Reengineering polymers for liquid formulations: Reactor design for monomer recovery

The project aims to address the growing environmental issue of plastic pollution, particularly focusing on the depolymerization of waste methacrylic polymers to recover valuable monomers. Such methacrylics form valuable components of a range of products in the form of relatively cheap commodity plastics to higher value Polymers for Liquid Formulations (PLFs; prevalent in cosmetics, additives to automotive lubricants etc). PLFs are recognised by the RSC as a key issue in the context of plastic/polymer pollution.
The primary goal is to develop an innovative and sustainable approach by integrating machine learning and flow photochemistry to optimize a recently developed depolymerization process and subsequently utilize the recovered monomers for the synthesis of high-value compounds. Additionally, the project seeks to demonstrate the feasibility of creating a closed-loop polymer life cycle, showcasing the potential for infinite recyclability and carbon capture.
The initial step will involve synthesizing PMMA/PMA (the model PLFs) chains with controlled molecular weights ranging from 1000 to 100,000 to mimic PLFs and more commodity plastics respectively. Subsequently, a custom flow photochemical reactor will be created to facilitate the depolymerization process, converting PMMA into methyl methacrylate (MMA) monomers. The overarching reaction scheme encompasses the transformation from PMMA to MMA, followed by the conversion of MMA into a ketoester precursor and, eventually, the target molecule (a glochidine analogue). There may be several opportunities to develop in-line purification/separation techniques, which will be important to the success of this project. If the process is discovered to be infeasible for the selected polymer, there are several other options.

Common acrylate polymers to be evaluated as potential candidates: Poly (methyl methacrylate) - P(MMA), Poly (methyl acrylate) - P(MA), Poly (pentafluorophenyl acrylate) - P(PFPA)

To ensure the success of the project, the optimization of the depolymerization reaction and the characterization of monomer recovery are critical. Multi-point sampling, coupled with online analysis techniques such as High-Performance Liquid Chromatography (HPLC), will be employed to monitor the reaction in real time. In-line separation methods will also be evaluated to purify the monomer. These analysis and separation systems will facilitate the telescoping of the depolymerisation and small molecule functionalisation. Bayesian optimisation algorithms will be utilised to autonomously optimise these systems with respect to mixed variables.
Several challenges must be addressed during this research. One key concern is the efficiency of the depolymerization process compared to industry standards. An evaluation of the energy required for regenerating the monomer versus traditional industrial monomer generation methods will be conducted to assess the industrial viability of the process. An interesting challenge of the project could be to see if we can control the level of depolymerisation in a similar way to how the forward reactions are controlled (i.e. the amount of monomer each polymer chain is shortened by).
The scalability of the process is a pivotal consideration given the magnitude of plastic pollution. The project acknowledges the necessity of a solvent capture/recycle stage to mitigate environmental impacts associated with solvent use, especially as depolymerisation reactions happen more readily at high dilution.
This PhD project aspires to contribute to the advancement of sustainable polymer recycling by employing cutting-edge techniques in AI, flow photochemistry, and polymer life cycle analysis. By addressing the outlined challenges, the research aims to provide valuable insights into the efficiency and scalability of the proposed depolymerization process, ultimately contributing to the broader goal of mitigating plastic pollution and promoting circular economy Principles.