Dendronized polyurethanes showing improved mechanical properties and unprecedent thermoresponsiveness

Introduction of topological structures to polyurethanes (PUs) may impart them with different microphase separation, which would be beneficial to afford them novel properties and expand their applications. Herein, a series of dendronized polyurethanes (DPUs) were synthesized with polyols carrying three-fold dendritic OEGs as the soft segment and either aliphatic or aromatic isocyanates as the hard segments. Different from conventional PUs with linear polyols as the soft segments, DPUs contain soft segments with spherical pendants, which may contribute different phase separation. In addition, dendritic OEGs afford DPUs with excellent thermoresponsiveness. Films from aliphatic DPUs and those from the mixture of aromatic DPU and linear PU were prepared. These thermoresponsive DPU films show tunable regulation capacity for encapsulated guests during thermally-induced aggregation of the dendritic OEGs. Remarkably, the phase separations of DPUs were found to be closely related to the amount of dendritic OEGs, and the PU films exhibited excellent mechanical properties with suitable amount of dendritic OEGs as the soft segment. Therefore, dendronization of PUs not only can modulate their microphase separation, but also provides a unique approach to develop PUs materials with novel properties.