A quantitative study of the formation of breath figure templated polymer materials

Abstract

Self-assembled ordered arrays of pores are formed when a polymer-solvent solution is deposited in the presence of a humid airflow. These structures can be used as biological scaffolds, photonic bandgap materials and microfluidic beakers. Despite a wealth of material in the published literature regarding the growth of these structures, the dynamics of the process have received little attention from a quantitative perspective. Before the self-assembly mechanism can be understood, it is important to first look at the co-existent driving conditions. Here we develop such a computational model to describe this casting process, which finds excellent agreement with published data. The solvent evaporation profile is found to be near-linear for the majority of the casting process. During this stage a steady-state thermal system exists. The model shows that a humidity threshold exists for the creation of self-assembled structures, with threshold values which find excellent agreement with the literature. Measurement estimates taken of condensate deposition on to the polymer film match the order of magnitude and trend of computational values. Although not given attention in the literature before, slide thickness is shown to be a crucial parameter in this process. The model is able to identify the critical parameters in this system and show which should be controlled and specified to enable experimental results to be repeated. The ability of this model to accurately match experimental results sets it up as the basis for development of a full approach to capture the dynamics of the self-assembly formation process.