Development of a plasma polymer layer as tunable barrier coating for PLA

Biodegradable and derived from renewable resources, polylactide (PLA) is a potential alternative to conventional synthetic packaging materials. Nevertheless, PLA presents too high water and gas permittivity. In this work, we develop a highly cross-linked PLA-based plasma polymer film synthesized by PECVD that could be used as barrier coating. The control of both chemistry and cross-linking would allow tuning the degradation rate of the polymer which is known to occur by ester bond hydrolysis. [1]
The ELPPF chemistry, especially the ester function density, has been evaluated by XPS/chemical derivatization and compared to the plasma phase composition measured by RGA mass spectrometry (MS) and in situ infrared spectroscopy (IR). Supported by DFT calculations, our data allow proposing a clear fragmentation pattern of the precursor depending on the experimental conditions.[2] On the other hand, the combination of both MS and IR allow to unambiguously evaluate the ester density in the plasma phase. The latter data are understood using synthetic IR spectra generated by DFT. [3] In our experimental window, by increasing power, the ester content in the ELPPF decreases from 18 to 1.4 at.% which is perfectly correlated to the decrease of the ester density in the plasma phase from 2.2x1015 to 9.1x1012 fragments/cm³.