Spinodal dynamics of metastable glass transition domains in amorphous polymer towards thermomechanically tailorable shape memory effect

Glass transition plays a critical role to determine the dynamic behaviors of amorphous shape memory polymers (SMPs). However, the fundamental relationships between shape memory effect (SME) and dynamic glass transition have not been well understood, even though this topic has been studied for decades. In this study, we apply a mean-square displacement function of Adam-Gibbs (AG) domain size model to explore metastable glass transition between normal glass state and rubbery state of amorphous SMPs, based on both mode-coupling theory and mean-field model. A statistic viscosity equation is formulated to study the dynamic glass transition of metastable AG domains in an amorphous SMP. A dynamically spinodal model is also developed to connect dynamic glass transitions to thermomechanical processes, based on statistic viscosity equation and phase transition model. Furthermore, using the spinodal models, multiple shape memory behaviors have been predicted for amorphous SMPs with dual-, triple- and quadruple-SMEs, resulted from their different routes of themomechanical evolutions. Finally, the proposed models are verified using the experimental data reported in literature.

Automated summary

Glass transition is critical in determining the dynamics of amorphous shape memory polymers (SMPs), but the relationship between shape memory effect (SME) and dynamic glass transition remains unclear. This study uses an Adam-Gibbs (AG) domain size model and develops a mean-square displacement function, as well as a statistical viscosity equation and a dynamically spinodal model, to explore the metastable glass transition and thermomechanical evolutions in amorphous SMPs. Multiple shape memory behaviors are predicted and the proposed models are verified using experimental data.