Statistical enchainment of ester/ether and carbonate cleavable bonds to control copolymers’ erosion rate and trigger environment-specific degradation

Abstract

Polymers containing ester bonds undergo abiotic degradation independently from the surrounding environment as long as the hydrolytic conditions are provided. The hydrolysis of the ester bonds leads a bulk degradation of the polymeric matrix which, contrary to surface erosion, is unpredictable. The enchainment of diverse degradability functions was sought to expand the scope of the degradation mechanism and achieve a more predictable profile of the mass loss.The copolymerization of trimethylene carbonate and p-dioxanone enabled the synthesis of one class of copolymers with controllable erosion rate and susceptible to three degradation pathways depending on the surrounding environment. The synthetic strategy used organocatalysts and allowed the synthesis at room temperature of both random and block copolymers in high yield and with molar mass, Mn, in the range 12–22 kg mol−1. The composition and microstructure of the random copolymers were regulated by varying the monomers’ ratio. Diverse cleavable groups, i.e., ester/ether and carbonate bonds, were statistically incorporated along the same polymer chain to yield materials able to degrade under hydrolytic, oxidative and enzymatic conditions. Bulk degradation was the mechanism that took place under hydrolytic conditions, while the oxidative and enzymatic environments lead to surface erosion. The rate of mass loss of the random copolymers was regulated by varying the composition. These results showed how the statistical incorporation of different degradable bonds could pave the way to diverse and more predictable degradation pathways than simple hydrolysis by taking advantages of the surrounding environment to trigger surface erosion.