweat pore mapping. We recognized that materials appropriate for this purpose must have balanced sensitivities to water. Specifically, while they should not undergo light absorption and/or emission transitions under ambient moisture conditions, the materials must have sufficiently high hydrochromic sensitivities that they display responses to water secreted from human sweat pores. In this Account, we describe investigations that we have carried out to develop hydrochromic substances that are suitable for human sweat pore mapping. Polydiacetylenes (PDAs) have been extensively investigated as sensor matrices because of their stimulus-responsive color change property. We found that incorporation of headgroups composed of hygroscopic ions such as cesium or rubidium and carboxylate counterions enables PDAs to undergo a blue-to-red colorimetric transition as well as a fluorescence turn-on response to water. Very intriguingly, the small quantities of water secreted from human sweat pores were found to be sufficient to trigger fluorescence turn-on responses of the hydrochromic PDAs, allowing precise mapping of human sweat pores. Since the hygroscopic ion-containing PDAs developed in the initial stage display a colorimetric transition under ambient conditions that exist during humid summer periods, a new system was designed. A PDA containing an imidazolium ion was found to be stable under all ambient conditions and showed temperature-dependent hydrochromism corresponding to a colorimetric change near body temperature. This feature enables the use of this technique to generate high-quality images of sweat pores. This Account also focuses on the results of the most recent phase of this investigation, which led to the development of a simple yet efficient and reliable technique for sweat pore mapping. The method utilizes a hydrophilic polymer composite film containing fluorescein, a commercially available dye that undergoes a fluorometric response as a result of water-dependent interconversion between its ring-closed spirolactone (nonfluorescent) and ring-opened fluorone (fluorescent) forms. Surface-modified carbon nanodots (CDs) have also been found to be efficient for hydrochromic mapping of human sweat pores. The results discovered by Lou et al. [ Adv. Mater. 2015 , 27 , 1389 ] are also included in this Account. Sweat pore maps obtained from fingertips using these materials were found to be useful for fingerprint analysis. In addition, this hydrochromism-based approach is sufficiently sensitive to enable differentiation between sweat-secreting active pores and inactive pores. As a result, the techniques can be applied to clinical diagnosis of malfunctioning sweat pores. The directions that future research in this area will follow are also discussed.

Nanostructured conducting polymers for energy applications: towards a sustainable platform

Recently, there has been tremendous progress in the field of nanodimensional conducting polymers with the objective of tuning the intrinsic properties of the polymer and the potential to be efficient, biocompatible, inexpensive, and solution processable. Compared with bulk conducting polymers, conducting polymer nanostructures possess a high electrical conductivity, large surface area, short path length for ion transport and superior electrochemical activity which make them suitable for energy storage and conversion applications. The current status of polymer nanostructure fabrication and characterization is reviewed in detail. The present review includes syntheses, a deeper understanding of the principles underlying the electronic behavior of size and shape tunable polymer nanostructures, characterization tools and analysis of composites. Finally, a detailed discussion of their effectiveness and perspectives in energy storage and solar light harvesting is presented. In brief, a broad overview on the synthesis and possible applications of conducting polymer nanostructures in energy domains such as fuel cells, photocatalysis, supercapacitors and rechargeable batteries is described.

A Magnetically Responsive Polydiacetylene Precursor for Latent Fingerprint Analysis

A magnetically responsive diacetylene (DA) powder was developed for the visualization of latent fingerprints. A mixture of the DA and magnetite nanoparticles, applied to a surface containing latent fingermarks, becomes immobilized along the ridge patterns of the fingerprints when a magnetic field is applied. Alignment along the ridge structures is a consequence of favorable hydrophobic interactions occurring between the long alkyl chains in the DAs and the lipid-rich, sebaceous latent fingermarks. UV irradiation of the DA-magnetite composite immobilized on the latent fingerprint results in the generation of blue-colored PDAs. Heat treatment of the blue-colored image promotes a blue-to-red transition as well as fluorescence turn-on. A combination of the aligned pale brown-colored monomeric state, UV irradiation generated blue-colored PDA state, as well as the heat treatment generated red-colored and fluorescent PDA state enables efficient visual imaging of a latent fingerprint, which is deposited on various colored solid surfaces.

A 3D networked polydiacetylene sensor for enhanced sensitivity

Immobilization of polydiacetylene (PDA) vesicles on the surface of the modified carbon nanotube (CNT)-networked pillared structures afforded a 3D networked sensor system. A more than three order increase in the sensitivity was observed with the 3D networked sensor matrix in comparison with a conventional 2D PDA sensor system.

Photoinduced reversible phase transition of azobenzene-containing polydiacetylene crystals

A photoinduced reversible phase transition with a simultaneous crystal tearing phenomenon was observed in an azobenzene-containing supramolecular polydiacetylene (PDA) crystal.

