Ultra-thin films aging behavior

Aging Behavior in Thin and Ultra-thin Films... 

The results presented in this chapter suggest that the accelerated aging of ultra-thin films of gas separation membrane materials is caused by an enhanced mobility near the film surface that allows the polymer to relax towards an equilibrium state more rapidly than bulk samples. This deviation from thick film behavior is also strongly dependent on the polymer structure, complicating efforts to predict thin film behavior from bulk properties. Although some modeling efforts capture thickness dependent properties, estimating thin film behavior from bulk measurements only provides a first-order approximation. 

However, direct investigation of the interphase properties inside an adhesive bond is very difficult, for experimental reasons. In contrast, ultra-thin polymer films on metal substrates provide access for a number of analytical techniques. Hence, to some extent, they are suited to monitoring of interphase properties and processes. By varying the film thickness, it is possible to discriminate the influence of the metal substrate on the aging behavior in the interphase. 

This paper reports the study of the aging behavior of ultra-thin epoxy films on PVD layers of Al, Au, and Cu under varying environmental conditions by FTIR external reflection absorption spectroscopy (ERAS), to reveal influences of interphase interactions on crosslinking and on chemical aging processes at moderate temperature. 

Figure 3.3 Diagram of film structure used by Rowe et al., which enabled the study of gas permeability properties and physical aging behavior of ultra-thin glassy films. Reproduced with permission of Elsevier. ...

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