Polyesters by a Radical Pathway: Rationalization of the Cyclic Ketene Acetal Efficiency

Abstract

Radical ring‐opening polymerization (rROP) of cyclic ketene acetals (CKAs) combines the advantages of both ring‐opening polymerization and radical polymerization thereby allowing the robust production of polyesters coupled with the mild polymerization conditions of a radical process. rROP was recently rejuvenated by the possibility to copolymerize CKAs with classic vinyl monomers leading to the insertion of cleavable functionality into a vinyl‐based copolymer backbone and thus imparting (bio)degradability. Such materials are suitable for a large scope of applications, particularly within the biomedical field. The competition between the ring‐opening and ring‐retaining propagation routes is a major complication in the development of efficient CKA monomers, ultimately leading to the use of only four monomers that are known to completely ring‐open under all experimental conditions. In this article we investigate the radical ring‐opening polymerization of model CKA monomers and demonstrate by the combination of DFT calculations and kinetic modeling using PREDICI software that we are now able to predict in silico the ring‐opening ability of CKA monomers.

Degradable Polystyrene via the Cleavable Comonomer Approach

“…To have a better understanding of this phenomenon, DFT calculations were performed to determine the enthalpies of reaction as well as the activation energies of i) the addition of alkyls radicals onto the thionolactone functionality and ii) the β-scission of the intermediate radical that either leads to thioester and a second released alkyl radical or gives back the thionolactone and the propagating vinyl macroradical (Scheme 3).To perform such theoretical study, we choose the UB3LYP/6-31G(d) level of theory due to the large number of atoms that are involved in the system. Moreover we already showed that this level of theory allowed us to have a good understanding of the homopolymerization of CKA 19 or the copolymerization behavior of CKA with various vinyl monomers. 20,21 Scheme 3.…”

“…led to similar results but with increased computational time. 19,20,22 The results of the calculations are gathered in Table 2. We can first observe that the β-scission reaction of the radical intermediate is not affected by the nature of the radical adduct since both enthalpies of reaction ΔHr and activation energies are rather similar (close to -23 kJ mol -1 for ΔHr and close to 60 kJ mol -1 for the Ea,β).…”

“…We rather opted for conservative estimations of the pre-exponential factors using previously reported values. 19,22 This approach was experimentally validated with cyclic ketene acetals. 19,22 In particular for radical addition reaction, we used Aadd = 10 8 L mol -1 s -1 for secondary radical as recommended by Fischer and Radom.…”

“…19,22 This approach was experimentally validated with cyclic ketene acetals. 19,22 In particular for radical addition reaction, we used Aadd = 10 8 L mol -1 s -1 for secondary radical as recommended by Fischer and Radom. 25 For the unimolecular β-fragmentation, a value of Aβ = 10 13 s -1 was used.…”

Multi-scale reactive extrusion modelling approaches to design polymer synthesis, modification and mechanical recycling

“…The design of biodegradable and bio-based plastics is an appropriate, ecoefficient approach to enhance the environmental quality of many products. [113][114][115][116] Up until now, many biodegradable plastics still struggle to compete with petroleum-based bulk products especially in terms of cost-competitiveness and thermo-mechanical properties. To increase their commercial scale-up and competitiveness while still maintaining biodegradable properties, these type of polymers are generally mixed with organic/inorganic fillers.…”