Local demixion in plasticized polylactide probed by electron spin resonance

• Published in: Journal of magnetic resonance (1997) 2013-08, Vol.233, p.37-48
• Main Authors: Courgneau, Cécile, Vitrac, Olivier, Ducruet, Violette, Riquet, Anne-Marie
• Format: Article
• Language: English
• Subjects: Agricultural sciences; Citrates - chemistry; Crystallization; Diffusion; Electron paramagnetic resonance; Electron Spin Resonance Spectroscopy - methods; Film thickness; Glycols; Life Sciences; Magnetic resonance; Microphase separation; Plasticizers; Plastics; Polyesters - chemistry; Polyethylene Glycols; Polylactides; Risk; Separation; Spin-probe ESR; Temperature
• ISSN: 1090-7807; 1096-0856
• DOI: 10.1016/j.jmr.2013.04.006

•ESR technique to assess microphase separation or heterogeneities in plasticized PLA.•Probing the chain mobility and microphase separation along the film thickness.•Equivalence time/spatial scales in diffusion phenomena to get spatial resolution.•Reconstruction of temperature profile along the PLA film thickness.•Measured excess temperatures related to local shifts in the Tg along the film thickness. Improving the barrier properties to gas and organic compounds of biosourced polyesters, such as polylactides (PLAs), by increasing their crystallinity has been suggested by several authors. This paper investigates the risk of microphase separation for a technological approach that would involve a plasticization of PLA, to further its crystallization kinetics, with common plasticizers: Acetyl tributyl citrate (ATBC) and Poly(ethylene glycol) (PEG). Overplasticization effects following microphase separation were monitored along the film thickness by exposing dynamically thermo-compressed films to nitroxide spin-probes. The method enabled a scan of the local polymer mobility for different concentration profiles in spin-probes, with in particular a maximum moving continuously in time towards the geometric center. The results were interpreted as excess local temperatures that would give similar ESR spectra motion in the bulk. It was shown that measured excess temperatures could be related to local shifts in the glass transition temperature along the film thickness.