Strong toys from sugar Novel rigid polyesters with high impact strength and high Tg

Polyesters are useful materials for a number of applications, like water bottles, packaging materials, clothes fibres. They have, however, drawbacks like typically high stiffness with low impact strength, making them relatively brittle for certain uses, and relatively low glass transition temperature (Tg), limiting their temperature exposure. In this work we developed novel polyesters by use of high boiling reactive solvents. This method, developed in our group, enables the incorporation of large amounts of isosorbide, a biobased compound with secondary hydroxyl groups. Isosorbide is a key monomer, in polyesters, for achieving a good balance between Tg, stiffness and impact strength. When present in polymer chains, it increases the Tg and disrupts the crystallinity of the system due to its bulky hindered structure.
The polyesters synthesized in this work were partially biobased, composed of isosorbide and other diols, and were designed to be used mainly as toy materials, specifically as more (potentially) sustainable materials for LEGO bricks. The syntheses with reactive solvents produced molecular weights above those seen in literature for relatively high isosorbide content (>30 %). A group of polyesters are synthesized and evaluated for their mechanical and thermal properties and a select few are chosen for accelerated aging experiments. These studies present a couple of good candidates for the intended application, which balanced well impact strength (>15 kJ/m²), Tg (>90 °C), stiffness (^~2 GPa) and aging behavior compared to commercial polymers like ABS, PET and Tritan. The work shows, overall, a useful pathway to synthesize and evaluate novel polyesters.