Poly Ethylene Oxide Thin Films Research Articles

Optical and Chemical Investigations of PEO Thin Films Incorporated with Curcumin Nanoparticle: Effect of Film Thickness

Using the spin coating technique, polyethylene oxide (PEO)-Curcumin nanocomposite thin films have been deposited on a quartz substrate. The film thickness role on the optical properties was investigated. SEM investigated the morphology of the thin films and revealed that curcumin NPs have a spherical shape with an average size of less than 100 nm. FTIR bands observed at 1023 and 1120 cm–1 correspond to C–O stretching vibration. New bands observed for the thin films at 804, 1237, 1280, and 1340 cm–1 correspond to C–H, C–O, and O-H bending. The thin films’ optical properties with thickness 250, 500, and 750 nm were acquired from transmittance, reflectance, Tauc plot, extinction coefficient, and reflective index. The refractive index obtained from UV-Vis data falls between 1.5 and 2. Bandgap energy obtained for PEO thin film is 4.16 eV, while for both curcumin NPs and PEO-Curcumin nanocomposite thin films, the bandgap energy is 2.49 eV. Our results indicate that the optical absorption coefficient increases with decreasing film thickness. The obtained results are in good agreement with the existing reports.

Quantitative analysis of biomolecule release from polystyrene-block-polyethylene oxide thin films.

Block copolymers have garnered recent attention due to their ability to contain molecular cargo within nanoscale domains and release said cargo in aqueous environments. However, the release kinetics of cargo from these thin-films has not yet been reported. Knowledge of the release quantities and release profiles of these systems is paramount for applications of these systems. Here, Polystyrene-block-poly(ethylene oxide) (PS-b-PEO) was co-assembled with fluorescein isothiocyanate isomer I-lysozyme (FITC-LZ) and fluorescein isothiocyanate isomer I-TAT (FITC-TAT), such that these molecular cargos arrange within the PEO domains of the thin films. We show that high loading ratios of cargo/PS-b-PEO do not significantly impact the nanostructure of the films; however, a loading limit appears to be present with aggregates of protein forming at the microscale with higher loading ratios. The presence of lysozyme (LZ) within the films was confirmed qualitatively after aqueous exposure through photo-induced force microscopy (PiFM) imaging at the Amide I characteristic peak (∼1650 cm-1). Furthermore, we demonstrate that LZ maintains activity and structure after exposure to the polymer solvent (benzene/methanol/water mix). Finally, we demonstrate quantitatively 20-80 ng cm-2 of cargo is released from these films, depending on the cargo incorporated. We show that the larger molecule lysozyme is released over a longer time than the smaller TAT peptide. Finally, we demonstrate the ability to tune the quantity of cargo released by altering the thickness of the PS-b-PEO thin-films during fabrication.

Thermally modified amorphous polyethylene oxide thin films as highly sensitive linear humidity sensors

Polyethylene oxide (PEO) is a polymer hydrogel possessing ionic conductivity that varies with different percentage of absorbed water molecules and ions. This property makes it a good candidate to be used in humidity sensors’ active layers. The degree of crystallinity of PEO thin films decrease with increasing humidity that facilitates the ion conduction in the thin films, thus reducing the film impedance. In this research work, the humidity sensing properties of the thin films of semi-crystalline PEO have been investigated and the material is then modified to its amorphous dominant phase by heating the thin films beyond the melting point of the polymer. The slowly cooled resulting thin films had a waxy solid like appearance and showed an excellent response towards quantitative detection of relative humidity in the surrounding environment. The results show a roughly linear impedance versus relative humidity curve in the range of 0% RH to 90% RH with a very high maximum achieved sensitivity of ∼35kΩ/%RH. The response and recovery times measured for the modified sensors were 2.8s and 5.7s respectively. The 30day trial of stability readings showed a standard deviation of only 1%. The results prove thermally modified amorphous PEO thin films to be strong candidates for high end electronic relative humidity sensors.

Ag/PEO nanocomposite fabricated in a planar magnetron sputtering

Thin films of silver (Ag)/polyethylene-oxide (PEO) nanocomposite were fabricated by a co-deposition of Ag sputtering particles and PEO thin film on substrates using a planar magnetron sputtering system. The PEO were polymerized from the monomer ethyl glycol dimethyl ether in the magnetron sputtering (MS) plasma. The nanocomposites were characterized by using UV-visible spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and atomic force microscopy (AFM). The correlation was performed between the concentrations of Ag and functional group density in Ag/PEO nanocomposites with the discharge parameters, such as sputtering gas pressure and the distance of target-to-substrate. By using AFM and XRD, it is illustrated that the Ag particles distribute uniformly in the body of nanocomposite and remain in atomic status with preferential growth in facet of (111).

Ion-beam modifications of the surface morphology and conductivity in some polymer thin films

Studies on the surface micromorphology and surface conductivity in thin polymer films of poly vinyl alcohol (PVA) and poly ethylene oxide (PEO) in both as-grown and ion-implanted polymer films have been carried out to reveal certain specific features of the ordered state in these materials. Optical microscopic investigations revealed the existence and enhanced formation in number of spherulites and dendrites in ion-implanted films relative to the as-grown films. The number and rate of formation of spherulites indicated an increase in the degree of crystallinity in these films. Measurements of surface conductivity of as-grown and ion-implanted polymer films, employing four-point probe method, indicated a decrease in electrical conductivity on ion-implantation. Photomicrographic analysis of the PVA and PEO thin film surfaces, has enabled to propose a temperature-stress induced mechanism of crystallization in conjunction with the surface conductivity measurements. The decrease in surface conductivity on ion-implantation in both PVA and PEO thin films, is attributed to a decrease in mobility of macromolecular charged species due to an increase in degree of crystallinity as has been observed by optical microscopy.

PULSED LASER ABLATION—THIN FILM DEPOSITION OF POLYETHYLENE OXIDE

Polyethylene oxide (PEO) thin films have been deposited by pulsed laser ablation technique. Films with a maximum thickness of 2500 Å were obtained. Films were characterized using IR, XRD, SEM and optical microscopy. IR studies confirmed the formation of PEO thin film and XRD studies indicated a crystalline structure similar to that of the target PEO pellet. Films deposited with a laser fluence of less than 1.6 J/cm 2 were found to be smoother than films obtained with higher laser fluences. The dependence of the nature of the thin film on the molecular weight of the target PEO has been studied. Low molecular weight targets gave more particulate ejection compared with the high molecular weight targets. Dispersion of fine ZrO 2 powder in the target PEO matrix resulted in lowering the ablation threshold and increasing the film thickness. The best film obtained in this work corresponds to PEO (molecular weight 5×10 6 a.m.u.)+10 mol% ZrO 2 target at a laser fluence of 720 mJ/cm 2 under high vacuum conditions. The laser irradiated spots on both pure PEO and ZrO 2 mixed PEO target surfaces were found to be hardened compared with the rest of the surfaces.