We are investigating the use of glassy shape-memory polymer networks as responsive substrates to enable high fidelity elastomeric printing. This application demands tough, deformable, and moldable materials that can undergo multiple, fully recoverable, shape-memory cycles to high strain. Glassy acrylate shape-memory networks containing poly(ethylene glycol) oligomers were designed and synthesized to achieve high strain-to-break with a targeted glass transition temperature of 45°C. A formulation that satisfied our criteria was chosen for extensive thermomechanical studies. Strain-to-break tests at different temperatures and strain rates were compiled to define a failure envelope. Thermomechanical tests conducted using different paths significantly affects the measured strain-to-break. Shape-memory thermomechanical cycles showed a reduction in trigger temperature (glass transition temperature) for samples fixed at high strains. These results are attributed to internal stresses that develop within the material during cycling. To further evaluate how stress affects the glass transition temperature, dynamic mechanical analysis was performed using an external tensile load. These experiments allow us to investigate how internal versus external stresses affect the network’s glass transition temperature. Our results are being applied to optimize topographical shape-memory of surfaces containing patterned features.

Thermomechanical path dependence of glass transition temperature and failure in glassy shape-memory networks

254th National Meeting (2017)

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