title: Τhe effect of silica nanoparticles on the thermomechanical properties and degradation behavior of polylactic acid.
abstract: In this work a series of polylactic acid/SiO2 nanocomposites have been prepared by a melt mixing procedure. The dispersion quality was examined by scanning electron microscopy. To study the degradation behavior of the polylactic acid/nanocomposites prepared, the samples were immersed in a buffer solution at a temperature of 37℃ with a pH of 7.4 for a time period of up to 23 weeks. These conditions simulate those in the human body, appropriate in medical applications. In order to assess their suitability in biomedical applications, we investigated the biocompatibility of these materials in terms of cell viability, growth, and morphology. A good initial cell adhesion has been detected, supporting their potential use in bone tissue engineering applications. The hydrolytic degradation of polylactic acid, under the prescribed conditions, was studied by the molecular weight reduction in terms of size exclusion chromatography, whereas the progress of thermal stability of polylactic acid and polylactic acid/nanocomposites during aging was tested by thermogravimetric analysis. The evolution of the materials' thermomechanical properties during aging was studied by differential scanning calorimetry, dynamic mechanical analysis, and tensile testing. The crystallization behavior in polylactic acid and the way it is affected by the presence of nanofillers during degradation procedure has been studied and values of 44% crystallinity increment have been found. At the specific aging conditions studied, silica nanoparticles accelerate the degradability of polylactic acid, having a higher impact on Young's modulus, under the specified aging conditions, for 7 weeks and hereafter this acceleration is retarded, due to the crystallinity increment, as a result of the molecular weight reduction.
authors.affiliation: School of Applied Mathematical and Physical Sciences, Department of Mechanics, National Technical University of Athens, Athens, Greece.
authors.forename: P
authors.initials: P
authors.lastname: Georgiopoulos
authors.affiliation: School of Applied Mathematical and Physical Sciences, Department of Mechanics, National Technical University of Athens, Athens, Greece ekontou@central.ntua.gr.
authors.forename: E
authors.initials: E
authors.lastname: Kontou
authors.affiliation: Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, Athens, Greece.
authors.forename: A
authors.initials: A
authors.lastname: Meristoudi
authors.affiliation: Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, Athens, Greece.
authors.forename: S
authors.initials: S
authors.lastname: Pispas
authors.affiliation: Department of Materials Science and Technology, University of Crete, Heraklio, Greece Institute of Electronic Structure & Laser, Foundation for Research & Technology Hellas, Heraklio, Greece.
authors.forename: M
authors.initials: M
authors.lastname: Chatzinikolaidou
mesh_terms: D016475:3T3 Cells; D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry*; D002152:Calorimetry, Differential Scanning; D049109:Cell Proliferation; D002470:Cell Survival; D003460:Crystallization; D055119:Elastic Modulus; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D019344:Lactic Acid / Q000737:chemistry*; D008422:Materials Testing; D051379:Mice; D008855:Microscopy, Electron, Scanning; D008856:Microscopy, Fluorescence; D008970:Molecular Weight; D053761:Nanocomposites / Q000737:chemistry; D053758:Nanoparticles / Q000737:chemistry*; D011091:Polyesters; D011108:Polymers / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry*; D013314:Stress, Mechanical; D013696:Temperature; D013718:Tensile Strength; D013818:Thermogravimetry
chemical_list: D001672:Biocompatible Materials; D011091:Polyesters; D011108:Polymers; D019344:Lactic Acid; C033616:poly(lactide); D012822:Silicon Dioxide
keywords: Biodegradation; crystallinity; cytotoxicity testing; mechanical properties; nanocomposites