Controlling the actuation rate of low-density shape-memory polymer foams in water

摘要

SMPs have been shown to actuate below their dry glass transition temperatures in the presence of moisture due to plasticization. This behavior has been proposed as a self-actuating mechanism of SMPs in water/physiological media. However, control over the SMP actuation rate, a critical factor for in vivo transcatheter device delivery applications, has not been previously reported. Here, a series of polyurethane SMPs with systematically varied hydrophobicity is described that permits control of the time for their complete shape recovery in water from under 2 min to more than 24 h. This control over the SMP actuation rate can potentially provide significant improvement in their delivery under conditions, which may expose them to high-moisture environments prior to actuation. A controlled rate of actuation of ultralow-density shape-memory polymer foams in water is reported. The time of complete shape recovery is controlled from 2 min to >24 h based on material composition. This ability to control the actuation rate may significantly improve the delivery of SMP medical devices under conditions that require exposure to high-humidity environments prior to actuation.