The demand for plastics is vast, with 348 million tonnes being produced in 2017 alone,1 and the trend for plastic production is increasing exponentially year-on-year. The broadcast of Blue Planet, and the ensuing response from popular media has heightened the demand for a reduction in plastic use.
However, this is not feasible whilst maintaining the technology necessary for 21st century life. Recycling via reprocessing has limitations in maintaining the required materials properties for reuse, and not all polymers are re-processable. Most physically degrade into microplastics, and only a very small proportion (ca. 1%) are truly biodegradable.2,3 Hence there is a huge demand new plastic (polymer) materials that are environmentally benign (degrade chemically into non-toxic components), cheap to produce from sustainable feedstocks, and can be depolymerised for recycling at the molecular level, keeping valuable chemicals in circulation.
A solution can be found in anhydride-epoxide co-polymers.4 These are ester-based and can be depolymerised,5 and there are > 100,000 chemically distinct variations. We have recently developed a series of catalysts that are able to make anhydride-epoxide co-polymers, and we have exemplified their potential by making additive-free flame-retardant polymers. In order for these co-polymers to find widespread application, we need to ascertain their degradation, both in chemical recycling and in the environment.
Project aims and methods
The project will establish the recycling potential of a new class of co-polymers that could help to alleviate the plastic waste problem. This is to be achieved by addressing the question of anhydride-epoxide co-polymer degradation, and monomer recovery and reuse.
A series of 9 co-polymers (3×3 matrix, varying both monomer types) will be prepared using existing catalyst technology from the Ward group, optimising conditions to obtain high molecular weights. Solution behaviour (solubility, phase/aggregation) will be determined to address catalytic access to degradation sites and provide a correlation with chemical structure (Paul).
Two-fold degradation studies will focus on chemical depolymerisation (e.g. zinc catalysts reported by Jones) and environmental modelling (laboratory salt- and freshwater conditions with Durance since these co-polymers are not yet commercial and there are no native environmental samples to undertake degradation testing with), followed by environmental testing using the experimental testing flumes at Brianne.
A key objective will be to recover and identify the degradation products to explore reuse in co-polymer synthesis. There will be foci on optimising the catalyst for selected systems as well as searching for degradation behaviour as a function of polymer structure/size; the relative balance of these two facets will be considered as the student-led project design.
You must hold (or expect to hold) a chemistry degree at the 2:1 level or higher. A high level of competence in synthetic chemistry is essential, and experience in organometallic chemistry and polymer synthesis would be a significant advantage, but not requisite since full training will be provided.
CASE or collaborative partner
The Jones group have a track record in the catalytic degradation of polylactic acid, and the chemistry involved in the degradation of anhydride-epoxide co-polymers is identical.
Their expertise will be vital to the project and will enhance the student experience through enhanced training and working in their laboratories. The Paul group have expertise in monitoring polymeric materials in solution/suspension. The Durance group have expertise in determining the environmental consequences of plastic pollution.
The project team therefore provides expertise in all areas of the project: synthesis, degradation, and behaviour of polymers, which will provide a rounded training experience and thus a first-rate student experience across multiple areas of expertise and locations. The Ward and Jones group already hold regular whole-group joint meetings to discuss collaborative projects, and this will be extended to include the Paul and Durance groups so that supervision across the entire supervisory team can be effective and adequately support the student.
You will be trained in synthetic organometallic chemistry, and in the full range of spectroscopic and analytical techniques required to characterise the polymers and their breakdown products. This includes NMR spectroscopy, mass spectrometry (MALDI), FTIR, and Gel Permeation Chromatography. This equipment is all available in the host institutions. You will be expected to undertake laboratory work in both Cardiff and Bath, at Brianne for environmental testing.
How to apply:
You should apply to the Doctor of Philosophy in Chemistry with a start date of October 2020.
Application deadline: 16:00 on 6 January 2020.
Shortlisting for interview: by 31 January 2020.
Shortlisted candidates will then be invited to an institutional interview. Interviews will be held in Cardiff University between 10 February and 21 February 2020.
EU applicants must have been ordinarily resident in the EU for at least 3 years before the start of their studies.
EU applicants who do not meet the residency requirements may still be eligible for a fees-only award.
Additional funding to the value £11,000 is available over the course of the programme for conference attendance, fieldwork allowance, travel allowance and other project costs. A further £3,250 is available in the form of as a training credits over the course of the programme for specialist training courses and/or opportunities (plus £750 ringfenced for travel and accommodation on compulsory cohort events).
References and background reading
Plastics - The Facts 2018, PlasticsEurope, 2018.
G. L. Gregory, E. M. López-Vidal and A. Buchard, Chem. Commun., 2017, 53, 2198–2217.
R. Geyer, J. R. Jambeck and K. L. Law, Sci. Adv., 2017, 3, e1700782.
J. M. Longo, M. J. Sanford and G. W. Coates, Chem. Rev., 2016, 116, 15167–15197.
L. Feng, Y. Liu, J. Hao, X. Li, C. Xiong and X. Deng, Macromol. Chem. Phys., 2011, 212, 2626–2632.
For project enquiries, please contact Dr. Benjamin D. Ward.