Oral Presentation Royal Australian Chemical Institute National Congress 2026

Closing the loop on silicone through depolymerisation-repolymerisation and vitrimer strategies (136592)

Erin M Leitao 1 2 , Andrew D Battley 1 2 , Mahsa Rokni 1 2
  1. University of Auckland, Auckland, AUCKLAND, New Zealand
  2. The MacDiarmid Insitutute for Advanced Materials and Nanotechnology, Wellington, New Zealand

Silicone-based materials are ubiquitous due to their unique properties such as biocompatibility, flexibility, tunability, and integrity over a large temperature range.[1] They are used across many sectors including healthcare, consumer goods, and construction.[2] Since their development as alternatives or complements to oil-derived polymers, more than 80 years ago,[3] the silicone industry has grown to produce over 3 million tonnes/annum worldwide valued at over 20 billion USD.[4] Although silicones are often used in single‑use applications and their manufacture carries a substantial carbon footprint (e.g., > 6 kg CO₂e per kg PDMS produced),[5] their end-of-life management has only recently become a priority.[6] Strategies to transition silicone away from a linear economy into a circular economy include reuse, mechanical downcycling, conversion to vitrimers, or depolymerisation-repolymerisation. Here, we will discuss our investigation into the latter two approaches to close the loop. One approach incorporates dynamic S-S bonds during curing to produce elastomers that are repairable via thermal self-healing.[7] Our second approach applies a simple hydrolytic degradation processes that generates useful silicone precursors that can be repolymerised into new silicone elastomers.[8] Both strategies aim to improve the longevity of silicones while retaining essential materials properties and minimizing their environmental impact.

  1. Muller, F.; Silber, S. Polysiloxanes. Polym. Sci. A Compr. Ref. 2012, 10, 443−451.
  2. Clarson, S. J.; Owen, M. J.; Smith, S. D.; Van Dyke, M.; Brook, M.; Mabry, J. Advances in Silicones and Silicone-Modified Materials, 2013.
  3. Owen, M. J. The Polysiloxanes. Silicon 2016, 8, 617−618.
  4. Market Research Report: Silicone Market by Type (Elastomers, Fluids, Resins, Gels), End-use Industry (Industrial Process, Building & Construction, Personal Care & Consumer Products, Transportation, Electronics, Medical & Healthcare, Energy), Regio – Global Forecast to 2026.
  5. Brandt, B. et al. Silicone-Chemistry Carbon Balance; Global Silicones Council, 2012.
  6. Recent examples include: (a) Rupasinghe, B.; Furgal, J. C. Full Circle Recycling of Polysiloxanes via Room-Temperature Fluoride-Catalyzed Depolymerization to Repolymerizable Cyclics. ACS Appl. Polym. Mater. 2021, 3, 1828-1839. (b) Krug, D. J.; Asuncion, M. Z.; Laine, R. M. Facile Approach to Recycling Highly Cross-Linked Thermoset Silicone Resins under Ambient Conditions. ACS Omega 2019, 4, 3782−3789.
  7. (a) Rokni, M.; Park, K. W.; Ho Leung, W.; Zujovic, Z.; Leitao, E. M. Converting commercial-grade silicone into a vitrimer using elemental sulfur. Mater. Adv. 2024, 5, 5433-5441. (b) Rokni, M.; Zujovic, Z.; Leitao, E. M. Silicone vitrimers prepared by vulcanisation of pendant vinylpolysiloxanes with elemental sulfur. Polym. Chem., 2026, 17, 465-475.
  8. Andrew Battley’s PhD thesis, under preparation.