Photochemical Isomerization and Topochemical Polymerization of the Programmed Asymmetric Amphiphiles

Mechanical Properties of Polydiacetylene Multilayers Studied by AFM Force Spectroscopy

The blue-to-red chromatic phase transition of polydiacetylene (PDA) is accompanied by the twist and rearrangement of its side chains, which results in shortening of the conjugation length in the backbone. However, how these morphological changes affect its mechanical properties remains elusive. In this work, force spectroscopy mapping by atomic force microscopy was employed to quantify mechanical parameters of PDA thin films such as breakthrough force and Young's modulus at the monomer, blue, and red phases during the chromatic transition. We found that the breakthrough force increased by 113% and Young's modulus decreased by 21% during the blue-to-red transition, highlighting that the subtle change in the side-chain configuration has a dramatic impact on its mechanical properties.

Photochemically and Thermally Programmed Optical Multi-States from a Single Diacetylene-Functionalized Cyanostilbene Luminogen

To develop advanced optical systems, many scientists have endeavored to create smart optical materials which can tune their photophysical properties by changing molecular states. However, optical multi-states are obtained usually by mixing many dyes or stacking multi-layered structures. Here, multiple molecular states are tried to be generated with a single dye. In order to achieve the goal, a diacetylene-functionalized cyanostilbene luminogen (DACSM) is newly synthesized by covalently connecting diacetylene and cyanostilbene molecular functions. Photochemical reaction of cyanostilbene and topochemical polymerization of diacetylene can change the molecular state of DACSM. By thermal stimulations and the photochemical reaction, the conformation of polymerized DACSM is further tuned. The synergetic molecular cooperation of cyanostilbene and diacetylene generates multiple molecular states of DACSM. Utilizing the optical multi-states achieved from the newly developed DACSM, switchable optical patterns and smart secret codes are successfully demonstrated.

Aptamer-functionalized polydiacetylene biosensor for the detection of three foodborne pathogens

Rapid, simple and sensitive screening of foodborne pathogens is of great significance to ensure food safety. In this study, an aptamer-functionalized polydiacetylene (Apta-PDA) biosensor was developed for the detection of E. coli O157:H7, S. typhimurium or V. parahaemolyticus. First, aptamers responding to the target bacteria were modified on the surface of magnetic beads by covalent binding to form MBs-oligonucleotide conjugates for bacterial enrichment. Then, an Apta-PDA biosensor was obtained by connecting the aptamers to the PDA nanovesicles using the carbodiimide method. Molecular recognition occurred in the presence of the target bacteria, whereby the aptamer folded into a sequence-defined unique structure, resulting in an MBs-Apta/bacteria/Apta-PDA sandwich structure. Due to the optical properties of PDA, the blue-red transition of the detection system could be observed by the naked eye and quantified by the colorimetric response percentage (CR%). Under optimized conditions, the detection limits of E. coli O157:H7, S. typhimurium and V. parahaemolyticus were 39, 60 and 60 CFU/ml, respectively, with a selectivity of 100% and a reaction time of 30 min. Compared with the gold standard method, the accuracy of the three target bacteria detection reached 98%, 97.5% and 97%, respectively, and the sensitivity and specificity were both greater than 90%. The entire detection process was rapid and easy to execute without any special equipment, making this technology particularly suitable for resource-poor laboratories or regions.

Stereoselective Plasmonic Interaction in Peptide-tethered Photopolymerizable Diacetylenes Doped with Chiral Gold Nanoparticles

Designing polymeric systems with ultra-high optical activity is instrumental in the pursuit of smart artificial chiroptical materials, including the fundamental understanding of structure/property relations. Herein, we report a diacetylene (DA) moiety flanked by chiral D- and L-FF dipeptide methyl esters that exhibits efficient topochemical photopolymerization in the solid phase to furnish polydiacetylene (PDA) with desired control over the chiroptical properties. The doping of the achiral gold nanoparticles provides plasmonic interaction with the PDAs to render asymmetric shape to the circular dichroism bands. With the judicious design of the chiral amino acid ligand appended to the AuNPs, we demonstrate the first example of selective chiral amplification mediated by stereo-structural matching of the polymer-plasmonic AuNP hybrid pairs. Such ordered self-assembly aided by topochemical polymerization in peptide-tethered PDA provides a smart strategy to produce soft responsive materials for applications in chiral photonics.

