Synthesis of degradable linear and bottlebrush thioester- functional copolymers through atom transfer radical ring-opening copolymerization of a thionolactone Qamar Nisa 1, William Theobald 1 , Kyle S. Hepburn 1 , Ian Riddlestone 1 , Nathaniel M. Bingham 1 , Maciej Kopeć 2 , Peter J. Roth 1 1 University of Surrey, UK, 2 University of Bath, UK Vinyl polymers are common and useful materials but, because of their carbon–carbon backbones, they are not degradable. This poster will present the first example of adding degradable thioester linkages into vinyl polymers with concurrent control of the polymer architecture. This was achieved by optimising the atom-transfer radical copolymerization (ATRP) of the thionolactone dibenzo[c,e]oxepin-5(7H)-thione (DOT) with acrylic comonomers. Cu(I)Br and tris[2-(dimethylamino)ethyl]amine (Me 6 TREN) were used as catalysed and ligand, respectively. During the initial studies, it was observed that the polymerizations were impeded by a side reaction of dethionation of DOT to give large quantities of a non-polymerizable lactone which limited the final copolymer DOT content. Through a series of optimization experiments, traditional ATRP methods were found to minimize this side reaction when performed under anhydrous conditions. Anhydrous condition led to the successful preparation of degradable acrylate-based copolymers with higher DOT content. Subsequently, the architectural control of ATRP was leveraged through the synthesis of a water-soluble bottle-brush polymer containing poly(ethylene glycol) methyl ether acrylate (PEGA) side-chains. Due to the reactivity ratios of DOT and PEGA, the thioester units in the arms were localized near to the bottle-brush backbone and permitted selective cleavage under oxidative conditions, presenting opportunities in smart drug delivery systems. Expanding the scope of the ATRP and TARO methods, this work presents facile access to polymer materials with tailored architectures and degradability. References 1. Tardy, A.; Nicolas, J.; Gigmes, D.; Lefay, C.; Guillaneuf, Y., Radical Ring-Opening Polymerization: Scope, Limitations, and Application to (Bio)Degradable Materials. Chem Rev 2017, 117 (3), 1319-1406. 2. Agarwal, S., Chemistry, chances and limitations of the radical ring-opening polymerization of cyclic ketene acetals for the synthesis of degradable polyesters. Polymer Chemistry 2010, 1 (7), 953-964. 3. Bingham, N. M.; Nisa, Q. u.; Chua, S. H. L.; Fontugne, L.; Spick, M. P.; Roth, P. J., Thioester-Functional Polyacrylamides: Rapid Selective Backbone Degradation Triggers Solubility Switch Based on Aqueous Lower Critical Solution Temperature/ Upper Critical Solution Temperature. ACS Applied Polymer Materials 2020, 2 (8), 3440-3449. 4. Bingham, N. M.; Nisa, Q. u.; Gupta, P.; Young, N. P.; Velliou, E.; Roth, P. J., Biocompatibility and Physiological Thiolytic Degradability of Radically Made Thioester-Functional Copolymers: Opportunities for Drug Release. Biomacromolecules 2022, 23 (5), 2031-2039. 5. Bingham, N. M.; Roth, P. J., Degradable vinyl copolymers through thiocarbonyl addition-ring-opening (TARO) polymerization. Chem Commun (Camb) 2019, 55 (1), 55-58. 6. Ivanchenko, O.; Authesserre, U.; Coste, G.; Mazières, S.; Destarac, M.; Harrisson, S., ε-Thionocaprolactone: an accessible monomer for preparation of degradable poly(vinyl esters) by radical ring-opening polymerization. Polymer Chemistry 2021, 12 (13), 1931-1938. 7. Matyjaszewski, K.; Xia, J., Atom Transfer Radical Polymerization. Chemical Reviews 2001, 101 (9), 2921-2990. 8. Yan, J.; Bockstaller, M. R.; Matyjaszewski, K., Brush-modified materials: Control of molecular architecture, assembly behavior, properties and applications. Progress in Polymer Science 2020, 100, 101180.
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