The Role of Nanoscale Confinement of Adhesion Promoting Molecules on the Adhesion and Resistance to Moisture Attack at t
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0924-Z08-18
The Role of Nanoscale Confinement of Adhesion Promoting Molecules on the Adhesion and Resistance to Moisture Attack at the Polymer/Silicon Nitride Interface Bree M. Sharratt1, and Reinhold H. Dauskardt2 1 Aeronautics and Astronautics, Stanford University, 416 Escondido Mall, Bldg 550, Stanford, CA, 94305-2205 2 Materials Science and Engineering, Stanford University, 416 Escondido Mall, Bldg 550, Stanford, CA, 94305-2205 ABSTRACT The interface between a highly-crosslinked polymer film and a thin silicon nitride layer can be regulated using adhesion promoting molecules. This work compares the effects of both indirect polymer/inorganic interface chemistry modification by blending organosilane adhesion promoting molecules into the polymer layer, and direct modification by confining the organosilane molecules to the substrate surface. Of particular interest are the effects of these modifications on the occurrence of an anomalous subcritical debonding phenomenon previously observed for the unmodified interface. While significantly different adhesion values were measured, the influence of the blended organosilanes was limited to moderating moisture diffusion through the polymer layer, which correllates with moderated near-threshold growth rates. Conversely, nanoscale confinement of the adhesion promoting molecules did not result in expected universal increases in adhesion energy but did inhibit anomalous debonding behavior. INTRODUCTION The use of organosilane molecules as adhesion promoters is widespread and much effort has been devoted to the study of such techniques with respect to polymer/inorganic interface adhesion (e.g. [1-3]). While the majority of these efforts have studied organosilane molecules as primers, confined to the substarte surface, there exist a few instances where their use as additives, blended into the polymer layer, has been explored [4-5]. Even fewer studies, however, have addressed organosilane use with respect to the issues of subcritical debonding and threshold or near-threshold debond growth [6-8]. The latter is of considerable importance for the materials system under consideration, which exhibits anomalous behavior in the near-threshold region [9]. In previous work [9], interfacial bonding at the interface between a technologically-relevant model polymer, diglycidyl ether of bisphenol F, and a silicon nitride film was hypothesized to consist primarily of weak hydrogen and Van der Waals bonds due to the low measured adhesion energy. Such weak interfacial bonding facilitates a stress-dependent transport mechanism whereby moisture diffuses through the polymer layer and ahead of the debond tip where it preferentially sorbs onto the hydrophillic substrate surface. Water molecules collected at the interface displace the weakly-bound polymer layer and encourage continued debond growth. While applied stresses marginally accelerated debond growth, debonding can occur even in the absence of an applied load. In this study we demonstrate that debond growth rates in this anomalous region can
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