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Foaming of highly-crystalline PLLA filmswith CO2-philic hybrid liquid cell nucleators

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2019
Çulhacıoğlu, Yağmur
Supercritical CO2 (scCO2) foaming of poly(L-lactic acid) (PLLA) composites with CO2-philic additives was carried out to obtain polymeric matrices as carriers for drug delivery applications. Highly crystalline PLLA (>45%) generally requires high processing temperatures close to its melting point (~450 K), and pressures about or over 20 MPa for foaming with scCO2. In this study, in order to decrease the saturation temperature and obtain ductile PLLA films with homogeneously distributed uniform porosity, two different novel CO2-philic organic-inorganic hybrid liquid POSS (isooctyl POSS and methacrylisooctyl POSS) were used as cell nucleators. Porous thin films were obtained by the solvent-casting of the polymer with these additives even prior to scCO2 foaming of composites. Meanwhile, scCO2 processing of these films at 313 K and 21 MPa, increased the pore density. Also, foaming of highly crystalline PLLA composite films (>45%) was achieved at low temperature with the help of two novel CO2-philic components used as cell nucleators. scCO2 processing enhanced the mechanical and thermal properties such as elastic modulus and Tg of the highlycrystalline PLLA porous films. scCO2 processing of composite films also allowed extraction of almost all cell nucleator from matrices. Drug release studies with a model antibiotic (Ceftriaxone Sodium) showed that the porous films exhibit burst release characteristics, which is suitable for local antibiotic applications.