Effects of Temperature on the Microscale Adhesion Behavior of Thermoplastic Polymer Film

Adhesion tests were carried out under various temperature conditions to investigate the effects of temperature on adhesion behavior between a fused silica lens and a poly(methylmethacrylate) (PMMA) film, materials used for molds and as thermoplastic polymer films in nanoimprint lithography (NIL). The pull-off force and the contact area were measured as the temperature of the PMMA film was increased from 300 to 443 K, and as it was decreased back to 300 K. As the temperature increased, the PMMA film changed from a glassy state to a viscous flow state, and the adhesion behavior showed significant variation corresponding to this change in state. In the glassy state (below 363 K), the pull-off force did not change noticeably as the temperature increased. In the rubbery state (383-413 K), the pull-off force increased significantly as the temperature increased. In addition, the contact area was enlarged. In the viscous state (above 423 K), fingering instability was observed in the contact area and the pull-off force decreased, while the contact area increased, as the temperature increased. The adhesion behavior was also found to vary markedly with thermal history of the PMMA film. The causes of these changes are discussed.