There is an increasing trend towards replacing synthetic polymers with their natural counterparts and applying environmentally friendly processing techniques [1]. For both industrial and biomedical applications, natural originated biodegradable polymers are intensely studied due to their environmentally benign and biocompatible nature. Supercritical carbon dioxide (scCO2)processing of polymers is a green approach since it reduces or eliminates the use of organic solvents and thus emissions of volatile organic compounds [2,3].ScCO2, which is non-toxic, non-flammable and inert with relativelylow critical temperature compared to other supercritical solvents, has a plasticizer effect on polymers having CO2 affinity by decreasing the glasstransition temperature of the polymer. Therefore, it can be used as a foaming agent for such polymers. In the first step of the foaming process, the polymeris saturated with scCO2 under high pressure [4]. Next,rapid depressurization and thus supersaturation of the polymer-scCO2 system is achieved, which leads to nucleation and growth of the pores in thepolymer matrix. Poly(L-lactic acid) (PLLA) is abiodegradable and biocompatible polymer that can be replaced with petroleum based polymers [4,5]. PLLA foams can be used inbiomedical applications such as drug delivery, scaffold for bone tissue or artificial vasculature systems. Due to its highly crystalline structure, high saturation temperatures close to the melting temperature of PLLA (about180°C) and pressures over 20 MPa are necessary for the foaming of the polymerwith scCO2, especially when the crystallinity of the polymers aregreater than 30% [4,6,7]. In this study, foaming of highlycrystalline PLLA composite films (>40%) was achieved only at 40oCand 21 MPa with the help of two novel CO2-philic components used ascell nucleators. These cell nucleators are liquid polyhedral oligomericsilsesquioxanes (POSS), which are monofunctional isooctyl POSS and bifunctionalmethacrylisooctyl POSS. These molecules have recently been identified to be CO2-philicwith different levels of CO2-philicity and physicochemicalproperties [8]. When PLLA film was processed with scCO2at the same conditions, pore formation was not observed within the polymermatrix. Therefore, POSS molecules act as not only cell nucleator but they also allow dissolution of CO2 in the matrix. The foam properties were analyzedwith various techniques. The EDX analyses show that the majority of the cell nucleatoris extracted by the scCO2 during the process. The mechanical tests show that the tensile moduli of the films increased by at least 80% after the CO2processing. Both films reached a tensile modulus of around 1100 MPa. Thenano-indentation analyses also revealed similar trend in the indentation hardness and moduli. The glass transition of the films increased by at least40% after the CO2 treatment and reached a value about 57 oCwhile the crystallinity of the CO2 processed films increased by 3%. The water contact angles of the films show that the process did not change the hydrophobicity of the polymer. The drug release studies are currently carried out and the results will be presented.


Ultrasonication for Environmentally Friendly Preparation of Antimicrobial and Catalytically Active Nanocomposites of Cellulosic Textiles
Kwiczak-Yigitbasi, Joanna; Demir, Mine; Ahan, Recep Erdem; Canlı, Sedat; ŞEKER, URARTU ÖZGÜR ŞAFAK; BAYTEKİN, BİLGE (2020-12-01)
The global demand for sustainable and functional fibers and textile materials is increasing with the pressure to limit the synthetic petroleum-based counterparts. In this study, we use ultrasonication for the preparation of eco-friendly cellulose fabrics bearing silver or gold nanoparticles (NPs). The mechanochemistry of cellulose is based on the breakage of glycosidic bonds and the formation of mechanoradicals. These mechanoradicals can reduce Au3+ and Ag+ ions in solution, and the reduced metals can be st...
Synthesis and characterization of hyperbranched and air drying fatty acid based resins
Bat, Erhan; Gündüz, Güngör; Department of Chemical Engineering (2005)
There has been a considerable effort in the last years to decrease the amount of volatile organic compounds (VOCs) present in organic coatings. The risks to human health and environmental hazards associated with VOCs, governmental directives, and economic factors are the main driving forces behind this effort. One way of achieving less or no VOC containing coating systems is to produce low viscosity resins. Hyperbranched resins owing to their globular structure have low viscosities and are promising materia...
Supercritical fluid extraction and temperature-programmed desorption of phenol and its oxidative coupling products from activated carbon
HUMAYUN, RASHINA; Karakaş, Gürkan; Dahlstrom, PR; OZKAN, UMIT S; TOMASKO, DAVID L (1998-08-01)
Activated carbon remains one of the most economical adsorbents for the removal of contaminants from water. In particular, activated carbon is known to have an extremely high affinity for phenol and its derivatives. This has been shown to be the result of a catalytic process wherein activated carbon catalyzes the oxidative coupling reactions of phenol in aqueous solution when molecular oxygen is present. These reactions are believed to be the source, of the difficulty of regenerating activated carbon loaded ...
Production of hemicellulose-based biodegradable films from agricultural wastes
Bahcegul, E.; Özkan, Necati; Bakir, U. (2009-09-01)
Owing to the increasing environmental awareness and restrictions together with the depletion of fossil-based resources, production of biodegradable films receives increasing attention to substitute at least a part of the largely consumed conventional synthetic plastics. Despite there are a variety of polymers that are used for biodegradable plastic production these alternatives are either more expensive compared to their non-biodegradable petroleum-based counterparts or obtained from sources such as corn or...
Fabrication of Highly Catalytically Active Gold Nanostructures on Filter-Paper and Their Applications towards Degradation of Environmental Pollutants
Khan, Ghazanfar Ali; Nalbant Esentürk, Emren; Bek, Alpan; Bhatti, Arshad Saleem; Ahmed, Waqqar (2021-10-01)
Supported metallic nanoparticles (NPs) have recently become a promising candidate for the degradation of environmental pollutants. In this work, we report the fabrication of highly catalytically active, surfactant-free interconnected Au nanostructures directly on filter paper. The width of nanostructures is only a few nanometers and they contain high concentration of low-coordination atoms. Our approach involves the immersion and evaporation of Au precursor solution on the filter paper and its subsequent re...
Citation Formats
Y. Çulhacıoğlu, N. Hasırcı, and Ç. Dilek Hacıhabiboğlu, “SUPERCRITICAL CO2 FOAMING OF PLLA WITH LIQUID CO2-PHILIC CELL NUCLEATORS,” 2018, Accessed: 00, 2021. [Online]. Available: