Optical diffusion diagnostics of evolving polymer foams

Abstract

Various approaches to the optical diagnostics of evolving polymer foams formed as a result of a decrease in the external pressure according to a given scenario in the "polymer-supercritical fluid" systems are considered.Formed polymer foams are considered as a material platform for the creation of scaffolds for biomedical applications. Diagnostics of the current state of the foam was carried out by statistical analysis of the spatiotemporal fluctuations of the probe laser radiation,multiple scattered in the volume of the evolving foam, or by analyzing the fluorescent response during foaming of the "polymer-fluorophore" mixture, pumped by laser radiation in the absorption band of the fluorophore. A relationship has been established between the average lifetime of dynamic speckles in scattered laser light and a generalized parameter characterizing the foam expansion dynamics. It was also found that the waveguide effect in the walls of the formed pores has a significant influence on the fluorescent response of the evolving foam, leading to an increase in the characteristic dwell time of fluorescence radiation in the walls and, accordingly, to an increase in the contribution of the induced component to the fluorescent response. Keywords: fluorescent response, speckle correlometry, polylactide, foaming, supercritical carbon dioxide.