11 research outputs found
The effect of permodified cyclodextrins encapsulation on the photophysical properties of a polyfluorene with randomly distributed electron-donor and rotaxane electron-acceptor units
We report on the synthesis as well as the optical, electrochemical and morphological properties of two polyrotaxanes (4a and 4b), which consist of electron-accepting 9,9-dicyanomethylenefluorene 1 as an inclusion complex in persilylated ÎČ- or Îł-cyclodextrin (TMS-ÎČ-CD, TMS-Îł-CD) (1a, 1b) and methyltriphenylamine as an electron-donating molecule. They are statistically distributed into the conjugated chains of 9,9-dioctylfluorene 3 and compared with those of the corresponding non-rotaxane 4 counterpart. Rotaxane formation results in improvements of the solubility, the thermal stability, and the photophysical properties. Polyrotaxanes 4a and 4b exhibited slightly red-shifted absorption bands with respect to the non-rotaxane 4 counterpart. The fluorescence lifetimes of polyrotaxanes follow a mono-exponential decay with a value of Ï = 1.14 ns compared with the non-rotaxane, where a bi-exponential decay composed of a main component with a relative short time of Ï1 = 0.88 (57.08%) and a minor component with a longer lifetime of Ï2 = 1.56 ns (42.92%) were determined. The optical and electrochemical band gaps (ÎEg) as well as the ionization potential and electronic affinity characterized by smaller values compared to the values of any of the constituents. AFM reveals that the film surface of 4a and 4b displays a granular morphology with a lower dispersity supported by a smaller roughness exponent compared with the non-rotaxane counterpart
Synthesis, Properties and Adsorption Kinetic Study of New Cross-Linked Composite Materials Based on Polyethylene Glycol Polyrotaxane and Polyisoprene/Semi-Rotaxane
New composite materials were prepared via cross-linking of polyethylene glycol/2-hydroxypropyl-ÎČ-cyclodextrins polyrotaxane (PEG/HPÎČCD) and polyisoprene/HPÎČCD semi-polyrotaxane (PI/HPÎČCD SR) with 1,6-hexamethylene diizocyanate (HMDI). Advanced instrumental methods (such WAXS (wide angle X-ray scattering), AFM (atomic force microscopy), SEM (scanning electron microscopy), and thermal and dynamic vapor sorption) were employed for the structural, morphological and thermal characterization of the resulting composite materials. The roughness parameters calculated using AFM indicate a smoother surface for the composite material with 10 wt% of PI/HPÎČCD SR, denoting that a homogeneous film was obtained. SEM analysis reveals porous morphologies for both composite materials and the pore sizes increase with the increasing concentration of PI/HPÎČCD SR in the matrix. Dynamic vapor sorption/desorption measurements and type IV isotherms confirmed the hydrophilic and porous materials, which are in agreement with SEM analysis. The composite with a higher PI/HPÎČCD SR concentration in the matrix showed increased thermal stability than that of the pure cross-linked material. This material was further tested as a sorbent for methylene blue (MB) dye removal from an aqueous solution. The adsorption capacity of the composite film was found to be 2.58 mg gâ1 at 25 °C
Synthesis and electro-optical properties of polyfluorene modified with randomly distributed electron-donor and rotaxane electron-acceptor structural units in the main chain
International audiencePolyfluorene PFâąÎłCD rotaxane copolymer, composed of randomly distributed 9,9-dioctylfluorene, methyltriphenylamine (electron-donating) and 9-dicyanomethylenefluorene complexed with Îł-cyclodextrin (ÎłCD) (electron-accepting) structural units, has been synthesized by Suzuki cross-coupling reaction. The chemical structures were proved by FTIR and 1H NMR spectroscopy. The surface morphology, thermal, optical, electrochemical behavior, and adhesion characteristics of the obtained rotaxane copolymer have been investigated and compared with those of the nonrotaxane counterpart (PF). Relatively high fluorescence efficiency, almost identical normalized absorbance maximum in solution and solid-state of PFâąÎłCD rotaxane copolymer, and a more uniform and smoother surface with lower adhesion forces provides the role of ÎłCD encapsulation on the lower aggregation propensity. PFâąÎłCD and PF copolymers exhibit n- and p-doping processes and blue-light emission in the film state. The optical and electrochemical band gaps (ÎEg), as well as the highest occupied molecular orbital/lowest unoccupied molecular orbital positions in an energetic diagram indicate that both copolymers are promising blue-emitting electroluminescent materials. Copyrigh
