Characterization of polyimid-multi-layer thin films combining laser ultrasonic measurements and numerical evaluations

Grünwald, E.; Nuster, Robert; Hammer, René; Asmann, H.; Paltauf, Guenther; Brunner, Roland

doi:10.1109/eurosime.2016.7463353

Cited by 2 publications

(1 citation statement)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Polymer coatings serve a wide array of purposes, where many specific applications require multicomponent coatings. − These coatings are typically applied in a layer by layer fabrication process. In addition to the deposition of each layer for its desired application, adhesive binders are often required between layers to prevent peeling and improve durability of the entire coating system .…”

Section: Introductionmentioning

confidence: 99%

Elucidating the Kinetic and Thermodynamic Driving Forces in Polymer Blend Film Self-Stratification

2018

View full text Add to dashboard Cite

Self-assembly of immiscible polymer blend films during deposition presents an attractive avenue to fabricate structured multicomponent thin films. Depth profiles formed by self-stratification during spin-casting can be varied simply by modifying processing conditions, even on short time scales. However, the current practice of self-stratification utilizes polymer blends that are specific for optimizing properties of a desired application and provides little insight into the underlying driving forces that guide the process of stratification. Our research seeks to fill this gap by using neutron reflectivity to monitor the stratification of blends consisting of poly(3-hexylthiophene-2,5-diyl) (P3HT) and poly(methyl methacrylate) (PMMA) as a function of sample and processing condition: spin-casting speed, polymer blend composition, and polymer molecular weight. Each of these parameters was varied individually, and each parameter provided orthogonal control of the extent of stratification. An increase in the concentration of P3HT in the blend composition increased the immiscibility between the two polymers, which leads to an increase in stratification. A reduction in the similarity of polymer molecular weights in the blend reduced the entropic driving force of stratification. Additionally, when casting speed was decreased, and all thermodynamic conditions were left unchanged, we observed a longer film formation time and an increase in extent of stratification. Longer film formation times allow more time for the thermodynamic driving forces to dictate the rearrangement of polymer toward equilibrium. Furthermore, by changing the relative molecular weight of the polymers, the purity of the P3HT layer at the air interface improved, where the largest molecular weight PMMA resulted in the purest P3HT-rich layer. The interfacial width between the P3HT-rich layer and the PMMA rich-layer was also controlled by changing the composition of the blend, where the blend with the highest concentration of P3HT resulted in the sharpest interface. We attribute the differences in vertical morphology to the control of the thermodynamic properties of each blend, including total entropy of the system, surface energy, and the χ interaction parameter. Through careful regulation of the processing conditions of P3HT:PMMA thin films, these results provide insight into both the kinetic and thermodynamic factors that direct the self-stratification of polymer blend films. This fundamental study of stratification for P3HT:PMMA blends provides the foundation to develop a global understanding of self-stratification and to impact a wide range of technologies by developing cost-efficient protocols for multilayer film deposition of structured thin films without postmodification processes.

show abstract