Sasha Ivanchenko, PhD student at Softmat, has defended his thesis on novel synthetic strategies for radical ring-opening polymerisation

For the first time, a comprehensive mechanistic investigation of the reactivity of thionolactone derivatives in radical ring-opening copolymerisation (rROcoP) and the degradability of obtained copolymers is reported.
He presented the access to three different classes of thionolactone-like monomers, which are able to radically copolymerise with vinyl esters, (meth)acrylates and styrene. A structure-reactivity relationship study in rROcoP has been conducted for thionolactones and thionoglycolides. For unsubstituted thionolactones, the fraction of ring-opened units follows the order 7>16>5>6 membered thionolactone. DFT calculations in combination with experimental results have shown the importance of the stabilisation of the intermediate ring-retained radical for the thionolactone reactivity. For thionoglycolides the effect of the substituent in the β position to the C=S is revealed while the stabilisation of ring-opened radical plays a less important role. A chain-terminating effect was found for thionolactones and thionoglycolides in the copolymerisation with vinyl monomers.
The identified presence of both ring-opened and ring closed units was evidenced by polymer degradation studies. A substantial decrease in Mw after chemical degradation was observed for obtained copolymers from vinyl pivalate, t-butyl acrylate and styrene. Orthogonal degradability is reported for thioketal and thioester links incorporated in the copolymer backbone. The degradation profile of copolymers was characterised with the help of model compounds mimicking degradable units in the copolymer.