One of the challenges faced by modern society is the realization of a circular economy for polymer products. A bottleneck is the understanding of (co)polymer synthesis and degradation routes on...

Chemical or feedstock recycling of poly(methyl methacrylate) (PMMA) by thermal degradation is an important societal challenge to enable polymer circularity. The annual PMMA world production capacity is over 2.4 × 106 tons, but currently only 3.0 × 104 tons are collected and recycled in Europe each year. Despite the rather simple chemical structure of MMA, a debate still exists on the possible PMMA degradation mechanisms and only basic batch and continuous reactor technologies have been developed, without significant knowledge of the decomposition chemistry or the multiphase nature of the reaction mixture. It is demonstrated in this review that it is essential to link PMMA thermochemical recycling with the PMMA synthesis as certain structural defects from the synthesis step are affecting the nature and relevance of the subsequent degradation reaction mechanisms. Here, random fission plays a key role, specifically for PMMA made by anionic polymerization. It is further highlighted that kinetic modeling tools are useful to further unravel the dominant PMMA degradation mechanisms. A novel distinction is made between global conversion or average chain length models, on the one hand, and elementary reaction step-based models on the other hand. It is put forward that only by the dedicated development of the latter models, the temporal evolution of degradation product spectra under specific chemical recycling conditions will become possible, making reactor design no longer an art but a science.

Bulk and solution radical polymerization is important in daily live. A challenge is still to maximize polymerization rate and control over molecular characteristics such as the molar mass distribution. The last decades have made clear that kinetic modeling is indispensable with originally most focus on deterministic implementations such as the method of moments (MoM) and only more recently promising results for event‐driven kinetic Monte Carlo (kMC) simulations that belong to stochastic methods. Computationally, a critical reaction is termination for which one has both distinguishable and nondistinguishable distributed species, which requires a delicate treatment of a stoichiometric factor 2. Proper benchmarking of MoM and kMC simulations demands thus a careful translation of this factor in the Monte Carlo (MC) reaction probabilities. However, limited attention has been paid in the kMC field to the detailed description of such translations. Here, a rigorous derivation is presented on the level of individual termination rates. Emphasis is on termination by recombination and disproportionation. It is highlighted that six types of factor 2 exist that all need to be incorporated with care, including an IUPAC‐based one. The consistency is demonstrated by a successful benchmark of essential modeling results for free radical polymerization of methyl methacrylate.

Reactive extrusion (REX) is an important processing and production technique with applications in the field of polymer synthesis, modification and recycling. A full REX design demands a multi-scale approach recognizing...