Time of flight secondary ion mass spectrometry surface and in-depth study of degradation of nanosheet poly(L-lactic acid) films.

With the advent of novel fabrication technologies, free-standing poly(l-lactic acid) (PLLA) nanosheets have been shown to have enhanced performance over their micro- or macroscale equivalents as tissue engineering and drug delivery constructs. In the present research, the authors investigated the surface degradation behavior of PLLA films as a function of confinement to a quasi-two-dimensional structure, and the degradation behavior of nanoscale PLLA films as a function of the initial molecular weight and depth, using time-of-flight secondary ion mass spectrometry. The authors found that nanofilms exhibit less segregation of shorter chains to the surface than microfilms, due to the constrained geometries of these morphologies. It was also concluded that the degradation rate at the surface of nanofilms related to the inverse of the initial molecular weight, as is the case in bulk-scale systems.