Aurica Farcas

Cucurbit[n]urils (CBn, n = 5–8) are macrocyclic hosts that form stable inclusion complexes with a variety of guest molecules, including amino acids a

Herein, we report the thermal transitions and structural properties of poly(3,4-ethylenedioxythiophene/cucurbit[7]uril) pseudopolyrotaxane (PEDOT∙CB7-PS) and polyrotaxane (PEDOT∙CB7-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 PEDOT∙CB7-PS and PEDOT∙CB7-PR thin films. X-ray diffraction of PEDOT∙CB7-PS and PEDOT∙CB7-PR powders displayed the presence of interchain π-π stacking revealing a characteristic arrangement of aromatic rings in the internal structure of the crystallites. AFM imaging of PEDOT∙CB7-PS and PEDOT∙CB7-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 PEDOT∙CB7-PS and PEDOT∙CB7-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.

New composite materials were prepared via cross-linking of polyethylene glycol/2-hydroxypropyl-β-cyclodextrins polyrotaxane (PEG/HPβCD) and polyisoprene/HPβCD semi-polyrotaxane (PI/HPβCD 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/HPβCD 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/HPβCD 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/HPβCD 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 g⁻¹ at 25 °C.

Two poly(3,4-ethylenedioxythiophene) polyrotaxanes (PEDOT∙TMe-βCD and PEDOT∙TMe-γCD) end-capped by pyrene (Py) were synthesized by oxidative polymerization of EDOT encapsulated into TMe-βCD or TMe-γCD cavities with iron (III) chloride (FeCl₃) in water and chemically characterized. The effect of TMe-βCD or TMe-γCD encapsulation of PEDOT backbones on the molecular weight, thermal stability, and solubility were investigated in depth. UV–vis absorption, fluorescence (F_L), phosphorescence (P_H), quantum efficiencies, and lifetimes in water and acetonitrile were also explored, together with their surface morphology and electrical properties. Furthermore, dynamic light scattering was used to study the hydrodynamic diameter (DH) and z-potential (ZP-ζ) of the water soluble fractions of PEDOT∙TMe-βCD and PEDOT∙TMe-γCD. PEDOT∙TMe-βCD and PEDOT∙TMe-γCD exhibited a sharp monodisperse peak with a DH of 55 ± 15 nm and 122 ± 32 nm, respectively. The ZP-ζ value decreased from −31.23 mV for PEDOT∙TMe-βCD to −20.38 mV for PEDOT∙TMe-γCD, indicating that a negatively charged layer covers their surfaces. Surface pressure–area isotherms and Brewster angle microscopy (BAM) studies revealed the capability of the investigated compounds to organize into sizeable and homogeneous 2D supramolecular assemblies at the air–water interface. The control of the 2D monolayer organization through the thermodynamic parameters of PEDOT∙TMe-βCD and PEDOT∙TMe-γCD suggests potential for a wide range of optoelectronic applications.

Herein, we report the synthesis of inclusion complexes (ICs) based on 3,4-ethylenedioxythiophene (EDOT) with permethylated β-cyclodextrins (TMe-βCD) and permethylated γ-cyclodextrins (TMe-γCD) 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 EDOT∙TMe-βCD and EDOT∙TMe-γCD 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-βCD. 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 EDOT∙TMe-βCD 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.

The UV-Vis absorption, fluorescence, and phosphorescence spectra of poly(3,4-ethylenedioxythiophene/cucurbit[7]uril), polypseudorotaxane (1), and polyrotaxane (2) in water and acetonitrile solutions were investigated. To achieve a deeper insight into the optical properties, the transient absorptions, lifetimes, and quantum yields have been carried out on compounds 1 and 2. The transient absorption demonstrated an excited-state processes and involvement of high energy electronic states (S_n > 1). The transient absorption map in acetonitrile revealed at 210, 240, 300, and 315 nm a ground states bleaching bands (GSB), whereas at shorter wavelengths an absorption in excited states (ESA) and more than one excited state (S_n > 1). At 382 and 420 nm wavelength two negative bands appeared which were assigned to the stimulated emissions (SE). At longer wavelengths, i.e., 605, 625, and 710 nm, other stimulated emissions appeared that are probably a result of the triplet manifold, confirming their phosphorescence properties. Additionally, the quantum yield with absolute values in the range 5–25%, and phosphorescence lifetime with values in the range 1–9 μs were evaluated.