Evaluation and comparison of analytical methods for monitoring polymer depolymerization: Application to poly(bisphenol A carbonate) methanolysis

Polymer depolymerization after use represents a significant challenge to reduce both the environmental impact of plastic pollution and the utilization of non-sustainable raw materials. Recently, there has been a demand to form a coherent strategy for the analysis of polymer degradation, of which, some approaches have been observed to be used inappropriately or incompletely. This article proposes an analysis strategy for monitoring the depolymerization of poly(bisphenol-A carbonate) (PBPAC), using methanolysis as a model method. It is based on five analytical methods, which our study attempts to combine and compare according to their ideal use case: size exclusion chromatography (SEC), high-performance liquid chromatography (HPLC) and Fourier-transform infrared (FT-IR), nuclear magnetic resonance (NMR) and Matrix Assisted Laser Desorption Ionization − Time of Flight spectroscopy (MALDI-TOF). This strategy allows both a qualitative approach, where the depolymerization products can be identified and a quantitative one, where the percentage of polymer degradation can be determined, together with the detection limit of each associated technique (i.e. 0.06 %, 20 %, 10 %, 8 % and 0.5 % for SEC, HPLC, FT-IR, NMR and MALDI-TOF respectively). As a result, the range of applications for each analytical method is assessed, and a guide to determine the minimum methods to be used to qualify and quantify degradation is proposed, in relation to the progress of degradation and the yields obtained. This has enabled us to characterize and propose a new quantitative FT-IR-based methodology, compatible with high-throughput screening, to study the degradation of PBPAC, allowing for quantification of degradation from 10 % onwards.