Light-Activated Shape Memory Polymers and Associated Applications

摘要

Continuous product development and technology integration efforts using shape memory polymers (SMPs) have uncovered a need for faster response times. As with most smart materials, SMP responds to a specific stimulus. Traditionally SMP is triggered by thermal stimulus; increasing the temperature of the SMP above a T_g will transition the polymer from a glassy state to a rubbery state. The transition is reversible upon cooling below the T_g. It has been determined that many SMP applications can be significantly enhanced with non-thermal triggering. Non-thermal triggering eliminates the need for heating mechanisms and reduces cycle time. Furthermore, it has been found that with a faster response time many new applications become viable. Previous successful attempts have been made to improve response time of SMP by increasing its thermal conductivity with various thermally conductive additives. However, thermal heating and cooling of polymers and composites of substantial thickness, thermally conductive or not, takes time. In an effort to facilitate system integration and increase the response time of SMP, researchers at Cornerstone Research Group, Inc. (CRG) have sought to eliminate the thermal dependency of SMP by developing light-activated shape memory polymer (LASMP). In this work, monomers which contain photo-crosslinkable groups in addition to the primary polymerizable groups were developed. These monomers were formulated and cured with other monomers to form LASMP. The mechanical properties of these materials, the kinetics, and the reversibility of the light-activated shape memory effect were studied. The near-, mid-, and far-term potential of this new material technology for system level applications is discussed.