Nanocomposites of Polydiacetylene and Rare Earth Ions with Reversible Thermochromism

We report a facile approach to water-dispersible polydiacetylene/rare earth ions nanocomposites with reversible thermochromism. The nanocomposites were prepared by doping rare earth ions Dy^3＋ or Sin^3＋ into layer-structured 10,12-pentacosadiynoic acid （PCDA） nanopar- ticles to obtain PCDA/rare earth ions nanocomposites （PCDA-RE） and subsequently annealing PCDA-RE at the temperature slightly higher than the melting point of pure PCDA crystals, followed by topochemically polymerizing the annealed PCDA-RE. The polymerized PCDA-RE, i.e. poly（10,12-pentacosadiynoic acid）/rare earth ions nanocomposites （PDARE： PDA-Dy or PDA-Sm）, are largely reversible （PDA-Sm） or even completely reversible （PDA-Dy） in the thermochromism, while, without the doping, pure PDA is completely irreversible. It is confirmed that, PDA-RE are also layer-structured with a d-spacing of 5.4 nm, higher than the d-spacing of pure PDA （4.7 nm）. In PDA-RE, the rare earth ions form a layer in-between and interact strongly with the PDA bilayers, being responsible for the high degree or even the complete reversibility. This is the first example to make PDA completely reversible through the doping of rare earth ions; the annealing process is essential for the complete reversibility since it removes any defects in the structure.

Fabrication of Melamine/Tb^3+-Intercalated Polydiacetylene Nanosheets and Their Thermochromic Reversibility

Polydiacetylene(PDA)is one kind of the conjugated polymer with layered structure,which can serve as a host to accommodate the guest components through intercalation.In these intercalated PDAs,some of them were reported to have a nearly perfect organized structure and perform completely reversible thermochromism.Till now,these reported intercalated PDAs were made by only introducing a single component for intercalation.Here,we chose 10,12-pentacosadiynoic acid(PCDA)as the monomer,of which the carboxyl-terminal groups can interact with either Tb^3+ ions or melamines(MAs).When the feeding molar ratio of PCDA,MA,and Tb^3+ ion was 3:267:1,only Tb^3+ ions were intercalated though excess MAs existed.Such Tb^3+- intercalated poly-PCDA exhibited completely reversible thermochromism,where almost all the carboxyl groups interacted with Tb^3+ ions to form the nearly perfect structure.When the feeding molar ratio of PCDA,MA,and Tb^3+ ion was 3:267:0.6,both Tb^3+ ions and MAs were intercalated.There existed some defects in the imperfect MA-intercalated domains and at the domain boundaries.The MA/Tb^3+- intercalated poly-PCDA exhibits partially reversible thermochromism,where the backbones near the defects are hard to return the initial conformation,while the rest,those at nearly perfect organized domains,are still able to restore the initial conformation.

Self-suspended Pure Polydiacetylene Nanoparticles with Selective Response to Lysine and Arginine

We demonstrate a very convenient access to self-suspended pure poly（10,12-pentacosadiynoic acid） （PDA） nanoparticles （NPs） simply by adding the ethanol solution of diacetylene monomer to water, followed by UV irradiation. The as-obtained PDA NPs are of high purity because no any initiator, catalyst or stabilizer was used during the whole process. The stabilizer-free PDA NPs are stable in the aqueous suspension. Due to the high purity and stability, the PDA NPs can respond sensitively and selectively to lysine and arginine among 18 kinds of water soluble natural amino acids; without the competitive interaction from the stabilizer, the sensitivity was enhanced.

THE CRYSTALLIZATION BEHAVIOR OF URETHANE SUBSTITUTED POLYDIACETYLENE

The crystalline behavior of urethane substitute polydiacetylene was studied by using pohrized light and electron microscopy. The lamellar morphological structure was observed in the crystallized films. The thickness of lamellae is about 300A, being independent of the crystalline temperature. But the size and density of lamellae were dependent on the crystallization temperature. If the molten film was sheared during the crystallzation process the oriented lamellae grew with their long axes perpendicular to the direction of shear and the chain direction was normal to the lamellar surface.

Order-Disorder Transition of Carboxyl Terminated Chains in Polydiacetylenes Vesicles Probed by Second Harmonic Generation and Two-Photon Fluorescence

To understand and control the interfacial properties of polydiacetylenes(PDAs)vesicles withπ-conjugated backbone is very important for their colorimetric sensing of chemical and biological targets.In this work,we adopted 10,12-pentacosadiynoic acid(PCDA)as the model molecule to prepare PDAs vesicles in aqueous solution with different forms(from monomer to blue-to-purple-to-red phase)by controlling the UV irradiation dose.The variations of the interfacial conformation of PDAs vesicles during chromatic transitions were inspected by the adsorption behaviors of probe molecules(4-(4-diethylaminostyry)-1-methylpyridinium iodide,D289)on vesicle surface with surface-specific second harmonic generation(SHG)and zeta potential measurements.Resonant SHG signal from D289 adsorbed on vesicle surface attenuated sharply,and the adsorption free energy as well as the corresponding two-photon fluorescence signal decreased slightly in chromatic transitions.While,the change in the surface density of the adsorbed D289 molecules for PDAs vesicles with different forms was relatively small as estimated from zeta potential measurements.The attenuation of the SHG intensity was thus attributed to the overall order-disorder transition and the changed orientation of D289 molecules caused by the gradual distortion of carboxyl head group driven by backbone perturbation.

