Catalyst-Free Partially Bio-Based Polyester Vitrimers

Most of the vitrimers based on ester linkages reported so far contain a Lewis acid or a strong organic base as the transesterification catalyst. The recyclability and reusability of these vitrimers are dependent on the catalyst retention, stability, and sintering issues. Herewith, a set of β-activated ester-based vitrimers are reported that can be thermally reprocessed at ∼150 °C under catalyst-free conditions. The relaxation temperature decreases to 110 °C in the presence of Sn(Oct)2. Importantly, the precursor of these vitrimers, malonic ester, is a cost-effective naturally occurring ester and can be extracted from various fruit juices. As a proof of concept, poly(hydroxyethyl methacrylate) is used as the hydroxyl precursor for the synthesis of vitrimers. These vitrimers display an adequate tensile strength (11.3–33.0 MPa), elongation (80–290%), and resilience. The materials can be effectively self-healed and reprocessed in the presence of heat without sacrificing the tensile properties. The vitrimers based on Sn(Oct)2 exhibit mechanical properties similar to that of the catalyst-free analogues and reprocess at ∼110 °C. These vitrimers may potentially be utilized for the development of coatings, hydrogels, biomaterials, adhesives, and commodity plastics in the future.