(204d) Density Functional Approach for Modeling Polymer-CO2 Interfaces | AIChE

(204d) Density Functional Approach for Modeling Polymer-CO2 Interfaces

Authors 

Tomasko, D. L. - Presenter, The Ohio State University
Kusaka, I. - Presenter, The Ohio State University


Over the past decade supercritical carbon dioxide (scCO2) has emerged as a significant solvent for polymer processing. However, despite numerous advances on the experimental front, optimization of many processes involving polymer-scCO2 binary mixture is still a challenge primarily due to the lack of theoretical models that can describe the binary system at the molecular level. This work is aimed at bridging the gap between theoretical and experimental knowledge through polymer density functional theory (PDFT). The basic idea of PDFT is to express the free energy as a functional of spatially varying density distribution, from which equilibrium density distribution and other thermodynamic information can be derived including solubility of CO2 in polymer, interfacial tension, and Glass transition characteristics (especially across the polymer-CO2 interface). An interesting feature of glass transition is that the glass transition temperature Tg of a polymer thin film or polymer surface layer varies continuously across the surface. It is also observed that the presence of scCO2 depresses the Tg. Since the characteristic length scale of the system is very small, it is difficult to analyze these characteristics using experimental techniques. This is where our theoretical tool proves useful. Before studying the interfacial properties, it is essential to ensure that the PDFT model captures important characteristics of the pertinent polymer-CO2 mixture. In this talk we will show results from the parameterization of our model based on the phase behavior of the polymer-CO2 binary system and discuss how we extract detailed information about the equilibrium structure and properties of polymer-CO2 interface.

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