Topochemical polymerization of unsymmetrical aryldiacetylene supramolecules with nitrophenyl substituents utilizing C-H∙∙∙π interactions

Diacetylenes are versatile building blocks, in which many functional groups can be incorporated for the construction of new materials with desirable properties. In this study, 6-(p or m-nitrophenyl)-3,5-hexadiyne-1-ol (4a or 4b) containing nitrophenyl groups (host) and 2-hydroxyethyl groups (guest) in different diacetylene terminals were designed to establish an ordered supramolecular assembly that is complied with the strict requirements for the topochemical polymerization of diacetylenes. Crystal film and bulk crystals of compound 4b were obtained successfully by cast film and re-precipitation methods. Both of these could photopolymerize to the corresponding regular poly(diacetylene) polymer, as evidenced by UV-vis, IR, FL and Raman spectroscopy. The electrochemical properties and behaviors of 4a and 4b were also investigated, and the results show that the differences between the para and meta positions of the mono-phenylacetylene substituents probably result from the topochemical polymerization. Thus, m-nitrophenylbutadiyne derivatives with sizeable C-H∙∙∙π interactions seemed to be effective for the formation of a polymerizable packing, which is appropriate for topochemical polymerization.

Polydiacetylene-embedded microbeads for colorimetric and volumetric sensing of hydrocarbons

Rational design of a hydrocarbon sensor that enables visual differentiation of saturated aliphatic hydrocarbons (SAHCs) is very difficult owing to the lack of useful functional groups that can interact with the sensor system. Here, we report a microbead embedded with polydiacetylene that undergoes faster swelling and faster blue-to-red color change in response to the hydrocarbons of shorter alkyl chains. Accordingly, visual differentiation among n-pentane, n-heptane, n-nonane, and n-undecane was readily achieved. By taking advantage of the collective effect, construction of a sensor system with amplified response was possible. Combination of microfluidic technology (for bead preparation), PDMS (swellable polymeric matrix), and polydiacetylene (colorimetric material) was key to enabling this unique hydrocarbon sensor.

Hierarchical assembly of a dual-responsive macroscopic insulated molecular wire bundle in a gradient system

Here, we report the hierarchical self-assembly of a cationic gemini amphiphile, Azo 1, in a composition gradient solution generated using solvent evaporation. As the gradient solution is formed, Azo 1 forms nanorods in the lower region of the solution. Depending on solvent composition, these nanorods can further develop into nanofibres, which can then intertwine to form double helices and other types of nanohelices in the upper region of the solution. Finally, a macroscopic wire bundle is formed via the fusion of nanohelices; this ribbon-like bundle exhibits elasticity and linear ohmic resistance properties. More intriguingly, this bundle exhibits photoresponsive properties that affect its deformation and conductivity, as well as a rapid electroresponse that affects its conductivity, indicating that it is feasible to control the charge pathway.

Conducting polymer nanofibers with controlled diameters synthesized in hexagonal mesophases

Conducting poly(diphenylbutadiyne) (PDPB) nanofibers with controlled diameters (5 to 25 nm) and relatively high conductivity were synthesized in soft templates using UV and gamma irradiation.

Improving the reactivity of phenylacetylene macrocycles toward topochemical polymerization by side chains modification

The synthesis and self-assembly of two new phenylacetylene macrocycle (PAM) organogelators were performed. Polar 2-hydroxyethoxy side chains were incorporated in the inner part of the macrocycles to modify the assembly mode in the gel state. With this modification, it was possible to increase the reactivity of the macrocycles in the xerogel state to form polydiacetylenes (PDAs), leading to a significant enhancement of the polymerization yields. The organogels and the PDAs were characterized using Raman spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM).

Chemical designs of functional photoactive molecular assemblies

Molecular assemblies with defined structures capable of photo-induced electron transfer or photochemical reactions are reviewed, emphasizing their supramolecular features.

Synthesis, gelation and topochemical polymerization of meta-linked oligophenylenebutadiynylene derivatives

Rational design ofmeta-linked oligophenylbutadiynylene (OPBD) derivatives was conducted in order to gain insight into their gelation properties and reactivity toward topochemical polymerization to yield polydiacetylenes (PDAs).

Controlled Synthesis of Carbon Nanoparticles in a Supercritical Carbon Disulfide System

Carbon nanoparticles with large surface areas were produced by the reduction of carbon disulfide with metallic lithium at 500 °C. The carbon nanoparticles account for about 80% of the carbon product. The carbon nanoparticles were characterized by X-ray powder diffraction, field emission scanning electron microscopy, transmission electron microscopy, high resolution transmission electron microscopy and N₂ physisorption. The results showed that carbon nanoparticles predominate in the product. The influence of experimental conditions was investigated, which indicated that temperature plays a crucial role in the formation of carbon nanoparticles. The possible formation mechanism of the carbon nanoparticles was discussed. This method provides a simple and efficient route to the synthesis of carbon nanoparticles.