%0 Journal Article
%T Structure/Property Relationships of Poly(L-lactic Acid)/Mesoporous Silica Nanocomposites
%A Javier Gudi£¿o-Rivera
%A Francisco J. Medell¨ªn-Rodr¨ªguez
%A Carlos ¨¢vila-Orta
%A Alma G. Palestino-Escobedo
%A Sa¨²l S¨¢nchez-Vald¨¦s
%J Journal of Polymers
%D 2013
%R 10.1155/2013/162603
%X Biodegradable poly(L-lactic acid) (PLLA)/mesoporous silica nanocomposites were prepared by grafting L-lactic acid oligomer onto silanol groups at the surface of mesoporous silica (SBA-15). The infrared results showed that the lactic acid oligomer was grafted onto the mesoporous silica. Surface characterization of mesoporous silica proved that the grafted oligomer blocked the entry of nitrogen into the mesopores. Thermal analysis measurements showed evidence that, once mixed with PLLA, SBA-15 not only nucleated the PLLA but also increased the total amount of crystallinity. Neat PLLA and its nanocomposites crystallized in the same crystal habit and, as expected, PLLA had a defined periodicity compared with the nanocomposites. This was because the grafted macromolecules on silica tended to cover the lamellar crystalline order. The g-SBA-15 nanoparticles improved the tensile moduli, increasing also the tensile strength of the resultant nanocomposites. Overall, the silica concentration tended to form a brittle material. 1. Introduction Poly(L-lactic acid) (PLLA) is a linear aliphatic polyester widely used in biomedical applications because it is biodegradable, biocompatible, and nontoxic for the human body. It is also approved by the Food and Drug Administration (FDA) for applications in orthopedic devices [1]. Moreover, PLLA is used as scaffold for bone tissue regeneration [2¨C6]. However, its slow crystallization, slow degradation rates, low stability during degradation, and relatively poor mechanical properties have limited the applications of this polymer, in particular as a scaffold material [7]. Therefore, new applications for this polymer have proposed the preparation of nanocomposites with inorganic reinforcements as a convenient alternative [8, 9]. Some examples are PLLA nanocomposites with nanoclays [10, 11], nanohydroxyapatite [12, 13], carbon nanotubes [14, 15], and silicon dioxide [16, 17]. In general terms, the mechanical and thermal properties of the resultant nanocomposites have been improved, and the degree of crystallization, and hydrolytic degradation resistance has also been enhanced [14]. However, certain inorganic materials, such as carbon nanotubes [18], are considered to be toxic or harmful to cells. A new class of polymeric materials, for which there are few published studies, takes advantage of mesoporous silicas. These are synthetic materials with ordered arrangements of channels and cavities of different geometries and siloxane walls. One example is SBA-15, a mesoporous material synthetized using triblock copolymer surfactant as a
%U http://www.hindawi.com/journals/jpol/2013/162603/