EVIDENCE FOR THERMOTROPIC LIQUID CRYSTALLINITY OF A FUSIBLE POLYDIACETYLENE

The thermotropic liquid crystalline behavior of a fusible polydiacetylene has been studied by using polarizing optical microscopy and wide angle X-ray diffraction. It was found that the typical threaded texture can exhibit in the melt and the banded texture can be observed when applied a gentle shear to the melt. The results indicate that this polydiacetylene is really a thermotropic liquid crystalline polymer.

Nonlinear Optical Properties of Two Different Nanoassemblies of Polydiacetylene (PDA): PDA Nanovesicles and PDA Nanocrystals

We have synthesized and characterized two different nanoassemblies of polydiacetylene (PDA), PDA nanovesicles and PDA nanocrystals, in order to study the influence of chain packing geometry of the two nanoassemblies on their third order nonlinear optical properties. The second molecular hyperpolarizability γ(-ω,ω,-ω,ω)of the two samples was investigated by antiresonant ring interferometric nonlinear spectroscopic (ARINS) technique using femtosecond modelocked Ti:sapphire laser in the spectral range of 720 nm - 820 nm. The observed spectral dispersion of γ has been explained in the framework of three-essential states model involving the ground state, a one-photon excited state and a two-photon excited state. The observed optical nonlinearity has been correlated with the electronic structure of the two samples. The energy of two-photon state, transition dipole moments and line width of the transitions have been estimated. Our studies show that the arrangement of polymer chains in polydiacetylene nanocrystals is more favorable for higher nonlinearity.

Preparation and Structure-Property Regulation Mechanism of Reversible Thermochromic Polydiacetylene

The thermochromic mechanism and the structure-property regulation principle of reversible thermochromic polydiacetylene(PDA)materials have always been a challenging issue.In this work,a series of diacetylene monomers(m-PCDA)containing phenyl and amide or carboxyl groups were synthesized from 10,12-pentacosadiynoic acid(PCDA)through the esterification or amidation reactions.The effects of the number and the distribution of the functional groups in m-PCDA molecules on their solid-state polymerization capability,and the thermochromic mechanism of their corresponding polymers(m-PDA)were investigated and discussed in detail.The results show that the m-PCDA monomers containing both benzene ring and groups that can form hydrogen bonding interactions have strong intermolecular interaction,and are easy to carry out the solid phase polymerization under 254-nm UV irradiation to obtain the corresponding new thermochromic m-PDA materials.The thermochromic behavior of m-PDA depends on its melting process.The initial color-change temperature(blue to red)is determined by the onset melting tem perature,and the temperature range in which reversible color recovery can be achieved by repeat heating-cooling treatment is determined by its melting range.According to the proposed thermochromic mechanism of PDA,various new PDA materials with precise thermochromic temperatu res and reversible thermochromic temperature ra nges can be designed and synthesized through the appropriate introduction of benzene ring and groups that can form hydrogen bonding interactions into the molecular structure of linear diacetylene monomer.This work provides a perspective to the precise molecular structure design and the property regulation of the reversible thermochromic PDA materials.

A thermally reversible supramolecular system based on biphenyl polydiacetylene

A new type of diacetylene monomer which includes a biphenylcarboxylic acid group as its head group is synthesized.Polymerization was performed after monomer form spherical vesicle by self-assembly in the water.The polydiacetylene displayed completely thermochromic color change in the range of 20-95℃ owing to the presence of strong π-π interaction caused by biphenyl group and hydrogen bonding between head group.

Recent advances in the development of polydiacetylene-based biosensors

Biosensors that effectively and selectively detect biomolecules and monitor biological processes have become an important component of biological and medical studies. Because they possess several attractive features, polydiacetylenes(PDAs) have been employed as frameworks for fluorometric and colorimetric sensors. PDAs are formed in their non-fluorescent blue-colored state by UV light induced polymerization of head group functionalized diacetylene monomers(DAs) and they undergo a transition to form fluorescent red-colored PDAs in response to a variety of stimuli. Importantly, by properly choosing a headgroup in the DA, the formed PDA can be designed to undergo a fluorescence/colorimetric change in response to a specific biological stimulus. This review summarizes recent advances that have been made in the development of PDA biosensors with an emphasis being given to design strategies and applications.

