Recent Advances in the Titanium-Based Catalysts for Ring-Opening Polymerization.

At present, economic development and daily life cannot be separated from organic synthetic polymers. However, a large number of nondegradable polymers have caused serious pollution to the environment. It is necessary for sustainable development to use biodegradable materials instead of traditional polymers, but it is not yet comparable in performance and cost to the competitor it will replace. Therefore, there is a long way to go to develop effective synthesis methods. Through ring-opening polymerization, some cyclic monomers, such as ε-caprolactone or lactide, can be synthesized into biodegradable polymers, which can not only replace traditional synthetic polymers in some fields but also have applications in drug delivery, surgical consumables, human implant materials, bone materials, etc. Ring-opening polymerization is a potential candidate for solving environmental pollution. For ring-opening polymerization, catalysts are very important, among which titanium catalysts have attracted much attention because of their high efficiency, economy, and nontoxicity. In this paper, the development status of organotitanium compounds as ring-opening polymerization catalysts is reviewed, including the effects of different ligand structures on polymerization behavior and polymer structure, and its development trend is prospected. We hope that this review will be helpful for developing efficient ring-opening polymerization catalysts.