Simultaneous measurement of glass transition, crystallinity, and order-disorder transition of polymers through restitution height after collision

Abstract

The glass transition temperature (Tg) and degree of crystallinity (Xc) are important properties when determining processability and thermomechanical stability of polymers and the order-disorder transition temperature (TODT) is another crucial temperature for utilizing the microphase separation behavior of block copolymers (BCPs). However, conventional techniques have some inconveniences when measuring these properties at the same cycle of measurement. Consequently, based on the contact mechanics and rheology, we developed a new intuitive technique to measure Tg, Xc, and TODT by analyzing the restitution height of a dropped material after the collision with polymeric sheets or films. This novel method is more straightforward and can simultaneously measure all three properties with a small amount of sample. Using various types of polymers, including BCPs and conjugated polymers, we demonstrated that Tg can be determined by the onset of a dramatic decrease in restitution height, Xc is closely related to the normalized minimum restitution height, and TODT is another significant restitution height decreasing point at higher temperatures. All Tg, Xc, and TODT values measured by the collision method corresponded well with the theoretically estimated and/or conventionally determined values. On the basis of these findings, it is anticipated that the collision technique will be applicable to unknown polymers, and an approach to measure Tg, Xc, and TODT of sub-micrometer-thick films will be addressed.