The optimal ratio of diisocyanate and polyol for synthesizing polyurethane with the highest possible mechanical strength depends on the specific types of diisocyanate and polyol being used, as well as the desired properties of the final product. In general, a 1:1 molar ratio of diisocyanate to polyol is used to achieve a stoichiometric balance, which can result in a polyurethane with good mechanical strength.However, this ratio can be adjusted depending on the desired properties of the polyurethane. For example, increasing the diisocyanate content can lead to a more rigid and strong material, while increasing the polyol content can result in a more flexible and soft material. It is important to carefully control the ratio and reaction conditions to achieve the desired balance of properties in the final product.To determine the optimal ratio for a specific application, it is recommended to perform a series of experiments with varying ratios and test the mechanical properties of the resulting polyurethane materials. This will allow you to find the best balance of diisocyanate and polyol for your specific needs.