Çiğdem Atalay-Oral

Fatty acid-based polyurethane films for wound dressing applications

Fatty acid-based polyurethane films were prepared for use as potential wound dressing material. The polymerization reaction was carried out with or without catalyst. Polymer films were prepared by casting-evaporation technique with or without crosslink-catalyst. The film prepared from uncatalyzed reaction product with crosslink-catalyst gave slightly higher crosslink density. The mechanical tests showed that, the increase in the tensile strength and decrease in the elongation at break is due to the increase in the degree of crosslinking. All films were flexible, and resisted to acid solution. The films prepared without crosslink-catalyst were more hydrophilic, absorbed more water. The highest permeability values were generally obtained for the films prepared without crosslink catalyst. Both the direct contact method and the MMT test were applied for determination of cytotoxicity of polymer films and the polyurethane film prepared from uncatalyzed reaction product without crosslink-catalyst showed better biocompatibility property, closest to the commercial product, Opsite®.

Estimation of interphase properties of various mixed matrix membranes

ABSTRACT A generalized course of action was proposed for determining the separation properties of the interphase between filler and polymer phases in various mixed matrix membranes (MMMs). Accordingly, the permeability and thickness of the interphase were estimated by using the modified form of effective medium theory (EMT) and CO2, N2 and CH4 permeability data at two different filler loadings obtained from the literature. In spite of the sensitivity of the estimations to experimental inconsistencies in the data used, significant information could generally be obtained about the interphase permeability and thickness. It was observed that the interphase in different types of MMMs could have dissimilar separation properties even when the polymer used was the same. The CO2/CH4 ideal selectivities of the interphase between graphene oxide and polyether block amide (Pebax) polymer and the interphase between zeolite Y and a polyimide polymer, Matrimid, were determined to be higher than the selectivities of the pure polymers. Tailoring the interphase by having good knowledge of its properties, is expected to provide significant means for further improvement of the performances of mixed matrix membranes. Graphical Abstract

Effects of Using Different Polymers in Post-Synthesis Treatments of Zeolite a Coatings

Zeolite A coatings were prepared by the substrate heating and repeated conventional syntheses methods, targeting their use especially in adsorption heat pump applications. The coatings, grown on stainless steel, were then covered by polyvinyl acetate, polyvinyl alcohol, and cellulose acetate as post-synthesis treatments for improving the stabilities of the coatings. The water desorption properties of the metal-zeolite-polymer integrated systems were investigated by thermogravimetry (TG). Their stabilities were determined by the application of consecutive ultrasonic treatments and heating/cooling cycles. The zeolite coatings prepared by substrate heating contained void fractions of about 45%, significantly higher values than those obtained by repeated syntheses, which remained below 10%. When the former coatings were covered by polymer, they exhibited water desorption of about 0.13–0.15 g/g sample which was higher than the amount of water desorbed from both pure zeolite (0.12–0.14 g/g sample) and pure polymer (0.038–0.083 g/g sample) under the conditions investigated. Such behavior was absent for the more compact zeolite coatings prepared by repeated syntheses. This might signify that the zeolite coatings with larger intercrystalline void regions provided higher amount of surface and/or interactions between the polymer and zeolite phases, which mostly favored water desorption properties of composite coatings. Zeolite coatings prepared by both synthesis methods exhibited high stabilities after the post-synthesis treatments applied.