Shape Memory Polymers (SMPs) are stimuli responsive materials. Based on the type of stimuli, SMPs are classified as Thermo-responsive, Chemo-responsive, Electro-active, Photo-active etc. My research focusses on Thermo-responsive SMPs.

Thermo-responsive SMPs rely on the dramatic change in relaxation times across the rubber-glass transition temperature (Tg) to exhibit shape memory behavior. Below the Tg, a SMP is glassy, brittle and has very long relaxation times. Above the Tg, it is rubbery, compliant and has very short relaxation times.

A typical shape memory cycle involves reshaping at high temperature (T>Tg), cooling under constraint to cold store a temporary shape (T<Tg) and load free recovery at high temperature (T>Tg). SMPs have lots of potential applications in consumer, health care, electronics, manufacturing, automotive and aerospace sectors.

However, somewhere above the Tg, there exists a temperature known as 'Chemo-rheological temperature' (Tcr), above which the SMPs undergo chemical degradation, which, involves scission (breaking of bonds) and re-crosslinking (formation of new bonds). This chemical degradation can manifest as residual strain, mechanical property changes, discoloration etc. depending up on the chemistry of the polymer and the mechanism of degradation. For successful development of applications, it is imperative to understand and quantify this chemical degradation behavior.

The major goals of this project are:

  • Quantify the fundamental thermo-mechanical behavior of a SMP
  • Characterize the degradation behavior of SMP and establish a design and operation space
  • Develop a comprehensive mathematical model of SMP to aid production, product design and life cycle analysis