Analysis of Binary Solvent Diffusion into Cross-Linked Poly (Butadiene) Using Fast Scan Fourier Transform Infrared Imaging Spectroscopy

Abstract

The diffusion of a binary solvent mixture into cross-linked poly (butadiene) (PBD) was observed using fast scan FT-IR imaging spectroscopy. Spatial correlation of solvent ingress and polymer swelling was established with a temporal resolution of 20 s. Binary solvent mixtures included a good-good solvent pair of benzene-cyclohexane (50/50 wt%) and a good-poor solvent pair of toluene-methanol (50/50 wt%). A set of FT-IR images was collected over time, from which the profiles of solvent ingress and polymer swelling were extracted. The Boltzmann transformation, which explains diffusion phenomena with respect to both time and position simultaneously, was used to obtain a curve, which indicates that benzene and cyclohexane diffuse similarly, but toluene and methanol have different diffusion behavior. The good-good solvent pair (benzene-cyclohexane mixture) ingressed into polymer together, while the good-poor solvent pair (toluene-methanol mixture) showed independent ingression behavior. The good solvent (toluene) aggressively diffused into polymer while the poor solvent (methanol) remained in solution.