A Synergistic Coassembly of Block Copolymer and Fluorescent Probe in Thin Film for Fine-Tuning the Block Copolymer Morphology and Luminescence Property of the Probe Molecules

Here, we investigate a synergistic coassembly of a block copolymer, polystyrene-<i>b</i>-poly­(4-vinylpyridine) (PS-<i>b</i>-P4VP), and a fluorescent probe molecule, pyrenebutyric acid (PBA), in thin film using block copolymer supramolecular assembly (SMA) strategy for a wide range of compositions tuned by varying the molar ratio (<i>r</i>) of PBA and 4VP units. The PBA molecules form supramolecules with PS-<i>b</i>-P4VP through H-bonding between the carboxylic acid group of 1-pyrenebutyric acid and pyridine ring of P4VP. For compositions <i>r</i> = 0, 0.1, 0.25, and 0.5, the SMAs exhibit cylindrical morphology, whereas for <i>r</i> = 0.75 and 1, the SMAs generate lamellar morphology. Interestingly, it has been observed that the orientation of the microdomains depends on the solvent used for annealing and can be switched reversibly on exposing the SMA films to corresponding solvent. In a nonselective solvent like chloroform, the microdomains are oriented normal to the substrate, whereas in a selective solvent like 1,4-dioxane, the microdomains are oriented parallel. The synergistic coassembly of PS-<i>b</i>-P4VP and PBA in SMAs with higher molar ratio results in a structure-within-structure pattern characterized by two length scales from phase separation of block copolymer and parallel π–π stacking of the pyrene moiety of PBA molecules inside the comb block. The photophysical properties of PBA in different SMAs of varying composition were studied both in solution and in thin film state and compared to pure PBA. The UV–vis study shows the H type of aggregation of PBA molecules inside the comb block by parallel stacking of the pyrene units, and the PBA molecules orient parallel to the substrate when the microdomains are oriented normal to the substrate. The pure PBA molecules in thin film exhibit excimer emission extensively, whereas the PBA molecules in different supramolecular assemblies exhibit emission ranging from monomer to mixture of monomer and excimer. The SMA shows more intense fluorescence emission compared to pure PBA both in solution and in thin film

One-Dimensional Anhydrous Proton Conducting Channel Formation at High Temperature in a Pt(II)-Based Metallo-Supramolecular Polymer and Imidazole System

One dimensional (1D) Pt­(II)-based metallo-supramolecular polymer with carboxylic acids (polyPtC) was synthesized using a new asymmetrical ditopic ligand with a pyridine moiety bearing two carboxylic acids. The carboxylic acids in the polymer successfully served as apohosts for imidazole loaded in the polymer interlayer scaffold to generate highly ordered 1D imidazole channels through the metallo-supramolecular polymer chains. The 1D structure of imidazole loaded polymer (polyPtC-Im) was analyzed in detail by thermogravimetric analysis, powder X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and ultraviolet–visible and photoluminescence spectroscopic measurements. PolyPtC-Im exhibited proton conductivity of 1.5 × 10^–5 S cm^–1 at 120 °C under completely anhydrous conditions, which is 6 orders of magnitude higher than that of the pristine metallo-supramolecular polymer

Platinum(II)-Based Metallo-Supramolecular Polymer with Controlled Unidirectional Dipoles for Tunable Rectification

A platinum­(II)-based, luminescent, metallo-supramolecular polymer (PolyPtL1) having an inherent dipole moment was synthesized via complexation of Pt­(II) ions with an asymmetric ligand L1, containing terpyridyl and pyridyl moieties. The synthesized ligand and polymer were well characterized by various NMR techniques, optical spectroscopy, and cyclic voltammetry studies. The morphological study by atomic force microscopy revealed the individual and assembled polymer chains of 1–4 nm height. The polymer was specifically attached on Au-electrodes to produce two types of film (films 1 and 2) in which the polymer chains were aligned with their dipoles in opposite directions. The Au-surface bounded films were characterized by UV–vis, Raman spectroscopy, cyclic voltammetry, and atomic force microscopy study. The quantum mechanical calculation determined the average dipole moment for each monomer unit in PolyPtL1 to be about 5.8 D. The precise surface derivatization permitted effective tuning of the direction dipole moment, as well as the direction of rectification of the resulting polymer-attached molecular diodes. Film 1 was more conductive in positive bias region with an average rectification ratio (RR = <i>I</i>(+4 V)/<i>I</i>(−4 V)) ≈ 20, whereas film 2 was more conducting in negative bias with an average rectification ratio (RR = <i>I</i>(−4 V)/<i>I</i>(+4 V)) ≈ 18

Selective DNA Recognition and Cytotoxicity of Water-Soluble Helical Metallosupramolecular Polymers

Water-soluble helical Fe­(II)-based metallosupramolecular polymers ((<i>P</i>)<b>-</b> and (<i>M</i>)-polyFe) were synthesized by 1:1 complexation of Fe­(II) ions and bis­(terpyridine)­s bearing a (<i>R</i>)- and (<i>S</i>)-BINOL spacer, respectively. The binding affinity to calf thymus DNA (ct-DNA) was investigated by titration measurements. (<i>P</i>)-PolyFe with the same helicity as B-DNA showed 40-fold higher binding activity (<i>K</i>_b = 13.08 × 10⁷ M^–1) to ct-DNA than (<i>M</i>)-polyFe. The differences in binding affinity were supported by electrochemical impedance spectroscopy analysis. The charge-transfer resistance (<i>R</i>_ct) of (<i>P</i>)-polyFe increased from 2.5 to 3.9 kΩ upon DNA binding, while that of (<i>M</i>)-polyFe was nearly unchanged. These results indicate that ionically strong binding of (<i>P</i>)-polyFe to DNA chains decreased the mobility of ions in the conjugate. Unique rod-like images were obtained by atomic force microscopy measurement of the DNA conjugate with (<i>P</i>)-polyFe, likely because of the rigid binding between DNA chains and the polymer. Differences in polymer chirality lead to significantly different cytotoxicity levels in A549 cells. (<i>P</i>)-PolyFe showed higher binding affinity to B-DNA and much higher cytotoxicity than (<i>M</i>)-polyFe. The helicity in metallosupramolecular polymer chains was important not only for chiral recognition of DNA but also for coordination to a biological target in the cellular environment