Thermal Transitions and Structural Characteristics of Poly(3,4-ethylenedioxythiophene/cucurbit[7]uril) Polypseudorotaxane and Polyrotaxane Thin Films
Herein, we report the thermal transitions and structural properties of poly(3,4-ethylenedioxythiophene/cucurbit[7]uril) pseudopolyrotaxane (PEDOTâCB7-PS) and polyrotaxane (PEDOTâCB7-PR) thin films compared with those of pristine PEDOT. The structural characteristics were investigated by using variable-temperature spectroscopic ellipsometry (VTSE), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and atomic force microscopy (AFM). VTSE and DSC results indicated the presence of an endothermic process and glass transition in the PEDOTâCB7-PS and PEDOTâCB7-PR thin films. X-ray diffraction of PEDOTâCB7-PS and PEDOTâCB7-PR powders displayed the presence of interchain Ï-Ï stacking revealing a characteristic arrangement of aromatic rings in the internal structure of the crystallites. AFM imaging of PEDOTâCB7-PS and PEDOTâCB7-PR thin films exhibited significant differences in the surface topographies compared with those of PEDOT. A high degree of crystallization was clearly visible on the surface of the PEDOT layer, whereas the PEDOTâCB7-PS and PEDOTâCB7-PR thin films exhibited more favorable surface parameters. Such significant differences identified in the surface morphology of the investigated layers can, therefore, be clearly associated with the presence of surrounding CB7 on PEDOT skeletons
Anionic ring-opening polymerization of ethylene oxide in DMF with cyclodextrin derivatives as new initiators
International audienceAnionic polymerization initiated by cyclodextrins suffers from a poor solubility of those derivatives in standard polymerization solvents. The possibility to perform ethylene oxide polymerization initiated by monofunctional initiators (allyl alcohol, 2-methoxyethanol) by living ring opening polymerization in DMF, a good solvent for any CD derivative, was demonstrated by SEC, 1H and 13C NMR analyses. The study was extended to the use of native CD as initiator, leading to the synthesis of ill-defined structures, explained by the reactivity scale of the various hydroxyl functions. Two selectively modified CD derivatives are then used to synthesize a new family of star-shaped poly(ethylene oxide) polymers with CD core, having 14 or 21 arms. The polymerization was found to be living and DOSY experiments confirmed the well-defined structures for the synthesized star-polymers
Structural characteristics and the label-free detection of poly(3,4-ethylenedioxythiophene/cucurbit[7]uril) pseudorotaxane at single molecule level
Inclusion Complexes of 3,4-Ethylenedioxythiophene with Per-Modified ÎČ- and Îł-Cyclodextrins
Herein, we report the synthesis of inclusion complexes (ICs) based on 3,4-ethylenedioxythiophene (EDOT) with permethylated ÎČ-cyclodextrins (TMe-ÎČCD) and permethylated Îł-cyclodextrins (TMe-ÎłCD) host molecules. To prove the synthesis of such ICs, molecular docking simulation, UV-vis titrations in water, 1H-NMR, and H-H ROESY, as well as matrix-assisted laser desorption ionization mass spectroscopy (MALDI TOF MS) and thermogravimetric analysis (TGA) were carried out on each of the EDOTâTMe-ÎČCD and EDOTâTMe-ÎłCD samples. The results of computational investigations reveal the occurrence of hydrophobic interactions, which contribute to the insertion of the EDOT guest inside the macrocyclic cavities and a better binding of the neutral EDOT to TMe-ÎČCD. The H-H ROESY spectra show correlation peaks between H-3 and H-5 of hosts and the protons of the guest EDOT, suggesting that the EDOT molecule is included inside the cavities. The MALDI TOF MS analysis of the EDOTâTMe-ÎČCD solutions clearly reveals the presence of MS peaks corresponding to sodium adducts of the species associated with the complex formation. The IC preparation shows remarkable improvements in the physical properties of EDOT, rendering it a plausible alternative to increasing its aqueous solubility and thermal stability