Developing\nHydration Maps of Polymer Latex Film Formation\nUsing Terahertz Time-Domain Spectroscopy

The dynamics of the\ndrying process of polymer latexes after casting\nas a wet film onto a substrate are important to track as they influence\nthe physical and mechanical properties and performance of the dried\npolymer films. Current methods used to follow this drying process\ninclude gravimetric analysis, coupled with advanced techniques like\nGARField-NMR or optical coherence tomography. The latter two methods\nprovide height and spatial information in the <i>z</i>-direction,\nnormal to the substrate, and occasionally in the xz- or yz-planes.\nTerahertz time-domain spectroscopy (THz-TDS) is a welcome addition\nas it provides both the structural and spectroscopic information in\nthe parallel xy-plane, filling the geometric gap. Herein, we utilize\nTHz-TDS to study the drying and film formation process of various\npolymer latexes with a broad range of glass transition temperatures.\nWe showcase the applicability of this technique in obtaining 2D parallel\nhydration maps of the drying dispersions, in the form of droplets,\nusing latex-dependent calibration lines. Our findings display known\nphenomena arising from the drying of the colloidal dispersions.