Thionolactones and derivatives for degradable polymers through radical ring-opening copolymerization – HOLYGRAIL

In HOLYGRAIL, the objective is the synthesis and study of five different classes of thionolactone monomers and derivatives by radical ring-opening polymerization, and then evaluate the influence of their structure on their chemical degrability in different media. These copolymers are known to possibly contain a mixture of ring-opened (thioester) and ring-closed (hemithioketal) units, with relative proportions depending on cyclic monomer nature and polymerization conditions. Thioester and hemithioketal groups are known to exhibit very different reactivities towards nucleophiles and oxidants.This specific feature wil be advantageously considered to propose original strategies for the complete degradation of the cleavable units. To meet our objectives, a structure-reactivity study of cyclic/non-cyclic monomer combinations will be performed, with a selection of non-cyclic monomers over a broad spectrum of reactivity and polarity. For a given class of cyclic monomer, polymerization conditions will be optimized to target polymers with either predominantly thioester units, or predominantly hemithioketal units or a a mixture of both. The effect of copolymer structure on their degradability will be evaluated in aminolytic, thiolytic and oxidative conditions. This will allow the study of the selectivity of some of the chemical treatments towards degradation, and their complementary in some cases. Common degrading agents for both types of cleavable units will be sought.