Polydiacetylene-based poly-ion complex enabling aggregation-induced emission and photodynamic therapy dual turn-on for on-demand pathogenic bacteria elimination

Poly-ion complex(PIC)integrating non-antibiotic theranostics holds great promise in the combat against drug-resistant bacteria.Photosensitizers with aggregation-induced emission(AIE)characteristic are particularly intriguing theranostic agents,but incorporating them into antibacterial PIC to enable both fluorescence and reactive oxygen species(ROS)generation turn-on is deemed a great challenge.Here we report the development of a PIC that can dually boost the fluorescence and ROS generation in the presence of pathogen bacteria.The PIC is constructed based on an anionic polydiacetylene poly(deca-4,6-diynedioic acid)(PDDA),which completely degrades in the presence of ROS.A cationic polymer quaternized poly(2-(dimethylamino)ethyl methacrylate)(PQDMA)that can disrupt bacterial membrane is co-loaded together with a highly efficient AIE photosensitizer TPCI in the PIC.PIC is nonfluorescent initially in that PDDA can quench the AIE of TPCI in PIC.When pathogenic bacteria are present,they can disturb the assembly of PIC to release TPCI,whose fluorescence turns on sensitively to indicate the existence of bacteria.The on-demand irradiation can be subsequently applied to excite TPCI,which generates ROS to degrade PDDA and deform the PIC.As a result,TPCI and PQDMA are completely released to eliminate bacteria through a synergy of turned-on photodynamic therapy(PDT)and membrane disruption.The highly efficient detection and inhibition against both Gramnegative and Gram-positive bacteria have validated this polydiacetylene-based PIC system as an effective non-antibiotic antibacterial theranostic platform as well as a new strategy to enable“turn-on”fluorescence sensing and imaging of AIE fluorophores.

Polydiacetylene-Tb3＋ Nanosheets of Which Both the Color and the Fluorescence Can Be Reversibly Switched between Two Colors

Polydiacetylenes （PDAs）, an organic layered compound, show a series of intriguing properties, such as thermo- chromism and fluorescence emission in the red-phase. However, their irreversible color change, and weak and sin- gle-color fluorescence emitted only from the red-phase PDAs, have limited their applications. Herein, we report double-reversible PDA-Tb3＋ nanosheets of which both the color and the fluorescence can be reversibly switched between two colors. PDA-Tb3＋ nanosheets have the nearly defect-free intercalated structure in which a layer of Tb3＋ ions was intercalated in between each two PDA bilayers to tether almost all of the carboxyl groups at the end of the side chains of the PDA. When the PDA is in the blue phase, the PDA-Tb3＋ nanosheets emit the green fluo- rescence of Tb3＋ ions. When the PDA is in the red phase, the Tb3＋ fluorescence disappears while the intrinsic red fluorescence of PDA is effectively enhanced through the fluorescence resonance energy transfer （FRET） process; the PDA-Tb3＋ nanosheets emit stronger red fluorescence compared with the PDA in red phase. Moreover, the teth- ering of almost all of the carboxyl groups at the end of the side chains of the PDA endows the nanosheets with the double reversibility in both the color and fluorescence transitions.

Studies on Epitaxial Polymerization of 1,3-Bis(3-quinolyl)-1,4-butadiyne

During investigating what causes the low yield of the polymerization product of 1,4-bis(quinolyl)-1,3-butadiyne(DQ), we found that the DQ crystals formed on the surface of PDQ cauld be polymerized to give blue crystals, in which DQ could be sublimated and crystallized on the surface of PDQ film. According to the experimental results, the reason why the DQ crystals can be polymerized is that the sublimation of DQ changes the molecular orientation of DQ in the crystal. The crystals formed in epitaxial growth on the surface of DQ or PDQ during sublimation of DQ are suitable for 1,4-addition polymerization.

Synthesis of a Soluble Diacetylene with Phenylimidazole Ring

6-(2-Methyl-4-phenyl)-N-imidazole-2, 4-hexadiyn-1-ol was synthesized in a good yield by asymmetric coupling, and the corresponding intermediates were also prepared. The diacetylene monomer could be dissolved in common organic solvents. In addition, all kinds of conditions were also discussed effectively improving the formation of the diacetylene monomer.

Responsive Polymer Composite Fiber

Wearable devices are a mainstream for our future daily life,where responsive polymer composite fibers represent one of the key components.However,their practical applications are hampered by several challenges,including poor responsive reversibility,poor controllability and low stability as well as single function.Herein,we share our recent studies on overcoming the above challenges for achieving novel responsive polymer composite fibers,especially focusing on chromatic fibers,deformational fibers and their integrations.Furthermore,we introduce a type of novel materials for these responsive fiber materials,i.e.,aligned carbon nanotube sheets and fibers simultaneously with excellent electrical,optical and mechanical properties.For the future development,we further highlight the possible directions in this field.