Structure-Property Relations of Epoxy/PCL Based Shape Memory Composite Hydrogels

Shape memory polymers (SMPs) are a special category of polymers that undergo a temporary shape and recovery to a permanent shape when exposed to external stimuli such as heat or water. This makes them valuable in the medical device industry, specifically in areas such as endovascular applications, drug delivery and tissue engineering. Shape memory properties, in particular, allow for minimally invasive surgeries.

In this project, epoxy/PCL-based triple shape memory composites (TSMC) called polyethylene oxide-epoxy/poly(ε-caprolactone) or PEO-EP/PCL have been prepared using electrospinning. In order to create this TSMC a 20 wt% poly(ε-caprolactone) (PCL) solution dissolved in a 4:1 chloroform to DMF ratio was mixed for 24-36 hours, following which solutions were electrospun into thin fibrous mats. Subsequently, a miscible blend of diglycidyl ether of bisphenol-A (DGEBA) with Jeffamine ED2003 (2:3) was imbibed into the PCL fiber mat and cured to a pore-free translucent composite. Interestingly, because the ED2003 diamine features a water-loving poly(ethylene oxide backbone) the resulting composites swell in water, enabling formation of a composite hydrogel. We investigated the structure-property properties of the composites, including differential scanning calorimetry (DSC) to characterize the complex melting behavior of PEO-EP/PCL Further, dynamic mechanical analysis (DMA) was conducted to characterize the tensile storage and loss moduli, while tensile testing of the dry and wet forms of the composite enabled determination of ultimate mechanical properties of the unique materials. Shape memory properties were found to enable distinct heat/hydration recovery of the permanent shape from arbitrarily fixed temporary shapes.