Photoinduced Reversible Bending and Guest Molecule Release of Azobenzene-Containing Polydiacetylene Nanotubes

Creation of hollow, one-dimensional nanomaterials has gained great recent attention in the chemical and material sciences. In a study aimed at discovering new functional materials of this type, we observed that an amphiphilic diacetylene (DA) derivative, containing an azobenzene moiety and an oligo-ethylene group, self-assembles to form nanotubes and undergoes photopolymerization to form hollow polydiacetylene (PDA) nanotubes with a uniform wall thickness and diameter. The azobenzene-PDA nanotubes are photoresponsive in that on-and-off UV-irradiation leads to a reversible morphological change between straight and bent forms in association with E-Z photoisomerization of the azobenzene group. Owing to the UV-induced structural change feature, the new DA and PDA nanotubes serve as a controlled release material. Accordingly, fluorescent rhodamine B encapsulated inside the nanotubes are effectively released by using repeated on-off UV irradiation. Furthermore, photo-release of rhodamine B was shown to occur in an artemia (brine shrimp).

Topochemical polymerization of dumbbell-shaped diacetylene monomers: relationship between chemical structure, molecular packing structure, and gelation property

Herein, we have synthesized novel photopolymerizable dumbbell-shaped diacetylene liquid crystal (LC) monomers by locating a diacetylene dicarboxylic acid group at the center and chemically connecting swallow-tails, such as hydrophobic alkyl chains (abbreviated as AT₃DI) and amphiphilic biphenyl mesogens (abbreviated as BP₃DI), with bisamide groups. Major phase transitions of dumbbell-shaped diacetylene monomers were identified using differential scanning calorimetry (DSC), polarized optical microscopy (POM), and Fourier transform infrared spectroscopy (FT IR). Molecular packing structures were studied based on structure-sensitive wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) analyses. Mainly, due to nanophase separations and strong intermolecular hydrogen bonding, AT₃DI formed a low-ordered lamellar LC phase at room temperature. BP₃DI self-assembled into highly-ordered crystal phases (K₁ and K₂) at lower temperatures below a low-ordered lamellar LC phase, in which BP₃DI were intercalated with each other to compensate the mutual volume differences. From the photopolymerization of AT₃DI and BP₃DI, it was realized that the topochemical reactions of dumbbell-shaped diacetylene monomers were closely related to their chemical structures as well as molecular packing structures.

Controlling the enthalpy–entropy competition in supramolecular fullerene liquid crystals by tuning the flexible chain length

The supramolecular fullerene liquid crystal phase and structure can be regulated by controlling the enthalpy–entropy competition by tuning the flexible chain length.

Controlling the photochemical reaction of an azastilbene derivative in water using a water-soluble pillar[6]arene

A host–guest system in water based on a water-soluble pillar[6]arene and an azastilbene derivative, (E)-4,4′-dimethyl-4,4′-diazoniastilbene diiodide, has been constructed. Then this water-soluble pillar[6]arene was successfully used to control the photohydration of the azastilbene derivative in water as a “protective agent”.

A photo-responsive metallomesogen for an optically and electrically tunable polarized light modulator

A palladium(ii)-based metallomesogen containing the photo-responsive azobenzene was newly synthesized and was demonstrated to be an optically and electrically tunable polarized light modulator.

Hierarchical superstructures of norbornene-based polymers depending on dendronized side-chains

For understanding the self-assembly behaviours of norbornene-based main-chain polymers depending on side-chain pendants, a series of polynorbornenes containing the programmed dendrons is newly designed and successfully synthesized via ring opening metathesis polymerization.